which motor to use my 915s on?

[goose69]

I'm building a totally budget 440 for my Saturday night cruiser/race car (1966 Belvedere, primer black, mini tubbed, probably nitrous). Well here is the deal. I bought this car so I can have something to drive and thrash a bit while I build my Roadrunner. I have a nice pair of 915s with some heavy springs and nice valves in them that I'd like to use. The motors I have to put them on are as follows (all stock bottom end motors by the way and that's what I want to stick with): 1)1969 440, 1)1970 440, 1)1975 440, 1) 1978 440. I am looking for suggestions on a combo to put together here and not wanting my compression to skyrocket (so I can run pump gas)or have detonation problems. I know ideally people say not to use these heads on a 70's motor but will it really hurt or has anyone done that combo with success of failure?
Thanks for the help.

 

[696pack]

It should make no difference which of those engines you run those 915 heads on.

 

[goose69]

Well being the 69 motor is a 0 deck clearance motor I believe it comes out to having almost 13-1 compression and the 70's motors have the pistons I believe .80 in the hole and ending up with about 9.5-1 compression (these numbers with the 915's installed), but not sure if the quench on the 70's motor will work out.

 

[696pack]

It sounds like you are making a lot of assumptions.

You need to check the heads and each block as many things may have happened over the years such as milled heads and blocks.

The point is they are all 440 block which were basically the same from the factory and the 915s were 1967 440 heads which will work on ANY 440.

99% of factory engines back in the day when new were not actually up to the advertised factory compression and the pistons were typically down in the hole. This is why when you blue print an engine to "factory" specs for NHRA stock class you typically end up with about an 11.5:1 compression ratio engine.

 

[Osyman]

I have 915s on my 74 police interceptor has about 9 to 1 cr. Got heavy springs just like yours. It's running street hemi grind purple cam, runs great.

 

[goose69]

Cool Osyman I appreciate that. I was looking for someone that was running these heads on a 70's motor to see how they performed. What else do you have on the car/truck? Stall speed, gears, etc? Oh yea, which camshaft you running exactly? You like the set up? Thanks again.

 

[goose69]

Are you "Osyman" referring to the 284-484 camshaft? I was looking into one close to those specs.

 

[696pack]

I have 915s on my 74 police interceptor has about 9 to 1 cr. Got heavy springs just like yours. It's running street hemi grind purple cam, runs great.

As i recall there are two different sizes of valves in these heads depending on weather they were installed new on a 350 h.p. (C body) or on an R/T or GTX which got the bigger valves. You can put the bigger valves in in place of the smaller ones.

 

[goose69]

Mine has the larger factory 1.74 exhaust valve like on the GTX motors. I do have a set of rebuilt 515's that have the smaller 1.60 exhaust valve but no reason to use them...

 

[goose69]

Sorry, misprint, I meant I have the 516's, typing skills not up to par!

 

[Meep-Meep]

I've never seen a 69 440 with zero deck unless it was a six pack motor. The compression distance required to make a zero deck (or close to it) is 2.065". 69 Magnum pistons are something like 1.990" and it just gets shorter from there. I'm running a 77 440 with 915's and it CC'd at 10.1:1 with KB 237's (2.065" compression distance).

696pack is correct. 915's came with 1.6" and 1.74" exhaust valves. In my experience the big valve heads have an HP stamped on the ends. The HP is usually accompanied by a number 2 but that might mean something else.

516's have the same chamber as the 915 but have the 1.6" ex valve. The main difference that I can tell is the intake port has a flat floor as compared to the 915 and 906.

 

[Osyman]

Yes I am referring to the 284/484 grind "street hemi" cam. Choppy idle. My heads are off a 67 gtx so they have the bigger valves, stock rocker arm assembly, heavy duty valve springs, forged pistons, 6 pack rods, forged crank, stock stall converter from the 67 gtx( don't know what that is) and a built 727. It's in my 67 gtx convertible clone

 

[Meep-Meep]

The ".484" is not the street HEMI grind. That would be the ."474". I have seen much better results with the .474" cam over the .484". Or another one that seems to work well is the .455" / 272. I have this in my 440 and I really like it.

I recommend you pocket port the heads according to the templates, do a correct three angle valve job and use adjustable rockers and 3/8" push rods. If you do nothing else at least get the rockers and push rods.

If you have about 1" space between the edge of the converter body and the ring gear than it's a decent stall but still marginal for the .484" cam. It will work well with the .455" cam though. Also the factory intake and carb will work well with this cam.

All this is a round about way of saying to get rid of the .484" cam.

 

[goose69]

Meep-Meep, You like that 272 cam in your 440 ha? That cam pretty mild but torquey? I imagine it pulls pretty good off the bottom end? I'll be running a dynamics 3000 rpm converter, 355 or 391 gears depending on what I'm doing that night, 30" tall tires, and a torker II intake (maybe a holley street dominator intake if my buddy will sell me the one he has). I might want a little bigger cam?

 

[Meep-Meep]

Yeah, it's really mild with the 112 LC and it has some great mid range pull. I'm running an M1 with a 750 AFB because that's what I had ready but I built this engine with the intention of seeing how it will work with a factory six pack setup. As I understand you don't want to over cam those. I will also try a torker with 780 Holley and maybe the STR 14-4 if I can get it under the hood. What really attracts me to the STR is the runner length.

For your build I suggest the .474" cam. That should work well with the parts you have listed.

 

[goose69]

I'll look into that cam, Thanks.