At the track last night it would level off and loose power?

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NHscamp

NHscamp

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At 46-4800rpm? 1st gear she would go to 5300, 2nd gear level at 4700 and 3rd gear would not go past 53-5500 rpm s. Cool 60 degree night.
Timing? Now at 15 initial all in at 2500.
Thanks in advance for your thoughts.

1971 scamp
My build
360 la internally balanced with balanced flex and harmonic.
Stock crank, 340 hp rods
Comp cams 280H
Kb 107's NOT zero decked .012 in the hole
Prw stainless 1.6 roller rockers
Indy heads set up by IMM/ Brian 70cc chambers .29 head gasket
Edlebrock air gap intake and 750 cfm carb
Miloden pan and mp windage tray
Dougs headers , summit 2.5" exhaust
PTC 25-2800 stall torque converter and transmission full manual
8.75 rear with 355 gears posi , Mancini adjustable pinion snubber
Mp Ss springs and shocks
 
What do the plugs look like? Cooler air means it should be going leaner, if it's lean already might be too lean for the better air. Also, check your valve spring pressures. Whats the total timing at 2500?
 
Might be leaning out. Good way to cook an engine. :burnout:MT
 
Sounds like you need to fatten it up,its falling on its face..i'll be heading up there soon and putting more jet in mine before i go..
 
what fuel pump? 5/16 or 3/8 fuel line? if its a factory manual fuel pump it could be running out of fuel.
 
Could just be not enough HP. At higher speeds, you have a lot more air pushing on the front of the car. A 71 scamp does not have the most aerodynamic nose. 3600 pounds, 360, 3.55 gears, middle of the scale stall, should run high 12's or low 13's at 95 mph.
 
Generally, when an engine quits reving, and is not accompanied by misfires, It's either a little short on fuel, or it's not breathing right.The short on fuel has been mentioned.
The not breathing right, is usually a plugged/restricted exhaust, or as mentioned, valve float. When it's valve float or lifter pump up, the rev ceiling is usually the same,or close to the same, no matter which gear you're in. And you can really feel it coming on. And if you drop it into neutral, it usually won't idle, til the lifters bleed down.
When it's restricted exhaust, it usually gets worse with speed as the engine works harder and harder, and you can really feel it coming.
If the secondaries are not opening, it takes a long time to get to the end of the track, but it pulls redline, at least in first and second.
If the carb is really fat, as in choke-stuck-partly-on fat, well, that will kill performance.
If theres 2 qts too much oil in the pan, that might do it.
If the tranny's trying to catch two gears at once, that'd be like driving with the brakes on.
If the points are bouncing, it'll flatten out, but be accompanied by misfires. You're not running points, are you?
If the timing chain jumped a tooth or two, that would do it, but again it won't idle normally, cuz it's all messed up. If you put the timing back, it will run with a tooth or two out, but it won't breath right andwill flatten out real quick.
If the rotor gets to be out of phase with the correct towers, it will flatten out, and be accompanied by missfires. But this usually comes on at a much lower rpm, when the advance gets close to max. Say closer to 2800 to 3600.
A faulty rev-limiter?I have seen cheap ones act weird.
Anyhoo, those are some ideas that came to me.
 
Yup - You need to figure out total timing figure, list what type of distributor you have, and the carb setup. You should be running mid 12s with that on an average day.
 
I say an A/F gauge is damn fine thing to have these days. Grab one; +1 for AEM UEGO.
 
First time out or has it been run before? First time out, you need to be checking everything suggested here. Usually if it's lean, you will see it on the temp gauge.

If it's been run before, how did it do then? If it did much better, you need to figure out what has changed.
 
crackedback said:
Sounds like fuel delivery issues.
Click to expand...

yep, Sir, I gotta agree,
Lots of build upgrades & cudos NHscamp, don't see any fuel upgrades on your O/P though---

No lack of respect intended or implied NHscamp...
 
does sound like fuel, but a buddy of mine had a 5.0 mustang that really nosed over, swapped the valve springs and the difference it made was unbelievable
 
I have almost the exact same combination as you except I have aluminum heads. I am also having the EXACT same problem and I believe it's fuel related. I am completely re plumbing my car this winter with an electric pump hopefully that solves it.
 
Thanks for all the replies it is sounding fuel related, I built the engine and car but I know nothing about tuning and such.

To answer your questions It was the cars first time out.

Ran 150 degrees the 30 mile drive over and 180 degrees on the track.

Timing is 15 degrees and all in at 2500 35-40 degrees. Mancini elotronic distributor with built in performance curve, hei coil.

Exhaust is 2.5" with dynomax straight thru mufflers

Manual fuel pump 5/16 line and 5psi fuel pressure , Eddie performer 750 carb.
Run times were;

R/t. 1/8. 1/4
.159. 9.75@70mph. 89.42 mph
.574. 9.8@69mph. 87.58
.869 9.9@ 64. 80.22 mph
 
NHscamp said:
Thanks for all the replies it is sounding fuel related, I built the engine and car but I know nothing about tuning and such.

To answer your questions It was the cars first time out.

Ran 150 degrees the 30 mile drive over and 180 degrees on the track.

Timing is 15 degrees and all in at 2500 35-40 degrees. Mancini elotronic distributor with built in performance curve, hei coil.

Exhaust is 2.5" with dynomax straight thru mufflers

Manual fuel pump 5/16 line and 5psi fuel pressure , Eddie performer 750 carb.
Run times were;

R/t. 1/8. 1/4
.159. 9.75@70mph. 89.42 mph
.574. 9.8@69mph. 87.58
.869 9.9@ 64. 80.22 mph
Click to expand...

Did you pull the plugs? That will let you know if your running lean or rich just by looking at them. I would try to get a hard number for your total also.
Mine likes 36* at 2500 rpm.

My car used to have a pretty bad hesitation as well. If I was cursing and floored it quickly my car would stumble then come into power. I put a new carb on it last night and that helped the issue out a bit but I wasn't able to tell how the car was doing at high rpms in third gear.

If you have another carburetor then take it to the track next time and make a pass with each one and see if that helps at all.
 
With those numbers, especially the MPH that engine is making very poor power. Like about 170 at the flywheel. You have some serious tunning issues. I would start with fuel, like has been mentioned, and go over all the basics, firing order, ect. Total timing should be no more than maybe 36 degrees. Keep us posted
 
Here's one for you; if you really have close to 40*timing, all in by 2500.........That's a lot of timing. Ima thinking that mighta been too much.
And a 5/16 line....mighta been a little small.
 
750 cfm carb? holley?

even with a 5/16 fuel line...should be enough fuel in the bowl(s) to carry you thru 1st gear......

my 73 "Duster with 750 dp is fed by a 5/16 line with holley high volumn mechanical pump....has run 106 mph in quarter...

timing or valve springs....if hydraulic cam....check preload on lifters...
 
Are you using a Mopar electronics box orange/chrome/gold with the electronic distributor? I have seen these boxes (in my case orange) retard timing 10 degrees after 3500 RPM. The 35-40 you think you have could really only be 25-30. Have you checked for full advance with a dial back timing light?
 
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