906 valve size and cc
- Thread starter sc440
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Doorkicker
Well-Known Member
How much bigger are you going? Like @Lefty71 said, prolly not a lot change. The CC is listed at 80cc and with valve sizes of 2.080/1.740, the max you can probably get to is less than 2.18/1.78, which frankly isn't going to take much up from the stem, just not dished - so, -4 cc ish? Not to mention you're likely spending a lot of $$. May be better off with looking at cams and/or rocker ratio before beefing up the valves. Dunno... it all depends on the rest of the engine. Are you trying to reduce cc's or just curious what it would be after you change the valves?
sc440
Well-Known Member
just trying to figure out what heads I am going to run on a 440 I am building. Mild street engine icon .03 over 836 pistons-(12cc )molnar rods, stock stroke, exhaust manifolds and custom bullet sft cam. Was talking with Nick jr from Computer flow about some 906’s he is doing up, but might have home go through some stealth’s or really for the money might just go tf 240’s was really wanting to stay with a closed chamber with the pistons a have and to get quench
516, 915, stealth, tf240.
BSB67
Well-Known Member
I have a set of 836s and a couple sets of 915 heads laying around here that I’m planning to put together one day on a manifold motor.
Anyways, you really cannot answer the question without specifics. If it has 2.08s now that have had a couple low dollar valve grinds, and you switch to a thick margin 2.14/1.81 SS valve, it will be at least 4cc. But it is not the path to take if the only goal is to reduce head volume. Used 906 will be 90 to 92 cc. You could get it to the low 80’s with the valves and milling. Probably should unshroud the valves and do some bowl work. Add springs, guides, retainers, keepers and your probably past the cost of aluminum, but without quench.
Isnt the small combustion E. Street head like 75 ccs? It might be the one for you.
Anyways, you really cannot answer the question without specifics. If it has 2.08s now that have had a couple low dollar valve grinds, and you switch to a thick margin 2.14/1.81 SS valve, it will be at least 4cc. But it is not the path to take if the only goal is to reduce head volume. Used 906 will be 90 to 92 cc. You could get it to the low 80’s with the valves and milling. Probably should unshroud the valves and do some bowl work. Add springs, guides, retainers, keepers and your probably past the cost of aluminum, but without quench.
Isnt the small combustion E. Street head like 75 ccs? It might be the one for you.
The 836 is a reverse D type piston, intended to allow quench and a 9.2-9.5 C/R with a 915 style (closed chamber) head.... Using them with 906's is a mistake IMO...
BSB67
Well-Known Member
I think the intended application for the 836 was for closed chamber aluminum heads. I'm at 10.1 CR with my 915s.
Certainly not a good fit for open chamber heads considering all of todays options
Certainly not a good fit for open chamber heads considering all of todays options
sc440
Well-Known Member
Need to talk to Nick about how much these (the 75cc e streets)would cost to get them ready to run pretty sure valve job needs redone. Springs could probably be used they are $1563 for the pair + what ever needs fixed. I have some older adjustable direct connection rockers that I ran on another engine could they be used on the e streets? If it gets to close to tf 240 $$ idk
sc440
Well-Known Member
I was thinking the same thing. I was originally intending on going closed chamber. But wanted opinions on the 906’s
What do your chambers cc at? I've opened my chambers out to the cylinder bore, bolted the heads to the bare machined block & scribed the bore on the head, then opened the chambers to the line & blended it out... Polished the chambers, 2.14 & 1.88 valves... They cc at 82-83 cc's... pistons are .012 in the hole & head gasket is .039 compressed... The Wallace racing calculator shows 9.48...
I agree aluminum heads especially with small chambers would also be a very good match....
sc440
Well-Known Member
Are you using the 915’s?
Yes... I'm building a visually stock engine.. I want iron heads & exhaust manifolds... But it's gotta run..
BSB67
Well-Known Member
Two sets.
One is 77cc. They have 2.08/1.74 stainless valves with one grind on the valves, and one on the seats. Heads had a 0.010" clean-up.
Other set is at 78 cc. Std replacement valves w/ one grind, head clean-up.
BSB67
Well-Known Member
My plan as well. Are you using the 836?
If you were so inclined there are a few cc's hiding behind un-needed cast iron...
Yup 836...
BSB67
Well-Known Member
Oh yes. I've run these heads in the past as is, and want to try them again unchanged on a better motor. Then go back and upgrade the heads.
Post Your 13 Second Combos
Last edited:
4406bbl
Well-Known Member
I did this exact procedure with 915 heads, traced to the block, thick margins 2.08/1.74 valves, no milling on head gasket surface, flat spots in chamber milled .040 so all are the same, every chamber is 84cc. Pic before valve job. Bigger valves will not lower ccs much.
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