I will be swapping out my 3.42's for a set of 4.10's since my days of evening dew and street tire ravaged starting lines are over. Plus I need a little stress removed from my transmissions with such a heavy car.

I was looking to see if anyone who has increased their DCR has seen a bonafied improvement in Torque measured in ET and 60 ft.. By design My current SCR is 10.1 with a DCR of 7.4. I have been spec'ing out some rough cam designs to get me up to around 8.3-8.4. I want to keep running 93 pump gas.

This will be an on-going research for the next couple of weeks and would appreciate any input that could save me time since that seems to be very limited with work and family these days.

I will list up my entire combo later tonight.

Tom,
Not quite sure if this is the info you're looking for but my two cents...
My CR is 10.49, DCR is 8.19
Running Harold's designed Lunati solid roller
287/295, 256/264 @ .050, .660/.660 lift, 110 LSA on 105. Timing locked at 37*...Chevelle is 3700 lbs with me, 3.73 gears.
Works fine with pump gas!

Bill,

here is my current cam (with a messed up fuel pump lobe)

110 LSA, 292/288, 254/260 @0.050, .660/.666 lift. Timing 38 at 1800 RPM

how low do your cars idle down too? My 540 has a smaller cam and will idle to maybe 8-900 if pushed, but I am thinking about a bigger cam to kill some torque.

Where do you want to shift and what will you be going through the traps at?

Doug, here is my combo with other info at the bottom..

Combo:

Merlin II Block 4.5" bore
10.2:1 SRP pistons (10 cc dome)
Eagle H-beams with ARP L-19 260K bolts
4.25" Callies Dragonslayer Crank
ATI balancer
Motor internally balanced
Comp Cams Solid Roller 292R 254/262 & .660/.666 with a 110 lobe separation installed on a 107.5 intake centerline.
Canfield 310 CC Rect. Port heads stock out of the box, nothing done to them at all.
Edelbrock Victor Jr. Intake box stock as well.
This intake/head combo is to establish a baseline for the possibility of future port matching and bowl blending.
Holley 4781 850 DP (Box Stock)
Carter 172 mech pump fed by -10 (5/8) line Temporarily using Mallory 140 electric
2" Hooker Competition (no ceramic coat)
3" Torque tech to the bumper with GM SS tips
Trans. Specialties 9 1/2" converter with Mechanical Diode (TS says good to 925 ft/lbs). Built to flash at between 4000 and 4400.
Hughes TH400 forward manual valve body. Secondary trans filter system using radiator and external cooler
Dennys Nitrous Driveshaft w/1350 Joints
GM 12 bolt with welded tubes, TA cover, Powertrax Locker, Mark Williams axles, C-clip eliminators
3.42 Richmond street/strip gears
Hoosier QT Pro 28x13.5 on 15x10 weld prostars at 20 psi
205/70/15 Cooper street radials on 15x6 prostars up front at 35 psi.
Dick Miller No-hop bars, upper and lower control arms with nylon bushings -4.0 Pinion Angle
QA1 12 way shocks with cargo coils and air bags in the rear, Moog stock 6 cylinder coil springs up front with KYB Gas Shocks and shock nut trick
Front Sway Bar removed
70 chevelle manual steering box.
Dual 12" Flexlite Fan system with a "No Name" Alum radiator (made by AFCO)
Stock GM Cast Iron Water Pump
Stock GM HEI distributor triggering a MSD 6AL. (just because of the rev limiter feature 6400 chip installed)
36 degrees total timing in at 2000 RPM

Shifted at 5600, crosses stripe at 125 mph at 6100 RPM.
Best ET 10.76, 125.3 mph, 1.51 60 ft
Pump 93 octane fuel.

Tell you what Tom, I am just amazed at how you manage to get that full steel body Monte down the track at 10.76/125 shifting at 5600 on "street tires". Amazing how times have changed. Going back 25 years, it would have taken a 427 running out 5.13's and a fully tubbed wheelhouse stuffed with a 14/32 slick in a 3000# car to do the same.

