Posted By: MNobody
Piston top thickness - 04/11/13 03:09 AM
If a guy had some 10:1 Ross flat top pistons with the valve reliefs in the top and wanted to cut them a little deeper to gain some piston to valve clearance is it possible? Thanks
Piston top thickness
Posted By: RapidRobert
Re: Piston top thickness - 04/11/13 03:20 AM
I'd call Ross & barring that I'd put a pointed tip pencil type metal pointer vertical in a vise then set your magnetic dial indicator next to it & rig it so the plunger comes straight down vertical touching the pointer then zero the dial & lift the plunger & insert the piston inbetween the two & let the plunger go to the bottom of the valve relief & direct read what deck thickness you have (& therefore how further you can go). Umless Ross tells you otherwise for their pistons .150" is the bare minimum
Posted By: goldmember
Re: Piston top thickness - 04/11/13 03:24 AM
Yes.
Posted By: dOc !
Re: Piston top thickness - 04/11/13 03:30 AM
Quote:
If a guy had some 10:1 Ross flat top pistons with the valve reliefs in the top and wanted to cut them a little deeper to gain some piston to valve clearance is it possible? Thanks
DEPENDS on how much they were milled on the uNderside .....
Goldie .....wear are those TQ's you promised me ? ....
Posted By: goldmember
Re: Piston top thickness - 04/11/13 03:35 AM
I told you I'd put them on the side of I-75 anytime you wanted them,you never hit me back so I sent them to the dump. As far as the OP not enough info given to answer but yes there is some left to take,what do you need to have clearance,etc should be the question. I love RR getting all whacked out trying to help but this is not too hard.
Posted By: MNobody
Re: Piston top thickness - 04/11/13 03:47 AM
Great info but the pistons are still in the block, just wondering if i could take .020-.030 out of the relief area so i can go a tad thinner on my head gasket...piston is .092 in da hole.
Posted By: Cab_Burge
Re: Piston top thickness - 04/11/13 07:11 AM
Quote:
Great info but the pistons are still in the block, just wondering if i could take .020-.030 out of the relief area so i can go a tad thinner on my head gasket...piston is .092 in da hole.
How much V to P clearances are you looking to get? How much V to P clearance do you have now and what type, duration and lift cam are you using? Did you degree the cam or install it straight up or? 
Posted By: MNobody
Re: Piston top thickness - 04/15/13 02:43 AM
Piston to valve clearance is already too tight on the intake valve, the only reason it still lives is the .528 solid cam. Right now the compression figures out to 8.25:1 just trying to help that out with a thinner gasket.
Posted By: JohnRR
Re: Piston top thickness - 04/15/13 01:52 PM
Quote:
Piston to valve clearance is already too tight on the intake valve, the only reason it still lives is the .528 solid cam. Right now the compression figures out to 8.25:1 just trying to help that out with a thinner gasket.
Are you sure you are measuring it right and how is ANY ross piston .092 in the hole ? are you using a stroker piston in a non stroker application ? I don't think a .528 cam has enough duration to have a piston to valve clearance , especially on a piston with valve reliefs that far away ...
Posted By: MNobody
Re: Piston top thickness - 04/18/13 04:03 AM
No idea John i didn't build the motor. I was told they are 10:1 ross pistons but they are still in the block so i can't verify. Pistons .092 in the hole, .528 solid .026 lash I and E. 360 j heads have 2.02 intake and stock 1.74? Exhaust, chambers measured 72 cc. Head gasket is a fel pro .057 thick. All this gives me .017 clearance on the intake and .042 on the exhaust. And a compression of 8.25 if i figured it right.
Crap i screwed up and used the wrong stroke, it's actualy 7.5
Crap i screwed up and used the wrong stroke, it's actualy 7.5
Posted By: GTS340
Re: Piston top thickness - 12/07/13 01:32 PM
Ross blower pistons? I cant imagine them offering such a short compression height on a non forced induction application. If that .528 cam is the MP purple flat tappet cam Id say you don't have the cam degreed in correctly with those pistons and that little piston to valve clearance. Maybe pistons are in backwards with valve reliefs on wrong side? Or maybe rockers higher than 1.5 ratio?
Posted By: BSB67
Re: Piston top thickness - 12/07/13 05:31 PM
Quote:
No idea John i didn't build the motor. I was told they are 10:1 ross pistons but they are still in the block so i can't verify. Pistons .092 in the hole, .528 solid .026 lash I and E. 360 j heads have 2.02 intake and stock 1.74? Exhaust, chambers measured 72 cc. Head gasket is a fel pro .057 thick. All this gives me .017 clearance on the intake and .042 on the exhaust. And a compression of 8.25 if i figured it right.
Crap i screwed up and used the wrong stroke, it's actualy 7.5
Either I'm not following, or something is way wrong in the build or measurements. My first thought was backwards pistons too. But I still don't think that the valves would be this close even under that condition. Maybe 0.17" and 0.42"?
What is up with that stroke statement? Motor must be a real stump puller.
Posted By: GTS340
Re: Piston top thickness - 12/07/13 07:49 PM
A real stump puller Im sure! 7.5:1 static combined with that 528 cam I bet that engine has some SERIOUS cylinder pressure LOL...Not exactly an ideal choice of camshaft.
