im looking to buy a pair of slicks for my chevelle and have a few questions regarding size, traction and rpms at the stripe.

my combo just in case its needed

1966 Chevelle SS396

Engine:

512 block 427
11:1 forged pistons
840 rectangle ports
2.125 x 3.5 headers(too big i know)
305H comp magnum cam
edelbrock performer rpm
gm lifter valley shield
3310 vs sec holley
carter 172 fuel pump(thanks tom!)
stock 3/8ths line
-6 to carb
3 inch pipes from headers to mufflers with dumps

Driveline:

trans/clutch

rebuilt 904 iron case super t-10
cast iron mid plate
2.43 first gear
hurst shifter
lakewood blow shield
centerforce dual friction clutch
cf flywheel
3.5 inch custom driveshaft
1350 series yokes/joints

rear end
12 bolt 3.90 gears
new eaton posi
new superior axles
1/2 inch studs

suspension

front:
stock with tom aka mc71454's shock nut trick

rear:
ssm lift bars
stock "4 speed bars"
air bags left and right
adjustable drag shocks(rear only)

ignition:
mallory unilite
blaster 2 coil
msd 8728 rev control(rev limiter only)
msd 2 step box
2 adjustable rpm modules
low speed module 3000-5200
high speed module 4600-6800

misc
line lock
15x8 rally wheels

first let me say this car is a street strip car that will probably only see test and tune days.
the car will be trailered to the track though, so im not concerned about having a dot slick.
my goal is to run low 12s, high 11s if possible and traction is a big concern. im not looking to spin this engine any higher than 6000-6500 and with the 3.90 gears and 26 inch slicks i should cross the stripe a little shy of 6000rpm.

to the point

im looking at either a 28x10 slick or a 26x10 slick. i know that the diameter plays a role in increasing the contact patch of the tire, but im
not sure if i should trade traction for rpms at the stripe.

which would i be better off with with my combo? the better traction of the 28" slick or the increased rpms at the stripe with the 26" slick?

another thing i have 15x8 rallies, and i notice that the 26x10 is recommended for a MINIMUM 9 inch wheel where a 28x10 has a minimum of 8(both hoosier). if i do decide to go with the 26x10 will i be okay using a 8 inch wheel?

just for kicks while i have your attention, any of you have any 1/4 mile et predictions? smile.gif

thanks

The biggest thing (IMO) is where the engine starts to make power. With a slick, you should dead hook at the line. That means the instant you drop the clutch, the engine RPM's begin to fall in order to properly correlate with vehicle speed. The point where the engine starts build RPM again needs to be the beginning of your powerband.

Lets' say you start to make good power at 4600 RPM's. Let's also say that 4600 RPM's equates to 30 mph in first gear. That means that you basically have to catapault the car to 30 mph on launch or the engine is going to bog when it tries to go from losing RPM to building RPM.

I guess what I am trying to say, is that if you make enough power to sling the car to optimum RPM almost instantly, go for the 28 inch tires. If not, the 26 inch tire may be the best bet. Or you could always come off the line on a 100 shot of nitrous...

The 8 inch wheel will hurt traction some, but I wouldn't worry too much about it. The other issue that may arise from the small wheel is a "floating" feeling at the end of the track. Sometimes it can feel out of control enough for people to back off the throttle. Just be careful your first time out.

As far as ET prediction, that's tough. ET is almost all in the launch. a 1.6 sixty VS as 2.1 sixty is a huge difference in ET. My guess is your MPH will be somewhere between 110-115, maybe a tad higher. With a good launch, a manual transmission car that traps 115 should be capable of mid-high 11's.

