69Fury3

I have a 1968 440 i am currently building. The engine originally had 906 heads on it and i am thinking about putting 915's on (aluminums are out of my budget). I was wandering if this is worth my while. I have heard good things about these heads but have also heard that i might bump my compression up too high? This is the first 440 i have ever built as you can tell.

67 GTX

if you have stock compression for with the 906 heads, the 915 heads will jump compression to 13 to 1, and the tops of the pistons have to be grounded down a little

69Fury3

13:1 ?! That is a little excessive. I am trying to up my compression a little, but not that high. Would i be better off having these heads shaved or is there another casting number that would work better? Just out of curiosity what kind of compreccion could i make and still run pump?

67 GTX

10-1 is pretty much the limit for the 93 octane that we have

69Fury3

I believe 1968 440 with 906 are 10:1 stock, correct?

78D200

Those 915 heads would be great for a super charged BB.

69Fury3

I definately don't plan on super charging the engine but it would be really cool! Do you think it is worth swapping the heads out? I plan on having them ported (i know this is expensive, but cheaper than aluminum) but i have heard that the closed chamber design works better than the 906's open chambers.

67 GTX

the 906's were more an emissions head (i know they came out years before 72)
915 heads give a better flame front

78D200

I would leave the 906 heads on it and build them how you want.

69Fury3

Like i said this is the first RB i have ever built so i don't know much about them. I appreciate your input because i haven't had experience with either head design (i bought this motor already pulled). I have already got a few parts for the motor such as an Edelbrock RPM intake, Mopar prurple .509/.509 248in 248ex 108*centerline, and TTI full tube C-body headers. I am pretty sure having the heads ported would help quite a bit and that is next on the agenda if you don't think 915's are worth it.

67 GTX

i like the 915 better than the 906, but that just my opinion

69Fury3

I have heard good things about those heads but now i am afraid of what my compression ratio may turn out to be. If these heads wind up giving me 10.2:1 plus i am putting in a cam w/ over .500 lift i don't know if i will be able to run pump gas.

theomahamoparguy

the bad part about the 915's is just trying to find a set of them; short production span! 906's work good on a street car. BTW, a bigger cam [longer duration] will reduce your cranking pressure and make engine more pump gas friendly. Just keep the cranking pressure less than 150 psi with the iron headed big blocks, should get by with 92 octane with correct timing.

69Fury3

Is there a way to tell what my cylinder pressure will be without being able to start the motor? I do plan on having hardened valve seats installed on these heads if that makes any difference concerning the allowable cylinder pressure.

theomahamoparguy

There is a rough way to calculate it, dont have the info at hand
but I think you will be fine with the 509 cam and the 906 heads. also depends on the pistons. [stock pistons;no worries] My friend had a similar combo and was fine, [I'll try and find a calculation to use and post later]. Valve seats wont affect comp. unless severely worn out [sunk].

deadkelly

heads are everything this is where you spend your money . port the heads for sure , to make the most out your package . there's around 50 -75 hp in a basic port job . you will want 1 piece valves also too rev safely . heads always cost money , this is were the fun is .

rr69half6bbl

If you can afford a few more hundred bucks have bigger valves installed. i run the .509 cam and 906 heads on all my 440`s and never have a prob. I use trw 10.2-1 domed top forged pistons, then they install 2.14 intake and 1.88 exhaust valves in the heads, My machine work I have around 650.00 for all the work. you can do the port work yourself at home with a handdrill, just get the porting templates from a speed source like summit racing or mopar perf. I use the felpro thick head gaskets, like .39 thou thick. and run 93 octane gas no prob. when you port out the heads also port match the intake to them, or there isnt any sense in doing it. you have to have the same amount of space from 1 pc. to the next for it to have the desired effect. just lay a papper intake gasket up against the intake, color the metal with a highlighter around the inside of the gasket , then using an auger bit just start cleaning the inside of the intake ports till the colorings gone. The 915`s are a great head, but like earlier posts. theyre harder to find and more expensive, the cost difference to obtain a sets not worth the time to get them. good luck.

theomahamoparguy

Here is a "dynamic" compression calculator

http://www.kb-silvolite.com/calc.php?action=comp

I think you need to stay under 7.5 DYNAMIC COMPRESSION for 92 octane

69Fury3

I am running stock pistons on this motor. The next thing on my list will definately be having these heads ported and polished (maybe larger valves if the wallet allows it). Thanks for the link, i'll throw my numbers in it and see what i get. Also, i was wondering about my rocker arms, they are the stock stamped pieces. I really don't want to spend the money on roller rockers (running a hydraulic cam), but was thinking about putting new 1.5 or 1.6's in. If i did the math correctly 1.6's would give me somewhere in the neighborhood of .543in. lift. I don't want to lose my low end power or have valve clearance problems and like i said before it needs to run on pump. Just an idea i was throwing around but don't really know the reprocussions...

deadkelly

are those anti pump lifters ? 106* is getting a bit full on . 1.6 ratio rockers is the best way to keep your duration down , with hydraulic cams .
mate this thing will hammer with ported heads & 1.6 rockers + 509 cam

69Fury3

Do you think with that kind of lift and 1.6 rockers i will still be able to run on pump? Running on pump is a must. Also, the intake i got is matchef for this cam's power range (2200-6200) will this have a signifigant change on my power band?

Garys69RR

Well what did you end up doing? I think yhe 915 is the best head. But need to watch the compression. Use the calculator on the keith black pistons site to get an idea of where you will be on static compression. Go .015 deck clearance, .020 gaskets with flat top istons, and it should run great on premium 93 octane.