[TAQuest]

Originally Posted by pastry_chef

A larger cam will better use the heads and help manage your compression.
I'm partial to solid cams but for a hydraulic flat, maybe a Voodoo 703. Assuming you are around 400 cubes.
As Steve said, the Performer intake is limiting. RPM is much better.

The cam swap sounds interesting. As Steelcity mentioned, the RPM might be a problem with clearance on the ram air.

I drove it last summer. It would pull good up until about 5000K and then it just runs out of pull. It's just not as quick and fast as it should be. All the parts in the build check out. Compression test shows good compression. I'm going to look a little closer at the timing and the distributor.

[77 TRASHCAN]

Originally Posted by Stan Weiss

While it is old school I would look at an "068" installed on the factory ICL. While I am sure there are better more modern cams, they may need a change in springs or maybe have piston to valve clearance problems.

Stan

Yeah...That 204/214 cam is some what of a generic grind, like a 1/2-1 step above a stocker. The 068 would help keep this 400(?) of of the detonation zone.
The performer may be OK on a 400, a stock cast iron or RPM would be better...

[70GS455]

215 cranking pressure is about 8.5 DCR. Kind of high IMO for pump gas

Sent from my SM-T817V using Tapatalk

[TAQuest]

Took it out for a test and tune.
Added another bottle of 108 octane booster. Runs great up to 3200 RPM then it quits pulling. Some definite malfunction. Just don't know what it is. Everything is new. The whole fuel system is new. I switched the fuel pump again and did a volume test. Plenty of fuel. I tried adjusting the timing, didn't change the running out of pull at 3200. All I can think of is the distributor. I have had a lot of nice old Pontiacs and never had one built like this be such a dog. It gives hints of great power up to 3200 but that's it.

[Squidward]

I think the cam is too weak. I've run a similar cam (Summit 2800) in a 350, and it was a fun, yet tame, street motor. Those heads can take more lift.

702 or 703 Voodoo cam would be good - I run both. The 702 wouldn't take full advantage of the heads, but it has a little wider lsa for better management of the compression. Right now your cam is your performance constraint. I don't think you would have ANY complaints running a 702 Voodoo cam, especially in a lightweight 400 powered Firebird running 3.36's.

Aluminum heads can take a little more compression. I think 72cc E-heads are fine. Just get a cam that isn't on such a tight lsa.

You will be driving a convertible, which implies a large element of street cruising will be in play. You don't need a 550hp monster engine that will twist the body or frag the rear end.

In summary? All you really need is more cam with more lsa. The rest of the package is completely usable, including intake and carb.

[TAQuest]

Once I figure out why it's not pulling past 3200 I will get to actually commenting on the build.

[Squidward]

Originally Posted by TAQuest

Took it out for a test and tune.
Added another bottle of 108 octane booster. Runs great up to 3200 RPM then it quits pulling. Some definite malfunction. Just don't know what it is. Everything is new. The whole fuel system is new. I switched the fuel pump again and did a volume test. Plenty of fuel. I tried adjusting the timing, didn't change the running out of pull at 3200. All I can think of is the distributor. I have had a lot of nice old Pontiacs and never had one built like this be such a dog. It gives hints of great power up to 3200 but that's it.

Could you give us some timing specs? Initial, total, and vacuum advance? I would think you should get at least 4500-5k out of that cam.

If your timing is in the realm of "normal", then maybe your carb is not working right. Are the carb secondaries working? Throttle rod giving full open on carb?

I can't imagine your valves would be floating.

[Navy Horn 16]

Originally Posted by TAQuest

Took it out for a test and tune.
Added another bottle of 108 octane booster. Runs great up to 3200 RPM then it quits pulling. Some definite malfunction. Just don't know what it is. Everything is new. The whole fuel system is new. I switched the fuel pump again and did a volume test. Plenty of fuel. I tried adjusting the timing, didn't change the running out of pull at 3200. All I can think of is the distributor. I have had a lot of nice old Pontiacs and never had one built like this be such a dog. It gives hints of great power up to 3200 but that's it.

What does it do at 3200? Misfire, fall on it's face, or just not rev past it? Will it rev past 3200 when not in gear?

What is the ignition? A decent HEI and eliminating points would be a good place to start eliminating electrical issues.

