Building a 440 using 915 heads

[Chatt69chgr]

Has anybody built a 440 using 915 heads that runs on 93 octane pump gas?  I'am talking about a streetable engine (less than 6000 rpm).  I've looked at some of the piston offerings and don't see a piston right off that would give you around 9.3:1 static CR considering the 78cc chamber volume of the 915's.  And I'am talking about a quench engine (say 40-45 thousands piston to head clearance) since if you are not going to build a quench engine, then you might as well use the 452's which are a lot more plentiful and with the 88cc chamber volume, a lot easier to find a piston to yield the 9.3:1 CR.

[Rolling_Thunder]

My 440 has the 915 heads and is just shy of 10:1 compression...    should be able to run a 91 swill here in CA without problems...   


If close to 10:1 has you bothered - you can always run a thicker head gasket to effectively drop the compression

[Just 6T9 CHGR]

My 440 has 915's as well.....with the SpeedPro pistons I run it comes out to 9.3:1 (according to SpeedPro)
#L2266F .030"
Approximate compression ratios: 9.33:1 with 78.5cc and 8.66:1 with 88cc head.


IIRC the pistons came out to be .080 in the hole so no where near optimum quench.  I also know using the FelPro blues like I did also lowers the CR a bit....

[Chatt69chgr]

Thank you both for the reply.

Just 6T9 Chgr--Since you didn't achieve quench with the L2266F, wouldn't a 452 head work just as well with proper choice of piston to yield approximately 9.3 or so CR (for example, a Diamond 52402) and wouldn't it provide about the same performance potential?  Or does the close chambered 915 head still work better?


Rolling_Thunder--I talked to a guy who had built a 440 using all stock parts and was running 10:1 CR.  He said his engine ran OK most of the year.  When it got real hot in the summer here (Chattanooga) he said it would ping.  Now that was obviously audible detonation.  There very well could have been detonation going on that he couldn't hear I would think.  I have no idea where he had his timing set.  He was running a 906 head.

Playing with the KB Silvolite CR calculator, it looks like for a 78cc chambered head running at zero deck and a 40 thousands head gasket (30 over) that you would need approximately 20cc of dish to get into the 9.5:1 CR ballpark.  I'am thinking that on the dished pistons, there is a quench surface.  Obviously not as good as a complete flattop.

I wonder how much detonation reduction you really get with a quench setup?

[Rolling_Thunder]

hmmmm      interesting question....      honestly for just a street car you'd be fine with either the 915 or a 452/906...   just make sure your compression is up there around what you want....    i'm sure people will say this and that but honestly - I wouldnt mind loosing 4 or 5 hp if it meant just getting the damn thing built and running....     

I mean I threw my 440 together with almost what I had laying around...    means I now will end up swapping cams but overall I'll be happy with it...    almost a stock rebuild in the end... 

[firefighter3931]

Tight quench makes a big difference when trying to run pump fuel. To achieve the desired CR with the 915 heads you will need to order a custom piston. Diamond Racing will do this for an additional charge. 

The other option would be a set of closed chamber aluminum heads and a zero deck flattop piston build with 10.5:1 compression which will run all day on pump gas.

By the time you rebuild a set of heads with new valves, guides, retainers, springs etc...you'll be into it for about the same cost as a brand new aluminum head casting that flows 30-40cfm better. 



Ron

[Musicman]

 

[Just 6T9 CHGR]

Just 6T9 Chgr--Since you didn't achieve quench with the L2266F, wouldn't a 452 head work just as well with proper choice of piston to yield approximately 9.3 or so CR (for example, a Diamond 52402) and wouldn't it provide about the same performance potential?  Or does the close chambered 915 head still work better?

Chatt, you're asking the wrong guy when it comes to that stuff.....basically I built mine with what I had with a few good recommendations from the Guru's here at DC.com (namely Ron--firefighter3931)
Im happy that my engine starts & idles like a champ, works my power brakes, doesn't overheat, gets decent cruising MPG on the drive to Carlisle, PA & still pushes my sled to a moderate 13.55 @ 103!  With more track practice Im sure I could get it lower as well

[Chatt69chgr]

Thanks guys.  My questions were more to add to my own knowledge base than to necessarily build an engine with either the 915 or 452 heads.  In fact, I am doing exactly what you suggested, ie, using an aluminum closed chamber 84cc head with a zero deck flattop piston and a 40 thousandths head gasket with an Engle K56 cam.  Don't recall the P/N but the piston is a Diamond flattop and the static CR is approx 10.35:1 or so.  I figured out what I wanted to do based on advice from this board.

I was kind of curious about the iron heads since Aerohead Racing, a division of Indy Cylinder Heads, sells a reconditioned set of 915's with ss valves for $599 and a reconditioned set of 452's for $499.  I was thinking that some folks might want to use the iron heads for one reason or the other and was kind of trying to figure out what the pros and cons of the two types might be for a 6000rpm or less street car understanding that the power potential of the iron heads will not be as good as the newer aluminum heads now being offered by 440Source and Edelbrock but might still be adequate for a street cruiser. 

[Sublime/Sixpack]

Just 6T9 Chgr--Since you didn't achieve quench with the L2266F, wouldn't a 452 head work just as well with proper choice of piston to yield approximately 9.3 or so CR (for example, a Diamond 52402) and wouldn't it provide about the same performance potential?  Or does the close chambered 915 head still work better?

Chatt, you're asking the wrong guy when it comes to that stuff.....basically I built mine with what I had with a few good recommendations from the Guru's here at DC.com (namely Ron--firefighter3931)
Im happy that my engine starts & idles like a champ, works my power brakes, doesn't overheat, gets decent cruising MPG on the drive to Carlisle, PA & still pushes my sled to a moderate 13.55 @ 103!  With more track practice Im sure I could get it lower as well

I realize this thread is approx. 4 yrs. old but . . . . . 6T9 Chgr would you mind sharing what cam you ran with this combination?    Thanks

[Budnicks]

Tight quench makes a big difference when trying to run pump fuel. To achieve the desired CR with the 915 heads you will need to order a custom piston. Diamond Racing will do this for an additional charge.  

The other option would be a set of closed chamber aluminum heads and a zero deck flattop piston build with 10.5:1 compression which will run all day on pump gas.

By the time you rebuild a set of heads with new valves, guides, retainers, springs etc...you'll be into it for about the same cost as a brand new aluminum head casting that flows 30-40cfm better.  



Ron

4 years old or not... I would still tend to totally agree... Much better bang for the bucks, with the better flowing aluminum heads, higher HP/TQ, hard seats, new 11/32"- 2.14" & 1.81" high flow stainless valves, quality dual valve springs, retainers, Teflon seals & locks, blind exhaust bolt holes {not into water jacket}, better flow 291cfm out of the box, lighter weight {at least 50+lbs}, thicker decks, bronze valve guides cut to except 0.600" lift cam out of the box, better flame travel with angle plugs, even with 84cc or 88cc combustion chambers in the Edelbrock's & 10.5:1 - 11:1 compression, less chance of detonation...