340 Pistons

Have looked around alot and failed to find what im looking for.

Is there any forged of the shelf .030 over pistons for a stock stroke 340 available that would give about 11:1-11.5:1 compression?

Needs to work with a set of Edelbrock RPM 340 heads.
If i remember right the chambers are 67-68 CC My memory is alitle fuzzy on that part.

Yes i know those heads are stupid but i already have them.

Im weighing my engine options here,the car was parked along time ago and have started planing to finaly get it back on the road again for some fun times, i have a long way to go to get there but im trying to figure things out ahead of time so to speak:)

I would sell or trade them for the smaller combustion chamber (heart shaped) then you can go with a zero deck (quench motor).

You guys kill me. I ran 9.70’s with those junk heads and my sons running low 10’s with a stock stroke 360@3200 pounds with them

The market for these heads are not realy huge over here,but yeah in a perfect world that would be a nice option,thought i would never be anywhere near get my money back on the portwork on them.



Well its not that those heads are junk,they are just not very compression friendly on a little 340.

Your only choices I know of are the old TRW pistons. You can use the 10.5:1 flat tops and get the CR up by getting the piston out of the bore.

A better choice is TRW with the dome on it. It has a 1/16 1/16 3/16 ring pack and if you do it correctly you can mill off some of the dome and still get the CR you want.

Those domed TRW's weigh as much as a brick. They need a good set of aftermatket rods and heavy metal added to the crank.....

Ed

I ran those bricks with stock rods and crank in a 340 to 7200 street/strip deal. Never had an issue. They are very heavy.

I bought and paid big money many years ago for a set of Dirrect Connection 11.5-1 pistons and they looked exactly like the old TRW 13.2-1 pistons. 340 engine.

I use them and they don't require heavy metal.

They aren't bad for what they are.

Your a lucky man Dave.

Mine had .065 clearance and still stretched the rods enough to hit the heads.

Ed

I had a 4 speed behind it. Never raced it, just beat the crap out of it on the streets. Ran it with ported j heads. I think the slugs i had were listed as 12.5:1.

Thanks everyone im weighing my options here:)

TRW pistons could be done even thougth a lighter piston would be prefered,the remains of the present rotating assembly consists of a stock forged crank, Eagle H-beams and was previously balanced with a set of those dome TRW pistons that have had their domes and alitle of the tops cut down and some weight taken out of them at some point so going to a new TRW piston would probably require a bunch of heavy metal to get it balanced again but it is an option

If you wonder what im trying to do, it is to get the remains of a broken engine brought back to life with a new block while avoiding a ton of machinework. The old block was heavily decked and thats the reason for the odd pistons it had.

We will see where this ends up i have plenty of time still:)

Just add displacement. It's a stroker crank away if there is a piston with a CH compatible with your rods and deck height.

Kevin

That thought has crossed my mind more than once and is certainly one of the other options im thinking of.

You might look at the KB243 piston. I had those on my X heads set up for quench. I believe I was a touch over 10:1 with those, ran good on our 93 octane fuel and made good power.

Call Randy at RaceTec pistons...they will make anything you need and at good prices.

Thanks for your advice i do appreciate it alot!We will see where this goes,im pretty much all over the map on what to do with this car and engine

The way to use those heads is a custom piston that comes out of the deck enough to make squish.

When you start looking around at the shelf stock pistons and their prices, the additional cost to get what you truly desire isn't so big.

By using an aftermarket rod and custom lightweight forged piston you can take about 300grams off every unit, 2400 grams total. That's 5.28 lb!
Think of how that would wake up the engine.

To correct an earlier post, the stock 340 piston weighed 720 grams with a hefty pin added to that. It was internally balanced, no heavy metal needed. So, it stands to reason that one could use a stock replacement piston or anything lighter without adding heavy metal

R.

My old 340 had the trw flat top pistons in it at first.
889g piston and pin.

This was around 1992, and there were no off the shelf light weight pistons for it back then, or Eagle rods.

I had Ross make me some custom pistons with the "max weight removal" option, and set up for .927 pins.
I also got some 75g tool steel pins from PPP, and bushed some 360 rods down to fit the .927 pins(removed balance pads, completely polished entire rod, resized with ARP bolts).

The new piston/pin combo was 525g(450g piston/75g pin.......about 3/4 of a pound lighter than the trw's......each).

I probably still have the balance card somewhere...... Iirc the bobweight was about 1850g.

A lot of weight had to come out of the crank on that one.

I believe you are correct, there is no downside to lighter pistons,my poor beat up crank would probably appreciate it bigtime aswell.

To clarify the reason i cant use a stock type piston without heavy metal is that my crank has been balanced with lighter than stock pistons in the past.

I get it. The custom piston is your best chance then. RaceTech as mentioned above has a good reputation. Diamond is another.

Did you know that people are making billet pistons nowadays? Another option.

I just finished rewatching the Stieg Larsson Millenium trilogy. I saw the Swedish version first and it ruined the American version for me. An American film company getting ready to shoot the second book now with a different actress as Lisbeth.
My conclusion? You Swedes are crazy! And how about the Swedes who are into American cars? Double crazy. Everything you buy is twice the price!

We are having our national holiday Thanksgiving tomorrow. Traditional main dish is roast turkey. So every year the President has a ceremony in which he pardons a live turkey. The turkey is thus saved from the axe and lives out its days in the Washington DC zoo.

Happy Thanksgiving!

R.

If you have a forged crank, you can weld up the old balancing drilled holes, no need for mallory metal then.

Thats a whole lot lighter,i bet that crank and block loved having a whole lot less weight punishing it!

Sometimes remakes of things ruins the whole thing and sometimes they are a whole lot better:)
Sure there is a whole lot of crazy going on around here,but i also wouldnt want to live anywhere else,its a fantastic place to live regardless of some of the stupidness going on:)

I hope you all had a nice thanksgiving!

We will see where this goes but nice to see that there are a few options for the stock stroke option.

I did not think about that option,there are certainly a bunch of extra holes in that crank that could be welded up.
That poor crank looks like it has gone thru a metal butchery with all its holes,a slug of heavy metal and places where a piece of a counterweight have been cut of,if it could talk....

The NHRA blueprint specs. on the "stock" 1968 to 1971 340 called for between .015 to .030 positive deck height depending on which head gasket you used, that calculated out to be 11.25 to 1 compression with 63.?(CRS now) head CC
We had Ross make us some NHRA acceptable replacement legal pistons and then back cut the rings and so on