I recently rebuilt my 71 chevelle 350 with votrec heads and a xe262 cam. I am not satisfied with its' performance yet. What would it take to make 400horse/ftlb. torque. Would I be better off rebuilding it to a 383? What is involved?

What kind of performance do you have?

I believe that I am making somewhere near 300 hp and have run only high 10's in the 1/8th mile.

A bigger cam might help, seems a little small to me.

I have an 268-H and would prolly be happier with a XE268

What are the other details of your engine? What tranny and rear gear?

With an XE268 or XE274 400Hp should be no problem with the Vortecs. With a XE268, the Vortecs, 9.5:1 CR, Edelbrock RPM intake, 1 5/8" headers, Holley 650 carb, you should have no problem making 400hp in a 350. Now a 383 would be even better.

Steve

The tranny is a new TH350 w/shiftkit. I have a 12 bolt posi. with 3.31 gears. Dynomax headders 2 1/4" exhaust, the 350 is .030 over, near stock distributor, Edel. performer intake, and quadrajet. The engine runs great but I,m thinking that I should have installed flat-top pistons with the Vortecs, with the 64 cc heads what would my compression be? I have stock dished pistons in there now, any idea what my compression is now? I currently need to run it on at least 89octane. Thanks.

I have flat top w/ 4 relief pistons and 882 heads, my CR is about 8.5-9, I can run on 87 octane without a problem as long as its quality gas, not that EZ Mart crap...

Maybe get an upgrade kit for the ignition too, new cap rotor coil advance and some low resistance plug wires.

When I bought a summit hi-po cap rotor and coil and put on some MSD 8.5mm wires I could tell a big difference in response and mid-upper RPM power.

Gear change. I run 3.73's with a 408BBC. Running a 350CI smallblock - depending on what you are going to do, but for 1/8 mile drags, at least a 4.10 rear. Wouldn't want to take a 300 mile highway trip with 4.10's (although I have done it many years ago), but there is no other change that can make as big an impact.

Can you post your timeslip?
I would think you'd be in the 9's in the 1/8
Sounds like you need to do some good 'ole fashioned tuning
(timing,checking for WOT,etc.)

my setup is not that far from yours minus head and cam:

355 4 bolt
882 heads ported w/ swirl cast valves
hyper. pistons flat top 4 relief
stamped rockers
Comp 268-H .454 lift @ 212 or 214 or something...
High volume oil pump
Edelbrock performer intake
Holley 650 spreadbore
GM HEI with perf ugrade kit from summit
MSD Super Conductor 8.5mm wires
14x3 Holley Powershot filter, soon to be 14x4 non drop base
Headers, flowtech terminators, 2 1/4 over rear axle
power steering, A/C, stock fan
TH350 w/ viscious shift
12 bolt eaton posi, 3.08 gears

If i could only remember what my friend in this hopped up 5.0 used to run I could give you a good estimate of my 1/8 perf...we ran literally door to door last time we raced. He had a 5 speed and I could hear his rev limiter bangin every gear, he had 3.40 somthing gears, that was with my old motor which was a bit tamer than my current set up and sloppily built at that.

I know he was definately running under 10s ;)
With a better set of heads like that you should be able to gain some power somewhere, and my first guess would be a cam swap...I'm no expert but my dad has never put less than 268 cam in any engine he's built for performance, and he's generally mild with cams. His 468 BB only has a 270!

1.60...60ft.
10.72 1/8th@86mph
The 60 foot times always seemed way off to me to run high tens. I do have a high output coil, aftermarket ignition module, 8.5mm Taylor spiral core wires, new cap, rotorand installed the lighter springs to accomodate the vacuum advance.
The initial timing is set at 4 degrees it seemed low but the vortecs seem to like it. The total timing is at 58 degrees. Maybe a XE268 and mild stall converter would help out? The engine has less than a 1000 miles since the complete rebuild.

In that case...

give it some time ;)

Yes a bigger cam and stall are gonna help a bit, but you failed to mention it's barely broken in.
I wouldn't even be racing it until after the first oil change (we change oil after 1000, then every 3000, tend to be easy until after that first 3000 change).

