In 1996, Ford switched over to thinner metric piston rings 1.50mm x 1.50mm x 4.00mm (for lower friction?) for all 5.0 including F150 & my 1996 Explorer 5.0 which is going in my 64 Falcon. All 302 up to 1995 used the 5/64" x 5/64" x 3/16" piston rings. The only difference that I can find is the compression distance. The metric piston with 1.5mm piston ring has compression distance of 1.595. The standard piston with 5/64" piston ring has Compression Distance of 1.599.


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Speed-Pro Hypereutectic Piston and Ring Kits (5/64" x 5/64" x 3/16") $170:
Speed-Pro Piston and Ring Kits Z8KH273CP30 - SummitRacing.com

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Speed-Pro Hypereutectic Pistons (1.50mm x 1.50mm x 4.00mm) $118:
Speed-Pro Hypereutectic Pistons ZH816CP30 - SummitRacing.com
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Sealed Power Plasma-Moly Piston Ring Sets ZE458K30 $71:
Sealed Power Plasma-Moly Piston Ring Sets ZE458K30 - SummitRacing.com
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Is it going to make any difference if I use the pistons with the 5/64" or the 1.5mm piston rings ?

Is it safe to assume that the rotating assembly with 1.5mm x 1.5mm x 4.0mm rings is "lighter" than the 5/64" ?


I would think it would balance out better with 1.5mm rings & pistons which is what my motor came with originally.


Once I go 0.030” over, do I need to have my rotating assembly re-balanced ?

The old 302 pistons & rings kit is $170. For 96+ 302’s with 1.5mm rings, there is no kit and must purchase pistons and rings separate but he cost is only $20 more at $190.

My Mustang book lists the piston-to-bore clearance for a 1979-1987 to be 0.0018"-0.0026" and for 1988 on, the book lists 0.003" to 0.0038" (forged pistons ?). For the 96+ 303, the piston-to-bore clearance is tighter at 0.0012"-0.002".

Thanks

Waid

 

I don't have the Ford book at hand, but I recall the compression height of all the 302s starting in 1968 (excluding BOSS 302) as 1.595". If it were raised to 1.599", then the quench distance would be reduced by .004", which wouldn't cause any harm, and might be beneficial. That 1.599" spec., however, might be a misprint or rounding error.
Either metric ring or standard ring piston and ring sets would be fine in the rebuild. I would use the metric ring type as they were introduced to reduce friction ever so slightly. The balance will be the same, and since stock oversize replacement pistons are made to the same weight specs as standard, you do not need to rebalance.
Use the clearance specs that suit the pistons, or that come with them. As you suggest, the .003" to .0038" clearance is undoubtedly for forged pistons.
I always recommend going to a 0.020" overbore which means that you can rebore once more in the future to 0.040". It's always better to remove as little material as possible when remachining parts.

 

Beanscoot,

I have posted this similar question on few other Ford forums. You have given me more info than all of them put together! The Mustang guys want me to go all out with forge pistons and the works!

I did not realize that 0.030 & 0.020 over pistons are made so they are similar in weight as the original stock. Yes, Summit does have the .020 over pisons and rings for same price. There is no reason to go 0.030 over when 0.020 will do!


I am not finding a 0.020 over head gaskets. The 0.030 over are more common. Which one do I use ?

This is my first build and I want to do it right. I bought a dial bore gauge and my piston bores are reading any where from 0.002 to 0.004 over size aftering ball honing. I am going to use TFS-1 cam for this build with GT40 heads.

TFS Cam: TFS-51403001 - Duration at 050 inch Lift: 221 int./225 exh. Valve Lift with Factory Rocker Arm Ratio: 0.499 int./0.510 exh.:

Thanks

Waid

 

FWIW, with hyper pistons, follow the ring end gap instructions to the letter. Too tight an end gap will result in destroyed pistons, and probably the block and certainly the heads.

 

I'm glad my information was useful!

Head gaskets always have the cylinder bores made larger than the nominal size, so you can use the standard gaskets with any ordinary overbore. Special gaskets are made for huge overbores possible with aftermarket blocks, such as 1/8" or more overbores.

With the small amount of wear on your bores the block will certainly clean up at +0.020".

The common 0.030" overbore may have originated in the old days when production rebuilders would have their boring machines set up to bore four inch bore cylinder blocks to 4.030" all day long, so the machinists wouldn't have to upset their setup.

In the old days cylinders often had considerable wear, but nowadays most engines that come apart show very little. A major reason is due to fuel injection which avoids the raw fuel that often would get into the cylinders with carbureted engines, washing the oil off the cylinders.

Also people used to run engines without thermostats more, and bore wear increases dramatically as operating temperature is reduced.

 

I just checked Federal-Mogul's website and the weight is same for stock pistons, 0.020, 0.030, 0.040, 0.060 over pistons. All are listed as 731 grams!!!

Any good particular head gasket you guys recomend?

There us bunch of them on Summit.

Thanks

Waid

 

Not sure where you found that changeover date on the metric rings, but it certainly wasn't 1995. I've seen the metric pistons in earlier 5.0's. I think the switch was in the late 80's, not 1995. Low tension piston rings had a big role in reducing block wear. Check for core shift before commiting to any overbore. Last roller 5.0 block I had wouldn't go .020 over due to core shift. That was a 96-97 block.

 

Waid,

I think any name brand head gasket will work fine. If any is listed as thinner than others, then it might be a good candidate if you want to raise the compression ratio slightly.