I say use 26" tall slicks with the rectal port heads, will help you stay in the upper rpms,where those heads shine.Although the taller slick will provide better traction,I have a feeling that you're going to have a hard time getting a decent 60ft. time. High 12's, Low 13's.

i would go with the shorter slicks since you're under geared already with those 3.90's, no since in making it worse. you should be able to hook it up on 26x10 slicks with no problem. i have a pretty well stock set up on my 71 and i can 60ft 1.66's on a 26x10.5 SPORTSMAN PRO. all i have is SSM lowers and CE rear drag shocks, Moroso trick springs in the front. deciding factor for how fast is the 4-speed factor. i'm not good at predicting ET's for a 4-speed, but if it were an AT with about a 4000 stall, then i'd say you should be able to get mid to upper 11's.

thanks guys

I have a feeling that you're going to have a hard time getting a decent 60ft. time. High 12's, Low 13's. Bob, why do you say that? is it because of traction or just my combo. i know that the 60ft has a very big impact on e.t. and anything i do to make it better will improve the et.

i figure if Gene aka 427L88 can run low 12s with about the same gearing and soft 2.+ 60fts i should be able to do that or better with a decent launch and 60ft, wouldnt you think?

currently the car has no interior at all, no headliner, no carpet/insulation or door panels. all i have in the car right now is the drivers bucket seat.

i did take the car to the track once already(local eighth mile). but i was on street tires and was absolutely murdering the tires. my best 60ft was a 2.18 and that was bogging the car off the line, which with this combo hurts performance alot. on that run as soon as i hit second gear traction was non existent to the 1/8th mile stripe. when i banged third at the top of the track the car got sideways and i had to correct and let out of it. i could not power shift, and i had to peddle the throttle alot. because of this the 1/8th mile et and mph suffered severely. this was also before i changed to the performer rpm/lifter valley shield, and the carter 172 im getting from tom.

im not afraid to launch this car. i built the trans and have a muncie as a spare. having grown up around stick cars i feel i can bang gears with the best of them.

As far as ET prediction, that's tough. ET is almost all in the launch. a 1.6 sixty VS as 2.1 sixty is a huge difference in ET. My guess is your MPH will be somewhere between 110-115, maybe a tad higher. With a good launch, a manual transmission car that traps 115 should be capable of mid-high 11's thats good to hear and is exactly what im thinking. hopefully once i get everything sorted out the car will run the numbers im looking for. if not, ill make changes.

With those heads, that big of a cam and those big headers, I would also go with the shorter tires. I'd also prefer a DP carb vs a vacuum carb on a stick car. The 427 will like to rev a bit more also. What does the car weigh now? What are "stock 4 speed bars"?
just my $0.02

Jim,sounds like your old combo!

Originally posted by Epistuff:
With those heads, that big of a cam and those big headers, I would also go with the shorter tires. I'd also prefer a DP carb vs a vacuum carb on a stick car. The 427 will like to rev a bit more also. What does the car weigh now? What are "stock 4 speed bars"?
just my $0.02 the "4 speed bars" im referring to are the bars that connect the upper and lower rear control arms.

my next change will be a dp

and i havent weighed the car yet, but from past searches im thinking 3700-3800lbs.

i know the 427 will rev higher than im currently spinning it to. but i havent had any traction and revving it any higher hasnt done any good at this point. when the time comes i may spin it higher.

right now im working with what i have, if i dont run the numbers im looking for i will make changes. i know my goals and what the car runs are two different things. so i may be in for a dissapointment, but thats life.

Originally posted by mr 4 speed:
Jim,sounds like your old combo! i believe i remember Jims old combo, and while there are some similarities there are quite a few differences also.

you never know, i may be the one to prove that a combo like this can run the numbers im looking for, or maybe not. one thing is for sure, we will see!

i will post the results good or bad when the time comes.

My old combo.....
11:1 427, comp cams 292H, 840 heads, 4.10 rear, Hoosier 275/50/15 DOT slicks (25.8" tall) 4 speed>>>> 13 @103

103mph seems low for that combo, did you ever tune the old combo for mph? or did you just throw parts at it?

my family and i are from new castle pa, but im not sure where nazereth is. is that western pa? whats the track elevation? i live in nc on the coast, we are at sea level here so i may have an advantage as far as track elevation. it does get pretty hot and humid here but im hoping to catch some good weather before the track closes for the holidays.

what changes did you make to go from 103mph with the old combo to 112 with the new one?

what was the 60ft time and the 1/8th mile et and mph with the old combo?

what rpms were you launching at?

what fuel pump were you using?

what transmission(m20 or m21?) and what if any suspension mods were done to the car at the time?

did the car spin or dead hook? did you have to peddle the throttle at all?

