60 ft help
 

We have a mustang weighing 3120 at the starting line. 355 chevy. 12.4-1 compression. 263/267@.050, .710/.660 on 106 in at 102 ic. Strip dominator. 1050 quickfuel 4150 carb. Th350 trans w coan brake. Large heads....ported dart iron about 232ccs.
Flow good air, but we know they're very large on this combination. We know the cam is small, but this was a "use what we had" deal. Converter is flashing about 5800, and the fallback rpm is about 6500. After reviewing the gopro footage. It is very obvious that the fall back rpm needs to be closer to 7000, as the shift recovery on the 2-3 change is lacking. The car could use the extra starting line rpm as well. Currently the car runs 10.45@129.89. Runs 6.69@103.8 in the 1/8. 60 foots only 1.45 most times. I believed we've tuned most of the power out of this, but it was suggested that we try even more timing. Right now, best times and mph have been found with 40 degrees. But a very knowledgeable and fast friend has told me that he's found certain small chevy engines that performed the best with a much as 46 degrees, and that we should continue experimenting with it. Converter will get sent out to be loosened up over the winter another 500 rpm. Currently crossing at 8000 or so with a 4.88 and 28x10.5x15 stiff wall tires. Any ideas would be greatly appreciated.

Re: 60 ft help
 

Good morning to all,
Just off the top of my head, try changing the First and Second gear ratio's to somewhere in this area - 1st gear 2.70 range and 2nd gear 1.70 range.
You should dyno the engine and run your timing changes there, fuel used will have a bearing on your timing as well, coolant temps too. Try to bring and run as much of your combination on the dyno that you run in the car.
You'll need to see where the power is and where it falls off. One day dyno testing will probably give you more positive information then a season's worth of racing.
P.S. with the additional power you should find , you might have to go to a 30" tall rear tire.
Best of luck on your endeavors.

Respectfully,
Henry Kunz 1534 H/SA.

Re: 60 ft help
 

My Monte is very similar. Converter needs to be around 6100 before fall back. Right now my drops 100 rpms and drives thru first gear. With mine at 5800 and 488 gear with stock ratio 400 it was 1.43 area and 10.30 and 128. With 6100 I'm 1.37 10.0s at 130. But only 7500 with 28x10.5

Re: 60 ft help
 

What engine specs and weight of your car?

Re: 60 ft help
 

Carb and heads are really big for a fairly mild motor. Changing the cam and moving the power band up with a looser converter might work but it would be a lot of testing. I’m guessing a 6400 rpm converter would help you right now. A good 200 cc head would help a bunch.

Re: 60 ft help
 

i totally agree with you.

Re: 60 ft help
 

263/267 isn't a big cam for the size of the engine and the compression ratio. The cylinder heads yes way too big.Also change the intake manifold. Way too small of a cross section area.

Re: 60 ft help
 

Sounds like your convertor is pretty loose, slippage wise. My 85 Mustang was 3100 pounds with driver, also had 4.88 gears, although I ran 9 x29 and 9x29 1/2" slicks, and at 130 MPH, I was only revving 7000-7100 across the finish line. My car was a stickshift (Jerico 4 speed), so no convertor slippage, but 8000 RPM at 130 with a 28" tall tire seems awfully high. I previously ran the car in Stock, so it had factory type suspension, with Maximum Motorsport non adjustable LCAs, and adjustable uppers, with Strange single adjustable shocks, and typically ran mid 1.3 60 foots, with a best of 10.15 at 130 MPH with a flat tappet, pump gas 331 cube SB Ford engine. Seems that you have a pretty large carb, my engine was 24 cubes smaller, and a Holley 650 was plenty.

Re: 60 ft help
 

Actually, the math shows roughly 6 percent slip

That was a great running car! What was the whole engine combination?

Re: 60 ft help
 

The manifold has some work done, and I was trying to keep a little airspeed in the engine. The strip dominator is a pretty good manifold compared to most actually.