gcpecore

Hello all,

I've been doing some research on the forum: there is some great information here -- thanks. One topic that always seems to come up is the 86 5.0 with flat top pistons and 1.7 rr. Hopefully this thread is not too much of a repost as there have been some discussions on this in previous posts.

I know some of you guys know the 86 motor backwards and forwards, and after spending some time talking to Ford dealers performance shops etc, no one seems to be able to say that 1.7 rr will work with the flat tops -- but no one is willing to say they will not work either. The answer that I keep getting is to buy them and use some putty to check for clearance / tolerance -- but my bet is that someone here has already done that here, and so your thoughts would be appreciated.

Specifics:
86 Gt Mustang
Stock heads (ported)
Head milled .010
Intend to stay under 5000 RPM
Changing pistons not an option at this time (money)

Thanks for the help, sorry if this is a repost.
BTW I have a bet with my son on this one -- he thinks they will not work... so I would like to prove him wrong..
Gary

5IVE.OH

Every engine is different, just because somebody has and had enough clearance doesn't mean your engine will also.

Ninety5five0

Checking would be your best bet. I dont recall seing anyone using 1.7s on flat tops since i've been here.

gcpecore

Forgot one thing...

I know that I'll need new valve covers with the 1.7rr. Also has anyone attempted to use the special tool they sell for flat top pistons to cut small notches in the top of the pistons for extra clearance? I know that the compression will be decreased, but are there any other disadvantages to doing this that I am missing?

Thanks again,
Gary

frdmstng1986GT

it's called a piston fly cutter, no i havent used it though. and yes it will lower the compression a little. but 86 had a 9.2-1 compression ration wich was just a little bit higher then 87-95 that had 9.0-1 compression ration. also, i am pretty sure that the general consensus is that the valves will hit with 1.7rr's. check out foureyedpride.com. they will know more about it since they are all 4-eye guys over there. sorry i couldnt help more man.