Piston / Rod combo?

[brin0357]

I am planning on using Boss 302 rods w/ the football style rod bolts. I have a set of Keithblack pistons with a pretty large pop up. First off the number on these rods are C3AE D. They accept a .927 wristpin which is the full floating pin. How tight are these supposed to be? Will I need to freeze the pin and throw the rod in the oven or should it just slid in? From what I have heard this piston / rod combo came off a motor a while back but I dont know that the pin height is correct for my rod length. Whats a good way to tell if the pistons are forged or hypers? It says KB and 180 on the side of the piston and the other side says SL and 95. What do you guys think?

 

[66bluepony]

I think your pistons have a chev pin. .927 chev, .912 ford

 

[bnickel]

if they are full floating rods they should have a bushing in the piston end and they should slide right in and be held with spirolocks.

 

[brin0357]

The pistons have grooves like for c- clips. I miced the rod and it was .925ish so I assume that its the larger wrist pin, why dont they fit? Do I need to heat the rods some? Or are they press fit pins? Anyway to tell if the pistons are forged?

 

[D.Hearne]

If the rod end is .925 and the pins are .927, you have to have the pins pressed into the rods. Do NOT heat the rods yourself, unless you've done this before and know what you're doing. Original Boss 302 pistons have a pin height to work with a 289 length rod (5.155). Only way to use the 302 length rod is to use 351C pistons and mill them a bit.

 

[brin0357]

Ahh, thats interesting. So these keith blacks I have got that were supposedly off this rod combo and was a 302 wont work?

 

[D.Hearne]

Ahh, thats interesting. So these keith blacks I have got that were supposedly off this rod combo and was a 302 wont work?

That will depend on what the pin height of that piston is. Stock Boss 302 pistons had about a 1.55" pin height. If you're using Boss 302 rods with a std 302 pinheight, the pistons likely to not only have popups, but will also "popup" above the deck at TDC.

 

[brin0357]

Right, so I guess I need to measure pin height. Is that just center of the pin to the top ridge of the piston, minus the pop up?

 

[D.Hearne]

Pin height is center of the pin hole to the top of the piston ( the flat part on a pop up piston.)

 

[brin0357]

Cool thats what I thought. Thanks hearne, big help as usual.

 

[brin0357]

well here is the piston. http://kb-silvolite.com/performance.php?action=details&P_id=54 Its a freakin 350 chevy piston. bore and pin are correct, now how the hell do I figure in my boss 302 rod instead of the 5.7 inch rod length of that 350. Could this piston still work with my boss rods? Comp heigh is 1.561, which is about the same ass a boss piston no?

 

[D.Hearne]

You can't use a Chevy piston in a small block ford. The valve reliefs are different. Small block Ford valves are arranged differently in the heads. IE-IE-IE-IE, Chevy is something like; EI-IE-EI-IE.

 

[thumper460]

Sounds like you are Piecing parts to get what you want!!?? The .927 IS a chevy pin!! you can NOT get that pin into a .912 pin Ford piston ( well you can with the machine shops help) 2nd the C3 roc IS the correct 289 rod used for the BOSS!!

SOOOooo... you have a modified rod for floating 927 pins and 3/8 rod bolts!! KB will make a piston for the chevy 927 pin ( a lot of stroker kits use the chevy pin size to save money.. not having to make a bunch of pin sizse) Look for the BOSS 302 piston!! or the KB same type!! that 927 pin might be the down fall... they do use the chevy flattop 4 valve relief pistons in the Ford.. but like DH said.. there will be issues with the cleaveland head !!

Just a suggestion... maybe ditch the modified rods.. buy a set of 289 H beam/ or I beam rods from Scat/ Eagle/ Ebay.. with the 912 pins and then work from there.. they will be stronger than the moded stock 289 rods.. and matching parts will be easyer ??

The KB pistons for your application will be free floating!!
Have fun.. we have built two of those using the 351C heads..

Just me..........................

Thumper

 

[D.Hearne]

I wasn't thinking on interference with Chevy pistons on Cleveland heads, I was thinkin on this with Windsors too. I may be mistaken, but with the offset piston pins, doesn't that make it impractical to reverse the piston to orient the reliefs to match the heads? Or maybe I'm wrong here in thinkin the valve reliefs on the pistons tops are two different sizes for each valve? I know that some Ford pistons have an offset pin and that in itself would make it impractical to reverse them, seems the same would or could be true of Chevy pistons? Is he trying to run Boss rods in a Windsor? or Boss rods and Cleveland heads? Then too I don't know offhand the pin height of Chevy pistons either?

 

[brin0357]

I am trying to run boss rods, windsor heads, mexican block. block doesnt matter,m but this was the dudes setup along time ago. i am not piecing anything together, just trying to figure out what i have . I am gunna talk to my machinist.

 

[D.Hearne]

Look up your piston's specs on KB's website. Should be a part number on them somewhere.

 

[D.Hearne]

Come to think of it, you can't run those pistons on the Boss rods anyway, because of the pin diameter. You'd have to drill out the rod, bad idea in my opinion.

 

[brin0357]

Its the same size pin. .927 is the same as my rod. Well it was about .925 on my caliper.

 

[brin0357]

So heres the piston and my rod. For clarification I guess. Could reliefs be cut into the piston for clearance? I would be running 1.94 intake and 1.6 ex on windsors. Not sure on cam, .5-.65 lift.

As you can see the pistons have been run, and to my knowledge it was with these rods in a ford block...

 

[D.Hearne]

I looked again back on KB's site and they list a chevy popup with a .400 dome that's part # KB801. That what you have? The pin height's about right for a Boss rod length and the dome would be closer to a Ford Windsor head. Only thing is the popup needs to be oriented correctly for the head clearance. Or have the domes milled flat.