Posted By: moderncylinder
Re: Piston top thickness - 12/07/13 08:56 PM
Really need a Part # to reference or pull one out.
The underside of the piston may not be an issue it maybe the ring land
.092 in the hole + the head gasket and they have notches in them and your piston to valve is close notches cant be to deep
The underside of the piston may not be an issue it maybe the ring land
.092 in the hole + the head gasket and they have notches in them and your piston to valve is close notches cant be to deep
Posted By: GTS340
Re: Piston top thickness - 12/08/13 12:13 AM
Agreed! Looked in my Ross catalog and the compression height on the flat tops they list for both 340 and 360 calculate to be 18 thousandths below deck assuming an uncut deck at factory height of 9.600. Curious as to what slugs are actually in there?
Posted By: 80fbody
Re: Piston top thickness - 12/08/13 12:39 AM
My old 360 was in the 7.5/1 range with old school TRW flat tops. Don't believe they had valve reliefs & were stock compression height. These were way in the hole & still had crap for valve clearance. This was before they made hot rod pistons for the 360. Can't imagine Ross made a low compression piston but they could have been custom I guess. Is it possible they're not Ross?
BTW,I used the same block (uncut deck) & got it to 10.17/1 with 65cc heads & higher comp speed pros with valve reliefs.
BTW,I used the same block (uncut deck) & got it to 10.17/1 with 65cc heads & higher comp speed pros with valve reliefs.
Posted By: GTS340
Re: Piston top thickness - 12/08/13 01:50 AM
The .528 cam he is running would pair well with 10.17:1 compression ratio 
Posted By: RapidRobert
Re: Piston top thickness - 12/08/13 01:54 AM
Quote:Advancing or retarding the cam one of the two I forget which one would reduce intake VP clearance. You could easily mill the valve pockets .030" deeper & with some easy math (A=Pi x radius squared) figure out how many addit'l CC's you'd be adding. I'd weigh the pistons before/after to see how much weight change there is & not saying you'd absolutely need to rebalance but HF has a gram scale on sale regularly for $9.95 & you'd have the info in hand for a baseline. I'd confirm your measurements. Holler how it turns out.
Piston to valve clearance is already too tight on the intake valve, the only reason it still lives is the .528 solid cam. Right now the compression figures out to 8.25:1 just trying to help that out with a thinner gasket.
Posted By: GTS340
Re: Piston top thickness - 12/08/13 03:24 AM
Quote:Quote:Advancing or retarding the cam one of the two I forget which one would reduce intake VP clearance. You could easily mill the valve pockets .030" deeper & with some easy math (A=Pi x radius squared) figure out how many addit'l CC's you'd be adding. I'd weigh the pistons before/after to see how much weight change there is & not saying you'd absolutely need to rebalance but HF has a gram scale on sale regularly for $9.95 & you'd have the info in hand for a baseline. I'd confirm your measurements. Holler how it turns out.
Piston to valve clearance is already too tight on the intake valve, the only reason it still lives is the .528 solid cam. Right now the compression figures out to 8.25:1 just trying to help that out with a thinner gasket.
Valve relief volume calculation is a little more involved than solving for area of a circle (Area=Pi x R squared). See link below, not trying to be a know it all I'm just a stickler for accuracy when figuring static compression ratios.
http://www.lmnoeng.com/Volume/InclinedCyl.htm
Posted By: RapidRobert
Re: Piston top thickness - 12/08/13 03:37 AM
Hey I am a stickler for accuracy & I am wrong on occaision. I'll check that site out. EDIT I'm thinking (Area X Pi X radius squared) times .035" would be the addit'l volume removed then you'd convert from cubic inches to CC's then you'd add that number to the original valve relief CC amount. Sound good or bogus?
Posted By: GTS340
Re: Piston top thickness - 12/08/13 03:54 AM
Quote:
Hey I am a stickler for accuracy & I am wrong on occaision. I'll check that site out. EDIT I'm thinking (Area X Pi X radius squared) times .035" would be the addit'l volume removed then you'd convert from cubic inches to CC's then you'd add that number to the original valve relief CC amount. Sound good or bogus?
If the floor of the valve relief were parallel with the piston top, or if the existing relief is deep enough that it is a full diameter that would work but on a small block the valve reliefs are 18 degrees from being parallel and generally not deep enough to be a full diameter. Or just break out the burette and piece of Lexan if they are flat tops.
Posted By: RapidRobert
Re: Piston top thickness - 12/08/13 05:16 AM
Quote:Alright now I grasp the tilted cyl in the site
or if the existing relief is deep enough that it is a full diameter that would work.
Posted By: Oyvind Mopar
Re: Piston top thickness - 12/08/13 02:51 PM
I would have pulled that engine and find out all about the internals before doing anything destructive...Something is wrong, and small corrections may not be enough. My
Posted By: JohnRR
Re: Piston top thickness - 12/08/13 08:16 PM
Quote:
I would have pulled that engine and find out all about the internals before doing anything destructive...Something is wrong, and small corrections may not be enough. My
I might have first wondered why no reply 8 months ago before deciding to drag this one up from the dead .
But for the OP , I would have pulled a piston also , this sounds like a small block also ...