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Old 07-30-2012, 09:50 AM
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Change from HYWY gears to Drag and now have higher times than before?

Hello there,

I have a 1980 Trans Am with a small block 350 bored to 355cu, mild cam, MSD ignition, new electronic fuel pump, 8mm wires, 800cmf Edelbrock carb, a Street Fighter 350 Turbo transmission with shift kit, a "2500 stall", line lock, and a forward-facing scoop with risers on my carb to get the direct air flow.

I had .241s in it last year and was running 16.5s at 85-86 mph. The only change I have made is putting .410s in for the gears. I now run only 16.5-16.3s at 80 mph. I shift around 5k 1-2nd, 4.5k 2-3, with "scratches" with each shift.

The power feels like it is there, but I am just not getting down the track. Shouldn't the gear change make a bigger difference?

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Old 07-30-2012, 10:18 AM
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Quote:
Originally Posted by qwikrnu View Post
Hello there,

I have a 1980 Trans Am with a small block 350 bored to 355cu, mild cam, MSD ignition, new electronic fuel pump, 8mm wires, 800cmf Edelbrock carb, a Street Fighter 350 Turbo transmission with shift kit, a "2500 stall", line lock, and a forward-facing scoop with risers on my carb to get the direct air flow.

I had .241s in it last year and was running 16.5s at 85-86 mph. The only change I have made is putting .410s in for the gears. I now run only 16.5-16.3s at 80 mph. I shift around 5k 1-2nd, 4.5k 2-3, with "scratches" with each shift.

The power feels like it is there, but I am just not getting down the track. Shouldn't the gear change make a bigger difference?
What is the difference (if any) in the 60' times? That's where you should see some serious gains. A rough rule of thumb is the 1/4 mile ET will change at least 1-1/2 times the amount that the 60' ET changes, and in some cases the drop will be even more. Is it spinning off the line?

That said, one thing that's often seen is the engine is over revved before the next higher gear is hit because the rpm is increasing faster than it was w/the highway gears. By the numbers you posted it doesn't appear you're over revving it. But unless the tach face is big and you are really homing in on it or you have a shift light, the shifts may still be coming later than you think. And w/a mild cam- which it appears you do have judging by the numbers- over revving is even more detrimental to the ET. What rpm is it going through the lights at? What size tires do you have? With that info we can run the numbers through a calculator and see if there's some sort of losses through the drivetrain, like the TC or trans slipping. If you know the weight w/you in it ready to race, other things can be estimated like HP, etc.

Last edited by cobalt327; 07-30-2012 at 10:27 AM.
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Old 07-30-2012, 10:44 AM
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Thank you for your reply.

I do not have a shift light, however, I do carefully watch the stock tach and the shifts are pretty consistant. My 60' times were 2.7 last year, now 2.27 ish with the .410s, and around 10.6 1/8mi times. I do linelock around 1500 before the front brakes try to release and almost make me red light. It does sping off the line better than with the .241s. I thought of maybe dowing a flash stall off the line next time to see what it does. I am not sure of the rpm at the lights, I have never looked. I did try starting in 2nd and let it shift out of 1st by itself, and also in 3rd, letting it shift all gears by itself and it did run slower than manual jam. I run American Racers, G60s ( I believe they are 27.5" tires ). The approx weight with me in it is 3900#s (weight is stock). Running a 2500 rated stall..
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Old 07-30-2012, 10:54 AM
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Quote:
Originally Posted by qwikrnu View Post
Thank you for your reply.

I do not have a shift light, however, I do carefully watch the stock tach and the shifts are pretty consistant. My 60' times were 2.7 last year, now 2.27 ish with the .410s, and around 10.6 1/8mi times. I do linelock around 1500 before the front brakes try to release and almost make me red light. It does sping off the line better than with the .241s. I thought of maybe dowing a flash stall off the line next time to see what it does. I am not sure of the rpm at the lights, I have never looked. I did try starting in 2nd and let it shift out of 1st by itself, and also in 3rd, letting it shift all gears by itself and it did run slower than manual jam. I run American Racers, G60s ( I believe they are 27.5" tires ). The approx weight with me in it is 3900#s (weight is stock). Running a 2500 rated stall..
Judging by the 60', unless the engine is over revving (possibly through the lights, I haven't run the #'s yet to see what's up w/that), the decrease in the short time should have you much better than before. I'm familiar w/your tires- plenty of traction for a mild engine. You should try matting it from an idle to see if there's an improvement, but even doing what you are doing now there should be an improvement, regardless.

