Piston hits head options and advice needed.

[popinsmoke]

Gentlemen,

I am going to try to give you the readers digest version of my situation.

I bought a 408 stroker short block that due to my own error I did not catch the fact that this short block must be used with open chamber heads.

Shortly after taking delivery of the short block I have to have shoulder surgery on both shoulders 4 plus months recovery each side, so the short block sat for the better part of a year.

So last week I install the oil pump, pan, cam XE268H, and timing cover, mock up a head and clay they piston to check my piston to valve clearance and it hits me like a big bucket of stupid the piston hit the the head Doh!

The piston is a stepped KB with a raised quench pad that sticks above the deck, my heads are RHS LAX heads with a closed chamber just like the manufacture said not to use had I caught the warning.

So now I am looking at options and or solutions?

Do I dump money into a set of open chamber 596 heads that I have on the shelf?

Do I pull the rods and pistons out and have the quench pads milled?

Run a custom really thick head gasket?

Buy the Edelbrock heads that have the .60 machine into the chamber to clear the above deck pistons found in the 68-71 340's?

Start a shop fire and collect the insurance (kidding mostly)?

I am still kicking myself for not catching that the short block would not work with closed chamber heads which I already had.

Thanks for reading this far any advice is appreciated.

 

[toolmanmike]

Different heads have the machine shop take it apart and mill the dome off the pistons. Thick head gaskets may work but measure carefully.

 

[wagonman]

Hey Mike will he need to rebalance after milling the pistons?

 

[5.7 hemi]

I would!

 

[HEMI-ITIS]

Unless you know the dome thickness I would NOT mill the pistons!

 

[drobertson]

I'd try to sell those heads, and get some edelbrocks.

 

[MoparLeo]

Agreed. Replace the heads. then we go on to the next part. Hydraulic ? No, pushrods right length? Rockers. and on...

 

[dvw]

Easy to measure piston thickness. Stand del up in the vice and zero a dial indicator against it. Now gently lift the indicator shaft while sliding the piston between the indicator and dowel. Move the piston around and measure. .180" on a N/A motor is plenty. Then you will know if they can be trimmed. It wont effect balance enough to worry about.
Doug

 

[Badvert65]

You also need to factor what your compression ratio is/will be. I would cc what you have and see where things land. If your compression is high, you can calculate the cc of the added clearance notches and redo the math. You might be better off with something with a bigger chamber, especially if the 408 combo was created with a particular compression ratio based on open chamber heads.

 

[lewtot184]

i'd just do the edelborocks. you can sell off the other parts and not have the expense of a re-balance.

 

[WileERobby]

Sell your heads. Buy Edelbrock heads. Assemble engine.

 

[moper]

What's the part number on the top of the piston? Those are designed for milling down and will probably be fine. But - hypers are the last things I'd put in a stroker engine. I use them all the time on stock stroke builds, but they do have limits, and a 4" stroke gets close to them when the rpm expectation exceeds 5500. Really a poor choice there.
But - I'd pull them and have them milled unless researching the number tells you they can't be cut. You don't have to worry about rebalancing if it's just lightening the domes. It's not a big deal to have the crank a hair heavier, and the pistons are reciprocating weight - not rotating weight. So they have less of an impact on the harmonics.

 

[popinsmoke]

Seems to be the majority opinion here is to buy the Edelbrocks that are for the 68-71 high compress 340 that also stuck proud from the deck? According to the catalog they have .60 recess for the dome/quench pad anyone have any experience with them?

 

[moper]

They are exactly like the closed chamber versions - just with the chamber milled in. So plan to have them checked and corrected like any other aftermarket heads, and verify the supplied valve springs will work with your cam based on open and closed spring pressures in addition to lift figures.