[1965gp]

I had a 400 built by a highly recommended local builder for my 66 GTO.

It’s a 77 TA 6.6 block with #62 heads. Summit 2802 cam. ‘65 Tri Power set up rebuilt by another local well known builder. Nothing fancy, just fun and reliable. Enough to turn the tires over and look cool.

I was driving at about 2000 rpm and heard a bang and then a few knocks, then it felt like it was missing. This is about 300 miles on the motor. When we pulled the valve cover an intake and exhaust rocker were off to the side and the push rods were laying in the valley area.

I have used this shop for years and are close friends with them. This guy builds all of their motors and they said he has only had one issue and he took care of it right away. The engine builder has been very active in trying to get it resolved.

We put new push rods in it and the shop is saying that it runs great until it warms up. Once it gets hot it starts to get a rougher idle and they feel like the exhaust valves are sticking which could definitely break a push rod.

The engine builder pointed out that while it is an original Tri Power jetted for a 389, it’s now a bored out 400 with an aggressive cam and it isn’t getting enough fuel making it run lean. Running lean the exhaust is supposedly getting hot and causing the valves to stick.

Now, I am not an engine builder by any means, but I have 400’s and 455’s that run on quadrajets all day with the small primaries. Is that more fuel than a center Tri Power carb?

They said the exhaust was getting up to around 600 deg, but the engine never seemed to run hot so is that possible?

I don’t want to cause problems but I also dont want to get stuck with a car I’m scared to drive.

Thoughts?

[Lee]

Wrong valve springs, and/or push rods that are way too long. Rookie mistake, either way.

[ID67goat]

In the picture, the cam lobes don't line up with the lifters very well which looks strange.

I agree with Lee, normally coil bind, pushrods, etc......maybe valve guide clearance is too tight and sticks the valve and bends the pushrods?

[1965gp]

It should be able to use stock pushrods right?

Lee I should have just put that 350 in it!

[Brian Baker]

Originally Posted by 1965gp

It should be able to use stock pushrods right?

Lee I should have just put that 350 in it!

Once you go with an aftermarket cam, which could have a different base circle height from a factory cam (on the lobe), and factor in machine work to block deck surface and/or cylinder head combustion chamber surface, etc. etc. etc...all of those variances add up and the notion that stock length pushrods can be used without measuring anything can be thrown out the window.

Engine should be checked for proper pushrod length at assembly, and lash set accordingly (ie - torqueing the rocker nut to 20 ft/lbs will no longer cut it).

[Tim Corcoran]

It is possible that if the exhaust temperature gets too high from a lean mixture the exhaust valves could bind in the valve guides. And it's possible that the valve to valve guide clearance is too tight and that can cause your valves to stick hard enough to do what you have. As already mentioned it could be wrong length pushrods, coil bind or valve guide to retainer interference. Anytime you make changes to your valve train, like a different cam, different rocker arms different heads etc. you must check the valve train geometry and get the correct length pushrods. Also you need to make sure your valve springs are correct for the new cam. Valve springs are not one size fits all same as the pushrods. The first thing I would check is the valve train geometry and check for coil bind. I don't think your problem originated from a lean mixture although it's possible but it may be tight valve guide.

[Joe's Garage]

We've seen a few rebuilds by non-Pontiac shops where it was left out.

It plays havoc with the valvetrain, lifters, pushrods and rockers, and could very well cause a problem like you're experiencing.

How much forward and back movement is there at the camshaft? Gently pry forward and back with a tape-covered screwdriver or dowel so as not to damage any lobes. Movement should be minimal.

Good luck!

[steve25]

Could you please pull the valve covers and take some clear pictures of each side?

[grandam1979]

Using adjustable lock nuts ( poly locks)?

[steve25]

Now that I look at those Cam spec' s it has too much lift if the tops of the Exh valve guides where not cut down for more retainer to guide clearance, especially if positive Exh valve seals where added, or if longer then the stock 5.095" valve lengths where not used!

Also stock springs can not be used with this Cam and the Intake valve retainers may be very close to hitting the tops of the valve guide seals with that .466" lift of that Cam.

I am willing to bet the OP of this a Macdonald's lunch that what I posted about first here is the cause of his bent push Rods if a adjustment nut or poly lock did not back off?

And with that said if they do back off then 90% of the times the push Rods do not bend from the result of that issue!

As I see it from here all of your problems fall squarely on your engine builders shoulders as he is responsible for making the needed checks!

Also casting 62 heads will not work with 389 / 421 lenght push Rods, which is something else to confirm.
The needed push Rods should be 9.130" long .