ive heard from local racers that stick cars dont hook well with drag radials/dot slicks, they said that i NEED a real drag slick to launch the car due to the manual trans shocking the tires. they also said that any peddling of the throttle would have a negative effect on the mph.

your car is heavier than mine, and i believe you drive the car to track correct? im trailering mine to the track and have no problems launching the car in the fat of the power band as i wont have to worry about driving the car home.

the last time i had the car at the track it ran 80mph through the 1/8th spinning to the stripe(smoke coming off tires the length of the track). i could not launch the car at anything over 1500-2000rpm, which as you know is way below the power band of this combo. i had to peddle the throttle alot, and got sideways banging third at the top end and had to let off. i also experienced a lean pop at the top end my last two runs, so it may be running out of fuel.

since then i have also switched from a torker 2 intake to a performer rpm with lifter valley shield. and i have a carter 172 coming from Tom aka MC71454.i also have a msd rev limiter, 2 step and line lock ready to be installed.

i feel if i can get the car to hook, launch the car in its power band and am able to stay in the throttle the length of the track it will mph higher than it did. then once that is accomplished ill tune the car for mph.

as i said, we will see. im an optimistic fellow so i cant believe it wont run the numbers until that happens. i feel confident i can get the car to run high 12s at least, and to be honest i wouldnt be dissapointed with that.

28" tall tires, change to 4.56 gears and be prepared to run it out to 6800+ in first,second and third gears (assuming the lifters won't pump up).

Just curious why you went that big on the cam and didn't go solid?

IMHO-- And with very limited racing experience, and probably a whole host of other factors, would not use 26" DOT or real slicks again. perhaps the true 26*10 slick would hook alot better than my 26*10.5 (8" actual tread) ET Street, but I find "hooking up" to be an essentially pointless effort even with my wide-by-huge rectangular ports and land barge weight vehicle.
This is just my experience, I don't know alot, so take it for what you think its worth.. but I am on the lookout in the local want ad for a deal on some 15*10 wheels for some 28*12.5 ET streets for next summer, and I expect my 1.8x 60's to drop to into the 1.6x's in my best estimation. A friend of mine in a similar situation (3.73s, 525-550 honest HP), went from 1.9x's on 26" DOT slicks to 1.72's on 28" DOT slicks. I am willing, I think, in my case, to sacrifice the RPM loss at the top end (26" slicks and my tighter converter put me at "about right") 28" would put me a bit low, but I bet in the end its better..

my 02.. taking advice from me could be risky though..

matt

Matt

Originally posted by GRN69CHV:
28" tall tires, change to 4.56 gears and be prepared to run it out to 6800+ in first,second and third gears (assuming the lifters won't pump up).

Just curious why you went that big on the cam and didn't go solid? i didnt build the engine, and if i did i would have done it differently. when the time comes i will go through the engine, but thats down the road.

i have ran the engine up to 6500 a couple of times on the street and it pulls hard. once i get more seat time in the car i will test different shift points, but until i can get the car to hook thats a moot point.

im 26 and this is the second time ive owned the car. when i first got the car it had 4.56s, when i sold it the guy swapped another 12 bolt in with 3.55s and sold the original rear. then when i bought the car back i rebuilt the rear end and put in 3.90s. if i were only concerned with track times i would have put 4.56s back in, but i plan on driving this car so that wasnt feasable.

even though the car has less rear gear than before i went from a m21 to a 2.43 first super t10. the starting line ratio is only a half point less than before with the 4.56s and m21 (9.5 compared to 10.00). i realise 4th is still one to one, and the car will turn less rpms at the stripe than before, but it should launch nearly as hard.

im setting the car up for the 1/4 mile but the 1/8th mile track is closer. when we went it was the first time i had the car at the track and i wanted to get some shakedown runs in the eighth before heading to Jacksonville(1/4 mile track).

my 02.. taking advice from me could be risky though.. Matt

i got a laugh out of that, thanks. your advice is appreciated.

