Hot Rod Forum banner

1 - 18 of 18 Posts

·
Registered
Joined
·
90 Posts
Discussion Starter #1
I can get a new old stock TRW 350ci forge pistons...these are odd one's TRW No L2417 ....I have to see if I can find some moly face top rings ....oil control grove has 4 holes drilled in them for oil drain control.. Pistons comes with pins and lock rings. I just wonder are these just to old to use them for stock replacement....

A flat top piston with valve notch in top ( 10.25 to 1 with 64cc head ) it is what info I have found, Pistons have lock ring grooves and can be assembled full float or press fit....And ring groove widths are 5/64, 5/64, 3/16. that part is good for the street....

Just wonder is it possible to use these in a stroker motor ? I think the pin is too low for that ? Thanks for all your info and help...
 

·
Registered
Joined
·
17,613 Posts
I can get a new old stock TRW 350ci forge pistons...these are odd one's TRW No L2417 ....I have to see if I can find some moly face top rings ....oil control grove has 4 holes drilled in them for oil drain control.. Pistons comes with pins and lock rings. I just wonder are these just to old to use them for stock replacement....
I would not hesitate to use these L82 pistons in a performance build. Read up on them......
https://oldcarmemories.com/1973-1980-chevrolet-l-82-l82-350-cid-v8-corvette-performance-1970s-style/

A flat top piston with valve notch in top ( 10.25 to 1 with 64cc head ) it is what info I have found, Pistons have lock ring grooves and can be assembled full float or press fit....And ring groove widths are 5/64, 5/64, 3/16. that part is good for the street....
That notch is worth 3.5 cc's, so they're probably worth about 10.55:1 with a zero deck and 0.040" gasket and 64cc head, 9.6:1 with a 72cc head and 9.2:1 with a 76cc head. 10.55:1 would be very doable today on premium pump gas and zero deck, 0.040" gasket and 230-235 degree @0.050" on the intake cam. Here's an example.....Use with ~2800 rpm converter.......
https://www.summitracing.com/parts/hrs-110265-10/make/chevrolet

Just wonder is it possible to use these in a stroker motor ? I think the pin is too low for that ? Thanks for all your info and help...
Pin is 1.560", just like any other performance piston for a 350. Go for it.....:thumbup:
 

·
More for Less Racer
Joined
·
19,885 Posts
The only stroker possibility for that piston is a short rod 383, using stock 5.565" long 400 SBC connecting rods.

Virtually nobody builds 'em this way anymore, they were the old school way of building a 383 before we had lower budget rod and piston assemblies, back in the days when your rod choice was rebuilt stockers or Carrillo full race $$$ H-beams, with nothing in between.

Only way most guys would consider it today is if they had a pile of old parts like a set of resized 400 rods and a block just sitting around, maybe a cam and lifter set that never got used, an old aluminum intake, maybe some good leftover heads and they could just pick up a online deal on a crank and the pistons you've found.... and use it all to just throw something together on the cheap. I did one that way in the mid-1990's.

Nothing wrong with using them for a 350, they are the stronger version of the flat top due to the drilled oil returns rather than big half moon slot in the oil ring groove.
 

·
Registered
Joined
·
13,919 Posts
Decent piston but you'll need to both work a rod length that keeps the piston close about deck at TDC and allows the counterweights to pass the piston skirt at BDC.

Bogie
 

·
Registered
Joined
·
13,919 Posts
Thanks BogiesAnnex1 what is the best way to do that ?
You are thinking stroker motor or stock stroke 350 or exploring both. Obviously a stock stroke 350 makes this easier, after that we need to explore the possibilites. Strokers adjust pin height and ofter rod length as well as skirt length. Getting off the standard begets a lot of research and work.

Bogie
 

·
Registered
Joined
·
90 Posts
Discussion Starter #9
What if I machine the lower part of the piston skirt to make it shorter in length, and this will give way for more clearance and piston weight too.
 

·
More for Less Racer
Joined
·
19,885 Posts
What if I machine the lower part of the piston skirt to make it shorter in length, and this will give way for more clearance and piston weight too.
If you plan to use them in a short rod 3.75" stroke(383) application there may be a slight interference with the crank counterweights when the crank swings through bottom dead center.
This interference will be on the curved section of the piston skirt, roughly 3/8" to the side of the skirt tang.
The times I've run into this it is less than 1/8", you can do it in a mill but I just used a die grinder and a carbide burr, finished with a 60-80 grit cartridge roll.
Test fit a piston and rod assembly, mark the skirt where contact occurs or is closer than .040" with a black sharpie marker, pull it back out and cut it. It's just a little 1/4"-1/2" or so long half moon shaped scallop cut on the skirt .
It won't be all the pistons, and it won't be both sides of the skirt. IIRC it was just 4 pistons needed a slight clearancing.

You don't want to just machine the entire skirt shorter, that will give the piston less stability leading to it rocking in the bore and increasing bore and ring wear.
 

·
Registered
Joined
·
13,919 Posts
thanks for the info, better just take off what is needed for clearance for rotation..

You will have to balance the engine. With these modifications standard parts including damper and flexplate or flywheel will not come close to adaquate crank assembly balance.

Stroker motors especially those using old school methods are always a pain and often expensive to bring into balance.

