Zane's 71 327 Ram Horn - restrictive?

[burnin oil]

You dont see it often on street motors but maybe a valve spring harmonic is occuring and limiting RPM. This is normally on a full race motor. Do your valve springs have a rotator inside? This would look like another valve spring inside but made out of a flat wire instead of spring wire. You could try to pull those out and see if the RPMs change. If that is the problem I would be very suspect of the valve springs and would have them replaced with another set.

Another thought is a cam wiping a lobe. I had one that started to wipe an exhaust lobe and that really made the motor run like crap. Before it got really bad it would basically not exhaust that cylinder but was still trying to fill it and run. Lot of back pressure there.

[Molino]

[QUOTE=rcazwillis;8482074]I remember when I was a teenager, the truck was weak in the engine department. Decent low end, but would not pull any RPM. I always thought it was just the way the engine was built.

When you floor the accelerator pedal are the butterflies in the carburetor wide open. Is the transmission kick-down cable limiting throttle actuation, if so equipped. This engine should scream.

[rcazwillis]

Originally Posted by burnin oil

You dont see it often on street motors but maybe a valve spring harmonic is occuring and limiting RPM. This is normally on a full race motor. Do your valve springs have a rotator inside? This would look like another valve spring inside but made out of a flat wire instead of spring wire. You could try to pull those out and see if the RPMs change. If that is the problem I would be very suspect of the valve springs and would have them replaced with another set.

Another thought is a cam wiping a lobe. I had one that started to wipe an exhaust lobe and that really made the motor run like crap. Before it got really bad it would basically not exhaust that cylinder but was still trying to fill it and run. Lot of back pressure there.

No, single spring. Heads are vortec with GM blue beehive springs. GM Parts 12499224. Should be good to 6500 rpm based on the ole' internet data. Same valve spring run in LS1 motors.
Cam is a roller. Will add checking issues with cam lobes to my list. Could still be an issue of some sort. Had one lifter clicking on startup. It was far enough out of adjustment that you could see the nut was higher than the others. Adjusted it and have not heard anything out of it since. May be something weird going on there.

[rcazwillis]

[quote=Molino;8489467]

Originally Posted by rcazwillis

I remember when I was a teenager, the truck was weak in the engine department. Decent low end, but would not pull any RPM. I always thought it was just the way the engine was built.

When you floor the accelerator pedal are the butterflies in the carburetor wide open. Is the transmission kick-down cable limiting throttle actuation, if so equipped. This engine should scream.

They are opening up and move freely. Need to recheck if the throttle cable is pulling them open. TH400 so no kick down cable.

[rcazwillis]

Okay, it was the timing. Truck will bump 5500 and force the 1-2 shift. Had some time to drive it and realized it works well. It does not make a lot of power in the upper RPMs, which is the stock cam.

Thanks for those that pointed me to that area.