103mph seems low for that combo, did you ever tune the old combo for mph? or did you just throw parts at it?
I tried all sorts of stuff, cams, carbs, timing curves... Who knows, maybe my heads just sucked

my family and i are from new castle pa, but im not sure where nazareth is. is that western pa? whats the track elevation?
Northeast PA, near Allentown and Easton. Track elevation is around 600', The DA' is typically 1500-2500

what changes did you make to go from 103mph with the old combo to 112 with the new one?
Swapped to a nicely ported set of 063 ovals, then put the Ultradyne 288/296 hydraulic in there. the times in my sig were also achieved with the Hoosier QT DOT's I ran last year (26" tall). So far I was not able to surpass that with my new taller ET streets. Didn't lose anything, just didn't run any quicker.

what was the 60ft time and the 1/8th mile et and mph with the old combo?
1.96 60' time and around 8.35 in the 1/8th @ 85MPH compared to 1.72 60' 7.85 in the 1/8th @ 89MPH

what rpms were you launching at?
3500 RPM

what fuel pump were you using?
Carter mechanical 172

what transmission(m20 or m21?) and what if any suspension mods were done to the car at the time?
Back then it had ladder bars. Now it has SSM's and I like them much better. The SSM's are a more recent change and had nothing to do with me getting low 12's. Always had an M20 since I bought the car 20 years ago.

did the car spin or dead hook? did you have to peddle the throttle at all?
I always shoot for a few revolutions of tire spin off of the line, my driveline is not buleltproof smile.gif . No, I never pedal it. 3500 RPM, last yellow sidestep the clutch and mash the throttle. Next season I go with an MSD 2-step

ive heard from local racers that stick cars dont hook well with drag radials/dot slicks, they said that i NEED a real drag slick to launch the car due to the manual trans shocking the tires. they also said that any peddling of the throttle would have a negative effect on the mph.
Depends on what you want to do. I think I am fine with my tires, I currently run 28x11.5x15 ET Streets and like it. I would have to upgrade a few driveline parts if I used a true slick and went to 6K clutch dumps. I did try a 4500 launch earlier this year, but it didn't net me anything, I spun a little more.

your car is heavier than mine, and i believe you drive the car to track correct?
Yes, I drive it everywhere.

Originally posted by MadMarv:
IMHO-- And with very limited racing experience, and probably a whole host of other factors, would not use 26" DOT or real slicks again. perhaps the true 26*10 slick would hook alot better than my 26*10.5 (8" actual tread) ET Street, but I find "hooking up" to be an essentially pointless effort even with my wide-by-huge rectangular ports and land barge weight vehicle.
This is just my experience, I don't know alot, so take it for what you think its worth.. but I am on the lookout in the local want ad for a deal on some 15*10 wheels for some 28*12.5 ET streets for next summer, and I expect my 1.8x 60's to drop to into the 1.6x's in my best estimation. A friend of mine in a similar situation (3.73s, 525-550 honest HP), went from 1.9x's on 26" DOT slicks to 1.72's on 28" DOT slicks. I am willing, I think, in my case, to sacrifice the RPM loss at the top end (26" slicks and my tighter converter put me at "about right") 28" would put me a bit low, but I bet in the end its better..

my 02.. taking advice from me could be risky though..

matt

Matt i know of guys cutting 1.30 60ft times on 26x8" slicks, so if you're not hooking it ain't the tire size. these cars are all stock suspension too. shoot, i'm doing 1.66's with Sportsman Pro 26x10.5's. track has alot to do with it, i'll admit i race at what's got to be one of the best prepped starting lines in America. ;)

It takes a lot of power and a lot of bite to cut 1.30s. Of the cars iv'e seen only very light Mustangs and Novas cut these 60' times regularly. More like 1.40-1.50 for most good bitting Chevelles.