[TAQuest]

I have the timing at 36 total advance. I have tried changing it on the test drive and couldn't get any improvement.
Carb secondaries are working. Goes wide open throttle.
It does act like valve float. Seems like a long shot with this build, everything is new.
It will rev high but there is no power past 3200 rpm. Once you hit 65-70 mph in 4th it's all done. If you shift before 3200 it will tear ass until you run out in 4th.
It's definitely rpm related.
The distributor is a new aftermarket 50K HEI. Could be that but it looks perfect. Vacuum advance works.

[Squidward]

Long shot here. Pull a valve cover and verify that the inner springs are installed. Given the history where the previous owner passed before things were finished, maybe he did a cam break in with inner springs removed (common practice), and never had a chance to get back to it.

BTW, what are the specs on the fuel system? I know you already checked the fuel, but mechanical pumps can sometimes have a diaphragm leak, giving poor performance that is short of a total fail. Other brainstorm is maybe a plugged filter or pickup sock, or maybe cracked soft hose on the suction side that is allowing air to suck in.

[TAQuest]

Originally Posted by Squidward

Long shot here. Pull a valve cover and verify that the inner springs are installed. Given the history where the previous owner passed before things were finished, maybe he did a cam break in with inner springs removed (common practice), and never had a chance to get back to it.

BTW, what are the specs on the fuel system? I know you already checked the fuel, but mechanical pumps can sometimes have a diaphragm leak, giving poor performance that is short of a total fail. Other brainstorm is maybe a plugged filter or pickup sock, or maybe cracked soft hose on the suction side that is allowing air to suck in.

That long shot fits better than anything yet. That is right where the build was when he died. Thanks for your help.

I replaced the whole fuel system last winter and it didn't change a thing. New tank and all new lines. New mechanical pump replacing the new pump that was on there.

I will be checking those springs tomorrow.

[chiphead]

I second the cowl mounted fuel pressure gauge to confirm fuel pressure at load. A Q-jet that runs dry will just go dead like you turned key off. A Holley or other carb design may go lean and surge or just lose power and lay over without stalling.

It does need a cam with at least 15* more duration at .050 (and inherent later intake closing) to keep it out of detonation.

[Navy Horn 16]

Set timing to 36 total all in, disconnect vacuum advance. See what that does for you.

[STEELCITYFIREBIRD]

That cam is the Eddy Perfomer.
https://www.summitracing.com/parts/e...7/make/pontiac
Are you sure you have Full battery voltage to the Dizzy.
Appropriate spark plugs?

[mchell]

That’s one itty bitty cam

[TAQuest]

Originally Posted by Squidward

Long shot here. Pull a valve cover and verify that the inner springs are installed. Given the history where the previous owner passed before things were finished, maybe he did a cam break in with inner springs removed (common practice), and never had a chance to get back to it.

BTW, what are the specs on the fuel system? I know you already checked the fuel, but mechanical pumps can sometimes have a diaphragm leak, giving poor performance that is short of a total fail. Other brainstorm is maybe a plugged filter or pickup sock, or maybe cracked soft hose on the suction side that is allowing air to suck in.

Took the cover off and checked. Both springs are there and the rockers are 1.5. Thought for sure that was it.

[TAQuest]

Originally Posted by Navy Horn 16

Set timing to 36 total all in, disconnect vacuum advance. See what that does for you.

Tried the timing every which way.

[TAQuest]

Originally Posted by chiphead

I second the cowl mounted fuel pressure gauge to confirm fuel pressure at load. A Q-jet that runs dry will just go dead like you turned key off. A Holley or other carb design may go lean and surge or just lose power and lay over without stalling.

It does need a cam with at least 15* more duration at .050 (and inherent later intake closing) to keep it out of detonation.

I will have to try that gage. It doesn't act like that though. More like valve float at 3200 rpm.
I have a new gas tank with one piece braided line all the way to the pump. New pump and new line to the carb.

[TAQuest]

Is it possible the rockers were not set up right? Wouldn't I have more symptoms? It doesn't pop or backfire. Just acts like floating valves at 3200.

[Steve C.]

Are they the single valve springs with no damper ?

p/n 5767 ?

If they are then take a look at the valve lift capacity of those springs, assuming 1.800 installed height and 1.130 coil bind. Then consider he has only 0.420" lift, assuming a 1.5 rocker ratio.

"Depending on the intended use and the spring and cam-lobe design, coil-bind safety margins can now vary from 0.015 to 0.120 inch, with tighter numbers predominating on very stiff valvetrains. Anything more than 0.150 inch may cause spring surge, which can greatly reduce the available spring load needed to close the valve."

https://www.hotrod.com/articles/how-...rance-is-safe/


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