Originally posted by GRN69CHV:
Tell you what Tom, I am just amazed at how you manage to get that full steel body Monte down the track at 10.76/125 shifting at 5600 on "street tires". Amazing how times have changed. Going back 25 years, it would have taken a 427 running out 5.13's and a fully tubbed wheelhouse stuffed with a 14/32 slick in a 3000# car to do the same. Thanks...It sure is a fun ride. I am trying to catch up with Ken Jett this year though ;)

Originally posted by mc71454:
</font><blockquote>quote:</font><hr />Originally posted by GRN69CHV:
Tell you what Tom, I am just amazed at how you manage to get that full steel body Monte down the track at 10.76/125 shifting at 5600 on "street tires". Amazing how times have changed. Going back 25 years, it would have taken a 427 running out 5.13's and a fully tubbed wheelhouse stuffed with a 14/32 slick in a 3000# car to do the same. Thanks...It sure is a fun ride. I am trying to catch up with Ken Jett this year though ;) </font>[/QUOTE]That shouldn't be too hard ;) I've made a couple of big changes to the car in the past two weeks (suspension and fuel system related). I'm testing tomorrow over in SC. Should be fun :D

Well really Quick Time Pros arent a "street tire" at least i wont drive mine on the street. More of a DOT slick. Ill drive mine too the track, and throw my street tires back on to drive home. But thats not to take anything away from your 2 ton Monte. Your motor's making some pretty good power right now, properly geared/cammed youll be flying assuming you can hook!!!

Yeah, the QT Pro's are a stretch for a street tire, but the car does hook better with a true race slick. I have it down to a science swapping the tires when I get to the track, just have to deflate them to fit them in trunk for the drive back and forth :D

This season will be the first time I ever trailered the car to the track.

I am very confident it will hook or I will be able to adjust it to hook...Thanks

Originally posted by mc71454:


Shifted at 5600, crosses stripe at 125 mph at 6100 RPM.
Best ET 10.76, 125.3 mph, 1.51 60 ft
Pump 93 octane fuel. Tom, is 6100 the current finish rpm with 3.42's and a 28" tire?

Originally posted by JOHN WILSON:
</font><blockquote>quote:</font><hr />Originally posted by mc71454:


Shifted at 5600, crosses stripe at 125 mph at 6100 RPM.
Best ET 10.76, 125.3 mph, 1.51 60 ft
Pump 93 octane fuel. Tom, is 6100 the current finish rpm with 3.42's and a 28" tire? </font>[/QUOTE]Yes, when it runs 125+ mph in decent air.

Maybe somebody can double check me but I'm coming up with around 19% slip. If so, somethings up with the converter or tranny. Going with the 4.10's will bump the finish rpm by ~1100rpm assuming the same slippage. Any thoughts????

John,

are you using the actual "rolling diameter" for your tires in your calculations?

Tom, on yours I used a rollout of 88" for a 28" tall tire. I didn't factor any tire growth since it's an unknown (to me at least) and would only worsen the slip %.

Have you tried to calculate it? Like I say, maybe my calc's are off. There are also some online calcs for converter slip.

Just for comparison, I'm crossing at 7200@129 with a
29.3" tall tire (roll out ~93in) and 4.56 gears which works out to around 8% slip.

real quick...I remeber it coming out to about 12%, the rolling diameter of 26.5" +/-

Tom, how do you measure "rolling diameter". Thanks.

Tom or John would you guys mind enlightening me on what the formula is for calculating slippage? I'm running a 28x10.50 Stiff Sidewall Mickey Thompson, car dead hooks most of the time! Would my rolling diameter be the same as yours Tom?

Thanks, Matt

Rolling Diameter:

Draw a line on the bottom of your tire, then draw a line on the ground which lines up with the line you just drew on your tire. Then move the car until the tire makes (1) full rotation. Then mark the ground where the line on the tire is at the bottom again. Next measure the length between the two marks and divide by 3.143. The result is your rolling diameter.

For those who can't do this right now or an estimate is OK, usually it is 1" to 2" less than the diameter when the tire is laying on its side on the ground, also depends on tire pressure and growth, if any. I assume my DOT tires don't grow at the top end..I can't verify this though.


To determine slippage - the formula involves your gear ratio, mph, tire diameter (rolling + growth) and RPM. This is your theoretical RPM.

Then you record your actual RPM and mph from a drag strip pass.

The slippage is determined by dividing the theoretical RPM by the Actual RPM and then subtracting that quotient from 1.00.

I have always used the formulas on my friend Marks website www.prestage.com, (http://www.prestage.com,) there you can just fill-in-the blanks, so I have to say I can't write them down right now. His site is temporarily down today. I gotta log off right now too. But this should get you started.

Ok- Gotcha. We're measuring our tires differently. I've been measuring my roll-out (circumference) with a string around the middle of the tread with the tire mounted on the wheel (wheel off the car) with 15lbs of air. I get 93" that way. Advertised is 92" per Hoosier website.

With this method I get 7.8% slip.

Measuring your way I get a roll out of 89.75" and a tire calculated tire diameter of 28.55" which works out to 4.00% slip.

I guess it just comes down to how you measure your tire. Which way is correct or preferred by the converter companies I don't know. When I had my converter freshened in December the tech was figuring my current slip and asked what my tire diameter was and I simply gave him the 29.3" measurement that Hoosier advertises. With the 29.3" # he said the slip was where it should be.

tom
i see you been busy.
hope to see you at Lebanon this year. blew my 468 last year. got a 496 for this year. can't wait to see what the car can do with the new gears.


thanh.