Jim

thanks for answering my questions, but i have one more for you. by any chance did you change carbs when you changed the heads/cam? or change anything fuel related?

ive read that a car should pick up 22-24mph in the back half of the track and some stick cars may gain up to 26mph. your old combo was only picking up 18 in the back half compared to your new combos 23mph.

while its too late now, i still think your old combo was capable of more. but regardless of what it could have run before, its running damn good now. id be pretty happy if i were able to run those times. graemlins/thumbsup.gif

now all i have to do get some slicks and improve on my very crappy 60fts. i know the car will e.t. much better then it did, but how much remains to be seen.

thanks

Originally posted by Harold Sutton:
It takes a lot of power and a lot of bite to cut 1.30s. Of the cars iv'e seen only very light Mustangs and Novas cut these 60' times regularly. More like 1.40-1.50 for most good bitting Chevelles. yes most are Mustangs, but i have a buddy who is doing it in an 83 monte carlo @ 3500lbs as are a few other guys. i'm doing 1.66's in my 71 with STOCK uppers, SSM lowers, and 10 year old CE 50/50 rear drag shocks. front has moroso drag springs, stock gas shocks with the swaybar still bolted up, no air bags, or rear swaybar. and i'm doing it on Sportsman Pros, not slicks or even ET streets, just 10 year old worn out 26x10.5 Sportsman pros. if i can cut 1.66's with that set up anybody should be able to. graemlins/thumbsup.gif

Interesting post. I am also considering tire size gear swap. Strip / street rides require compromises in alot of areas, gearing being a big decision in my mind. Having relized from two seasons of use on the current combo, how I have used the car, and what I enjoy doing with it. Current set up is 10.5 X 30 Hoosier radial slick on 8 inch rims and 3.70 gear. Car will dead hook on a prepped track, consistant 1.7x sixty foot times, Runs 12.1x at 111.xx. Heres the deal, wanting to improve the 60's down to 1.6 times or better. I seem to recall low 5000 rpm level at the stripe in top gear with current gear and tire combo. Considering much more gear (4.5x) and keeping the 30" tire, or more gear (4.1x)and a 28" tire. Current street tire has got to go, I believe they are 26" tall. Looks like I am leaning towards more strip than street, looking for the "best compromise". Your thoughts? If I was having a high reving rec port 427 with a stick, trailering to the track with no seats and such.......Lots of gear, as tall and wide a tire that will fit, rev it to the moon and BANG them gears. Traction issues first, nothing else matters until it will hook. Hey, you already have the spare trans, go for it. :eek:

Originally posted by m71:
</font><blockquote>quote:</font><hr />Originally posted by MadMarv:
IMHO-- And with very limited racing experience, and probably a whole host of other factors, would not use 26" DOT or real slicks again. perhaps the true 26*10 slick would hook alot better than my 26*10.5 (8" actual tread) ET Street, but I find "hooking up" to be an essentially pointless effort even with my wide-by-huge rectangular ports and land barge weight vehicle.
This is just my experience, I don't know alot, so take it for what you think its worth.. but I am on the lookout in the local want ad for a deal on some 15*10 wheels for some 28*12.5 ET streets for next summer, and I expect my 1.8x 60's to drop to into the 1.6x's in my best estimation. A friend of mine in a similar situation (3.73s, 525-550 honest HP), went from 1.9x's on 26" DOT slicks to 1.72's on 28" DOT slicks. I am willing, I think, in my case, to sacrifice the RPM loss at the top end (26" slicks and my tighter converter put me at "about right") 28" would put me a bit low, but I bet in the end its better..

my 02.. taking advice from me could be risky though..

matt

Matt i know of guys cutting 1.30 60ft times on 26x8" slicks, so if you're not hooking it ain't the tire size. these cars are all stock suspension too. shoot, i'm doing 1.66's with Sportsman Pro 26x10.5's. track has alot to do with it, i'll admit i race at what's got to be one of the best prepped starting lines in America. ;) </font>[/QUOTE]The difference here is I am trying to balance a street-strip ride that weighs 4,000lbs or more depending on which wheels I have on, a relatively stiff "pro-touring" stance, brakes, wheel-tire-brake combo, rect port, solid roller, etc... I don't have the weight transfer, and I am trying to push 550+ ft-lbs to the rear tires with little transfer. IMHO, in my case, the taller and wider the tire, the better off I am. There is near 1000lbs difference between my car at full race wt on street tires, (more than 4020lbs) or on its 26" ET streets 3998lbs, when i see guys in mustangs with the driver at maybe 3200lbs.. Different story.
I am just saying in my particular application, where I am not going to get wild weight transfer, I have a heavy car, with abundant torque despite the rect port heads, the more tire I can get the better off I will be. I've played with pinion angle, shock settings, front sway bar, etc, right now I just run an adjustable upper boxed regular rear end setup, and I am feathering the throttle off the line with a 26*10.5ET Street.
I'm not a pro here, don't race alot, I just know from driving my car that I would benefit 10x from more bite at the start than dropping a few hundred RPM at the line where my hp/tq is essentially the same from 5800-6500 anyway (according to a dynojet anyway)..

