[TAQuest]

Swapped out the ignition module and there's no change.

[dmac]

Originally Posted by "QUICK-SILVER"

Stan,

Cranking compression for 69' 400's factory rated at 10.75 CR, was 185-210.
Guessing low number was for 041 cammed engines and high number for 068 or 067?

OP's 278° cam with 105° ICL has got to be adding to effective stroke and running the cranking compression up.

Don't remember now but did the math in my head when you recommened the 068 cam for this. Big difference in intake close between it and whats being used.

Clay

I tried a little math years ago, and figured out that factory CR ratings were based on a zero deck, zero valve relief, and an exact match to chamber volume as blueprints, and maybe even no head gasket.

The one thing about factory ratings, even if their claimed 10.75:1 was really 9.25:1(or whatever) they still recommended the fuel of the day, which was 98 to 104 octane, and I think octane ratings changed on the pumps, where now it is an average of two ratings. You can't really compare CR going off factory ratings to run today's fuel.

[TAQuest]

Recap;
I purchased the 67 Firebird 400 convertible out of an estate long distance in New Jersey. Had the car shipped to Michigan. Talked with the owner's sister many times. Asked a fellow Pontiac enthusiast in New Jersey to look at the car for me. He said it was nice so I bought it. They sent all the records with the car. It has $7000+ in receipts for the drive train. The build was done but there were a few things left to do before it could be driven. We have had it running for a few years now but there has been a problem with the engine. At 3200 rpm it loses power (posted video).
I checked the compression on 1 and 2 and they both read 215 psi cold and dry.
Made sure it has fuel pressure under a load by taking a video of the fuel gage on a test drive.
Swapped a carb off another vehicle that runs good.
Made sure there was 12 volts to the distributor.
Switch the coil and ignition module.
I have tried changing the timing every which way.
If you were to start the car and not drive it you would think it's a really nice running Pontiac 400. Runs good up to 3200 rpm.
After making sure there wasn't anything wrong with the ignition and fuel system I have to turn to the build and internal problems.
I have searched through the receipts and I see that two set of roller rockers were purchased.
Also two sets of head bolts.
One set of head bolts was for heads made before 3/15/02 and one set for heads made after that date. Two different part numbers.

What would be the next move?

[STEELCITYFIREBIRD]

Originally Posted by Stan Weiss

OK, Pull the valve cover so you can see the valves for number 1. Rotate the crank until the mark on the balance lines up with timing mark. Make sure that this is the overlap TDC where both valves are open. If the intake valve is open more than the exhaust valve, the cam is installed to far advanced.

Stan

^This... if you haven't already

[dmac]

Have you checked the timing with vacuum advance connectedto see if you are getting too much advance- either mechanical or vacuum-
at higher rpms?

[chiphead]

Good job eliminating fuel delivery. I watched video. Motor sounds labored or restricted. It sounds like its not pulling crisp. Almost like secondaries aren't opening. Things to check in order:

Is carb opening to WOT?
Is coil good?
How do plugs look, rich, lean, etc?
Is exhaust restricted, heat riser stuck, etc?
Is cam installed correctly per cam card?
Are valvesprings too weak?

[TAQuest]

Originally Posted by dmac

Have you checked the timing with vacuum advance connectedto see if you are getting too much advance- either mechanical or vacuum-
at higher rpms?

The vacuum advance is working correctly.

[TAQuest]

Originally Posted by chiphead

Good job eliminating fuel delivery. I watched video. Motor sounds labored or restricted. It sounds like its not pulling crisp. Almost like secondaries aren't opening. Things to check in order:

Is carb opening to WOT?
Is coil good?
How do plugs look, rich, lean, etc?
Is exhaust restricted, heat riser stuck, etc?
Is cam installed correctly per cam card?
Are valvesprings too weak?

WOT is function properly. No cobbled linkage. Installed just like it should be. I swapped the carb with another earlier today.
Tried two different coils.
New plugs. Replaced fairly clean old plugs.
Exhaust is clear.
Haven't looked at the cam.
Valvesprings; These are preassembled Edelbrock Heads with low use. If the springs are weak they were defective. I hear that's a long shot.

[TAQuest]

Originally Posted by Stan Weiss
OK, Pull the valve cover so you can see the valves for number 1. Rotate the crank until the mark on the balance lines up with timing mark. Make sure that this is the overlap TDC where both valves are open. If the intake valve is open more than the exhaust valve, the cam is installed to far advanced.

Stan


I put the covers back on for the test drives today. Before I did I took the picture below of the left side. I'll most likely have them back off tomorrow.
Thanks,

https://share.icloud.com/photos/0EdQ...r_Township,_MI

[TAQuest]

With all the cards on the table this really looks like weak valve springs. Anybody hear of weak springs on these heads? What's the test for weak valve springs?

[72LuxuryLeMansLa.]

remove the springs and have the machine shop test them.

[TAQuest]

Originally Posted by 72LuxuryLeMansLa.

remove the springs and have the machine shop test them.

If I'm going to do that I'm just going to swap them.

What is the best spring for this application?

Thanks

[72LuxuryLeMansLa.]

Originally Posted by TAQuest

If I'm going to do that I'm just going to swap them.

What is the best spring for this application?

Thanks

I,m no expert! Someone else should tell you that. I will say that in my non-expert opinion, there is something that doesn't add up here. An engine pumping 215psi should pound like sledge hammers on pump gas....

[pastry_chef]

Originally Posted by TAQuest

What is the best spring for this application?

The optimal valve spring for that tiny cam won't be the same spring for a higher lift cam. Also determine your installed height.

Do you know of a good shop close by?

[TAQuest]

The plan right now is to take it apart and install a new cam, lifters and valve springs. I can do that myself. Can you recommend the parts for this?
I'm going to do a compression test on all cylinders first to see if they are all 215 psi.
Do they have a good kit with the cam lifters and springs?

[Formulas]

After all thats been checked if 215 is indeed cranking psi i suspect cam position is a strong culprit. What would a 1969 ram air III pump at cranking? I suspect less than 215 psi

[68 Firebird]

my 68 400 with 16's and 068 cam has 182-185 on all cylinders. She was rebuilt 14 years ago and has about 10,000 miles. Gerry

[promptcritical]

E heads come with springs too soft for that tiny cam? Seems doubtful.

[TAQuest]

Either way, the puny cam has got to go. lol

What's that Lunati Voo Doo 703? Is there a kit?

[Squidward]

Kit linked below. The Voodoo cames like a little extra advance, like an extra 2 degrees ICL beyond what the cam card states.

I run it in my 400:
https://www.summitracing.com/parts/lun-10510703lk

I also run Crower cam saver lifters on that engine:
https://www.summitracing.com/parts/c...w/make/pontiac

I used the Lunati lifters as a cam/lifter kit on my 350 with the 702 Voodoo cam, no problems. I thought i would try the cam savers on the 400 build.

Here's a vid of the 703 Voodoo in a 400...
https://youtu.be/w_RmgPVNwMI