im replacing my stock 302 pistons with these <TABLE cellSpacing=0 cellPadding=0 width="100%" border=0><TBODY><TR onmouseover="this.style.backgroundColor='#f5f5f5'; " style="BACKGROUND-COLOR: #ffffff" onmouseout="this.style.backgroundColor='#FFFFFF'"> <TD class=overview-c1 width="25%">Brand:</TD><TD class=overview-c2 width="75%">Speed Pro</TD></TR><TR onmouseover="this.style.backgroundColor='#f5f5f5'; " style="BACKGROUND-COLOR: #ffffff" onmouseout="this.style.backgroundColor='#FFFFFF'"> <TD class=overview-c1 width="25%">Product Line:</TD><TD class=overview-c2 width="75%">Speed-Pro Hypereutectic Pistons</TD></TR><TR onmouseover="this.style.backgroundColor='#f5f5f5'; " style="BACKGROUND-COLOR: #ffffff" onmouseout="this.style.backgroundColor='#FFFFFF'"> <TD class=overview-c1 width="25%">Bore (in):</TD><TD class=overview-c2 width="75%">4.000 in.</TD></TR><TR onmouseover="this.style.backgroundColor='#f5f5f5'; " style="BACKGROUND-COLOR: #ffffff" onmouseout="this.style.backgroundColor='#FFFFFF'"> <TD class=overview-c1 width="25%">Bore (mm):</TD><TD class=overview-c2 width="75%">101.600mm</TD></TR><TR onmouseover="this.style.backgroundColor='#f5f5f5'; " style="BACKGROUND-COLOR: #ffffff" onmouseout="this.style.backgroundColor='#FFFFFF'"> <TD class=overview-c1 width="25%">Piston Material:</TD><TD class=overview-c2 width="75%">Hypereutectic aluminum</TD></TR><TR onmouseover="this.style.backgroundColor='#f5f5f5'; " style="BACKGROUND-COLOR: #ffffff" onmouseout="this.style.backgroundColor='#FFFFFF'"> <TD class=overview-c1 width="25%">Piston Style:</TD><TD class=overview-c2 width="75%">Dish</TD></TR><TR onmouseover="this.style.backgroundColor='#f5f5f5'; " style="BACKGROUND-COLOR: #ffffff" onmouseout="this.style.backgroundColor='#FFFFFF'"> <TD class=overview-c1 width="25%">Compression Distance (in):</TD><TD class=overview-c2 width="75%">1.599 in.</TD></TR><TR onmouseover="this.style.backgroundColor='#f5f5f5'; " style="BACKGROUND-COLOR: #ffffff" onmouseout="this.style.backgroundColor='#FFFFFF'"> <TD class=overview-c1 width="25%">Valve Reliefs:</TD><TD class=overview-c2 width="75%">Four</TD></TR><TR onmouseover="this.style.backgroundColor='#f5f5f5'; " style="BACKGROUND-COLOR: #ffffff" onmouseout="this.style.backgroundColor='#FFFFFF'"> <TD class=overview-c1 width="25%">Wrist Pin Style:</TD><TD class=overview-c2 width="75%">Press fit</TD></TR><TR onmouseover="this.style.backgroundColor='#f5f5f5'; " style="BACKGROUND-COLOR: #ffffff" onmouseout="this.style.backgroundColor='#FFFFFF'"> <TD class=overview-c1 width="25%">Pin Diameter (in):</TD><TD class=overview-c2 width="75%">0.912 in.</TD></TR><TR onmouseover="this.style.backgroundColor='#f5f5f5'; " style="BACKGROUND-COLOR: #ffffff" onmouseout="this.style.backgroundColor='#FFFFFF'"> <TD class=overview-c1 width="25%">Top Ring Thickness:</TD><TD class=overview-c2 width="75%">5/64 in.</TD></TR><TR onmouseover="this.style.backgroundColor='#f5f5f5'; " style="BACKGROUND-COLOR: #ffffff" onmouseout="this.style.backgroundColor='#FFFFFF'"> <TD class=overview-c1 width="25%">Second Ring Thickness:</TD><TD class=overview-c2 width="75%">5/64 in.</TD></TR><TR onmouseover="this.style.backgroundColor='#f5f5f5'; " style="BACKGROUND-COLOR: #ffffff" onmouseout="this.style.backgroundColor='#FFFFFF'"> <TD class=overview-c1 width="25%">Oil Ring Thickness:</TD><TD class=overview-c2 width="75%">3/16 in.</TD></TR></TBODY></TABLE>

are they the right pistons i dont want to loose comp i.thanks

 

you will with those......

