piston clearance? 915 w/domed?

Posted By: KryslerKid

piston clearance? 915 w/domed? - 04/06/09 06:50 PM

I just removed my 906's and would like to bolt on a pair of 915's. I have trw dome pistons, but so far can't find the number on them. I believe the factory used flat tops with these heads. Will these heads work with these pistons? thnx

KK

1969 440 6bbl

Posted By: ademon

Re: piston clearance? 915 w/domed? - 04/06/09 07:24 PM

I think all the factory pistons were flat exc hemi, Not sure but i would think not, clay it up and see what you get. the pistons might still be down the hole.

Posted By: RapidRobert

Re: piston clearance? 915 w/domed? - 04/06/09 07:39 PM

You have the trw dome pistons in there now? Put one at tdc & see what deck height you have with the dome. You'll need a head gasket to give you enough clearance(piston to head)& .035"-.040" piston to head clearance for correct quench would be ideal & if you have more than that you're good but wont have a quench benefit. I'd CC the old/new head(s) to calculate what your actual CR is for reference.

Posted By: KryslerKid

Re: piston clearance? 915 w/domed? RAPIDROBERT - 04/11/09 02:19 PM

My existing/running 440-6bbl has 2295 TRW's currently in it. Seems to run fine. I'm not sure what block work was done by the previous owner, but the holes are punched .030, and the approx deck height on a couple cylinders is about .046 (waiting to get proper tool). I'm new to this, but I am measuring to the lower part of the piston, not the dome, is that correct? My approx dome height measured .130 from the flat portion, and the advertised for this piston is .140. Do I need to be concerned about the dome for this setup? Or do I just concentrate on the flat portion of the piston? Also, I'm hearing about .040 is where I want to be with closed chambered heads for optimum quench. If my pistons in fact correctly measure about .045 or so in the holes, what's my best bet without machining the block or heads? I'm using factory 4 bbl rods, factory steel crank, and I'm assuming the block has not been shaved. 509 MP cam, Rhodes lifters, factory rockers, auto. Any help would be much much appreciated! KryslerKid

Posted By: therocks

Re: piston clearance? 915 w/domed? RAPIDROBERT - 04/11/09 03:10 PM

I ran Ross 12.5 domes with my 516s.Never a problem.I ran the FelPro 1009 gaskets.Changed to the Stealth heads last year.I run a .588 Comp solid in my 440.Rocky

Posted By: KryslerKid

Re: Deck height with 915 heads w/domed trw's - 04/23/09 04:35 PM

Dumb question, measuring deck height with domed pistons, I'm assuming I need to measure the flat portion of the piston? Also, do I need to be concerned with the domed portion for 915 heads? Also I'm told .035-.040 for optimum quench. If my slugs are .045-.050 in the hole, what's my best bet without shaving the block? Thank you!

KK

Posted By: JohnRR

Re: Deck height with 915 heads w/domed trw's - 04/23/09 05:14 PM

Quote:

Dumb question, measuring deck height with domed pistons, I'm assuming I need to measure the flat portion of the piston? Also, do I need to be concerned with the domed portion for 915 heads? Also I'm told .035-.040 for optimum quench. If my slugs are .045-.050 in the hole, what's my best bet without shaving the block? Thank you!

KK

you'd have to cut the block , no way around it , I assume you are running race fuel now anyway , quench really comes into play when trying to build a pump gas friendly engine with compression on the edge of detonation , I'm guess you're compression is too high already and will go up with the 915's , the dome shouldn't even be an issue so throw on a set of steel shim gaskets and

Posted By: RapidRobert

Re: piston clearance? 915 w/domed? RAPIDROBERT - 04/23/09 08:24 PM

Quote:

but I am measuring to the lower part of the piston, not the dome, KryslerKid

Measure both as you'll need both dimentions, the dome for piston to head(quench) and the flat area around the circumference and the dome for CR. Using a dial indicator in a bridge. when you have all your dimentions plug them in here(to get your ACTUAL CR). http://kb-silvolite.com/calc.php? and when you find the part # for the pistons you'll be able to get a listed spec for the piston dome in cc's.

Posted By: JohnRR

Re: piston clearance? 915 w/domed? RAPIDROBERT - 04/23/09 08:37 PM

Quote:

Quote:

but I am measuring to the lower part of the piston, not the dome, KryslerKid

Measure both as you'll need both dimentions, the dome for piston to head(quench) and the flat area around the circumference and the dome for CR. Using a dial indicator in a bridge. when you have all your dimentions plug them in here(to get your ACTUAL CR). http://kb-silvolite.com/calc.php? and when you find the part # for the pistons you'll be able to get a listed spec for the piston dome in cc's.

Double R, TRW dome pistons are not step head pistons like KB's , it's a regular domed piston. the dome is in the deepest part of the combustion chamber, the piston he has is probably the 2295 ???

Posted By: RapidRobert

Re: piston clearance? 915 w/domed? RAPIDROBERT - 04/23/09 08:46 PM

Yeah I been using KB's pretty much exclusively for years now. To me they dont look real solid(the hypereutectics) but they have the CH & step dome that I need and to date I have not had one go KaBoom.

Posted By: KryslerKid

Re: piston clearance? 915 w/domed? RAPIDROBERT - 04/23/09 09:17 PM

Yes they're the 2295 trw's. Going by memory the dome height is .130. But not sure how I would get chamber depth, unless I convert the dome height into cc's, then subtact that from the chamber cc's, then convert the diff to thousands? But wouldn't that tell me volumn, not depth? Hope I made sense. I'm picking up the 915's tomorrow from being cleaned up and surfaced. I guess I could live with whatever quench I could get from this setup. I just want to use the right head gasket for optimum performance. Ballparking the pistons are down about .046 with factory 915 large valve heads. Thanks guys, you're helping quite a bit!
KK

Posted By: JohnRR

Re: piston clearance? 915 w/domed? RAPIDROBERT - 04/24/09 12:49 PM

Quote:

Yes they're the 2295 trw's. Going by memory the dome height is .130. But not sure how I would get chamber depth, unless I convert the dome height into cc's, then subtact that from the chamber cc's, then convert the diff to thousands? But wouldn't that tell me volumn, not depth? Hope I made sense. I'm picking up the 915's tomorrow from being cleaned up and surfaced. I guess I could live with whatever quench I could get from this setup. I just want to use the right head gasket for optimum performance. Ballparking the pistons are down about .046 with factory 915 large valve heads. Thanks guys, you're helping quite a bit!
KK

Just throw steel shims on it , spray with coper coat and run them as long as the block deck surface looks good, you'll never achieve quench with that piston without decking the block and I'm thinking you already have too high a compression ratio for pump gas .

If you are concerned with the head to dome clearance pop some clay on the top of a few pistons , put on the head without the gasket , or reuse your old gasket, and rotate the engine over a few times. Spray some WD in the chamber so the clay doesn't stick to the heads and see how much clearance you have between the head and the dome .