Author Topic: 836 piston ID? (Read 3465 times)

scottly · « **on:** March 17, 2012, 07:07:02 PM »

Does anyone recognize these pistons? The PO of my bike didn't give me squat as far as what parts when into it. The valves left marks, either from over-revving, or insufficient clearance, or both.
Thanks.

MRieck · « **Reply #1 on:** March 17, 2012, 07:25:25 PM »

Are they cast or forged?

scottly · « **Reply #2 on:** March 17, 2012, 07:38:33 PM »

Mike, I took that pic over 30 years ago; I don't know. I'm hoping someone might recognize the crowns. I always suspected they are Wiseco 11:1, but that's only a guess... In any case, they were reinstalled in the K1 motor in my Seeley a week or so after the pic was taken, and they're still in it today!

MRieck · « **Reply #3 on:** March 17, 2012, 08:23:17 PM »

I understand. There are strike marks on all the pistons after looking more closely. Exhaust side a presume.

scottly · « **Reply #4 on:** March 18, 2012, 04:16:25 PM »

Here's another pic. It looks like 4 01xxx? is stamped in the crown. I found that the Wiseco # for the 10.25:1 piston is 4016M06500, but could not find the # for the higher compression piston. Also, in the pics I have seen of the 10.25 pistons, the crown is a rounded dome, while mine are stepped. I didn't see the notch at the top of the pic in any of the many, many piston pics I have looked at today.

Big Jay · « **Reply #5 on:** March 18, 2012, 05:14:05 PM »

That is a Wiseco number, but I don't recognize the dome. The Wiseco K model 836s were a direct copy of the cast 836s I was making back in the day, and still are today.

Wiseco did make an 836 for the F2, and that might be what that is.

scottly · « **Reply #6 on:** March 18, 2012, 07:06:36 PM »

Thanks Jay.
If anyone has any pics of the old Wiseco high-compression/F2 pistons, please post them....

kmb69 · « **Reply #7 on:** March 18, 2012, 07:17:57 PM »

I think they may be TRW's. Saw a NOS set just like them recently on eBay.

scottly · « **Reply #8 on:** March 18, 2012, 07:54:53 PM »

Quote from: kmb69 on March 18, 2012, 07:17:57 PM

I think they may be TRW's. Saw a NOS set just like them recently on eBay.

That would be somewhat ironic, as I was working for TRW when I bought the bike that came with the pistons..

Big Jay · « **Reply #9 on:** March 21, 2012, 02:33:50 PM »

If they were TRW, it would say so up inside. Also the exhaust pockets were not machined, but forged in the top, and they were wrong.

We sold those when they first came out, and had to remachine the exhaust valve pockets in all of them.
Also, the TRWs had big wide Hastings oil rings.

scottly · « **Reply #10 on:** March 21, 2012, 08:23:38 PM »

Were the Hastings oil rings 1 piece or 3 piece? Zooming in on a high-res scan, these are definitely 3 piece. Also, there was definitely a valve clearance issue, more than just a case of the valve "kissing" the piston. The cam appears to be a re-grind, with a smaller base circle than a stock K7 cam. Lift at the exhaust valve is .310 (not accounting for tappet clearance), while the K7 measured .296. This is just an archeology expedition, BTW

754 · « **Reply #11 on:** March 22, 2012, 09:16:23 AM »

Try hunting up a pic of a FORGEDTRUE set for 750's...may be one on this forum...

Big Jay · « **Reply #12 on:** March 22, 2012, 02:31:09 PM »

Quote from: scottly on March 21, 2012, 08:23:38 PM

Were the Hastings oil rings 1 piece or 3 piece? Zooming in on a high-res scan, these are definitely 3 piece. Also, there was definitely a valve clearance issue, more than just a case of the valve "kissing" the piston. The cam appears to be a re-grind, with a smaller base circle than a stock K7 cam. Lift at the exhaust valve is .310 (not accounting for tappet clearance), while the K7 measured .296. This is just an archeology expedition, BTW

Three piece, but something like 3/16 wide. I think the Forgedtrues were TRWs.

754 · « **Reply #13 on:** April 15, 2012, 08:23:34 AM »

There was set set of Forgedtrues to compare in for sale in the last week..

scottly · « **Reply #14 on:** April 15, 2012, 06:25:08 PM »

Found some history about Forged True and TRW pistons here, starting just under the pic of Russ Collins.

http://www.performancemotorsportsnews.com/newsdisplay.php?newsID=529

The TRW pistons just sold look very similar to mine, with the notch at the top, and the wide notch at the bottom. (I didn't notice the wide notch on mine until after seeing Jaguar's pics.) My dome is a fair amount higher, but the valve relief pockets are shaped the same.

754 · « **Reply #15 on:** April 15, 2012, 08:36:28 PM »

Told ya they looked like Forgedtrues..
Are your skirts thick or thin, those were thick I think..

scottly · « **Reply #16 on:** April 15, 2012, 09:08:34 PM »

Apparently Forged True didn't make the pistons, TRW did. TRW paid royalties to Forged True for their forging process. The TRW pistons, in time, were merged into Federal Mogul's Speedpro line..

srbakker · « **Reply #17 on:** April 15, 2012, 09:13:27 PM »

Those TRWs are on their way to me. I'm gonna need some help sorting them out to make sure the clearances work, especially after Scotty pointed me here. Frank, I may have to pay you a visit yet!

scottly · « **Reply #18 on:** April 15, 2012, 09:25:43 PM »

Glad you joined the discussion here! When you get the pistons, please look inside for a TRW marking. Also, it appears your pistons are marked 3.0 MM on the top? I suspect mine may actually be marked 4.0 MM, not 4 01xx.
The "easiest"? way to check valve clearance is with modeling clay on top of the pistons; assemble the motor with old gaskets, turn it over a few times and measure the thickness of the clay at the interference area.

Big Jay · « **Reply #19 on:** April 17, 2012, 05:56:03 PM »

Forgetrue didn't forge anything. They had their stuff forged by Alcoa just like everyone exceptt TRW and Wiseco. Both of them forged in house.

The Forgetrue Honda pistons were something they just contracted TRW to make for them. TRW had cams and valves too. They quit that market after a short time, and turned me on to who was making the cams. I eventually bought them all.

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Author Topic: 836 piston ID? (Read 3465 times)