Hot Rods Identify 396 TRW pistons?

Hi Guys,

I have this set of old forged TRW pistons with a big dome and I would really like to use them in my 402 BBC engine. Aiming for high compression but can not find anything about my pistons on the inter web. Can You help? Would also like to know where I can find piston rings for them.

It is 396 (427) pistons marked "0.30 379P" on top and "TRW 98 190 A" on the under side.

Thanks

 

what is the bore size? Compression height?

 

they cannot be 396 and 427 pistons both. A stock 396 bore is 4.094 and a stock 427 is 4.250.

The .030 indicates that they are .030 over stock so if they measure 4.124 they are .030 over 396 pistons, if they measure 4.280 they are 427 pistons. if they are .030 396 pistons you come within .001 of being a 402 (stock bore 402 is 4.125) a 402 is a 396 + about .030. To be within .001 you can call it 402 easy enough.


I looked up the number on flatlander racing and this is what popped up:

NewRefine 1. Flatlander Racing - TRW Chrysler Pistons
Pistons (sets of 8) (you can use a TRW # for specific compression unless you want ... 9.47 9.82 9.92 9.98 10.07 11.94 11.93 8 ... FT FT FT FT FT .225 dome .190 dome $51 $54 $54 $54 $54 $66


Looks like you don't have chevy pistons at all.

 

Thanks for Your reply. The guy I bought them from was very shure they where from a 396 0.30 over engine. I measured them across the skirt and they are 104.75 mm or 4.124" .

 

Those are definitely BBC. If I have time later, I will try to look them up. Benno is right, they cant be 396/427, they are one or the other.

 

I'm pretty sure that 379P is an old Speed Pro number. They used TRW blanks, so TRW forging numbers would show up inside the piston.

 

TRW made piston forgings for several companies who would then finish them. 379P sounds like a Sealed Power number but I can't find anything on the web. I think they changed number systems after they became Federal Mogul.

 

That info that I posted actually came from the speedpro site. When I googled the TRW number that is what popped up I then entered the number in the search on the speedpro site.

 

Thanks for your help.

I would like to use the pistons in my 1970 402 engine with 241 open chamber heads. Both engine block and pistons are used but does not look worn. What gap between bore and piston would be acceptable?
Also which piston rings should I choose?

Aiming for fairly high compression about 11.1 or higher. Will run 98 octane fuel.

 

Those are 375 hp. 396 pistons + .030" which makes them 402 pistons. They were 11-1 compression with the large rectangle port, closed chamber heads. Available up to and including 1970.

Most oval port heads, open or closed chamber, will hit the piston dome on the outer edge, exhaust pad. Rectangle port heads have different shape combustion chambers. Remedy is to lay the exhaust side combustion chamber back about 1/16" in contact area. Check fit.

These are old style, old low silicon alloy pistons. 5/64" ring width. Same rings as a std bore 400 SBC. These pistons were fit at .005-.006" cyl. wall clearance for street use. Using open chamber heads lowers the compression ratio badly, on a 396-402 engine. Depending on the chamber volume. Most open chamber heads are 119-122 cc. Closed chamber heads are in the 90 cc. area. do the math..

Cast iron rings are used in worn bores. Chrome or Moly will not seat correctly.

 

Way back in the later 60's/early 70's, there was a way to "cut" those pistons, and "grind" for clearance, the combustion chambers of the closed chamber heads to make them work well together. At least as well as having so little room for the flame to travel in could be done. My machinist at the time, did my 375HP, 396 pistons and closed chamber, oval port heads in his own garage at home, using he said, "some hacksaw blades, dremel rolls, and steel cutters". I believed him, they looked fine, and he did't charge me much. He said he did the same thing with his 68, 427 powered Camaro Bracket Car engine. It worked fine for me until I took on a partner, who blew that motor all to h*ll. I guess guys did things differently out of necessity back then. My current machinist learned the trade from him as a matter of fact. Now, Mr. BOBCRMAN, are YOU still selling the MS1110+1 spacer type bearings for running a small journal crank in a large journal (medium actually) block? Last time I was on E-Bay I did't see them. At leastwise I "think" that was you. PM me if it's you please and they're available. I am Butch/56sedandelivery.

 

Sorry, those were Childs and Albert, old bankrupt stock and some King bearings. Long gone and as far as I know, no longer available.. BOB ps. I got tons of .040 under large journal mains and rods if anybody needs em CHEAP.

 

those look like 12.5 TO 1 to me

 

Because of the small bore, 396-402 pistons have to have a huge dome to fill the head.. Even tho they look tall, the pistons were only rated as 11-1.

 

Yup, speed pro. TRW numbers are formatted as L****-F with the oversize on the end. If the part number ends in a P, and its stock replacement, its Sealed Power, non factory is Speed-Pro.

 

I built an Oval port 427 this way, 396 crank with a slug of Mallory in the front counterweight, closed chamber oval port heads with big valves and the chamber laid back around the intake valve, and worked over TRW L-72 pistons. Tight piston/head, 12.5/1, 278 @050 on a 108 lsa roller, ran it on Chevron 94 pump gas, and made around 650hp. Strong street/strip motor for minimal $$. Lots of time "romancing the dome" good colour all over the piston top, right to the back of the quench.

 

My 1984 Speed pro catalog doesn't list that number, must be an oldy. I will take a look farther back when I have time.

 

Just read down, looks like Bob pretty much has it covered.

 

first, measure the bore in your block. probably be a pretty loose fit, most 402s got a lot of miles on them and wore quickly. I have a standard bore 396 block that I've been hauling around and storing since 1979, but they're kind of hard to find these days.

Should be a fun engine.

 

Thanks for your replies. What a great forum.

I will measure the bores and pistons as soon as possible. I also thought they would be higher compression than 11:1 with a closed chamber head, the dome is really big.

 

L2287F

http://www.summitracing.com/parts/trw-l2287f30

 

The dome on those pistons look pretty much spot on like mine. I will meashure the dome height as well. Thanks.

 

Ok, so if I use the compression calculator on Summit and ***ume 1mm thick head gasket I get a compression ratio of 11.54. Of course I will check all meashurements but it gives me a indication of where I will be.

 

Old Speed Pro catalog lists the L2287F as 11.88 compression ratio with a 106.9 cc head.

 

I checked the piston clearance and the biggest clearance is 0.004in, the tightest 0.00375in.

Dome height is 0.508in

 

It seemed to tight for a used engine, remeashured and got 0.0055in as the most clearance and 0.0053 as the tightest.

 

.508 dome can't be a 11:5 to 1???

 

I haven´t measured the deck clearance or gasket thickness properly, just used the oem numbers.
I am not shure why You say the .508 dome can´t be a 11:5 to 1?

 

My TRW book shows 12,5 to 1 with a 106 cc head.

 

Hakno, many years of working with BBC. I'm certain you have the 12:5 to 1