When using a cast rebuilders piston Sealed Power, Silvolite, etc. what is the max. compression ratio advisable? For drag race only with what ever race gas it needs. At what point are head studs advisable? Thanks for the input.

I think that with a combination of deccking the block and milling the head you can get the compression about as high as you need it. The more squeeze you get the more cam you can run, etc..

If it's going to be a race motor I would put head studs in it anyway, just for the peace of mind.

_________________
Official Cookie and Mater Tormentor.

i ran 11.4/1 with no more than 25degs total timing on av gas and supreme 50/50 mix, the piston were silvolites, never hurt any after i got the timing and ring end gaps right.

Not just because I'm in the business but I highly recommend a forged piston for 11:1 compression or higher especially if combining with nitrous.

Why (forget nitrous)? I have a set of NOS cast 12.5 domed pistons (very heavy).

_________________
Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

If you build a strong race engine you would know what you want. My race engine uses forged pistons and the best parts I can get for a Slant. So why not ask this what is the best Slant race engine parts avalable. Thanks Ron Parker.









It Aint Over Until I Win

Why (forget nitrous)? I have a set of NOS cast 12.5 domed pistons (very heavy).

I don't know where you got the "cast 12.5 dome pistons" from; sounds like a rare set of pistons. My take on in this matter is for the current and best part for a high compression engine I recomend to go with a forged custom piston. Better material & performance hands down!

They are Jahns. The newspaper packing was dated 1978. My questions still remains, why forged custom pistons? Why are they better?
I am not being a "smart ass", I run them in some of my engines, but also run cast pistons in some, without problems. The main advantage I can see is the strength to weight ratio. I figured since you are in the "trade" you could give a difinitive answer, as to why they are beter. Do custom forged pistons, give enough "bang for the buck" to justify their use in a "normal" hopped up SL6 engine?

_________________
Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

like charlie i would like that answer, in my experience i have only used cast because of price and availability, i have found that if a cast piston is setup looser in the bore and larger ring gaps, they can take a little more punishment, at the track i have seen forged and cast pistons hurt when the tuneup has been missed.

Hello gentleman,
Honestly the best "bang for the buck" pistons for a mild to moderate race engine would end up being a decent cast piston with the right piston & ring gapping.
Yes the forged (like ours at CP) are not cheap by any means. Cast and forged pistons will both suffer from the same troubles such as detonation but in most cases the forged (especialy 2618-T61 alloy) will put up with more abuse.
Finally I believe for those who can afford and want to build an exotic & (max high compression,turbo,supercharged or heavy nitrous)very powerful engine; the forged piston is the way to go.
I do invite any questions any of you might have .

What about Hyperteutic pistons?

_________________
Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Give them enough abuse and you can make them do this:



A forged slug wouldn't break, but it would still be junk.

_________________
Official Cookie and Mater Tormentor.

I think that the smaller bore size (3.400) in the SL6 has a lot to do with being able to use cast pistons in higher compression / high horsepower build-ups. A good quality cast piston will hold-up in a 11-1, one HP per cube, 6000 RPM SL6 where a cast pistion in a simular built 11-1, 6000 RPM 440 will fail.

I agree that for all-out race engines, forged pistons are the way to go but you can use cast in many performance SL6 applications with-out problems.
DD

Stanzilla has the perfect example pictures of what can happen to a cast or hypereutectic piston under severe use and catastrofic failure. The root cause to the failure of a cast,hypereutectic and 4032 alloy piston is the silicone content.
Silica being the main hardening material in the forementioned pistons, is the same silica that is used to make glass. When super heated from detonation or high cylinder temp/pressure conditions, will crystalize and crack or shatter like glass.
In my experence I have seen many badly damaged sample cast, hypereutectic and 4032 alloy pistons, compared to the 2618 alloy (less than 2%) that we use at CP. One of the advantages of a good forged piston like ours is the improved tolerances, which do help with ring seal and that makes more power.

Mike and all,

The alloying material you are speaking of is the element silicon (Si on the periodic table). Silica is silicon dioxide (glass) and is not, I am pretty sure, added to aluminum alloys as a feedstock. Silicone is a form of rubber used in gasket sealer and gaskets and a million other uses (composed of carbon, oxygen, and silicon). If you are a sales person, it might be helpful to talk to one of your materials guys to explain the piston alloys in more detail. Sorry if this sounds uppity, I am honestly just trying to help.

The high silicon content does make the alloy more brittle, but a little bit stronger than lower silicon cast alloys.

I totally agree that forged pistons are the way to go for a high effort motor. No arguments there at all. I also agree with Doug's point that cast pistons can handle some abuse in a Slant as I have a couple of motors to attest to that.

The next motor I'm building will have forged slugs, which I have on the shelf already. I'd love to see what CP has to offer there!

Thanks for listening,

Lou

_________________
Home of Slant6-powered fun machines since 1988