Need to buy cheap pistons, recommendations? KB pistons junk!

[Reumster]

Ok first off the last two engines I've built I've ran KB Silvolites, and both times the upper ring/lip of piston broke off. Now I've heard there notorious for this. Any fact? I know you must special file upper ring. Both times it was done by a pro.

I'm running 60 over, and 68cc aluminum heads, so I think I want to lower compression with dish pistons any recommendations for a good cheap set of pistons, that I can just buy rings for that don't require filing? Prices/part #s?

[brad69C-10]

Speed Pro Hypereutectic pistons.......pretty strong parts, not too pricey and best of all, they use a standard ring gap, just like everybody else.......you can probably get a set from $80 for a 4 valve relief 350 or $170 for a 2 valve relief type for a 350.........just my 2 cents worth

[MikeB]

Speed Pro hypereutectic with the standard size (5/32"?) top ring. They have very good tech support, and helped me with my ring gap. They recommended .012" - .014", which is what my Sealed Power moly rings measured out of the box. Conventional wisdom says .016" for a 4" bore, but metallurgy is getting much better these days. Their piston-to-cylinder clearance is also really tight, which all combines for better cylinder pressure.

[Reumster]

So you think speed pros? They take standard rings?

[mikep]

Speed Pro, Sealed Power, TRW, Keith Black, and Silvolite are all the same company. Ive bought silvolite pistons before and they came in speed pro boxes. I'd guess theyre all the same alloy in HE form probably done on the same tooling.

[Reumster]

Are you saying that the Speed Pro Pistons are the same castings as the KBs? Are you sure Speed Pro piston require no special gaping?

[brad69C-10]

I have these in 2 of my engines and have run them several times before.....they don't have the wierd ring gap like KB's.......

[mikep]

Probably the same alloy but not the same pistons. KB's typically have more options than the sealed power/silvolites for compression height, valve relief and ring thickness. Iv'e used a few of each in different builds over the years and other than different packaging I certainly wouldnt say the KB's are superior to the sealed power/silvolites . Both require some prep for assembly. The KB's can be had with thinner ring grooves for low friction thinner rings which personally I would avoid for general street usage. They build more power but dont last nearly as long as the standard thickness rings and they tend to use more oil.

In my opinion the HE pistons are fantastic for stocker type rebuilds. They hold their shape and probably enhance ring life considerably over cast pistons. Theyre good up to 400 HP without nitrous. Over that you really need forged pistons which have some of their own drawbacks such as they need loose tolerances which doesnt help ring life or oil consumption. If you are breaking pistons in the ring groove area then you are detonating. I dont see any way around that. Too much compression or too much timing or a little of both.

With the 68cc aluminum heads I'd go with either flattop silvolite hypereutectics with the 4 valve reliefs which is going to give you in the 9.5:1 area or with thr TRW/Speedpro flattop forgings if you ever want to use nitrous.

[brad69C-10]

Mike is right..........I have also used KB and had no trouble, but my preference in a Hyper "U" piston is the Speed Pro's.........otherwise it will be FORGED all the way baby!!!!!!

[Reumster]

What are 4 valve relief pistons? They reduce compression? Will reducing compression help fight the detonation? Or is it just a matter of retarding timing a bit? If it's bad to have timing to far advanced what happens if its to far retarded?

So the speed pro pistons require special ring filing/gapping?

[Chevyman69]

4 valve reliefs are just that there are 4 notches in the tops of the pistons and yes it brings the compression down, basically they are the style of stock pistons used on most regualar factory motors. I notice that you have NOS in your signature so I assume you use it. You really shouldn't be running a cast piston at all then if thats the case. I too have heard a long time ago KB's were junk, had the trouble you mentioned, and I have just stayed away from them. However running nitrous on a cast piston is pretty hard on it and they will only last so long and you are back to sqaure one again. It may be time to invest in some forged slugs and then you can quit worrying about nitrous caused damage. Detonation is a lot of things but for the most part if the compression is not overly high( you can safely run 10-10.5:1 with aluminum heads on 92 gas) its mostly in the advance curve. My motor for example will run 12 degrees intial and 36 degrees overall. Kind of a basic general setup but it seems to work good on most motors, mine hasn't been run yet, but its also not the first engine with that particaulr timing setup I have seen either.

[Reumster]

Chevyman69 Man you 69 sounds pretty mean! What's it run in the 1/4?

I think I'm going with Speed pro 4 valve reliefs. I'm running 64cc Trick Flows, and 60 over so I need to drop compression a little.

[Chevyman69]

Originally posted by Chevyman69
, mine hasn't been run yet,

, That answers your question.