Is there any corlation between sk part# and factory part #?

[GJCAT427]

I have a line on some pistons part # c8ax-6110-a that have an SK-37816MOD stamped on the tops. They are supposed to be 427 dykes type pistons but I can`t see any port holes in the tops. I read some place they are 428 pistons but I also read John V said that number was a definite 427 part #.  Any Idea what they are?

[Posi67]

I have (or had) some of those and there are no "ports" on the piston tops. The Dykes ring is like a mini L shape and I'd be very surprised if you could even find a set of rings these days. Most guys would cut the "Dykes" step out of the top ring land in the piston and run a normal sized ring with a spacer. That's the way mine were back in the early 80's. Heavy piston with a lot of dome so unless you are getting them for cheap (as in free) I'd be looking at something newer and better. 

Also fairly certain these are for a 427 since I've never heard of a 428 getting such an animal. Quick check of the piston size will confirm that.

[wowens]

I ran dykes ring piston in a tunnelport in the early 70's, they had no gas ports. Came from H&M .

[gt350hr]

I have a line on some pistons part # c8ax-6110-a that have an SK-37816MOD stamped on the tops. They are supposed to be 427 dykes type pistons but I can`t see any port holes in the tops. I read some place they are 428 pistons but I also read John V said that number was a definite 427 part #.  Any Idea what they are?

       SK "numbers"  are blueprint numbers ( Ford called them SKetch numbers) used to make changes to parts. SK was used primarily by the "race" oriented group of engineers at the Engine and Foundry Experimental Engine Division ( AKA  "EEE" or triple E). ANY change to a part HAD to be noted in the form of a blueprint change and new number. Another number used was XE and these were primarily for "production based" engineering changes. I don't have your specific number in my vast collection of SK numbers and actual blueprints. I can give you some examples of changes I have seen on piston blue prints. Simple things like pin bore diameter tolerance , a change in valve pocket depth or secondary machining, piston diameter , compression distance, etc. The changes would not require the basic TRW forging to be changed or THAT would be an ESK number. I have had many "ESK numbered pistons with odd valve pockets , notched skirts etc. over the years and have a full size ESK/TRW blueprint hanging on a wall .

   Occasionally Dennis K (tbolt2) has information on stuff I don't have and vice versa.
     Randy

[preaction]

C8AX-A is in step #1 in the HI-Per parts book for building an all out competition 427, with a 80cc chamber they give you a 14 to 1 comp ratio. They also mention it being a dyke ringed piston.

[machoneman]

Dykes rings were the hot tip way back then to capture, in theory, 100% of the combustion charge. And yes, the Ford O.H.O. pamphlets did cover the pistons and rings. But, they did cause rapid wall wear.

Mahle and a few specialty nitro suppliers like Alan Johnson Racing do still make and sell Dykes rings although I don't know of off the shelf rings fit Ford 427 bores. 

[gt350hr]

   A "Dykes" ring is a modified 1/16th" ring. The "step" cut into the ring is either .017 ( top fuel as Bob mentioned) or .031 (non boosted / NOS applications). The piston ring groove can be remachined to accept a regular 1/16th" ring It will leave a small recess above the top ring that will actually aid in ring seal. Companies like Rebco Machine in Wichita KS are very capable of doing the rework. That can change a C8AX piston from a "paperweight" to a usable part.
    Randy

[Heo]

A piston with a Dykes ring or as we called it L-ring was the
hot ticket when i was a kid and we souped up our two stroke
mopeds