Are you running stock valve springs still? I'd say valve float, but that's usually pretty noticeable. Secondaries opening up as they should? Timing set correctly?

If I get a chance I'll do some calculating (or you can take a stab at it), until then maybe someone else will have an idea of what's up.
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Old 07-30-2012, 11:41 AM
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I really appreciate your input on this issue of mine. I am not mechanically inclinded, so I don't know how to run #s. I am just learning the basics you could say. It definately spins off the line, but only a few feet are really heard. I am running stock valves in the 350 crate. Both my brother and I ran it down the track several times this past weekend and thought it felt as if the tires were not grabbing through 1st gear until we shift to 2nd. Could that feeling be caused by the stall converter? Maybe the slippage is to much to the tranny? I have even thought of putting the stock converter back on, but would rather not if there is no possiblity of fixing the problem. I also heard that you should not reuse these after you have replaced the tranny to a new one due to possible shavings from the old tranny being present in the converter?

At the track, we set the timing advanced to 12, 34 at 2k. Others running their cars came up with that idea.

As far as the floating valve, I am not sure how to determine if it is floating or not. I have heard there would be ticking? I don't know. I am pretty sure the secondaries are opening up on the carb.
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Old 07-30-2012, 12:37 PM
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Quote:
Originally Posted by qwikrnu View Post
Thank you for your reply.

I do not have a shift light, however, I do carefully watch the stock tach
Check if the stock tach is still acurate. After 33 years of use i highly doubt it's still going to be as accurate as a new one. You should invest in a nice large face tach with a light. Good to have if you're racing the car.
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Old 07-30-2012, 01:55 PM
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What engine, and what's been done to it? I think you went too low a gear, and you might be reaching peak HP before you hit the end of the 1/4 mile. If that's the case you would probably have been better off with either 3.50 or .370 gear ratio so you'd still be pulling HP when you tripped the lights.
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Old 07-30-2012, 02:33 PM
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I would look at valve float-lifter pump up (valve springs), ignition problem, carb fuel starvation at high rpm,
transmission trouble.

What is the 1/8th mile et and MPH and 1/4mile et and MPH from a few time slips.

You have problem on the last half of the quarter mile that is killing engine power.

for best et and 60ft, get some tires that have traction at the track. Slicks, drag radials, et streets etc.
Most normal street radial tires do very poorly at the track.

Stage the car at idle, Rug it at or very near idle rpm. Do not preload up on the converter against the brakes.
This makes more wheel spin and slows you down.

When you find and correct the engine/trans problem that is killing top end performance the car will et and MPH better.

Often low cost "cheap" 2500stall converters are just restalled stock GM converters. The stall is modified by just bending the internal fins over more. This cheap high stall is very inefficient.

These low budget mild stall, 2500 stall stock diameter converters stink. and slip a lot .

if you want to go drag racing get a real deal 10" 3500 stall converter and some stIcky tires. Leaf spring cars work much better with traction bars too.

Last edited by F-BIRD'88; 07-30-2012 at 02:41 PM.
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Old 07-30-2012, 02:49 PM
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Are you spinning allot??
My old monte went 15.3 at 93 with the stock 2.41s and stock converter,befor I swapped them for 3.42s and 2400stall which drpped me to 14.5 .I had allot less motor than you also.A stock 350 with 305 heads a Summit 1103 cam and headers.
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Old 07-30-2012, 07:00 PM
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Thank you for everyone's ideas on this one. I am currently not able to get on here since I dropped my laptop today. I can only get on during college classes so if I do not answer your questions for a few days I do apologize. I am going to try to have it fixed tomorrow.

Just wanted to take some time and thank everyone.

When I get more time I will answer questions to get you guys the information you would need.

I have read your comments thus far and I greatly appreciate them all.
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Old 07-30-2012, 08:32 PM
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80 miles per hour? the engine is running out of RPM or its damaged.Its not making any power,,,,
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Old 07-31-2012, 08:56 AM
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Quote:
Originally Posted by qwikrnu View Post
Thank you for your reply.

