Piston choice

[Duke W.]

Re: Piston choice

The only way to know is to take the measurements needed to compute the actual true CR. Anything else is just guesswork - not part of precision engine restoration!

The Duntov cam is not really that "big" - very similar to the L-79 cam duration but more overlap - and I recommend targeting a CR of 10.25:1 with this cam, which is most likely acheiveable with proper head gasket thickness selection once deck clearances and actual head chamber volumes are known.

By its very design nature, the 283/315FI engine's torque bandwidth is biased high due to both the cam and manifold design. It's a basic characteristic of the engine to get high power at high revs.

Duke

[Joe L.]

Re: Piston choice

Thanks for all the info. I appreciate it. I think I will go with the KB's. Summit does have them .I believe the one's I need are the KB UEM 166030 as listed on the Summit site. I was also checking on a cam/lifter kit for the same 315 HP engine. Do these suppliers have their own versions of the 097/Duntov cam? or do I have to get it thru GM. Summit lists a kit as stock for my car as a NAL1234054. Just in case somebody knows where I can get the correct piece? I will call Summit when they are open.

Thanks again.
Jack

Jack----


Forget GM as a source for the cam; it's long-since discontinued.

[Loren L.]

Re: Piston choice

In past Drivelines, Performance Chevy here in Phoenix has run engine ads. The owner's name is Bill Knobloch. Both the humped pistons and the 097 clone were obtained for my car from Bill - and even more scary, he had them on hand. No, I'm not going downstairs to pull out old Drivelines for his # - in the long run, you'll feel better if you do it. I can see it now, "Grandson, during the time period when I was trying to get your dad to remember his name, I made contact with a good ole Chevrolet buddy named Zora Duntov and he ...........

[Jack A.]

Re: Piston choice

My inclination to go with the Duntov Cam is based on conversations with Fulie Guru's like Jerry Bramlett and others who have advised that since I want to install the original F.I. unit, which I am rebuilding, I need to stay with the original Cam configuration for the Volumn it produces which is vital for the F.I. unit to work at it's peak.

Jack (35730)

[Rob M.]

Re: Piston choice

Hi Jack,

I'm just building up a '63 L84 setup with similar pistons as posted in the first reply:



See the piston just reaching over the edge of the cylinder to ensure maximum compression:



regards,
Rob

[Jack A.]

Re: Piston choice

Thanks Ray,

I will check it out. Looks like you have a couple of primo 61's. If you ever want to get rid of any extra parts I need quite a few items.

Regards,

Jack Alexander 35730

[Mark P.]

Re: Piston choice

Joe, Do you have a recommendation for the 265 in my 1956? It looks like I'll be boring .30 over also and need new pistons.

Thanks,
Mark

[Joe L.]

Re: Piston choice

Joe, Do you have a recommendation for the 265 in my 1956? It looks like I'll be boring .30 over also and need new pistons.

Thanks,
Mark

Mark-----


Pistons for an early 265 are getting hard to come by. I don't think that KB manufactures pistons for these engines. I don't think that Federal-Mogul manufactures them in hypereutectic cast but they do manufacture them in conventional cast. These will be equivalent to what was originally installed in your engine. Check available over-sizes BEFORE you have the engine bored, though.

Badger may also manufacture pistons for your application, but I don't know much about them.

[Jack A.]

Re: Piston choice

Hi Rob,

Thanks for taking the time to send the photo's. Great shots. Are those the KB Hyper's?

Regard,
Jack (35730)

[Jack A.]

Re: Piston choice

Ray Carney,

I hope this finds you Ray. You were kind enough to help with my engine rebuild. We were both building a 315 HP Fuelie. I went with the Federal Mogul Cam and pistons the same as you. I was wondering how that turned out for you. I have just postd a new thread on the Tech Discussion Board regarding some questions I had on the Federal Mogul Cam. You might look at that to see what I have run into regrding the lack of adequate vacum at idle. I was wondering if you found the 113r to be identical to the GM 097 and if you ran into a similar problem?

Thanks,

Jack Alexander 35730