Hanging valve?...NO, and another update

[cjshaker]

Are you sure you're not getting icing on or in the carb?.....

No carb on this one! 

I suppose that would make a difference in carb icing..lol

[Pentroof]

This morning I checked the temperature of the header pipes just after starting the motor.

Cylinders 3,4,7,8 are running cold at initial start. After warming for 2 minutes, all fine.

For the record, it’s a dual plane.

I’ll report once I get the covers off, but it looks like I’ll be re-setting all of them.

I find it strange that I’m not getting any popping through the carb, if it was a procedural thing.

[fryedaddy]

I think my t-stat is stuck open.my 428 dont start warming up for at least 15-20 minutes.if i take right off after 1 or 2 minutes of warmup it sounds awful for a mile or two,super cold natured.but when the temp gets up to 150 and above,it gets crisp and peppy and ready for anything till i shut her down

[Pentroof]

I think my t-stat is stuck open.my 428 dont start warming up for at least 15-20 minutes.if i take right off after 1 or 2 minutes of warmup it sounds awful for a mile or two,super cold natured.but when the temp gets up to 150 and above,it gets crisp and peppy and ready for anything till i shut her down

That is generally a cold start issue related to fuel delivery. In my case, I’m running EFI and I’m confident in the tune. There is no question that I have exhaust valves that aren’t closing completely when cold. I’ll get into it this weekend.

[My427stang]

I think my t-stat is stuck open.my 428 dont start warming up for at least 15-20 minutes.if i take right off after 1 or 2 minutes of warmup it sounds awful for a mile or two,super cold natured.but when the temp gets up to 150 and above,it gets crisp and peppy and ready for anything till i shut her down

That is generally a cold start issue related to fuel delivery. In my case, I’m running EFI and I’m confident in the tune. There is no question that I have exhaust valves that aren’t closing completely when cold. I’ll get into it this weekend.

Do you have the tools to do a cold leak down test?  Even if no gauge, just air may let you listen to a pipe

[Pentroof]

Yes, I have a set of leak-down gauges. Not a bad idea to confirm before I just start resetting the lash.

[Stangman]

Just a thought but valves should be adjusted properly before a leak down test no?

[My427stang]

Just a thought but valves should be adjusted properly before a leak down test no?

The idea is to verify that it is indeed a compression problem.  If it is a tight valve, you'll have big leak down numbers and noise out of the intake or exhaust depending on which valve is tight

[Pentroof]

Compression is good...which is another lesson to me that assuming isn’t the same as verifying.
Spark is good.
Rear cylinders still not firing when cold. Temp gun confirms, directly at each header pipe at the flange.

Started and shut down before the rear cylinders started firing (which they do, once things start warming up). Pulled the plugs and rear cylinders are dry and very light, as compared to the front cylinders.

So, my new theory is this Police Interceptor intake is not playing nice with the Holley Sniper. Sniper is only delivering fuel to the front bores at idle.

No vacuum leaks that I can tell, but my next move will be to pull and plug the brake booster...that’s at the rear center of the throttle body. I’ve got no other indicators that the booster is an issue, but I’m done assuming.

Anyone else experience this scenario with the PI, or any other dual plane?

[1968galaxie]

Certainly sounds like an EFI issue.
I have never liked the electronic carb type efi.
I prefer individual injectors for each cylinder.

I am sure you will figure this out. Have you sent a message to Holley?

[GerryP]

Just for giggles, throw plugs that are a couple heat ranges hotter in those non-firing cylinders.

[Pentroof]

Certainly sounds like an EFI issue.
I have never liked the electronic carb type efi.
I prefer individual injectors for each cylinder.

I am sure you will figure this out. Have you sent a message to Holley?

I’m a member on their forums...I posted over there, yes. I’m concerned that the progressive linkage and programming I have added may be the issue (even though offered by Holley). The rear two injectors do not flow during idle...at all.

I’m also using a a 4 hole carb insulator that could be contributing, as opposed to an open spacer. I don’t know.

[1968galaxie]

Do you know someone with a 735 Holley carb you could throw on?

[Cyclone03]

Wow efi and a dual plane....where have I heard questions about that?

Mixture distribution is a thing even with efi, if you have the clearance above the intake put a 1 inch or maybe more OPEN spacer on it and give it a try before you drive yourself nuts retuning.

Signal to the map sensor sometimes suffers with dual planes.

You may have the lifters tight too. Back the adjusters off 1/4 as suggested.
I’ve never had luck with the spin push rod till it drags adjustment method , I adjust till there is no up and down lash,or slack,then add 1/2 -1/4.

I’m running Brents non adjustable rollers so all my push rods are measured length plus .050.

[Pentroof]

Do you know someone with a 735 Holley carb you could throw on?

I have a 600 Holley from my GT motor, but I’m not going there. I know what you’re thinking, but the fuel supply would have to be rigged and I have the EFI controlling my timing.