I really must be. I am trying to build a 496 stroker BBC. So, I am trying to find pistons for this beast, and cant find any. The bore is 4.311 (.060 over 454) and the stroke is 4.250. I go looking through my summit catalog for pistons. That led me to a few questions:

It says in the Summit catalog under the rod and stroke heading numbers that arent close to mine, as my rod length is 6.135" and my stroke is 4.250". Does this mean I can't use these pistons because of the rod length and stroke? It also says the CR of each motor, but it gives a varrying number. What does the CR depend on? I am planning on using a 119cc head and want the compression ratio between 10-10.5:1 so it will run on 93 octane.

I am looking at the Keith Black performance
Silv-o-lite pistons.

Sorry for such a novice question, but that is exactly what I am when it comes to motors. Thanks in advance,
Chris

The pin height of the piston must match for the rod you are using. So if you use a standard BBC rod @6.135", you need a piston to match that. If you use a +.250" rod (6.385"), you need the correct piston for that was well. They are not interchangeable.
The CR in the catalogs for the pistons are based (loosely) on the head chamber size and it should list that. Ex; 9.8:1 with a 114cc head and so on. But your real CR depends on that plus the deck height, gasket thickness, gasket bore....

Those are not dumb questions. Dumb would be to blindly buy the parts and stick them in the motor. When in doubt,....ask.

You want to look for a piston with a 1.520 compressed height. ( the distance from the centerline of the pin to the flat area of the piston top ) There's lots to choose from. If you go to Flatlanderracing.com there are multiple choices. Even TRW makes one.

That assumes you are using a standard deck block, 4.25 stroke, and 6.135 rods.

You might find it cheaper to switch rods to a .250 long or even a .400 long rod and buy off the shelf pistons. Custom pistons like the BRCs I bought for the 27 I built were nearly $700.

Longer rods would be a big improvement and lesson the thrust load on the cylinder walls.

And with a 119cc chamber, you will need a piston dome of aprox 20cc for 10.5:1 static. You should consult your machinist BEFORE you buy anything.

Keith Black PN# KB397

Yes, use at least 1/4" longer custom rods b/c there is a good chance you will have to cam-cut your crank so the pistons don't hit the counterweights at BDC if you use stock length rods!!!

And if you do cam-cut your crank for needed clearance, you more then likely will have to rebalance it and add expensive heavi-metal to balance her..

Been there, done that!!

pdq67

PS., I bought ROSS pistons for my 496!! Pretty enough to sit out on the coffee table!! He, He!!

Red454,

Look up my thread "Wolplace to the Rescue". I just purchased a complete internally balanced ready to install rotating assembly : crank, 6.385" H beam rods (stroker crank clearanced), pistons, bearings and rings. This assembly will drop right in with minimal work in my .060 over block. Only thing I should have to do is double check for clearance. But this should be a non issue. By going with the longer rods and the shorter lighter pistons, the assembly is balanced by taking weight out of the crank instead of having to put more weight in.

Parts catalogs usually only show a fraction of what available from manufacturers, even though they can get anything. Here is a link to the Keith Black website. http://kb-silvolite.com/index2.php

If I were to go with the 6.135" rod, the pistons would hit the crank counter-weights? But if I went with the 6.385" rods I would not have too?

Would using the longer rods up my CR at all?

Also, now I am a little more lost, but on a different subject. I am going to stick with the 6.385" rods, as suggested. Now I got to looking at pistons. On my desktop dyno, I used the compression Math to find out my real CR. I used 119cc heads with 20cc domed pistons (meaning my head cc is 99cc right?) Head Gasket bore of 4.375 and .040 thickness. I found that my down bore @TDC should be -.008 to give me 10.51:1 CR. My next major question is what is piston down bore and how do I find out what mine is.

Also, TJC, I could not find those pistons on the KB website or through google.

Also, GRN69, does Wolfplace have a website. I think I will drop him an email.

Thanks a lot guys, but any more you could give is very appreciated.
Chris

Wolfplace : www.lewisracingengines.com (http://www.lewisracingengines.com)

Definitely worth talking to him, you are going about it the hard way trying to pull the pieces together from multiple sources and get everything to work without a lot of experience.

http://kb-silvolite.com/performance.php?action=search&mfg=CHEVY&EngSize=489&RodLen=6.135

Thanks GRN. Just got done writing him an email. Hope he can help,

And thanks for the link TJC,

Chris