Really SHort SBF 6 pistons

[ASMART]

I found the following in ACLs piston catalogue.
250 ford High Comp/High Perf pistom for use with 6.27 inch rod.

Part # 6mkry9412
The catalog recommends for off road use only and not to exceed 10/1 comp ratio.

28.7mm compression height(1.16929 inches) compared to 1.51 = 1.53 for most SBF 6 pistons. Would there be any reason that these pistons would not fit a 200? If you zero decked the block you would be taking .34 of an inch off just to match the drop of the piston into the hole created by the .34 difference. I understand that the stockpistons actually sit below the block deck also. Would you need custom push rods for that much of a short deck height if you had the adjustable rocker assembly?

 

[ASMART]

Wouldn't this short of a piston enable a 5.09 SBF 302 rod?

200 rod = 4.7515
piston compression height is .34 shorter
4.7515 + .34 = 5.0915

302 rod = 5.09!!!!

It would make for a better rod to stroke ratio. Of course, then you would no zero deck the block like I mentioned in the above post. It is food for thought.

 

[xctasy]

Yep, the piston would fit easy...it's designed for any Ford six as there were no major differences, even with the racy 1997 on OHC pistons which have a similar deck height. The V8 rod would possibly need to be done with a special fillet raduis on the six cylinder crank, as the SBF rod is a little narrower than the small 144-250 six rods, I think.

Personally, i'd resize to 5.075", and ensure the zero deck (7.808", methinks) is not going to take the head off at TDC. Allow for 25 thou streatch, machine to dovetail squench area in the head. Diesel guys know how to set the bump. Mark P's posts cover the detonation issues with the squench area in the head, and the head gasket margin on the block and head must be chamfered to remove any machined edges.

The rod ratio improves out of sight. In Aussie, 200 cube Holdens rev to 7000 rpm plus with a 1.615:1 ratio. Yours, with a 5.075" rod, would be better at 1.623:1, with a bullet proof 302 after market or 4V HO item.

This ACL piston is ultra strong. Because its not forged, its very light, very dimensionally stable (doesn't slap at 1500 rpm or rattle when cold like forged pistons can), and produces good compression.

 

[alloydave]

the 6mkry9412 suits a 6.27 "rod which is the aussie crossflow 3.3 (200)
rod .You may have to take a bit of material of the top of the rod to clear underside of piston.

cheers dave

 

[mugsy]

Do you have their web site address?

Tanx,
Mugsy