Ok, this is my problem. It all started 2 years ago. I had a 1977 camaro with a stock 350 with vortec heads. stock th350,coverter,4.10 gears. It ran 14.2 @98 mph. ok not to bad. then I put a 268 XE cam 3000 stall shift kit. than it ran 13.8 @ 98 mph. put a holly 750 carb msd ignition ( digital 6, blaster ss coil, pro billet dist) had ithe carb tuned at a shop than it ran 13.6 @ 98 mph. see a pattern? ok the next year. I put a 406 sbc in. 11.5:1,ported heads
team-g intake 750 holly erson cam ( 244 250@.050 .504) 3000 stall,spooled rearend 28" micky thomson et streets. it ran 13.5 @ 98 mph. thought the ignition was bad so I put in a differant ignition in 98mph differant carb 98 mph it dosn't matter what I do it always runs 98 mph. differant timing curv and advance same mph at the top end. I have a differant trany I'm going to put in see if the problem is there. let me know what to check.
VERY FRUSTRATING.

 

you change your rear gear yet? might be running out of gear at top end

 

Have you tried a different track?

What RPM are you crossing at?

http://www.kabamus.com/garage/gears.html

 

I cross the line at about 5300 rpm. the enginge pulls to a little over 6000 rpm

 

Are the valve springs in good condition? Weak springs won't necessarily lead to obvious valve float, engine can just lose power past a certain rpm. You might not see it winding out in a lower gear, but the drag of wind resistance at 98 mph in high gear, engine might not pull it.

Also, that's a lot of slip on that converter. With 4.10s, 28" tire, and 5,300 rpm, theoretical mph is ~ 108. Ten mph loss is a lot. My nephew used to have a Chevelle with a 454 and a B&M converter, saw similar slippage at the finish line, plus really mushy shifts. He was running a 224* cam, so I told him to try a rebuilt 6 lug Vette converter as a cheap experiment. Slippage was cut considerably, shifts were nice and hard, et dropped a couple of tenths.

 

I'm assuming it will do much better than 98 top in on the open road....

Does the tranny fluid smell burnt?..is it slipping...if not I dought it's a tranny problem....

What are you running for a fuel pump? might be running a little low on fuel at the top end..

Is it a vac secondary, if so have you changed the sec spring to a lighter spring?

How does it launch? Does it hook good...Do you have a lot of wheel spin?

Might be to much converter for the cam..may need more cam or less converter...

Do you run roller rockers? if not try a set of 1.6's....to get a little more lift.

I had a truck (4.11 28" posi) with a 454 a 282 comp cam and a switch pitch turbo 400...low stall was 1800, high stall was 2500....it launched and accelerated better in the low 1800 stall.....

G

 

come to think about it this whole problem started when I got a new converter. I changed alot of things with the converter, it was just part of an upgarde to the car. talking to my brother (the driver) he is actually crossing at 5500 or so. and that should be 110 mph. I'll put a new converter in cuz I have a new one sitting on the shelf and see how that works.

 

but the more I think about it, converters don't lock up 100% it's only about 92%-97% for my stall speed. and that works out to around 100 mph. so I don't think it's my converter. I had the car on the dyno and the power band STOPED at 5000 rpm and stayed there till 5600 rpm. It didn't move more than 1 HP

 

I don't think the converter is killing your power at 5000; like I said, sounds more like something along the lines of valve float, maybe a fuel issue. My comment about the converter was just that it seemed really inefficient at higher rpm.

 

Yes,what type of fuel pump are you running? Losing fuel on the big end is normal and happends to alot of cars including mine when I race 1/4 mile...my car hooks HARD.

What size/type of carb are you running? Holley,eddy,etc. vac. secondary?

What gears are you running?

 

That is a pretty interesting problem. I punched the engine and vehicle specs in the system to get a ballpark figure for what was going on. This is just a ballpark as I don't have all of the data or the physical car and track to work with, I took a rough guess with valve sizes etc. Doing the estimated math on the 406 with the Camshaft specs it appears to reach peak horse power around 57 to 5800 rpm and it appears to hold it to around 6200 rpm and then slowly drop off, there is also a slow climb and descent from 5500 to 6500 with a variation of only 6 hp. Again I emphasis that this is just a rough estimate based upon the data available. The engine appears to have a strong powerband and holds onto it through a good range. It really starts to take off just after 3000 rpm as torque and horsepower climb fast and steady with torque eventually crossing at 5200rpm and beginning to drop off. The only possible cause that I could simulate to create such a consistent problem was traction problems, have you consistently launched at the same rpm? Does the car hook right up and pull or is it sluggish or spins the tires? It may be that you need a higher stall torque converter to help adjust the shifts points so that they are more into your engines powerband. That and something put all of the power into the pavement would be my guess. I hope that this helps some.

 

well, I have a holly black fuel pump with 1/2 line all the way from tank. is there any way to check the fuel. flow it pums alot of fuel but how do I know if it's enough? as far as the carb it is a holly vacuum sec. 3310. it's funny I unhooked the secondairs and took it for a test drive and it pulled the SAME.
so I thought they weren't opening. so I put a screw in to lock them together and we ran 13.5 @ 98mph So ether they were opening but not doing anything. there's no traction problems with M/T ET STREETS. no spin 1.9 sec 60' i didn't think it's fuel because it dosn't cut out or pop or anything. but I don't know if that means anything????? that remainds me, does the holly black pump make ALOT of noise. some people said that the bearings are going out but I don't know. First electric pump I've used before.

 

I forgot shift at 6700 rpm. and the faster you go (rpm) it doesn't feel any more powerful. there no noticable power curve. 3000 rpm feel the same as 5000, 6000, rpm. any you can't feel it nose over. it just keeps going.

 

valve springs?

 

is there any way you can check? the reason I didn't think that it was the valve springs is because I've had two different sets on two different engines. and the same problem.