 

how much power loss are we talking .i called sumitracing tec and they said the pistons with lower compression distance make up for it by the piston deck .i dont understand why arent all pistons the same ??

 

what they are doing is sell you some pistons they can't sell........Ford used two different deck heigths on the small block 302, from 68 to 72 they used a shorter deck and after 1972 they went with a taller deck to get lower compression....Bla Bla Bla. but in 1977 they went back to the shorter deck to get the compression back up. they also used a taller piston that put it at 0 deck in (85 to 87 HO) meaning the piston was flat at the top of the block at TDC and was not .020 to .030 down the hole.

Your best bet would be to get some pistons for a '85-87 5.0L H.O. they have a 1.619 and will get you the most compression.....

go here and look for the trw hyper pistons for the sbf 302

http://www.flatlanderracing.com/index.html

 

this is much better......


Brand: Speed Pro
Product Line: Speed-Pro Hypereutectic Pistons
Bore (in): 4.020 in.
Bore (mm): 102.108mm
Piston Material: Hypereutectic aluminum
Piston Style: Flat
Compression Distance (in): 1.615 in.
Piston Head Volume (cc): +5.00cc
Valve Reliefs: Two
Wrist Pin Style: Press fit or floating
Pin Diameter (in): 0.912 in.
Top Ring Thickness: 1/16 in.
Second Ring Thickness: 1/16 in.
Oil Ring Thickness: 3/16 in.
Quantity: Sold individually.
Notes: Piston has coated skirt.

 

what pistons come stock for a 91 302 in a e150 van it not a HO .so what your saying is get 1.619 compression distance for the most compression .but 1.599 might be stock for a 91 302 non HO . oh and whats the compression ratio for a 302 HO it cant be 9.1 .thanks

 

I have no idea what came stock in a 91 5.0

I do know that ford used 1.605 and 1.619 the 1.599 is an aftermarket piston and has far as I know ford never made that piston....

I have no idea what the compression raito is for a HO might be 9.5.

The closer you can get the piston to the heads the better, I ran a 1968 302 with the pistons .010 out of the hole, makes for a good quench..........

 

Stangs were rated 9:1 with factory flattops and valve reliefs(except '86). Trucks were rated 8.5:1 and were equipped with dished pistons.

 

i cant find one with 1.619 .for a stock 4.000 bore also i called speed pro and the cc is -4cc .what does that mean

 

look for a trw #L2488F

 

http://store.summitracing.com/partde...5&autoview=sku

 

Thats a good thing, but what that means is the valve reliefs are 4cc in size....those other ones you first listed (if they are the same ones I'm thinking they are)are like 10cc,

 

ok thanks but i cant afford forged pistons .i guess im stuck with 1.599compression distance but i had a head job done and they shaved off 3 thos so hope fully thell be ok the stock rings are worn 200000 miles im just hopeing ill feel a difrence in power by changing the rings and pistons and getting a head job .any way what do u think my comp ratio would be with 1.599 comp distance .oh and i said minus 4cc valve reliefs is that still good .how come some pistons have 4 valve reliefs and some have two .my stock ones have two ?? thanks for your help man

 

Just use those pistons, if you're just doing a basic rebuild, not going for high performance. If you want to bump the ratio up, mill the block's decks .010 and the heads the same amount. You'll still get the same effect as the 1.615 pistons and ensure the decks and heads are straight and flat.

 

i am going for high performance but these pistons are coming tomrow so
how much a diffrence can it make . thanks