[4dblnkldude]

A good friend of mine has a 66 mustang race car. It went 10.50's all day with a 347 small block, and of course we all want to go faster. So he built a dart 8.2" deck block with all the good stuff. A solid roller cam, diamond pistons, scat crank, steel rods, heads I cant remember, a super victor intake, done up holley, crank trigger ignition, evac pump, 5500 converter, (same as the last combo), C-4 trans, and 9" with 4.11:1 gearing. He did run oxy 114 fuel, we got it together and it ran 11.0's first time out. He was hoping for low 10's and tune from there. The major problem is this... this thing leaves the like a slug. The old combo yanked tire almost the whole 60'. We kept playing with it for about 10 more runs, and I think he got one 10.99. He took it to a local guy that said it was the fuel system. So he put a new aeromotive complete system......same thing. He took it to a local carberator pro and had him dyno tune it and it ran a 10 flat on his dyno. But in the real world it still leaves like a slug. So Friday night we took it down...same thing. So in the trailer it goes and its beer time. Saturday he switched to an alky carb he had from another project. First pass today 10.58...ok back where he started. Next pass 2 degree more timing a 10.54..ok going the right way. Third pass we jetted up and a 10.58 again. It leaves better than it did but with a 1.60 60' but jeez. This engine made 675hp on the dyno. We never even got to the trans brake yet, he thought it would be so much faster that he just gonna get used to it a little, and work up to the 9's.

To describe the run the tree comes down, he leaves, the the tires come up a few inches, and then it falls over, regains a little, than takes off. In the top 1/8 it hauls the mail and looks awesome. Best run today was 1.58 60', 10.50 at 131 mph. I'm not a full blown racer here, just a novice, and hes only been racing for 5-6 years. Any ideas????

[Half-Inch Stud]

Darn new converter decision. Couldn't leave the old converter in huh.

[johnta1]

Why not use the tranny brake?


May be not getting into the power band of the cam.
It would be a pig until it got up in the RPM range.

What's the shift RPM?

[Stan Weiss]

What does the car with the driver weight?

Stan

[Dragncar]

He needs a converter.

[steve25]

Please post up all the difference between this new motor and the old one and any of the same with changes to the car.

Both motors where 347 cid?

[Lee]

Did he go with a bigger cam? And did he use the Super Vic with the last combo?

On my old stroked Windsor(Dart), I found 15rwhp peak and 25rwhp mid-range by testing valve lash on a chassis dyno. That showed up at the track as well.

It is hard to imagine anything only getting a 1.60 60' with a 5500 stall! Sounds like timing and/or squirters are off.

[4dblnkldude]

The new engine is 363. The race weight is 3000 with him in it. Shift point was 7900 rpm. He used a regular victor with the last combo. He did go with a bigger cam, i will try to post up the specs.

He changed alot, but prior to the fuel and some ignition system it was just the engine. If it was a Pontiac i would have every number memorized by now. Let me get a little info off of him. We did talk valve lash a bit.....some other guy at the track told him to lash .004 looser. Either way, I figure that engine is down about 100hp. I really appreciate your help!

[Lee]

My engine was 427 inches. I tried the Vic Jr. (Chinese copy) and a Super Vic. On my motor, the crossover was 4500rpm - below that the Jr made more power, but the Super Vic pulled away FAST after that. One interesting thing, as I tested the intakes back to back on my chassis dyno and with a wide-band afr, the Super Vic needed a LOT more jet. I had around 93's with the Jr., but even with 99s the Super Vic was still lean. I had to drill out jets to get it close, then later got a bunch of CompCams' MaxJets to dial it in.

Pics are the 3 intakes I tested. Graph 1 shows the rwhp for each intake, but that is with the 99 jets making the Super Vic run lean. Power was even lower before I put the 99s in, but I don't remember how much. Graph 3 is with the drilled out jets and the Super Vic, compared to the other 2 intakes.

The unpainted intake was a CHI. It looked like a Super Vic with a spacer built in, by far the tallest intake. It performed like the Chinese Jr, though.

[steve25]

I don't think 4.11s are enough gear even considering that the new motor is 6% larger.

3000 lb cars with far larger motors and much greater torque outputs can make good use of just 4.11 gears when going thru the 60 ft, but not with this size motor if you ask me!

I mean heck a very common rear gear for a full race built 400 cid Pontiac motor is 4.56!

[Scott Stoneburg]

You said he had it on a dyno..where did it make peak torque? Also where is the cam degree'd in at, or was it degree'd or just line up the dots on the timing chain?
My brother has a 86 Mustang with a 381" TFS heads and a .620 ish lift roller. Victor Jr. And a 850 Quick Time carb Converter flashes to around 4,000. 3.90 gears and runs bottom 10s. His needs more gear but I dont think thats what is killing your friend.

[4dblnkldude]

It made peak torque up high. But not by much, this thing had a beautiful flat torque from 4500-6300 or so. The cam is degreed straight up. He finally used the transbrake last night and ran a 10.30 and a 10.22 both at 130mph and change. Its getting better. The engine was dynoed on the same dyno my 462 was dynoed on, my rwhp #'s were right on through the drivetrain at 422 and 516 hp at the crank.

When he ran it on the track dyno, it did a 10.02 with 440 rwhp. Drivetrain loss is 235hp? Gimme a break. I thought converter from the very first run. I didn't make it last night and sorry I cant get any more info sooner. We both do air conditioning and we are very busy right now. Thanks for taking the time to help!!!

[tininjun68]

I’m a simple bracket racer and not a pro race car builder but seems like with a trap speed of 131mph from that 10.50 you mentioned at 3000lbs., car’s got more left. What’s rpm at the stripe? 10.22 sounds like you’re getting pretty close but I’d bet some more gear will make a noticeable (tenth or two) difference. Any bracket car I’ve ever driven had no LESS (numerically) than 4.56’s however most were SB Chebbies. Good luck with chasing down 9.90’s! That said, might have to install more safety goodies and wear the race pants (stupid hot in the summer) when you run 9.99’s. Check with Atco Tech (assume you’re at Atco) or NHRA.com.

[Lee]

Originally Posted by 4dblnkldude

When he ran it on the track dyno, it did a 10.02 with 440 rwhp. Drivetrain loss is 235hp? Gimme a break. I thought converter from the very first run. I didn't make it last night and sorry I cant get any more info sooner. We both do air conditioning and we are very busy right now. Thanks for taking the time to help!!!

I've seen 100rwhp "loss" by JUST changing a torque converter. Looser converters will give lower RWHP numbers, but still perform well.

Look at the three dyno runs represented on the two attached graphs. All 3 are the same car, same motor, same tune. The first shows two different "4000 stall" converters being compared. The 2nd graph is with a lock-up converter with the clutch engaged.

[Ken MacNicol]

60's should at least be in the low 1.40's