I'm doing a set of RHS heads for a customer going on a 408 that I thought might be interesting to post here.
What I'm doing is porting them heavy, beehive springs, 8mm stem valves.
It's a 408 he had built before he knew of me. Compression will be 10.2:1, solid cam (256-260 .590/600 net on 106lca)Hughes 1.6 rockers, M1 intake I ported the plenum, someone else did the port match.
I'll have it on the dyno in a week or so but I thought I'd post pics and some info.

With the intake on I've got 260cfm @.500, 268cfm @.550 and 272cfm @.600.
That was after the plenum porting. Most I got before the porting was 252cfm at any lift above .500!

Cut the spring pads down .100 with my cutter to locate 26918 beehive springs.
After sonic checking the spring pads, they are roughly .300 thick before machining so plenty of material unless you port too much below them in the bowl's roof!!

26918 spring:

8mm valves, 2.00 intake and 1.60 ex. and beehive springs:

The chambers cam in at 67-68cc even though they are advertised at 62!! I double checked them!

I also sonic tested the bowls to see how far I could push them and it's a good thing I did! There is water surronding the intake port bad!

After this porting, I found .180-.190 on both sides of the bowl. So IMO a 2.00 intake valve is about the limit if you want to keep some VENTURI in the bowl.

Intake opening: Lets say at .550 lift air speed is 327fps!!

Ex. port is very nice. I cut the valve job deeper than they come OOTB to help with chamber transition and help installed height.
I.H. will be 1.780 but 1.800 can be had by cutting down a little farther.

Ex. port went 200cfm at .500 lift with nothing more than slight guide boss slimming, and usual seat cut/blending. No port work was done, just minimal bowl blending. That flow was with a 1 3/4 pipe.

M1 before plenum work:

M1 after plenum work:

Thanks for sharing.

Todd

looking good. Thanks for the great info and pics!!

Thanks for sharing can't wait to here the final results.

Thanks for sharing Brian
Ran

Looks good Brian, Nicer looking then the first guys attempt. LOL

Hey Jesse.

I think 327 fps was "as cast". I was going to ask about the
enterance pictures and sizes after he opened them up.

How's it goin Vic?

I thought I could see some carbide marks but you are probably right-as cast. p.s. You guys going to enter EMC 2010? J.Rob

Quote:

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You guys going to enter EMC 2010?

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I'm not sure. We'll have to wait until after the PRI show for the new rules.

Keep up the good info, Brian.