Big block heads... so many to choose from... so confused

[cuda1965]

After i finish building my 360 mopar for an old CJ7 project I will be building a 440 for a 68 GTX street strip project. The only thing i have for the car other than the car itself is a 727 that i built for it.

Now on to my question. I have 4 sets of stock heads to choose from. 915, 906, 452, and 516. Ive heard a little bit here and there about all of them, but a good break down on which ones are better for this or that would be great...

I know some people would say junk them all and go aftermarket, I just prefer original stuff.

thanks for any advice. mike.

 

[mopar367]

They all flow pretty well, the 915 heads are a closed chamber to raise compression a bit. 906 and 452 are the most common best all around heads to choose. Not sure on the 516's. If you have to get them rebuilt though, Make sure they get hardened valve seats so you can run unleaded gas.

 

[Cranky]

Junk em all and send me the 915's! Heck, I'll even take the 516's lol. It just depends on what you are planning to do. Street/strip or all out race or bone stock? The 452's have factory induction hardened exhaust seats if that's a concern. The 915's would be my choice for a 10.5-1 pump gas street engine with a decent cam.....so long as they didn't need a ton of work. If so, a set of Eddy RPM's would do me.

 

[cuda1965]

As of right now the build could go a million different ways. For now a car that runs 11's or low 12's on pump gas is the plan. just didnt know if it was realistic with these heads. All of them are in stock condition with no prior machining that i know of.

just a ballpark on the cost of machining here in the dayton area... I just had a set of J heads cleaned, magnafluxed, decked and a valve job done for 250... not sure how much they charge for other stuff though.

 

[Meep-Meep]

The 915's are the best production head made for the BB. Designed with performance in mind and from lessons learned from the Max Wedge head. Out of the heads you listed I will choose, without hesitation, the 915's.

516's have the same chamber as the 915's but they also have the 1.6" exhaust valve, and if you do anything performance oriented you will want to go with at least the 1.74", and that also means hard seats for unleaded. The benefit of 516 is they are usually free and can boost compression on a 440 up to a full point when used with a steel shim gasket. Sort of cheap and easy bolt on performance upgrade on a late model short block.

The 452's can be a benefit because they are factory hard seat heads. This assumes the seat hardness is still in tact, and if it is, can provide a pretty cheap solution to get your car up and running on pump gas.

If all the heads you list need the same amount of work including hard seats then use the 915's.

 

[Meep-Meep]

Oh, the ports on the 516 and the 452 and other newer heads like 346 have a flat floor as opposed to the improved shape of the 915 and 906. This transition into the valve pocket and chamber was the big improvement in flow and the "lesson learned" from the old Max Wedge heads, which also have a flat floor. It's not all about CFM but a combination of velocity, wet flow and camshaft selection to get the most out of the port.

 

[RustyRatRod]

Porting them levels the playing field, so really, what difference does it make? From there, if you're lookin for THAT small of an improvement, you need better heads anyway.

 

[bigmanjbmopar]

I have the 906's on my stock 383 and before I pulled it out and put it on the stand it ran like a bat outa hell. I have not had a set of the others for comparison so my bias is for the 906's good luck with your build.

 

[ykf7b0]

Use the 915's for sure but get the hardened exhaust valve seats.

 

[67 B-body]

Read this:
http://www.moparmusclemagazine.com/techarticles/5115_cylinder_heads/

BTW, I use Big valved / Big Runner aluminum heads with small heart shaped combustion chambers.....(Victor style)

 

[Red63440]

I have a set of 915's for my 383 build that have been all reworked including the big valves. The guy I got them from told me that they had just had them all worked over and used them for 2 races before going to aluminium heads. He said that the gain that they got from the aluminum heads wasn't worth the cost and that the work done on the 915's was extensive and got them very close to what the aluminums ran. I couldn't argue with the price...

 

[Meep-Meep]

Porting them levels the playing field, so really, what difference does it make? From there, if you're lookin for THAT small of an improvement, you need better heads anyway.

Maybe from a CFM standpoint only but that's not the end all be all. It's all about the performance when bolted to a motor and running down the track, and there is no way to test that unless you bolt them on and go.

 

[Meep-Meep]

I have a set of 915's for my 383 build that have been all reworked including the big valves. The guy I got them from told me that they had just had them all worked over and used them for 2 races before going to aluminium heads. He said that the gain that they got from the aluminum heads wasn't worth the cost and that the work done on the 915's was extensive and got them very close to what the aluminums ran. I couldn't argue with the price...

That's pretty much my point.

 

[RustyRatRod]

......there is no way to test that..........

Sure there is. It's called a flowbench.

 

[383man]

If you want to stay with a factory head the 915 would be my choice. I mean an aftermarket aluminum head would be much better and remember the Stealth heads look just like a stock head. But the 915's are closed chamber so you could easily build quench in the eng to help fight ping and they can flow as good as any other stock head with the right porting. But I would seriously consider an aluminum head. Ron

 

[court9155]

Sure there is. It's called a flowbench.

A bench?? Like the one some people race on???

 

[Cranky]

Yeah you can compare heads on a flow bench but just because two different design heads both flow the same doesn't mean they will perform the same in the real world. Also, the major drawback to max porting stock heads is cracking. A set of out of the box Eddy heads will flow about the same as a max ported 906's but will perform better and are not prone to cracking. Also, if you want to max port a set of stock heads, it probably would be a good idea to sonic test the port walls where you plan on taking out the most amount of meat. I do know this...I will never again do a max port job on a set of stockers if I don't have to.

 

[Meep-Meep]

Sure there is. It's called a flowbench.

You can't duplicate a poppet valve opening and closing at high frequency or the elevated temps in the ports, or the pressure wave that runs back and forth through the intake runner, or the effects of different cam profiles as it operates the valves. A flow bench is a great tool but nothing can substitute actual running conditions. Do the flow work then put on a car and collect the data. Then keep doing that until something is learned from the process.

 

[Meep-Meep]

A bench?? Like the one some people race on???

My bench is faster.

 

[RustyRatRod]

A bench?? Like the one some people race on???

lol. Yeah it's been known to happen.