Flareside

I'm looking at the pistons on my 406, but I'm not sure how to tell if they're what they're supposed to be. I have the oil pan off, but there are no markings on the pistons that I can see. Any ideas? I've been told that they're Speed-Pro pistons. They have 4 valve indents, so I don't think that's correct. The Speed-Pro 406 pistons in the Summit catalog have 2 valve indents.

gkull

Four valve relief is probably TRW forged.

Flareside

Thanks Gkull.


Here's a picture:


They sure look like cast aluminum to me.


[Modified by Flareside, 1:02 PM 12/20/2002]

Flareside

Well, at these the pistons may be what the previous owner said they were. I found that the engine has a cast crank, not the forged crank that it was supposed to have, so now I'm verifying everything. Who the heck installs splayed caps, then uses them to hold a cast crank? :skep:

Flareside

Nope, that rod is number "1". The other rods and caps are all numbers 2 thru 8. It looks like the shop did a good job on the assembly, and it runs good, but the parts selection doesn't really make sense.

WashingtonRacer

You know I had the same issue, Anyone ever herd of stage 3 rods? well they look just like the one he has. stage 2 crank.. cast as well. 4 bolt main, supposive forged flattop pistons, well they look just like your from underneath too. Well you who may have read an earlier topic I made, those forged pistons cracked all to hell. Though it could have possibily been user error but I drove it for quite a while and never had any problems, so who knows. Anyways yeah it does **** me off that they said it has these so called parts and it doesn't. thats why I say purchase your parts seperately soyoucan verify the part numbers and make sure it's what you ordered.

danno85

Those are definitely cast pistons (in the pictures). You can tell by the
parting line from the mold running across the bottom and down the skirts,
as well as the texture of the aluminum on the pin boss. They may
be hypereutectic (sp?) (which are cast also but have a higher concentration
of silicone than regular cast pistons), but they're definitely not forged.

Dan

Lionsden

I agree---- cast pistons.

jackson

I agree with Dan ... parting line ... they're either cast or hyper. Pull the head off ... look on tops of pistons ...if TRW/SpeedPro there'll be number stamped into tops. Post the number & I can look it up in my SP book. The TRW/SP "numbers" usually consist of both numerals & letters. If it's a 5.7" or 6.0" rod 400-based motor ... with TRW/SP cast or hyper will probably have three numerals ... with TRW/SP forged will probably have four numerals. Typical hyper #'s may be: 615, 616, 623. If it's a 5.7" rod 400 w/ TRW/SP flattop hyper 4vr my guess they're H616P or H616CP (coated skirts). Post yer #'s ... will look it up. Nothing slack about a good cast crank & a good set of hyper pistons.


[Modified by jackson, 10:52 PM 12/21/2002]

ghoffman

OK, I hate to be **** but aluminum uses silicon as an alloying agent not silicone. It is not symantics, there is a really big difference between silicon and silicone but it must be one of the most error prone of any term around. Silicone is a man made chemical (like Silicone RTV and breast implants) whereas silicon is element number 14 and is essentially sand.
Your pic is a cast piston, no idea if it is hyper, need to see who made it to tell that.

danno85

Yes, you are correct on silicon, not silicone. I wrote that in a little too much
of a rush and was more focused on the question of forged vs. cast.

BTW, it's semantics, not symantics, and it is in fact a question of semantics
(the meaning) rather than of syntax (the spelling).

Thanks,
Dan :)

Flareside

Thanks all. The parting line is what originally got me thinking cast. Too bad.

I don't really mind cast pistons, but I bought the car with this engine in place, and it was represented as having a forged rotating assembly (including forged Speed Pro pistons). Live and learn...

Jackson, I'll post the numbers once I get a head off. Thanks!

-Joe