My '69 has a 396 ci motor from the 70's. It developed a miss on the drivers side and after a leak down test, I determined #1 exhaust valve was leaking.
I have not been this deep in this motor before. And I don't know very much about valves or pistons. I have left the heads in good local hands to be refurbished as necessary. So here is a shot of one of the pistons--does anybody recognize the brand or have any information worth sharing about the piston?

 

Seems like maybe an older version of these. https://www.jegs.com/i/Sealed-Power/...0NF30/10002/-1

 

For what it's worth: 1969 was the last year for a 'real' 396. Beginning in 1970, GM's 396 engine was actually 402 cubic inches. This was simply a 396 bored out an additional .030. Furthermore, some, perhaps all, were fitted with TRW pistons. In the early 60's GM took great pride in being the most vertically integrated of the Big 3 (GM, Ford and Chrysler). Vertical integration proved to be very costly as a union strike at any one components division would quickly shut down the entire enterprise. At some point GM started using TRW to supplement their internally manufactured pistons. TRW became a supplier to GM and their pistons became OEM parts. (Obviously they could also be aftermarket replacements also.)

TRW manufactured forged pistons designated L2240 and L2240N. I don't know the difference but I know they have a 21cc dome. When that portion of TRW was acquired by Federal Mogul, TRW piston were integrated into the Federal Mogul product line under the brand name Speed-Pro. Whether the current Speed-Pro piston is identical in weight and dimension to the original, I don't know.

TRW was a conglomerate, perhaps better known for its aerospace business. I found the following evolution of personal interest:

2002 - TRW Automotive was acquired by Blackstone Group
2014 - TWR Automotive was acquired from Blackstone Group by ZF Friedrichshafen AG - headquarters moved to Germany
2015 - Federal Mogul acquired the TRW Engine Componets Operations from the German company
2018 - Tenneco acquired Federal Mogul and split their larger operation into two parts: Tenneco Powertrain is now the parent company for that portion of Federal Mogul selling pistons under the Speed-Pro label

 

Which heads are you using,with those pistons?

 

Thanks for all the interesting responses. I'm not sure of much regarding my 396. The bore is 4.1 inch diameter and I know it's a two bolt main. The heads are passenger type, number 3917215 and dated 71, so nothing special. Here's peek at the offending valves...

 

FYI It was common in the '80's??? to switch to low compression heads in older high compression engines.
My '69 427 has '71 heads to compensate for the lower octane unleaded gas.
I've read that SOME engines actually ran better with the lower compression heads because they breathe better with newer technology.
Mine uses different, no gasket, spark plugs. That's how I found that they had been changed.

 

Forged stock replacement piston for pre 1970 396/402. Around 10 to 1 compression depending on how far the piston is in the hole and what head gasket you use. I get 9.9 to 1 using .0016 in the hole and a .039 thick gasket with a 4.200 fire ring diameter.
If your local guy is competent.....ask him about scribing the head and unshrouding the intake valve......this will improve flow and decrease compression a bit. Closed chamber stuff is unhappy with pump fuel over 10 to 1 especially with a smallish cam......now would be the time to measure piston to deck height too and record the number.

Jebby

 

I will ask about the unshrouding. When he and I spoke originally, he mentioned the intakes being tucked up. With your input, I have a better understanding of what to request be done. Number 1 seems to be at TDC but I will rotate to be sure then measure top of piston to deck. Thanks for the info. Any advice (brand and thickness) on the new head gaskets?

 

The Fel Pro 1027 is the old go to for these.......composite .039 thick, or you could use a steel shim gasket for .3-.4 more compression.......but the heads and block NEED TO BE FLAT.
The safe bet is the 1027.....can't go wrong.

Jebby

 

When they went from 396 to 402 CI i was a mechanic at a chevy dealer and I hate to say it but a bunch of problems with 402's getting 396 rings installed by buba mechanics that didn't check ring gap! Always wondered why, also there was a 400 SB.

Dom