Chris1973Rr
Well-Known Member
So my dad is giving me a set f 906 heads for my 383. Anyone have a general idea what the hp increase would be?
906 Heads Hp Increase?
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1967coronet440
Well-Known Member
Any porting? Valve job? Oversized valves? Either way it’s probaly going to minimal.
F castings get good flow numbers stock. Are they fresh? If not a good cleanup, valve job changing to stainless valves will help.
Officer Higgins
Well-Known Member
Open chamber heads, so many aftermarket heads now days makes the old heads seem lame but those iron heads did fine on those cars back then, and do now im using my original 915 closed chamber heads. And my car scoots very well and its cool to me to look original. Glad to hear your dad gave you those get good multi angle valve job use good quality valve springs. And not currently produced mopar springs either person in the know who used to recommend those had some valve train failures attributed to those current springs from forensic investigation of the springs. That said recommendation now are Manley springs from summit or jegs those springs are manufactured here in the usa and it does make a difference. I can find part number for springs if your interested.
PurpleBeeper
Well-Known Member
906's are good heads, but honestly the ports/valves are roughly the same as all the other iron heads. The good part is that they have larger exhaust valves vs. pre-'68 383's. The bad part is that they provide less compression vs. the pre-'68 383's and they don't have hardened valve seats like the '73+ heads. 68-71 383's used 906 heads stock. Don't get me wrong, they're good heads.
BSB67
Well-Known Member
What's on it now?
66Satellite47
Well-Known Member
Like others have said, depends on what you have now. 906's are very good iron heads, with a basic "pocket port" & a good valve job lots of power/torque gained. If you have pre-68 heads, you lose CR, but get bigger valves. That may or may not be a bad thing, depends on driving, performance expectations, fuel availability & lots of stuff. A 906 with good valve guides, pocket ported, good valve job is just great. If you want more power than a 906, modern aluminum heads are the answer, but then you need more CR. Good luck.
A related question - since the 906 heads had somewhat larger combustion chambers, was their a piston change in 68 -70 to maintain compression or did the real compression ratio go down after 1967 on 4bbl engines with 915 heads?
Officer Higgins
Well-Known Member
interesting question waiting to hear i sure dont know. I do know real 440 is turquoise and has 915 heads lol.
IQ52
Well-Known Member
You have a 1968 383 engine with 906 heads right now. No gain unless you do some work to the 906 heads you have been given......Unless the 383 was originally a 2bbl with the 250 head castings. Aaaaannd nope, I see it is from a '68 Road Runner.
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BSB67
Well-Known Member
The OP is asking about a 383, which never had 915 heads, but maybe 516.
And yes there was a piston change for both 383s and 440s from 67 to 68.
66Satellite47
Well-Known Member
As far as CR goes, you REALLY need to measure EVERYTHING. Otherwise it's a guess. 516 & 915 had the smaller closed chambers, the 906 & later had the larger open chambers. Advertised CR's are just that, advertisements. The 915, 906 & later had the 2.08/1.74 valves. A change from an early 383 516 head to a 906 gets a little more power IMHO, due to the larger valves & better intake port. Real power gains come from "pocket porting", good valve job & good valve guides, with any BB head.
I would guess so - remembering back to my high school and early college years my 64 383 Commando Sport Fury was a pretty strong performer in low gears and low to mid range rpm. But in 3rd gear getting up around 85 to 90 mph you could really tell it was starting to flatten off which I always attributed to the heads. A 280 Crowler cam did nothing but kill the low end and still struggled when it had to breath hard.
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Stock heads will benefit greatly by just cleaning up (porting) the valve pockets. This area has always been terrible from the factory.....
66Satellite47
Well-Known Member
For all you that are out there with any OEM BB head, a bit, or more grinding under the valve seat makes a lot of added power. If you have some courage & a die grinder, lots of power gain.
wyrmrider
Well-Known Member
most 915 had 1.6 exhausts only the HP had the 1.74
good thing is the 1.74 slip right in and you get new seats
OP can you look and see for sure what you have now.
If you have the time- meaning the car runs ok now no burned valves etc
take the time to do your new heads and do a swap
if your seats are bad go to the popular larger valves 2.14 x 1.81
good guides are the key
rough in the valve job and do the pocket port or DC Templet procdure
good thing is the 1.74 slip right in and you get new seats
OP can you look and see for sure what you have now.
If you have the time- meaning the car runs ok now no burned valves etc
take the time to do your new heads and do a swap
if your seats are bad go to the popular larger valves 2.14 x 1.81
good guides are the key
rough in the valve job and do the pocket port or DC Templet procdure
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