Can of worms, gt40p related (p for pain)

[Helmantel]

That makes sense. Your stock push rod basically had no play but zero clearance. Your new ones which are .200" longer take three turns from zero, which is about
.200" preload, which is too much.

What you need is a set of push rods that are ~.030" longer than your old ones.

If you're lucky, there's a stock application that has the correct lenght. There have been all kind of lenghts, over the 4 decades that Ford made small blocks. For example, they got longer some time in 1966, along with the switch to rail type rockers.

Otherwise, you can get custom ones from Comp Cams and others, but they may be more expensive.

 

[DJCarbine]

Well it explains the lack of performance because valves may be getting held open too long, lowering compression.
I'll get some measurements in the next hour or so, as well as side by side pictures of stock vs the ones in there now pushrods

 

[DJCarbine]

Ah. I double checked the rockers, the point from 0 preload to fully tight was about 1/4-1/2 a turn. That seems about right. The stock pushrod vs the longer ones is about the thickness of a penny.

Of course it takes 4 turns to tighten down some of them, because I should have realized that they were the ones with the valve open. I really should stop drinking while working on the car.

 

[Helmantel]

Problem solved. Now go work on your drinking problem

 

[DJCarbine]

Problem solved. Now go work on your drinking problem

I tell you what, a shot of rum before a 4 hour class makes it so much easier. The fact that the 4 hour class is spent watching obscure 1905 animated cartoons and popeye the sailor man makes it so much better

 

[bnickel]

I tell you what, a shot of rum before a 4 hour class makes it so much easier. The fact that the 4 hour class is spent watching obscure 1905 animated cartoons and popeye the sailor man makes it so much better

i don't know man, sounds to me like you should spark up a doobie before that class i don't even smoke anymore (since high school and that was a long time ago ) but i would do it before that class and laugh my ass off through the whole thing.

 

[D.Hearne]

Stock pushrods were and are available in .060 over or under sizes. Many cam companies sell these as well.

 

[RXTbone]

Did the header question get answered?

I'm about to pull a set of GT40P's off a 5.0, because I can't find a pair of headers to fit a '66 Mustang w/MS and a 4 speed...

 

[wicked93gs]

port some HiPo manifolds then, you know they will fit...I hear some headers will work with the P heads if you use a combination of straight and angled plug boots...dont know though(yet anyway, havent picked up a set of P heads just yet)

 

[bnickel]

Did the header question get answered?

I'm about to pull a set of GT40P's off a 5.0, because I can't find a pair of headers to fit a '66 Mustang w/MS and a 4 speed...

yeah post #4

 

[12sec67]

just called melvins and he said the new price is 310-325 but he has to check...

 

[Hack]

That may be true, but that doesn't mean that increasing the LSA increases the effective compression ratio. The effective compression ratio is the ratio between the cylinder volume at intake valve closing, divided by the volume at TDC (I guess you knew that already). Making the LSA wider, retards intake valve closing, so the volume at IVC is reduced and thus the effective compression ratio is lower.

I'm a little late to the discussion, but I know that D. Hearne and bnickel are correct on this one.

I'm pretty sure that a wider LSA means that the intake closes EARLIER. That's why you think that wider LSA gives less dynamic compression, because you have that one detail reversed.

I'm positive that a narrow LSA = lower dynamic compression and a wider LSA = higher dynamic compression.