help on performance decision

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duster731 said:
Ooo ok lol I'm upgrading the valves from the stock 178-150 to 188-160
Click to expand...

you know what, my bad...I keep thinking 360 heads.

Just know you can easily get 215 cfm with porting using the 1.78 valve, but the 1.88 should make it easier.

on the 318 exhuast...thats a good port, i get 145-155cfm easy with porting and valve job.
 
1wild&crazyguy said:
you know what, my bad...I keep thinking 360 heads.

Just know you can easily get 215 cfm with porting using the 1.78 valve, but the 1.88 should make it easier.

on the 318 exhuast...thats a good port, i get 145-155cfm easy with porting and valve job.
Click to expand...

With stock pistons would that not drop compression, or does it remain due to the closed chamber?. We have about the same combo's and I have been considering the 302's for a couple of years now. Just haven't quite decided yet.
 
Well it depends on the valves head/face and wether it's cupped or not, then consider how much higher the bigger valve will sit.

the 'tiny' gain would not be noticable in the compression depot.imo

not as much as if you milled .020 off the head, that would show 'at least 5 psi'* gain in dynamic compression, from my experience.
 
By milling off 0.20 would you need to get shorter rods? Or what's the max you can mill off without effecting the geometry of the drivetrain
 
Do you mean 0.20" or .020"? Big difference. Just .020", then no new pushrods shouldn't be required. But 0.20" is .200", so yeah, you'd need um then.....but you'd have a mighty thin deck.
 
duster731 said:
.020 lol what's the most I can take off the heads without the geometry changing
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Nevermind. I responded thinkin this was a slant discussion. Been another night with no sleep. Sorry.
 
duster731 said:
.020 lol what's the most I can take off the heads without the geometry changing
Click to expand...

As much as you want. Milling the heads or deck does not affect valve train geometry on a rocker shaft mounted system. It does affect the pushrod length but tha''s not the same as geometry. I don't think anyone can guess how much you can mill off without affecting he pushrod length because there are manufacturing tolerances that vary to affect things. You should always measure for proper pushrod length when doing a performance build.
 
fishy68 said:
As much as you want. Milling the heads or deck does not affect valve train geometry on a rocker shaft mounted system. It does affect the pushrod length but tha''s not the same as geometry. I don't think anyone can guess how much you can mill off without affecting he pushrod length because there are manufacturing tolerances that vary to affect things. You should always measure for proper pushrod length when doing a performance build.
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If I were to mill .030 off of the heads that means I should shorten the push rods .030 right? Or buy new ones that are .030 shorter then stock length and how much milling does it take to bump the cr up a number
 
Easiest thing to do is use adjustable rockers.
 
duster731 said:
If I were to mill .030 off of the heads that means I should shorten the push rods .030 right? Or buy new ones that are .030 shorter then stock length and how much milling does it take to bump the cr up a number
Click to expand...

Theoretically yes but if you will re-read my last post you will find the true answer. I said no one can guess what length pushrod you need because of manufacturing tolerances in blocks and heads. YOU NEED TO MEASURE FOR PROPER PUSHROD LENGTH, NOT JUST GUESS AT IT. If you guess at it and get it wrong you can destroy parts.

I have no idea on how much to mill the heads to bump up the compression. Maybe someone else can answer that.
 
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