Hey thanh,

Busy, yeah, nice snow storm today..went out plowing 1t 5 am, got to work by 9:00 and then back out at 4:00 for more plowing...

Hey, do you know about or are you thinking about coming up to the Hemmings weekend May 28 -29 ? A bunch of us are camping out and/or staying at the Bates Motel nearby, should be a great weekend two days of racing, car show, etc.

Too bad about the 468, too bad you had to make it a 496 :D

My bad crank in my 468 forced me to build the 540 :D at least that is what I told the wife..

Hi John and Tom, The M/T tire rollout figure is listed in their charts. The 10.5W x 28" x 15 has a figure of 88" if memory serves me correctly. The diameter to circumference ratio is pi (3.1415927) and is usually rounded out to 3.1416. Anyhow 88" will get you close enough without knowing how much tire growth there is. The 10.5W x 28" doesn't grow much on a 10" wide wheel. It appears that John's converter only has about 6% slippage which is pretty darned good. The trap speeds are all off now due to the way that NHRA measurers it. If you multiply your current trap speed by 1.0072 you will get your true 1320' average speed of yesterday instead of the current measurement of 1287'. Then you can get a more accurate idea of slip.

Originally posted by mc71454:

Busy, yeah, nice snow storm today..went out plowing 1t 5 am, got to work by 9:00 and then back out at 4:00 for more plowing...Just curious Tom...
how's the Toyo doing so far as a snowplow vehicle?
Had enough practice this year?? ;)

Harold, which figure did you use to calculate my slippage? The advertised roll-out or the observed "rolling diameter" as Tom described? J/K

I get 6.7% with the 92" advertised and 4% with the observed rollout of 89.75. Any idea which is correct measurement to use? Thanks.

Originally posted by BillsCamino:
</font><blockquote>quote:</font><hr />Originally posted by mc71454:

Busy, yeah, nice snow storm today..went out plowing 1t 5 am, got to work by 9:00 and then back out at 4:00 for more plowing...Just curious Tom...
how's the Toyo doing so far as a snowplow vehicle?
Had enough practice this year?? ;) </font>[/QUOTE]Bill,

It is like a bulldozer !!!
I lifted it 2 1/2", changed the front springs and shocks to progressive rate springs and Bilstein "HD" shocks, 1/2" drop for the differential for CV Joint angularity. I sold the factory supplied tires and put on 1 size up 10 ply Mastercraft AT's (Cooper Discoverers) at 65 psi. That gave me an extra 3/4" of ground clearance and no sidewall flex.

Practice? plowed for the 11th time yesterday graemlins/hurray.gif (that storm bought my weight distributing hitch and sway control)

Previous record in the last 10 years was 9 snow plows for the season (twice).

Hi John, I used the 88" advertised rollout and an old "power speed calculator" which shows a no slip figure of appx. 6750 RPM with no tire growth. The new age trap speed 128.9 MPH is an average 1287' speed but can be converted to the old trap speed of 129.8 MPH by multiplying it by 1.0072. This speed should be achieved at 6745 RPM with no slip. The following formula for speed is ( mph = rpm x tire diameter / gear ratio x 336 ) Using this formula, which came out of the Auto Math book, pg. 93 will tell you what the motor should be turning at 129.8 MPH. Subtracting the 6745 from your 7200 RPM figure leaves you with appx. 455 RPM of slippage. If you divide the 455 by the 6745 figure it comes out to appx 6.7%. I may have some flawed thinking here but the M/T 10.5 x 28W tire on a 10 rim has virtually no tire growth as my son uses this tire. All of the Hoosier's are much bigger around than their advertised sidewall numbers. A local uses the 10.5 by 29.5 and it has a 96" rollout and will hardly fit in the fenderwells. Their 10.5 x 30" tire has a rollout figure of 94", go figure and i think both of these tires grow some. The M/T 10.5 x 29.5 on a 8" wheel grows about 1/2" to 1". All the figures go haywire with much tire growth. My son's converter has shown huge amounts of slippage, generally running in the 900 RPM range so far, so we geared it back to 3.50 so we can get down the track this year. I still expect it to go over 7000 RPM but at least this will be within reason.

Originally posted by mc71454:


Hey, do you know about or are you thinking about coming up to the Hemmings weekend May 28 -29 ? A bunch of us are camping out and/or staying at the Bates Motel nearby, should be a great weekend two days of racing, car show, etc.
no i did not know about the weekend, i will try to make it. i'll be out in chicago that week. i'll let you know when it get closer.

thanh.