It has just been my experience that in street driven cars with actual lbs to them, a taller tire with a wider section is usually the way to go. The answer for drags is tire up, then gear to match, but when you want the best of both, you sacrifice somewhere.. Right now "guessing" how hard I can hit the throttle isn't working very well..

Matt

Originally posted by RatONaStick:
Jim

thanks for answering my questions, but i have one more for you. by any chance did you change carbs when you changed the heads/cam? or change anything fuel related? No, but I did change the intake because I went from rect port to oval port. I had a dual plane Weiand stealth prior and I swapped to a dual plane RPM airgap. Carb and fuel lines were the same.

Originally posted by RatONaStick:
ive read that a car should pick up 22-24mph in the back half of the track and some stick cars may gain up to 26mph. your old combo was only picking up 18 in the back half compared to your new combos 23mph.

while its too late now, i still think your old combo was capable of more. but regardless of what it could have run before, its running damn good now. id be pretty happy if i were able to run those times. graemlins/thumbsup.gif Maybe, but I was sick of trying and getting nowhere. Don't be discouraged from my previous results though or my lack of getting it done with the old combo. Other guys have run nice numbers with rect port heads. It is just a fact that I couldn't do it. Maybe a good solid cam would have woke it up, but I wanted to stay mild hydraulic like I have now.

Originally posted by RatONaStick:
now all i have to do get some slicks and improve on my very crappy 60fts. i know the car will e.t. much better then it did, but how much remains to be seen.
thanks Exactly, get some traction. Your ET will be determined by how well your car comes out of the hole. That first 60' is important. Good luck and post some results.

Originally posted by MadMarv:America. ;) [/qb]The difference here is I am trying to balance a street-strip ride that weighs 4,000lbs or more depending on which wheels I have on, a relatively stiff "pro-touring" stance, brakes, wheel-tire-brake combo, rect port, solid roller, etc... I don't have the weight transfer, and I am trying to push 550+ ft-lbs to the rear tires with little transfer. IMHO, in my case, the taller and wider the tire, the better off I am. There is near 1000lbs difference between my car at full race wt on street tires, (more than 4020lbs) or on its 26" ET streets 3998lbs, when i see guys in mustangs with the driver at maybe 3200lbs.. Different story.
I am just saying in my particular application, where I am not going to get wild weight transfer, I have a heavy car, with abundant torque despite the rect port heads, the more tire I can get the better off I will be. I've played with pinion angle, shock settings, front sway bar, etc, right now I just run an adjustable upper boxed regular rear end setup, and I am feathering the throttle off the line with a 26*10.5ET Street.
I'm not a pro here, don't race alot, I just know from driving my car that I would benefit 10x from more bite at the start than dropping a few hundred RPM at the line where my hp/tq is essentially the same from 5800-6500 anyway (according to a dynojet anyway)..

It has just been my experience that in street driven cars with actual lbs to them, a taller tire with a wider section is usually the way to go. The answer for drags is tire up, then gear to match, but when you want the best of both, you sacrifice somewhere.. Right now "guessing" how hard I can hit the throttle isn't working very well..

Matt [/QB][/QUOTE]
Matt, comparing your car to his more race oriented set up is like comparing apples and oranges. i knew there was some reason why you couldn't get better than 1.80 60's, your car is definately not set up to go down the dragstrip. if you had your car set up for more straight line performance rather than the pro touring or whatever, then you wouldn't need bigger tires either. ;)

I dunno, I used to dead hook in my 1992 vette with a 10.5 ET street. It was a 383 stroker that made 380 RWTQ on engine, and 620 RWTQ on juice. I know that's a totally different animal with IRS, but the fact remains the best sixty that I ever pulled in that car was a high 1.7. A dead hook with a 6k clutch drop, I don't know how much better it could get.