I do not have a shift light, however, I do carefully watch the stock tach and the shifts are pretty consistant. My 60' times were 2.7 last year, now 2.27 ish with the .410s, and around 10.6 1/8mi times. I do linelock around 1500 before the front brakes try to release and almost make me red light. It does sping off the line better than with the .241s. I thought of maybe dowing a flash stall off the line next time to see what it does. I am not sure of the rpm at the lights, I have never looked. I did try starting in 2nd and let it shift out of 1st by itself, and also in 3rd, letting it shift all gears by itself and it did run slower than manual jam. I run American Racers, G60s ( I believe they are 27.5" tires ). The approx weight with me in it is 3900#s (weight is stock). Running a 2500 rated stall..
Before gear change:
Observed:
85 mph = 2.17 sec. 60'; 15.6 sec. 1/4 mile ET

After gear change:
Observed:
• 1/4 mile speed: 80 mph
• 1/8 mile ET: 10.6 sec.
• 1/4 mile ET: 16.3 sec.

Some numbers (remember these are only estimates, not exact predictions):
• 80 mph = 2.3 sec. 60'; 16.56 ET
• 2.27 sec. 60' = 16.33 sec. 1/4 mile ET @ 81 mph 1/4 mile speed
• 10.6 sec. 1/8 mile = 61 mph w/a 2.34 sec. 60' and a 16.8 sec. 1/4 mile ET @ 79mph
• 16.3 sec. 1/4 mile = 2.27 sec. 60'; 81 mph 1/4 mile speed

It appears that you're losing ground in the middle to the end of the track because the 60' times are estimating your actual 1/4 mile ET closer than the 1/8 mile ET is estimating your 1/4 mile ET.

Using your current mph (80) and ET (16.3 sec.) and weight (3900 lbs.):
• Your HP from your ET is 160.19 rear wheel and 177.99 flywheel HP
• Your HP from your MPH is 143.92 rear wheel and 159.91 flywheel HP

It could be several things, a few are: valve float, over revving before shifting, carb tuning or secondary operation, restrictive exhaust, incorrect timing curve, trans or TC slippage.

Have someone sit in the car and floor the gas pedal while you watch to be sure the carb is fully opening up. Carpet under the pedal or bad linkage or cable can keep it from fully opening.

Next time you go to the track, watch the rpm through the lights. You shouldn't be too far past the powerband through the lights unless there's some serious slippage through the trans or torque converter.
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Old 07-31-2012, 09:31 AM
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2 things: A vac secondary 800 is a little big for this application. Yes I know vac 2ndaries will only use what it needs, but thats gotta be a bear to get tuned right. Have you tuned your carb with a vacuum gauge? How old and what make/model is your distributor? WHat kind of exhaust system are you running.
I wonder if your fuel pump is on its way out or not properly plumbed for this application. Ive never had much luck on a personal level with electric pusher pumps; you MAY be starving for fuel.

Also, I wonder if you could get an aftermarket, quality tachometer and mount it even temporarily, and see if your converter and shift points really are what they say they are.

All that being said; lets just give your car a good solid tune up; new plugs, properly gapped, new vacuum lines throughout, check your sparkplug wires and boots, and a 2.25 or 2.5" exhaust system (mandrel bent) with a quality muffler (no need to get caught up in mufflers that flow 1100cfm; just a basic 2 or 3 chamber performance muffler from walker etc will do just fine).
Also, lets check fuel pressure, compression (if possible) and if you can, do a leak down test. Make sure your carb is in proper adjustment (or see if you can borrow a 650-750cfm carb for testing). Verify your throttle is opening the butterfly the proper amount. I had a QJet that wouldn't open all the way when I stuck the gaspedal to the carpet. Oddball: make sure your timing marks are in the right spot; this could be throwing the whole works off.

Heres what I suspect:

Assuming the above parts are not just about broken; you wont magically pick up a few tenths with one change; it'll be a lot of small fixes, that combined, will give you the performance you're looking for.
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Old 07-31-2012, 10:16 PM
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quick note,dont everyone else laugh::: check throttle travel with the engine NOT RUNNING
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Old 08-01-2012, 08:02 AM
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eerie thought; are you using a high zinc oil? Was the proper cam break in followed?

Was the timing set installed properly?
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