why does my 455 not rev. high?

Just curious, I have a '70 GS455, '70 block, '72 heads. 350TH, 377 posi, it's really fast, but it shifts at 3000 rpm, if you manually shift it, about 3700 is pushing it. I know it's a torque motor, but isn't this a little low on the rpm shift point? thanks, Dale

 

one what is your build ie cam compression intake carb , also what is your timing curve initial vacuum and manual if your timing is way off all three fazes you could be killing your power band but more info is needed
jamie_my

 

It is supposed to have an RV cam, 9 to 1 compression, edelbrock intake and holly 750 double feed. no headers, stock exaust, ram air hood, not sure on the timing, I've advanced it some until it sped up the idle, have played with it advanced and retarded, not much diff. but I'm not sure where it should be set at. also only has stock distributor/coil. engine only has around 15K on it.

 

what carb do you have and where do you have your vacuum advance hooked up, i ask this because ihd a simulair problem whith a small block chevy i had the vacuum advance hooked up to a timed vacuum port not a constant vacuum port on the carb and had to advance the timimg to get it to idle low compression so no detonation but when the timed vacuum port kicked in it had too much timing and ran flat at about 4000 ruffly where you are at check you carb manual for timed and not timed vacum ports and try to check your timing fazes
jamie
_my

 

also ckeck to see that your vacuum advance is working at all? hook up your timing light check the timing then disconnect the vacuum line to the dist and plug the vacuun port on the carb with your finger and check the timing again your timing mark should drop a far amount if it does not then your in the wrong port or you vacuum advance is hooped i am pretty sure that tming is your issue and be happy this is an easy fix anjamie_my
\ you will be shifting higher soon:beer

 

Does It Shift Itself At 3700 Or It Dont Have Power After 3700.randy

 

Since timing was mentioned, I'll add a few questions:

1) What do you mean "3700 is pushing it"?

2) What are you using for a tach & is it functioning correctly?

3) Factory valvesprings?

4) Was the cam degreed in? or could it be way off?

5) Single or dual exhaust?

 

Hello,
If you can reach higher rpm in third gear then you have problem with your TH 350, governor or vacum modulator.
Christian

 

Here's what you need to do. First since you have stock ignition I would be sure I have a good (new) set of points in the distributor and that they are set correctly. That means that they are set at 30 degrees DWELL with a dwell meter. Once you have that correct, then tackle the timing. Find the marks and get them clean and readable. Then remove the distributor vacuum line and set the timing to spec. Now before you remove the timing light, rev the engine and see if the timing advances (mark moves up insuring the weights are not stuck). If that is good reinstall the vacuum line and give it a go. If you have been timing it by just twisting the distributor, it's hard to say you are anywhere close. Also, on a point car if they are off it sure won't rev.
Jim N.

 

Also check to make sure the carb is opening all the way. Have a buddy push it to the floor ( NOT while it's running) and manually check the carb to see if it's open all the way. Good luck.

 

trash in the tank,check your fuel filter.

 

I checked, it has some form of electronic ignition, no points, but otherwise looks stock, not sure if the tach is accurate, idle looks normal at around 700 rpm, has dual exaust, no headers, cuts out around 4K rpm like short of fuel, also stumbles if your going between 30-50 mph lite on the gas, backing off or giving it more gas smooths right out. 3700 rpm, sounds like it's turning 5K, has a fan that roars also, all the time, clutch bad? I did a video the other day, put it on youtube, shows the tach in the video, see what you think. It runs strong, just weird that it shifts so early or the tach is off? Thanks for your help, Dale
on you tube type in '70 gs455 0-100 it'll come up

 

I second this.
Right Artie?ou:

 

This won't solve your problem just something to eliminate
dead ends or wild goose chases. If your timing is off far enough to prevent your engine from going past 3700 it probably won't start either. It will also rev past 3700 on the primaries so not getting full throttle isn't the answer either.
It sounds like it may be starving for fuel. If you can find out what's causing it to miss you will most likely solve your problem. Good Luck.

Bob H.

 

What the heck is an RV cam?

And where would you buy one?

I see and hear guys talking about them, but so far it looks like a way to call the stock cam something special.

Color me confused....

 

Thanks, I'll start checking it out, starting with the fuel filter. Even only shifting at 3k rpm it's nuts to drive, is it supposed to be this fast? I've owned alot of fast rides but this thing is in a different league, pretty fun!

 

first thing I would be doing is verifying the tach is accurate. I had an autogage made by autometer that was way off.