Like I said in my original post, I really think the MPH in first gear where the power comes on plays a big part. With my vette, I was trapped in a world of bogging. No matter how hard I left the line (assuming the tires dead hook), the car would bog as the engine tried to recover from being forced to a lower RPM. 3.45 rear gears, a ZF6 transmission, and a dead hook made it nearly impossible for me to sixty very well. The problem would only get worse with a 4,000 lb. chevelle.

You need the steeper gear to get the car into the power band, an automatic, or a ton of power to catapault the car on launch to a speed where the engine makes good power. Imagine launching a 4 speed car that had 2.73 gears on slicks. The tires dead hook, and the engine is forced to drop back down to 1800 RPM's. No matter what you do at the line the car isn't going to 60 well. Unless you make 1,000 ft lbs. of torque and can instantly sling the car to 40 mph. See my point?

Originally posted by RatONaStick:
thanks guys

[

i figure if Gene aka 427L88 can run low 12s with about the same gearing and soft 2.+ 60fts i should be able to do that or better with a decent launch and 60ft, wouldnt you think?

Brandon, with sincerity I sure hope you nick that 12.24 time but good!

Old Red gear ratios are 10.06, 7.26, 5.30, 4.30. You are close, starting at 9.477.

Tough call on the tires. Having had both, I personally prefer the shorter tire for two reasons, 1.) it lets the car cross the stripe at 6700 rpm where the engine is really making some serious snot ( hence the nice 118 mph's), and 2.) since I have this weird deal of driving 300-750 miles and THEN racing, I felt the shorter sidewall will help eliminate some other parts breakage, i.e., some controlled slippage is fine for my purposes.

The bigger sidewall of the 275/60 will defintely take more hit, HOWEVER, the last time I raced the car ( one year ago almost to the day), I dropped the clutch at 3500 rpms is all for an easy 2.10 60'. Dead hook at that rpm, and my suspension is identical to yours, ex the solid uppers I have ( non-adj). This at 16 psi-18psi.

Next year, I'll set out on probing the limits of the launch with those small tires. All I need is a 1.90 60' to run consistent 11s, so my goals are easily doable.

My attitude is always, give the clutch car as much mechanical momentum as you can, i.e. gears, shorter tires, etc. ( which is why I do not believe torque motors are the way to go if you desire good ETs with a clutch. Something I'm going to explore during the next phase of Old Red's evolution).

You start cutting 60' times in the 1.5-1.6 range with a clutch ( which is like 'normal' for stalled autos), and the probability of breakage does an "asymptote near 1 ", i.e., it's gonna happen.

OK to answer your question, you might want to calculate whether you'll be shifting prior to, or after the 60' mark with the two sizes. I don;t mind shifting prior EXCEPT that is must be a powershift. No way on God's earth can you lazily shift 1/2 and cut a 60'. My prior 60' with an easy launch were 2.30, 1/2 shift was after 60' mark. Now I'm shifting prior to 60' , a 2.10 and I haven't used my motor yet ( i.e., the "system" needs to see around 4750+ rpms on the launch according to my rough math).

In short, agree with m71. 26". You don't have enough 1st gear ( 10.5:1 +) to go with a bigger tire imho...

Most importantly, will you PLEASE beat my 12.24!!! smile.gif

If for some weird reason you don't, I would encourage you to put a different cam in. Folks here don't like them rect ports, but when its what ya got, there are a few things you can do to help the intake velocities and it all involves cam timing, valve area. Running an older, gentler grind is not the most optimal deal here. Running a modern "race" profile ithat is asymetric and installed advanced seems to make it happen man! We also used some odd angles on the valves, but if I bring that up here, ya'll tell me that isn't right either. SO far as I can tell, to most here, I built the motor the "wrong way", my way, but that old motor doesn't seem to know that 'bse' engines are faster. Only trouble is rpm's of course. I shift at 6800 and need a 4.30 - equiv ratio to get the job done. Wouldn't do that for an 11 sec bracket car, btw.

