I have a 350ci with Speed Pro H345 flat top pistons in it. I want to drop in some Speed Pro H580 dish pistons instead. Summit Racing specs the H345 at 5cc of dish I have read that the H580 has a dish of .185" x 3.3" which is about 26cc of dish Summit Racing specs the H580 as a D shaped dish, but their pic shows no D shape Anyone know the real specs for the H580 piston in terms of: H580 Dish shape (D or complete circular dish)? H580 Dish volume is inches or CC? Piston weight of the H580 and H345? H580 compression height? I think Summit Racing's value of 1.54" is correct. I tried asking Federal Mogul the questions. They won't answer because I am an end user and not a re-seller. Thanks

I ended up finding all the info on the Speed Pro H580 pistons from Silvolite

http://www.21cgt.com/FMWebCatalog/default.htm

Put h580cp in the part number to find specifications on a part. If you wanna go with a thirty over piston change the part number to h580cp30.

Can i ask why you are wanting to get away from the 345s?

Thank you for the link, but it doesn't give the CC of the dish. I am pulling the H345 pistons so that I can put some boost to the engine. The H580P pistons fit the budget for this cheap build.

I had a hard time finding some speed pro pistons with less than a 5cc dish. You probably could have your heads milled to gain compression at a cheaper cost than a new set of pistons, balancing, and having pistons removed and pressed on rods.

He wants less compression, hence a bigger dish.
I didn't think you could get ones with that big of a dish, from speed pro. I'm tagging on to find out...

Here's the deal. I came across a set of fresh 193 TBI heads (64cc chambers). The block has H345 (5cc relief) pistons. The block was decked about .005" and the heads were decked by about .005". It has .039" fel-pro gaskets in it. Bores are 4.030". Overall, it is in the 9.5:1 to 9.8:1 range. Quench is WAY OFF with the 1.54" comp. height H345 pistons in it.

I want to push about 15 PSI of boost into it. OK, before anyone jumps on me about the 193 heads not flowing.......I know they don't flow like nice after-market heads. One, I will port them. Two, boost is a little easier on low flow heads. Three, they didn't cost much and I like playing with free and/or junk parts.

It is cheaper to buy a $100 set of H580P pistons & rings and swap them ($50 press time) compared to having a set of heads done. I need to loosen up the piston ring end gaps so the pistons need to come out anyway. I really want to try out the TBI heads. The H580P is a stock vin K truck piston equivalent to the Silvolite 1487 piston (check out the Keith Black website). Take a look at the Silvolite page and it lists the piston dish sizes. The H580P come out to about a 16-17cc dish. Silvolite has up to 22cc dish, but they say not for performance use. Ha ha, the Silvolite 1487 / H580P do not say that. I don't think that they are a high performance piston but I am going to give them a try probably. They are a hyperuetectic piston.

I am going to polish the 193 chambers and try to make them about 66cc each when I do the port & polish work. Probably put some GM .028" gaskets on the deck. Not like the quench matters that much because the H580P units are NOT a D-cup. They are a circular dish so that means a giant quench and no swirl/turbulence. But wait the 193 TBI heads are high-swirl designs......maybe a match made for each other. Yup the H580P are truck pistons. In the end, the engine will be around 8:5:1 compression late 80s TBI 350ci truck block with a 222* @ .050, 114* LSA cam in it.

If you want a lower compression piston, i would go with the h620cp. It has a -21 cc dish in it. Sorry for misunderstanding you. I thought you were NA and wanted a performance "boost".

I had looked at the Speed Pro H620CP pistons with the 21 CC dish early on but the price was over $25 each. I had also looked at the Keith Black KB101 pistons that are $235 a set. Roughly, the same price, but the KB pistons are D-cup and I think the H620CP are circular dish. The KB101 units have the advantage in that respect.

The H580P pistons are around $10 a piece. That is why I wanted to use them. The dish calculates out to around 14-16 CC. I like the compression using the 21/22 CC dish better than the 14CC dish. I may end up using the KB101s. Decisions, Decisions!