I have a 1969 Olds 455 in my 1972 Buick Skylark. It is backed by the factory th350 and has 2.56 gears in the rear. Ever since I've had the car, it just seems to run out of power on the top end. It may be the cam, as I have no idea what is in it(no lope). Currently, it has an Edelbrock Performer intake, no name headers, HEI conversion set to 10 initial with the good corvette vacuum advance can and heavy/light spring, accel coil and MSD solid core wires. Induction is a Holley 770 Street Avenger with the yellow spring and currently running an L88 non vented air cleaner base with a 4" filter. 2 1/4 inch exhaust with no name mufflers all the way to the bumper. It also has the Carter Muscle Fuel pump on it that is supposed to deliver 6-7 psi. The throttle is definitely opening all the way but that is kind of what it feels like the problem would be. It has plenty of response and is a blast to drive, it just falls on its face a second before it shifts at WOT(no tach, no idea of rpm). So, ideas? Thanks!

 

Sounds to me like you may be running out of fuel, at least a possibility. Check the rubber fuel lines between the tank & steel line, if they are soft & mushy replace them. Might be sucking closed under high demand.


I have had this situation before & others have run into it as well. You can bypass the fuel tank w/ 1 gallon fuel can, 2 litre soda bottle, etc secured behind right headlight w/ pump inlet line drawing from bottle. Beware - you wont get far after hitting full throttle. If the aforementioned lines are original or old it is easier (& safer) to just replace them & road test to see if any difference.

 

Ah, excellent idea! They're probably original so it may just be time to spring for total replacement with an olds tank unit and lines that are on the correct side. Thanks!

 

What is your total mechanical distributor advance without vacuum? What brand distributor? I would think an initial of 10 with an HEI your leaving power on the table.

 

I very well may be. The total is at 36 degrees but no idea what rpm that is coming in at although it is pretty low. This is with a dial back light. Again, no tach so I've been keeping it conservative. When I initially purchased the car, the timing was retarded 4 degrees and I've advanced it to 10 at idle. This eliminated the overheating issue and of course pepped it up. Pulling from full manifold vacuum for the vac advance. As far as I know, its a stock HEI from a donor. Left the factory weights, changed the springs and advance can and of course coil, cap and rotor. Looks to be the factory module and that may be an issue as well.

 

If its a stock distributor with factory weights it has around 21 degrees of mechanical advance, 36-21=15 initial. Try bumping your timing up to 15-16 at a very low rpm with vacuum advance disconnected. You really do need a tach for adjusting things.

 

Yeah, I know. I've been looking at different ways to mount it without it looking cheesy. Time to bite the bullet and do it, you are right. Thanks!

 

You could hook it up temporarily under the hood just to make your settings, then remove it.

 

When you say 2 1/4 inch exhaust I hope you mean a dual exhaust? If not, that would be a restriction.

 

Ha, yes dual exhaust without a cross over. And I'll be hooking the tach up under the hood Sunday to reset my timing advance and curve. Thanks for the help everyone!

 

I have seen different curves in the Oldsmobile HEI distributors, if it is an aftermarket distributor, 16 degrees is very possible. I have found 36 degrees the best at the track but a couple of extra degrees felt stronger, start with 2 degrees and go from there.

 

I'll see if I can get the numbers off of the distributor. I didn't have a chance to hook the tach up this weekend so that remains to be done to see where I'm truly at. It does hold a solid 20 hg at idle without fluctuation and I'll be t-ing into the fuel line to see what it does while driving as well. It runs exceptionally well with great response, just right before it shifts its just not making any power. Hooking up the tach will also let me see what my WOT shift point is of course. As far as I know, its the stock th350 that would have been behind the stock 350 Buick motor. No shift kit or noticeable stall. To be continued with timing results. Thanks!

 

It's also got CA heads on it which, from what I can find, are small valve units. I may have a lot of factors contributing but I've never had an engine do this so noticeably before. Granted, none were Olds but plenty of 350's, a 351C, a 396 and even a little 305 HO in an 84 Trans Am. I will say even with this problem, the 455 will walk off from cammed ls engines and rich kids with tuned up diesels! I'll get to the strip one of these days and do a baseline before I really start throwing money at it.