Help on 5.0 with DOOE heads w 2.02x1.6 valves

[Foxfan4life]

Ok I am new to this type of help but I think I've found a home in my home!! A little about me I have had 12 mustangs in 10 years and now have a 92lx 5.0(FOR SALE) 2 90 GT's one parts car 1 my pride and joy, an 84 GT turbo convertable and a 92 5.0 T-bird(technically a fox body sort of) Well I had a few thiefs help themselves to my 90 GT one winter night a few years back. They stole my AFR 165's and all the top end components that were installed including 24lbs inj. 75mm Pro M meter 70mmedel. throttle bod adj fuel reg and my GT-40 intake, oh and my 1.7 roller rockers. The car sat dormant till thismonth. I have bought all stolen items back FINALLY and went larger on all of them! The only difference was I bought a set of DOOE 1970 351W heads that had been redone recently with 2.02 X 1.6 valves and adjustable stud mount comp cams roller rockers along with guide plates. The thing is the bottom end of this car is ORIGINAL 1990 GT pistons. The thiefs didn't take the cam and I plan to use it. A F303 .512lift and 288dur. [email protected].... Does anyone know if piston contact is a DEFINATE or is it possible? I have a set of 86 GT flat tops I had professionally relieved to run a .542 cam back in 2001. These pistons have been sitting for a bit but are useable. If the 90 pisons are a no-no how bout the notched 86 flats?? Or should I find aftermarket pistons? I am on a tight budget so I need to get her rolling but I haven't a lot of extra money. Any help or past experiences will be greatly appreciated and I hope I am welcomed here in the group. Thanks ADAM!

 

[R2D2]

the 90 pistons will have valve reliefs, you may run into a radial clearance problem though with a 2.02 valve size. Remember, max valve lift is not the determining factor in clearance, when the intake valve is at max lift the piston is already traveling down the cylinder drawing in the intake charge. It all comes down to the timing events of said cam and the amount of overlap. Use the 90 pistons, check for clearance http://sbftech.com/index.php/topic,57.0.html and go from there.

 

[Foxfan4life]

re: thanks

Thanks for the advice keep it coming guys! IF the 90 pistons pose a problem I may try hte fly cut 86GT's

 

[jeremey thomas]

yeah take this one from experience learned.it is impossible to run 2.02's with factory notched pistons.here is the scenario.you put it together,turn it over by hand at the crank and you feel no resistence.so you decide to crank it up and bam it hits.this is what happened to me. it seems when you turn it over by hand ther is not enough pressure to make certain tolerances that close but when you crank it these tolerances close considerably.and then like me, you will need new pistons push rods and in my case another set of brand new edelbrock heads.yeah 2500.00 in one week on two sets of aluminum heads tends not to please the misses.

 

[Foxfan4life]

previous post

Yea I am boiling hot with the misses now!! What about the factory 86 GT pistons. They were flat tops with no reliefs and I had them professionally fly cut to run up to a .542 lift (X303) cam and they cleared the GT40 heads that was on my 1st pony the 86GT with no probs past 6000rpms. Can anyone recommend a good piston if all else fails? OR a place that sells them reasonable? I definately want forged now junk allowed!