Inliners International Forums General Discussion Hi Performance 250 piston purchase, forged

guy's,
talked with my handy machine shop. discussed with him the problems of buying good quality performance pistons for the 250. he is going to check pricing for us buying a group of pistons.

piston type forged
bore 3.875 .030, .040, and .060
piston top flat with no valve reliefs
designed for use in a block to be decked .015 and be zero deck.
.927 pin
5.7" rod

also checking on another piston
piston type forged
bore 3.875
5.7 rod
12cc dish
top ring land is designed for turbo use.


with this said, lets see a show of hands for getting into a purchase. i should know prices yet this week. tom

Also,
if there are guys that want to use a 6" rod,the LS1 piston should work & not too much $$$.Off the shelf piston.



MBHD

Is the second piston for a turbo application standard bore only? I'm not sure if I'm going to have to bore mine out.

dylan,
you will have to bore yours out.
the turbo piston also in 30, 40 and 60 overbores. tom

I'd be interested in a set of turbo pistons...

Can we get them drop-shipped to our shop so we don't have to pay twice for shipping?

I'd be interested in a set pending price then.

I'm in for one set of forged .030 flat tops as lightweight as is reasonable.

You beat me to it Tom. Thanks.

ok, i have prices and they aren't that bad either. this the way it can work, there has to be a group of pistons bought. 120 to be exact. that works out to 20 inline 6 sets. i am willing to help with this deal, at no real profit to me. just as i do with the cast iron turbo six manifolds.

pistons will be forged and weigh in around 440 grams with no pin. these pistons do come with a .927 pin. KB is the manufacturer.

compresion ratios figured with a .041 head gasket and zero deck.

they can come in 30,40 or 60 oversize 5.7 rod
flat top with no valve reliefs (9.5 cr w/70cc head)

they can come in -12cc dish with turbo ready top ring land. 5.7 rod
same overbores (8.5 cr w/70cc head)

also available same pistons w/ 6.0" rod

ring packages also available ( still working on that)

price per piston w/pin 65.00 each


do not know yet about drop shipping, doubt it though as i would probably have to stock the pistons.

tom

I am curious if any one has ran these F/T pistons without any valve reliefs and ran into any valves hiting the pistons and what lift/ratio cams are being ran. 283's use to have no valve reliefs and on an over rev the valves would make contact, those cams where not very big in these engines.

I can't address that directly, but short stroke motors (283: 3.00") always have less piston to valve clearance than longer stroke motors (250: 3.531", 307 & 230: 3.25") with a similar cam.

going to check a engine this weekend and see what clearances are needed. anyone else be able to check?

I checked a long time ago,when I had a cam of about .550" lift & 230 degrees duration @ .050 110 lobe center.

It had a mile of clearance on my 250 L6.

Really not necessary for any valve reliefs unless you are running a BIG cam.

MBHD

Checked a 250 today. Covered an OEM 307 piston top with bondo to create a true zero deck flat top with no valve relief. It was a STD piston in a .030 bore so I slipped a shim in to keep it square in the bore. .040 head gasket. Comp 260 hydraulic flat tappet cam installed at 3 degrees advanced. Head was 1184 casting with 1.89 intake and 1.6 exhaust valves. Stock pushrods and rockers, solid lifters. The minimum clearance I found was .240 inch on the intake. Exhaust clearance was more like .350.

Sent some photos of the operation to Tom.

Where was the piston in reference to TDC when you checked the intake and exhaust clearance. The reason I ask is because TDC is not the point at which either the intake or exhaust valve is closest to the piston. And since you mentioned needing to place a shim around the piston, it sort of implied you might have left the piston at some stationary point to do your checking. Just curious....

Nope, I rolled it around several times. The shim stuck on the piston and slid up and down the bore. Smallest I found was .240 on the intake. Pretty sure intake would gain and exhaust would lose clearance if the cam was installed at 0 relative to the cam card.

Good, your info should give others an excellent point of reference to draw from. I didn't recall if you mentioned the piston deck clearance in your earlier post, do you know what it was. Naturally, the closer to zero deck you get, the less P/V you will have also to take into account.

Zero deck. Filled the piston top with Bondo at TDC to flush with the deck. Won't get any closer to zero than that. .040 head gasket so exactly .040 clearance between head and piston top.

Now that you have created a virtual zero deck piston, can you measure the compression hgt. with it like that, and help determine what a theoretical compression distance is needed to get a near zero deck height. Maybe subtract .010" so someone could do a clean up deck cut if desired, and be right on the money.

stroker6,
great news for a true flat top piston.

cnc, i was planning on ordering pistons with a CH that will need a .015 cut of the deck to get a true zero deck.


these pistons will also have spiral lock groove cut into them.

so i need a show of hands on who is seriously interested in these pistons.

PM me with your interest. i would like to put a order together within 2 weeks. tom

Well I could measure the piston but my block has been decked so it won't tell us much.

Assuming factory deck is 9.150 the CH should be 9.15-5.7-3.53/2 or 1.685 for zero deck. Less .015 to account for machining the deck surface gives a CH of 1.670.

If you have a virgin deck and don't want to machine it, the .015 in the hole plus .020 steel shim head gasket will give the same result as zero deck and a .035-.040 composite head gasket.

stroker6,
1.670 is exactly the CH we used to calculate with. also, almost any block will surely cleanup at .010, .015 for sure.

Which aluminum alloy and what are the wall clearances for the new forged pistons?

I am seriously interested, if they are 2618 and can use a 1.5, 1.5, 3 ring pack.

I would prefer the rings down a ways for nitrous as well.

for those interested. the alloy is 2618. same as the performance forged SBC and BBC pistons. The ring pack also will be like the performance SBC. the turbo/nitrous version will have a tough top ring land.

if interested pm me. i will put you on the list. the purchase needs to be for 120 pistons. that 20 engines. like to have atleast 10 sets spoken for before ordering. tom