Now go out and run an 11.9X please! graemlins/thumbsup.gif

Aw you'll probably have a 12.60, 12.30 and then figure out how to lauch as hard as you can without losing traction and run a 12.1, adn then get serious!

My amatuer, eating lunch at my desk advice, so

FWIW my friend! Go out there and give 'er hell!

Gene

thanks for the reply

i agree, i think i would be better off with the 26" tires. my only concern is whether 26x10s will fit okay on my 8" rallies. im worried that using a wheel smaller than the mininmum recommended width might effect traction because of the tire bulging on the wheel. ive never owned or used slicks before so i dont know how much of an effect if any this will have.

in your opinion do you think this is a concern?

OK to answer your question, you might want to calculate whether you'll be shifting prior to, or after the 60' mark with the two sizes. I don;t mind shifting prior EXCEPT that is must be a powershift. No way on God's earth can you lazily shift 1/2 and cut a 60'. My prior 60' with an easy launch were 2.30, 1/2 shift was after 60' mark. Now I'm shifting prior to 60' , a 2.10 and I haven't used my motor yet ( i.e., the "system" needs to see around 4750+ rpms on the launch according to my rough math).
ill definitely be powershifting once im able to hook. im pretty sure that im shifting to second after the 60ft mark, even with 26" tires. when i was looking for a trans to replace the old leaky m21 i was concerned about gear spacing and didnt want to go to a trans that had large splits between gears. while the 2.43 first st10 is a close ratio box it is wider than a m21, but its not so wide the rpms fall below the power band in the next gear.

like you im thinking this thing needs to be launched at 4500-4800 rpm to be effective, and because of that i went with the 904 iron case and iron midplate when i built the st10. i believe there is a fellow here on tc that uses one and speaks highly of it. i plan on putting this thing to the test, well see how well it holds up.

Most importantly, will you PLEASE beat my 12.24!!! ill definitely give it my best and if i dont, it wont be from a lack of effort. ;)


If for some weird reason you don't, I would encourage you to put a different cam in. Folks here don't like them rect ports, but when its what ya got, there are a few things you can do to help the intake velocities and it all involves cam timing, valve area. Running an older, gentler grind is not the most optimal deal here. Running a modern "race" profile ithat is asymetric and installed advanced seems to make it happen man!
i definitely want to change the cam down the road, ill also be buying a new set of headers to replace the ones i have. i want to go with a more agressive solid, preferably one of harolds.

any thoughts on a cam for my combo??? it has to be able to run on premium.

Are you actually at 11:1?? Anyway, I'd get some 'time in the seat' before you swap cams. Your combo would love the Lunati A3,but the A3 won't like 11:1 for sure.

Hey, watch wheel/tire fitment for sure. I couldn;t fit the 275/60s bfg mounted on 8" rallys. The fit a friend's Camaro. Chevelle needed more backspace ( tire would have hit the fenderwhell ). I don;t know what they measured, but no more than 4" for sure. Seems like you might need 4.5-5.0" backspacing, but I'm unsure.

I like the beefy tranny you built there!

MOST IMPORTANTLY:

Have fun with it!

definitely, i dont plan to change the cam anytime soon. but i cant say it hasnt crossed my mind.

im at or around 11:1, while i didnt build the engine i have had the heads off and verified which pistons were in it. i dont remember the part number off hand but they are the trw 11:1 pieces.

i know it might be shy of the claimed 11:1 but i cant imagine its that much. unfortunately we (my dad and i) never checked piston to deck height but i do think this block has been decked as the suffix code looks very suspect, like it was restamped.

one day when i get everything sorted out ill probably pull the engine and detail the engine bay. ill put the 427 on the engine stand and check piston to deck height, have the heads ccd and go from there.

yeah the wheels arent exactly optimal, and to make things worse i have the wider 68 up 12 bolt in the car. but i do have a set of 27x12x15 nascar slicks i use for test fit purposes. i had them mounted on the rallies and they fit, but are real close to the outer lip with no air in the air bags. they clear just fine with about 8 lb in the bags, so im confident a 26x10 should fit fine. a word of caution, the oval track tires suck for traction.

hopefully ill be having fun soon enough, its taken me much longer than i anticipated to get to the point im at. but i have a feeling that it will all be worth the wait.