rpm problem

[buicktr7]

My v6 motor is not turning up the rpm's. Saturday at the track it would shift at 3500, then second to third at 5500 but at top end it is only turning out 4200 rpm's. I want to run about 6500-7000 at top end.

 

[b4black]

Is it running out of breath or out of gear? In other words, is it getting to 4200 and flattening out, or still climbing, but only reaching 4200 by the finish line?

 

[buicktr7]

The car at the burn out and on a free rev will hit 5500-6000 rpm's.
Is their a possability that their is a problem with our headers. They are 1 1/2 inches in diameter and 31 inches long. It seems like it is trying to climb up.

 

[b4black]

The '83 headers and very similar to the 86/87 design which reportedly are good 'til the 10's, so I don't think they're a problem for us. I would suspect the post-turbo pipes before the pre-turbo pipes. (Bigger down-pipe is better than a bigger up-pipe.) Plugged converter is a common problem.

What boost are you seeing thru the traps? If it's a breathing problem (restriced inatke or exhaust) you may not see max boost.


What trans and rear gear are you running? It seems to me that your running out of gear since the 2-3 shift is at 5500. 6500-7000 may be too high for the top end. It might be out of the power band.

 

[buicktr7]

The car is a non turbo 1976 triumph tr7 with a 1979 buick regal sport coupe block and heads and no turbo "N/A". The trany is a 400 trany with 4:68 rear gears and 27.5x12 15 inch goodyear slicks.

 

[unboostedV6]

Tell us your cam, carb, compression, converter, ET, expected ET and we'll give you a hand. GB

 

[buicktr7]

the cam is a hydrolic kenne bell 269 duration, afb carter 625 cfm,
hughes 4000 stall speed converter, 16.022 as of saturday which is the first time we actually got good runs out of it. The last time we blew up our transmission. The expected ET is 12.00. The car has a TH400 out of a 1984 cadillac with a 425 cid motor a ford 8 inch rear end and 4:62-1 gears in the rear end. The headers are 1 1/2 inch in diameter and the lenghth is 31 inches that are seperate and not collected at the end.

 

[b4black]

Originally posted by buicktr7
and no turbo "N/A

DOH! I thought you meant an '83 Turbo V6, since they came with factory headers (instead of cast manifolds).

Ignition problems? Valvesprings?

 

[unboostedV6]

The numbers don't make any sense to me. You have a 4000 rpm converter, yet the 1-2 shift happens at 3500? That cam's probably only good up to 5000, if the valvesprings are decent. The headers absolutely, positively must have collectors to work. Zoomies only work on blown and/or injected cars. The TH400 is stealing 20 horsepower more than a TH350 would in exchange for strength you really don't need. What carb, intake, and compression do you have? Assuming the car weighs around 2800 lbs., you can get into the 12's. But 12.0's? I don't think so. It's not revving because it isn't making enough power to go that fast.

 

[pat83t]

Also sounds a little over carbed try dropping down to a 500cfm. Gearing sounds a little steep but that could be just me. I am sure your 60' times are rather impressive but are losing it at the far end. And a 4000 stall? That sounds way to high to me but try getting other opinions. I would figure maybe around 2800 stall myself. What are you running for ignition? Have the heads been ported and polished? What fuel are you running?

 

[brewmeister7]

Sounds to me like you're having ignition problems.The standard HEI is only good to about 4500 rpm. under load.Try an aftermarket module and 45,000 volt coil and I bet your problem goes away.Good luck....

 

[buicktr7]

What does your tr7 run in the 1/4 mile and what temprature is it running at. We have also had a large over heating problem with the car. Any thoughts

 

[brewmeister7]

I'm a road racing guy.But,I have taken the car to the track a few times with a best time of 13.20.I think it can do better but I don't beat on it.I had the original radiator recored by a racing specialist.I run a 180 degree thermostat and have no overheating problems.It usually runs 190 on hot days.A good clean TR7 radiator usually works fine for a V6.Make sure you're not clogged anywhere.It also helps to install larger diameter water necks.I use a flexfan setup.I've seen electric setups that work also.You might want to try to modify a shroud off an old Monza or Starfire.You should be able to get this car in the 12's easy.I think your gearing is way high.The stock 3.90 rear would give you better results.I have run the 3.90 and a 3.45.I can only get about 115 out of the 3.90 with an overdrive tranny.So,I would imagine that your engine must be screamin for Jesus.The 3.45 is the best.Good acceleration and 140 top end.Your headers sound similar to mine.I run an Edelbrock (Carter) 500 on a stock aluminum manifold.In case you haven't heard,these units perform every bit as good as the aftermarket and are a lower profile.I know a few guys who run 600's but the general consensus is that is too much carb,unless you had some serious head work done.Hope this helps.By the way,nice choice of car.I'm partial to the convertibles myself.

 

[buicktr7]

do you have a picture of your tr7 if so I would like to see it.

 

[brewmeister7]

I'll send some email...