LR,

FWIW all the large valve stuff I have run ex) 2.125" valves in a 4.030" bore was done by Larry Meaux per his recomendation, and usually on a 205-215cc port at that.

Bret

 

The stuff Meaux is running with the big valves is 18* according to his post.(not all of it is 18*) That is a bunch different than 23* and large valves.
Not trying to say large valves don't work 'cause they do they just need to be sized for the application and RPM's.
I cut the reliefs in the block (like a BBC)to unshroud even my 2.080 and I think that will do the trick 'cause I couldn't get the flow number I wanted with smaller valves. Could have went with 2.100 and got more flow on the bench but would the engine have seen it with the increased shrouding. Don't know but wasn't willing to take a chance. It has enough flow now to make 700FWHP just need to make sure it all gets in so the engine can use it.

 

[QUOTE=1racerdude]
Not trying to say large valves don't work 'cause they do they just need to be sized for the application and RPM's.
I cut the reliefs in the block (like a BBC)to unshroud even my 2.080 and I think that will do the trick 'cause I couldn't get the flow number I wanted with smaller valves. [QUOTE]

Can you explain this more? Have any pics?

 

[QUOTE=pimpss96][QUOTE=1racerdude]
Not trying to say large valves don't work 'cause they do they just need to be sized for the application and RPM's.
I cut the reliefs in the block (like a BBC)to unshroud even my 2.080 and I think that will do the trick 'cause I couldn't get the flow number I wanted with smaller valves. No pictures and if I told ya I would have to shoot ya. Look at a big block and ya will see.

 

That was just one example was the 18* stuff, i've never seen it hurt going to more valve yet.

Bret

 

I have.

A guy with a BB had a set up down here and wanted more.
He bought another short block that had a bigger stroker and smaller bore and more CID.
He put his heads and intake on it and the car slowed down .2.
He asked everybody what was wrong but never got the answer and he fiddled with it for a year changing cams,intake headers,etc. He took it out and rebored it to the same size as his first engine and freshened it up. Put everything back as it was except the bore and freshen.
The first few passes it got the .2 back plus .15 and he is still fooling with it to get more.

The only thing I figured was valve shrouding. Soooo thats my story and I'm sticking to it.

 

So is there an agreement that the intake valve can be up to, and not much more than 50% of the bore annd still be very effective? So with a 4.030 bore I will be right on the edge with the 2.08? Will this be effective under 6800 or so? Or am I totally off on this?

Troy

 

I would get the AFR 210's opened up and use the ported LT4 intake and then get a cam designed for the cubes, gear, stall, weight, driving style, etc.

You are not gonna get these heads too big for any stroker as long as they are shaped right, the velocity will be there.

Lloyd

 

LR,

That's a big block and the change in bore can be a 1/4 of a inch. A BBC can just make more power with more and more bore. I've seen a head pickup 40cfm flowing it on a 4.5" bore to a 4.25" bore. What I'm talking about is throwing more and more valve in it till it doesn't help anymore, on a SBC with a 23 deg heads. Now if I had a SBC with a 2.18" valve on a 4.125"+ bore then went down to a 4.030" and thought it would work, well you would just have to call me stupid.

Bret

 

BB/SB the principal is the same for shrouding.

 

Kinda.... the canted valves and the bore ranges really really change things. I think shrinking the bore and getting the valve from a 51% of the bore to 54% is probably a big mistake.

Bret

 

So with a 4.03 bore and a 2.08 valve, I am sitting at right around 51.6%...is this ok? Too big? With the right shape of course!


Troy

 

Pimpss96 from the numbers I have seen posted you are right in the ball park at the 52% area. I will have a 4.030 bore and running a 2.05 valve. Again I'm no expert so take what I say with a big dose of salt.

 

Troy,
If it were only as easy as this simple math...

DC determines the heads performance ultimately against the valve. 50% to bore is common against most porting techniques... It really takes some talent to get up in the lower 50's. Though...with the wrong port, you can have a junk head at 48% or at 58%...doesn't really matter.

I have done a good bit of 2.15+ stuff on 4" bores. It certainly does work...but takes every last bit to make work.

Talk to Lloyd and see what he says. If either have any questions...I am availible.

Dennis

 

Thanks Dennis.

Bret