This not as simple as getting pistons and rods into equal weights as this is through a process that includes balancing rod weights end to end as well as overal which then requires the crankshaft counter weights be balanced against the apportionment of the piston and partial rod reciprocating weights plus the rod big end fraction of rotating weight. For an external balance crankshaft as often found on 383 strokers this includes the damper and flexplate or flywheel.

Money wise this is a big stumbling block of pieced together engines and is not completely eliminated even when using standarized build parts out of contemporary catalogs even though those modern "kitted" strokers are a damn sight closer on balance.

Even the simple use of forged pisons on an otherwise stock rotating assembly sends you down the balance road as the production crankshaft is balanced to the lighter cast piston and standard rod selection for that displacement engine.

So one needs to consider the cost of this when looking at a set of 'free' pistons especially if you need to carve on them to use 'em.

Bogie
 

·
More for Less Racer
Joined
·
19,885 Posts
If you have the machines to do it, that piston can also be used to build a 5.7" long rod 383 stroker.
You need a lathe or a milling machine or both depending on what you want for an end product, and you need to know what deck height your finished block is going to be, and what thickness head gasket you are going to use.

Juggling all those dimensions, you would then find a target dimension for cutting the top of the piston, either to a shorter flat top, or a custom mini dome.

If the block is left undecked, and an .053" thick head gasket is used, you could end up cutting the minimum amount off the piston and that figure would be about .098"....this would leave you at a tight .035" quench clearance to the head and result in 10.95:1 compression with a 64cc head.

If you were to mill just the quench and rim portion of the piston and leave an .098" tall dome there, then compression would jump to 13.0:1 with a 64cc head.

That was the old 383 build method the late, great "Big Joe" Sherman used to use to put 5.7" rods in a 383 back before we had any pistons specifically made for longer than 5.565" 400 rods. It is a featured build in one of my older Small Block Chevy build manuals and he specifically used that #2417 piston , or the slightly shorter version for the 3.562 stroke circle track 370" stroker piston TRW used to sell, I forget the number now.

I've done a similar thing with the dished 400 SBC TRW piston #2352, it has an .088" deep dish and gets turned into the flat top when you trim .098" off of it. used to do that before there were any long rod 400 pistons available.

The TRW pistons are more than thick enough, and have the top ring down far enough that this doesn't create any strength issues...just got to give a couple thousandths more gap to the top ring since it is closer to the heat.

This trimming approach is a lot of work now that 5.7" and even longer rod stroker pistons are now easily available. I just posted the info so you could know what is possible.
 

·
Registered
Joined
·
90 Posts
Discussion Starter #14
thanks for the info I might do that for my 327ci , and mill the 11.0-1 down... These pistons are flat top 10.25 CR when using with 64 cc heads ( is was I found for spec info ) ...I am using 68cc ported heads, so it will be a little lower then 10.25 CR down a bit ...
 

·
Registered
Joined
·
17,613 Posts
If you plan to use them in a short rod 3.75" stroke(383) application there may be a slight interference with the crank counterweights when the crank swings through bottom dead center.
This interference will be on the curved section of the piston skirt, roughly 3/8" to the side of the skirt tang.
The times I've run into this it is less than 1/8", you can do it in a mill but I just used a die grinder and a carbide burr, finished with a 60-80 grit cartridge roll.
Test fit a piston and rod assembly, mark the skirt where contact occurs or is closer than .040" with a black sharpie marker, pull it back out and cut it. It's just a little 1/4"-1/2" or so long half moon shaped scallop cut on the skirt .
It won't be all the pistons, and it won't be both sides of the skirt. IIRC it was just 4 pistons needed a slight clearancing.

You don't want to just machine the entire skirt shorter, that will give the piston less stability leading to it rocking in the bore and increasing bore and ring wear.
I did this to a 454 once, where the aftermarket piston skirts were in the way of some of the counterweights on a truck crank. No big deal, just don't make any corners in the skirts. Grind and sand everything smooth and round. I did all the pistons the same way, thinking that balancing would be easier that way.
 

·
Registered
Joined
·
90 Posts
Discussion Starter #16
Thanks Mr Tech.. I can borrow the pistons and see how they set up.. If its going to be too munch trouble ...I can get some claimer pistons with 5/64 rings and locks and made for a 400ci crank and 5.700 rods and save the forge for something else.
 

·
Registered
Joined
·
90 Posts
Discussion Starter #17 (Edited)
If I want to raise the compression back up I can use these SS-head gasket at .024 thickness ...do you guys remember these gaskets ? They are made by victor way back then... My first motor I took the heads off was a 1962 chevy Impala with a 327 CI HP, 4 speed, camel hump heads and carter 4bl carb...that motor had the same type of head gaskets but they were not made out of Stain Steel like these gaskets I have now..
 

Attachments

·
More for Less Racer
Joined
·
19,885 Posts
Yeah, I remember them. they were standard issue in stock SBC engines clear up into the 1970's at least.
Originals were just plain mild steel, then for a while the replacements were zinc plated to prevent rust while in storage.

Some of the modern versions are stainless, some are still just steel, and the Fel-Pro -.015" thick version has a elastomer coating on them.
I've seen .015", .016", .018", and .024" thick versions currently offered, and the thinnest composite I've found is the Mahle Original/Clevite(formerly Victor-Reinz) #5746 @ .026" thick
 
1 - 18 of 18 Posts
Top