It will pick up some more power once its broken in well, but I would def. consider the XE268

also theres the possibility it ate the cam too...but i would expect that to make it run poorly

ask mr mcfast about his when he turns up...just got it put in today and he's already psyched about the change

Something is choking up your combo. I have a MUCH more stock-type build and i ran a 2.1x 60ft to get my 10.17 1/8 ET.

With a pretty much bone stock 350(8.3:1 CR, smog heads), 212@.05 cam, 1 5/8 headers, 2.5 inch exhaust and a 600cfm Holley, TH350/2.73 non posi, i ran the 1/8 at 10.17/70MPH.

Your 86MPH puts you over 300HP. Your better gearing and better power should net you better ETs than me.

I think that you might be running out of gas somewhere down the track, but after that surge you re-coup and get enough gas to run the 86MPH you do.

Does your car happen to be an original I6/283/307 car? If so you might have crossed the limits of the 5/16 fuel lines and/or original pump.

Before you remove the lines though, make sure your filter(s) aren't clogged. And test your fuel pump to see how much it is pumping.

Your carb should more than support your engine, IMO, as i can run better ETs with roughly 100cfm less.

You say 58 degrees total timing? Are you including your Vacuum Advance also? I know i've heard vortecs like 32-34 degrees total (NOT COUNTING VACUUM ADVANCE).

(Ask one of these gearheads how to do the cranking test to figure GPH of a pump, i dont know how, but i bet they do.)

Something isn't right, you should not be running slower than me with much better combo set up.

A 1.60 60' time is leaving like a rocket. You'd have to be doing about 40 mph in 60' to make that time. 86 mph is about a 8.20 speed - you must have some serious problems between the 60' mark and the 1/8.
What is your total timing with the vac advance disconnected?

Yeah, see those 1/8 est sound right...

I could almost swear Tylers 5.0 was running 7.9-8.3 depending on traction and weather

Heres my combo 383, dont know what cam but is about .460 lift, Dart iron eagle 230cc heads(way too big, but I had them already) 9.5-10:1, air gap intake, 750 holley vacuum secondaries, MSD dist, MSD 6AL, 1 5/8 headers Dynoed at 400hp/425tq TH400 B&M Holeshot 3000 converter, 8.2" rear with powertrax and 3.36, SSM lift bars. Went too the track for the first time (driver and car) this weekend and ran a best of
.757 rt
1.88 60ft
8.361 1/8
82.72 mph
13.114 1/4
102.71 mph

This is on 235 street tires with a lot of soft pedaling on the start. Next time I plan too have slicks and new bushings in the upper control arms. High 12s shouldnt be a problem. Its weird too me that I ran 2 seconds faster in the 1/8 than you yet your speed was 4 mph faster than mine, I just dont know what that means. Nice 60 ft though. What tires do you run?

With a 1.60 60ft and 86mph in the 1/8, 10.72 sounds about what your 1000ft time should be.

You have good HP, don't change anything untill you get the timeslip figured out. The numbers don't add up. I don't see a 16 sec car hitting 1.6 60fts.

What are the times from the guy in the other lane?

I'm looking at a timeslip now: 2.59/10.88@65mph/16.80@83mph here it is: http://www.geocities.com/lonnie67_1966/redslips4.html 86 in 1/8 is about 107 in 1/4, 12.30's with your 60. Your timeslip is weird.

Yep, the timeslip sounds funny. Ours is a 350 with Vortec heads and it did a 8.2 sec 1/8 mile with a 60' of 1.87, so I'd think you'd be doing better with a taller gear or shorter tires. That 3.31 isn't very tall for the eighth mile. If you really don't care about highway driving, a steeper gear would do wonders, like 4.11s. If minimal highway driving is involved, then you could get by with 3.73s. Gearing will make a big difference, especially on such a short track.

I wouldn't go looking to build another engine until you get that one sorted out. Sounds like it has plenty of potential, just needs some tuning.

He needs to sort out the engine's tune before he goes and opens up the rear end.

Granted 3.55/3.73 gear will work better, and depending on what hispower-RPM range is and what gear he's crossing the line in, 4.11s might be better too.

Hey MDD, what gear are you crossing the line at???

