I'm rebuilding my 71' 350/270 and need new pistons due to .030 overbore. I bought a set of cast Speed Pro's and they are made in India. Sorry, just can't use made in India/China parts in the Vette. What is a good made in the USA piston ? This isn't a race engine, so I don't need anything high-tech. I would also like to bump the CR up t 9-9.5.

 

LT-1 clone would be good.
w/ 76 cc heads they will be ~ 9.4
call and ask where .....

 

Probe in L.A. probably makes some of the nicest, most competitively priced pistons on the market but they're forged so they're not THAT cheap-if your budget can handle around $400 they should have something that will work.

 

I understand and respect your patriotism, but you'd be hard-pressed to find anything that's 100% American made in this global economy.

A good hypereutectic piston is what you're looking for; they're only slightly more expensive than cast and will hold up better to any hard driving.

The '71 Corvette 350/270HP used the 3973487 head with 1.94/1.50 vales and a 76cc (75.47) chamber as noted.

Assuming a 5.7 rod and and a zero deck a typical flat-top piston with 5cc single valve reliefs will give about 9.5 CR with an .041 FelPro head gasket. The engine will probably require premium gas for full timing advance.

SRP's 138081 piston would meet this spec, although there are many, many others.

More information on your budget and power targets will help with a a little more specific guidance.

 

I'm just looking for something in the 300HP range. Budget for pistons in the $300 range.

 

What about Keith Black pistons, they may be what your looking for. Many of the crate engines on the market use these and I've been told are high quality. Not sure if made in the good ole USA though.
Check them out on Summit's website.

 

r u zero decking it? waste of ~125$ if not needed. milling heads? another waste?
my LT-1 pistons gave me 9.67:1 w/73cc heads

 

I believe all of the newer Federal Mogul and Speed Pro pistons will be from India, that is why a lot of their stuff is on back order, they are still a top notch supplier. Like Billa said, I would use some hypers or go forged.

 

No decking, no milled heads just stock # matching stuff.

 

Setting appropriate quench is not a waste in my experience, although I was just providing an example. I don't see anyone recommending milling heads.

1970 LT-1 pistons would give around 9.6 CR with 76cc heads, but these pistons are no longer available from GM...and they'd be pricey as they're forged.

Duke94, IMHO your best bet is to just pick up a good hypereutectic engine overhaul kit from Summit or Northern Auto Parts. I've used both the Sealed Power and Northern kits to good effect. Cast pistons would be fine at that power level if you're really on a tight budget. Get a price list from your machine shop as a) often they can put together a kit for less than you can buy it elsewhere and b) depending on their pricing for rod resizing, etc it may be cheaper to replace some parts than have them machined -specifically the crank and rods.

I would note that Sealed Power has had some QA problems as production moved as Scott noted.

Finally, start with your machine shop and work your way back. Your power targets are very reasonable for a stock overhaul, and you can get that number without going to a CR that would require premium fuel. I'd shoot for around 9:1 with a bit larger cam (happy to provide suggestions) and with your stock heads overhauled. I'd expect to see right around your power target in a very smooth, streetable package. Usually I'd recommend Vortecs for a budget build, but I'm sensing you want a pretty much stock engine at the lowest reasonable cost.

Happy to help spec this one out more specifically with you. What's your diff ratio, and what kind of trans do you have?

 

Just saw your post regarding matching numbers - that helps a bunch.

In that case, definitely just a good rotating assy' from Summit or Northern with hypers. Be SURE -REALLY SURE - that your shop knows to leave the stamp pad when they clean the deck - they'll almost certainly take at least an .003 clean-up cut regardless. Figure a budget of around $2K. Consider using a thinner head gasket (such as GMPP 10105117 @ .021) to get the quench into a bit more reasonable range with a stock .025 deck.

If you're sticking with the stock intake, carb and exhaust manifolds then cam choice becomes a lot more critical, and a dual-pattern cam would be your best choice. I'm usually not a "nostalgia" cam guy, but the CompCams updated L79 (grind 12-671-4) might be a great fit or the 300HP update (grind 12-670-4). I think these will leave you a little shy of your HP targets (around 270 - 290HP) but they'd be very responsive with a great torque curve and the 'sound' that you've come to love from your 'vette.

