Kent engine overbore?

[se7en]

Has anyone heard of a Ford Kent engine (as spec'd for FF) that has been legally overbored by .0005"? That's right - a half a thou'! Rumor has it that there is at least one out there. Inquiring minds, etc...
Thanks,
Ken

[John Merriman]

You can over bore the thing all you want and it would be perfectly legal......but the pistons have to be standard size - a maximum OD of 3.189".

[akilcoyne]

a .005" overbore is now permitted per 9.1.1.e *note* that's a .005" not .0005"

[SIZE=1]Standard size AE pistons P/N 18649, casting P/N 18634, standard size CP piston, part # 81-2 FF1600, [/SIZE][FONT=Univers,Univers][SIZE=1]or CP oversize piston, part # 81-2-FF1600+5 [/SIZE][/FONT][SIZE=1]may be used in the uprated engine.[/SIZE] piston available from Cp

[EACIII]

When did they allow the .005 piston? Can you get I noticed that reading my new GCR the other night (boy do I need to get out). Not that I am complaining, the block I was going to put aside since it needed sleeving and a trush bearing area repair I will get repaired now.

[Brian]

Right there in black and white (or the pixel equivalent)! Backed up by a new max size of 3.194" in the chart. I saw no change to minimum chamber size, so logically the effective compression ratio will be up a tad as well, maybe...

Brian

[EACIII]

I guess the next question is are there .010 rings available to hand fit to the new .005 pistons?

[Art Smith]

does anyone willing to share know the background on the 0.005" oversize piston change for FF in the 2007 GCR?? I'd be interested in the usual suspects: why; requested by whom; are 0.005" oversize pistons available; will 3.189" OD forged pistons continue to be available; who has 0.010" rings available in what configurations and materials?

the change comes as a complete surprise to me as I've seen no discussion here of a problem or the merits of 0.005" pistons being the best available solution.............. after all these years with 3.189" OD pistons for the uprated engines, what has changed?


Art
artesmith@earthlink.net

[John Merriman]

Oops, I stand corrected. Now I recall that this new piston was discussed some months ago within the Formula Car Advisory group an hey, there it is in black and white!! This represents yet another way to lower Kent rebuild costs by preventing - or at least deferring - the need to sleeve blocks back to standard bore. Hat's off, once again, to Jay Ivey who researched and developed the piston and whose dyno tests showed no appreciable difference in performance over the standard piston OD.

[AJWALKER]

Another question to go with EACIII's, are the .005 oversize available yet or is this just good planning. Get the rule passed, then make the pistons, sounds practical to me.

Kudo's again to Jay I. for the efforts to provide hardware to help FF1600.

[John Merriman]

Ivey Engines has them in stock. Tel 503-255-1123

[LFFR]

What's the price????

John Mihalich, Jr.

[John Merriman]

Art, I believe this approach to further cost reduction - by deferring sleeving -was kicked around from time to time. The idea of allowing .030" pistons was often proposed and always rejected. The idea of .005" oversize came up and sets were made and tested to confirm that there was no performance gain. The Advisory Committee received a proposal and after appropriate review, it was approved. As noted above, pistons are available (from CP, Ivey and other engine builders) and I am sure that required ring sizes are also available. I suggest a call directly to Jay on that. I also assume the 3.189" pistons will continue to be available - no reason they shouldn't. This is yet another prudent action which reduces costs for the FF racer. The forged pistons in either size when used with the SCCA/SCAT crankshaft can yield a 40-50 hour bottom end for the Kent engine with very little power drop-off and as a result, per hour running costs are very significantly reduced overall.