Originally posted by Slowpoke70:
He needs to sort out the engine's tune before he goes and opens up the rear end.
Yep, you're right. I just kind of threw that in there, because I knew it was one factor that would definitely affect his results - at least compared to mine.

Dish pistons and 38 might be ok...
Try less and see if the MPH picks up.
Back road test or something.
Also, make sure the secondaries are working.
I've seen the air valve get a little play and wear a notch/burr on it. Little bit of file work fixed it. I don't know all the different SB pumps, put check the whole fuel system as others have said. If it's a stock module HEI, they have a built in retard of a few degrees. Need to check that to get an accurate top end timing setting.
Also, you'll pick up some time if you get more static timing and keep your total the same or less.

My time slips do look strange but all are consistent. I checked with friend and his were right on and right next to me on each run.
1.7760ft 10.77@81mph 1/8th
As far as the timing w/0 advance is 28 degrees, just checked it this evening. I have wondered if I actually got the right cam in the box since their were no stampings on the end??? Yes it was originally a 307 vehicle. I am just into 3rd as it crosses the line. I did notice that it seems really flat at about 3600rpm then seems to regain. I did replace the fuel pump. It runs way to good at idle to be a wiped lobe. I was running a similar set up with 3.08's in my El Camino and was in the low 9's.
Not to change the subject but I was just offered an 87 454 for $550. It does however have a spun bearing. I guess I should ask for the numbers. It probably has the peanut port heads??

Try 34-36 total, no vac adv. connected while setting. I'd swear the stock msd vac can is 15 deg.

CR is about 9.35 with .020 deck ht and 9.7 with zero deck. 12cc dish, 1003 gsk, 62cc head.

Secondary popping open will do that....

Will need line hone or bore,different crank, and at least one rod to fix. Why did it spin the bearing?? Bare blocks are about $200-$250 and cranks are $100. Unless you can sell the heads....
Probably has a truck pan....

With a stock distributor you're probably gonna need 20-22 degrees of initial timming. Set the timming by unhooking the vacum advance, reving up the motor untill all the mechanical is advanced out, then set that to 34 degrees. (The modren Vortec chambers seem to like less than the standard 36deg) Don't worry where intial ends up. As I mentioned it should be around 22deg.

Steve

Assuming you have a 26-28 inch tall rear tire, you're crossing the line at below 4000RPM, which should be well under your peak HP RPM. If you're already manually shifting the tranny, try launching in 1st and then shifting to 2nd at a decent RPM and just leave the tranny in 2nd for the rest of the run. Again, assuming you have a 26-28inch tall rear tire, you'd be at around 5400-5800RPM depending on tire height and tranny slippage. This RPM range should carry you better in the top end of the track.

It probably still won't get you where you should be, but it'd let you know how much of it is drive train related and how much is engine related.

Since it is a 307 car originally, you may want to step up and change out your tank-to-pump hardlines to 3/8s which was OEM on 327(?)/350/BBC engine equipped cars. Your car may more than likely be gasping for fuel at somepoint in the run. JMHO. I am a rookie, but I've learned a few general/theoretical things about the drags.

Originally posted by mdd71:
My time slips do look strange but all are consistent. I checked with friend and his were right on and right next to me on each run.
1.7760ft 10.77@81mph 1/8thSince your buddys timslip looks wierd also, I think that track must have some timing equipment problems.

I agree, the time in the next lane doesn't look right either. With that 60 and ET his mph would be in the 60's, or with that mph his ET would be in the mid 8's or so.

Looks like the timing system is not right.

That's weird on how you're running 10s @ 86mph on the 1/8th, whereas my Velle is runnin an 8.80@79mph...lol weird. Maybe like the past 2 guys just said, that track's timing may be off :confused:

Yesterday we met at our alternate track and to my surprise ran a 8.60 @88mph with 2.2 60'. smile.gif Now thats more like it. My friends Nova ran just a couple of tenths slower and it was reflected in the time slip. After speaking to another person who had been at the same track for a test and tune night found that his times were way out and left because he was told there were no timing problems. I did absolutely nothing to the car. Maybe experimenting with the timing will get me another couple tenths?

That's about a 13.10 @ 109+. Runs great. 2.5" exhaust will help.