[1965gp]

Thank you guys- I am traveling for work this week but will try to get some pics this weekend when I get back in town.

I’m glad I asked- while I can see a lean mixture causing this I think it would be rare.

One question- the shop said the car runs great until it gets hot. Would this happen with the incorrect push rod length? I do not think it has poly locks on it but I will verify

[68lemans462]

Originally Posted by 1965gp

Thank you guys- I am traveling for work this week but will try to get some pics this weekend when I get back in town.

I’m glad I asked- while I can see a lean mixture causing this I think it would be rare.

One question- the shop said the car runs great until it gets hot. Would this happen with the incorrect push rod length? I do not think it has poly locks on it but I will verify

This has absolutely NOTHING to do with a lean mixture. Looks obvious that the valvetrain geometry is FUBAR. As others have said, check valve springs and pushrod length. If your builder thinks this is due to a lean mixture I would be questioning their competency, and RUNNING IN THE OTHER DIRECTION!

[steve25]

Sorry, to correct myself, the needed push rod lenght will be for a starting point somewhere in the 9.130" lenght.
This depends as has been posted in the base circle height of the new Cam and if a valve job was done to the heads which I assume is the case.

["QUICK-SILVER"]

Last Pontiac I saw that did this... Looked identical to the OP's valley pic.

Not a single oil puddle in sight. Not even the tops of lifters.

Replaced parts and FIVE quarts of oil had it back on the road and sounding like it was going to survive.


Ignition timing too low for RPM will super heat exhaust without the engine temps running way too hot. I've popped hoods on Pontiacs and seen exhaust ports and log manifolds glowing red hot from ignition timing being too low.
This happens a lot when people pull timing out for no ping on pump gas with high compression.

About the carbs:
Fuel flow goes up with more air flow. More cubes doesn't change the fuel/air mixture the carb supplies. Using 100% for VE and displacement.. A 400 flows 6 more CFM's at 2,000 RPM's than a 389 at 2,000 RPM's.

Something else going on here?
Clay

[steve25]

Very very good point made here in post 14, that lifter valley looks far too dry , and even the push Rods have no oil film on them!

If Exh valves are sticking it's due to that lack of oil, not jetting.

[John Milner]

I highly doubt your tripower is causing this. I ran a stock jetted 65 tripower on the exact same engine combination that you are running (400, 62 heads, 2802 cam) and it ran fine with the stock jetting. I'd be checking oiling, pushrod length, valve length and I would change to BBC rocker studs if they have not done that already. 62 head do take a longer valve than later model heads. If they put later model shorter valves in the heads your stem height will be way off causing the valve train geometry to be way off and could bend pushrods, especially if they are used the stock bottle neck studs/nuts.

[72projectbird]

I've had engines running super lean, and have never had something like that happen. I'm not saying it's impossible, but it's highly unlikely.

[Half-Inch Stud]

Bone dry valley. Tappity tap would be evident if the Right Rear Galley plug was left out. Got an Oil pressure gauge that shows anything relevant?

Tight exhaust valve guides are no fun; Running history of the 62 Heads or were the guides reworked?

Summit 2802 is .470/.490" lift with 1.5:1 and would seem okay if installed on-time.
Is the Cam Break-in in question, as well?

Since it looks like BOTH #6 Intake and Exhaust: #6 exhaust failed to open, then Number #6 Intake could not open under pressure and it too failed. Tight EXH guide(s). Gets real hot when there is no oil to pull the heat away.

[Skip Fix]

I like to pre oil with the valley pan off too. Lets you see where oil is going.

Coil bind,rocker bind something.

[torqhead]

Originally Posted by "QUICK-SILVER"

Last Pontiac I saw that did this... Looked identical to the OP's valley pic.

Not a single oil puddle in sight. Not even the tops of lifters.

Replaced parts and FIVE quarts of oil had it back on the road and sounding like it was going to survive.


Ignition timing too low for RPM will super heat exhaust without the engine temps running way too hot. I've popped hoods on Pontiacs and seen exhaust ports and log manifolds glowing red hot from ignition timing being too low.
This happens a lot when people pull timing out for no ping on pump gas with high compression.

About the carbs:
Fuel flow goes up with more air flow. More cubes doesn't change the fuel/air mixture the carb supplies. Using 100% for VE and displacement.. A 400 flows 6 more CFM's at 2,000 RPM's than a 389 at 2,000 RPM's.

Something else going on here?
Clay

As Clay said, there's an oil problem here and pretty obvious. All other input is a waste of time to pursue at this point. I'm amazed you have driven it as much as you have and gotten away with running it this long without more issues.