With stock heads, intake and manifold, putting in too much cam is just going to make a "doggy" engine - so I'd encourage you to stay on the mild side.

 

billla Thanks for the suggestions. The block was bored a couple years ago along with a valve grind on the stock heads. Just now getting around to building it back up. Comp Cams suggested the XE-262 Cam which I bought along with the springs to go with it. Summit Tech guy suggested the Speed Pro cast flat top pistons. All the rest of the parts will be the stock stuff (heads, intake/exh manifolds). I was looking at the Summit site for the KB Forged pistons and there were 2 listed, one with 1.565 compression distance and the other with 1.433. What's the difference?

 

Thanks, Duke - all great background.

The XE262 is a great choice - it's basically a roller-tappet cam profile on a flat-tappet cam and the numbers are right on for your engine. The 262 and 268 are my favorite cams. Be aware that you need to pay a bit more attention to initial lubrication for startup and use a good high-zinc oil. They do tend to be a bit noisy because of the lobe ramp, and they sound a bit different than the "old style" cams...but they do make more power. I'd expect you'll be up around 290HP and 340TQ at the flywheel with a much broader torque curve than the "nostalgia" cams I mentioned.

Another note is that you may find the spring pressures higher than an old-style spring compressor will do

Compression height (distance between the centerline of the pin and the top of the piston) is based on the length of the rod and the stroke - 1.565 is for a 3.48 stroke with a 5.7 rod (stock), 1.433 would be for a 3.75 stroke and a 5.7 rod (383).

You really don't want or need forged pistons for a low HP street engine. They're more expensive and return nothing in terms of durability or performance...unless you're planning to spray

Forged bore clearances are also much wider than cast or hypereutectic due to their greater expansion (.004+ vs. .001 for cast/hyper) and IMHO this isn't good for regular cold startups. Not a big deal by any means - but IMHO I'd stick to a cast/hypereutectic. -5cc relief flat-tops are fine - but recognize that anything over about 9.2 CR is going to require premium gas with full ignition advance. You can sneak it a little higher with less advance...and there are design tricks to take it a bit higher - but that's the max number I'd shoot for if you don't want to run premium.

 

got my TRW lt-1 pistons frm jegs in '94. they would be in the upper end of your CR range, but, if they are NA, forget it.
maybe u can squeeze 9:1 with a .015" gasket and the right flat tops. it will still run nice w/xe262, i have that cam w/9.7 on 87, but i run cold air & precise tuning for 87 u will likely need 91.
Quench is important imo. 25+15=40
make sure u don't get "rebuilder" pistons .025" down the hole; i sent a set of those back!

 

billla, I agree in not needing a big $ piston for this engine, I would really like a made in USA piece (at least nothing from India or China as their quality is typically VERY poor). Any cast pistons made in USA?

 

One thing I'd like to add, Billa is right on about the clearances. Be sure you check them before you install the pistons. I had a local shop tell me he bored my block 005 oversize for 001 hyper pistons because he knew more then the engineers at Fed/Mogul. I would have had some issues if I built that engine with those spec's,which I didn't.

Later found out this was "mo" of this shop to get some return work! He paid in court.

 

i use feeler gauges to spot check every piston.
only good to 1/2 a thou, but that finds the problems often

 

For the most part, you'll find that anything cast (including hypereutectics) is from outside of the US - I don't know of any that are still made in the US. As noted, there were some initial quality issues on even the brand-name stuff as tooling got moved and production spooled up...but I have not seen this in the last few boxes of pistons I've used. It's worth a chat with your shop to see if they can specify Sealed Power "black box" (overseas) vs. "white box" (USA) (colors corrected).

I would expect that most of the forged stuff is made in the US - but I honestly can't say for certain.

 

Using a feeler gauge to "spot check" something that is measured with a mic and bore gauge makes no sense to me. As for achieving .0005 accuracy with a feeler gauge, I have no idea how this would be achieved.

The shop will measure all the pistons and bores to .0001; they'll find anything amiss at that point.

 

a sad commentary on the state of our school system. my dad was a shop teacher and he always complained about students that can't even read a ruler. Thanks for your honesty billa, most guys wouldn't admit that