Piston Progress

[XtremeOverKill]

After 6 months of searching and talking to different companies I finally recieved pistons today.

Mahle pistons (prounced Marley - or so said by my machinist)
company webcite: http://www.mahle.com/home.nsf/out/2.1.0.0

Pictures of my pistons: http://photobucket.com/albums/v11/MikesJeep/Mahle%20Pistons/

They are big pics.... Beforewarned

Best regards
Mike

[Lifted79CJ7]

Look nice! Care to share any info about them?

[XtremeOverKill]

I'll share what I know...

It is an SBC piston 4.125 bore
Forged But not sure about Hypereutectic
Coated Skirts
Weight is 438 Grams
Flat Top - Single Vavle releif
10.2 : 1 CR
Moly Rings 1.5, 1.5 3mm Rings.

Final Cost was $765 for the set - including Pins and labor for the pin issue.


One of the major problems with this piston is the pin... 0.927" SBC v 0.933" - AMC

These have not been honed out yet, but that is next on the "To-Do" list.

[Elliott]

... or bush your rod ends smaller to match?

[XtremeOverKill]

That thought crossed my mind yesterday...

I'm honestly not qualified enough to make a decision as to which one to go with. My machinist says that bushing the piston a little larger to fit will not be a problem, and I trust his work.

[Elliott]

Yep, depending on the piston and your intention it's a toss up. Only when you ream bigger you can't go back (on a $700 set of pistons). I'm not saying that you should, but if the rod was bushed then you retain the option of offset reaming bushings to set your piston height at different levels... say if your block was decked, heads milled, ect. All that may not make a hill of beans worth of difference for the little variance, unless you were also running a high lift cam, needed a lil more valve clearance without having to deepen the valve relief and have to rebalance/re-cc eight pistons. Just thought I'd toss that out there for consideration.

[jeepsr4ever]

They shouldnt have been that expensive dangit. Looks like you are going to run a chevy rod with a stroker crank. Consider the 650hp stroker amc idea and run honda rod bearings with a extended stroke...you will find excellent results as you can extend the stroke beyond that of the average AMC 426 and still use a chevy 6" rod. The Honda bearings are thicker and the outside diameter fit a chevy rod....good combo! Then again the 401 being a close bore to the 302 ford yet is like a 302 over stroked really can be built powerfull without much work....I do enjoy overkill though Mike......Let me know if I can help out in any way :t:

[XtremeOverKill]

I like the idea of bushing the rods...

From what Raymond - machinist - said the piston would have a deck clearance of 0.030 down in the block. This is probably prior to decking the block.

This was not quite my intent, as I wanted to push about a 0.035 Quench. but to acheive the compression ratio we were looking for we had to go with the 0.030 instead of the initialy 0.013 deck clearance.

It is a toss up... The 0.927 pins are shorter than the stock AMC pins. Raymond's going to shorten a new set of AMC pins to provide for lighter weight and fit the .933 rod.


And Ok I know I've been away from the BullTear list for quite some time, but MC what is this about a 650 "kit" with Ricer bearings??? I really feel that I missed something.

The plan is to run the Stock AMC rod - beams have polished of all casting flaws - I just wish I had a picture of them to show - And I'll be using the stock 360 crank.

My goal is initially set at 1 hp per cubic inch. And if I can go beyond that, I hope I don't push more than 500 hp for fear of over stressing the crank. And pushing the most HP is not really my direct goal... I want to make as much torque as I can, while having a reasonable and efficient street engine. (some of this may seem contradictory, but I'm hoping to match components together in hopes of creating a well balanced machine) And Yes the assembly will be balanced - within 1 to 2 grams.

As for bearings... lets start another thread for that.

[jeepsr4ever]

The 650 kit is a local who is getting 650hp out of a 447AMC using honda rod bushings a 6" aluminum H-beam eagle rod set and a offset stroked crank. Recipe for fun for sure!

[Lifted79CJ7]

OK MC, so you have my interest peaked here!! Since I am getting closer to the machine work part of my rebuild, can you give some more details about this setup? What exactly needs to be done, part numbers, etc. Or can I email this guy? If I am about to get a bunch of machine work done, why not get it done to produce more HP? Given 650 is waaay too much HP for me right now (maybe on the 2nd rebuild I'll kick it up a notch), and knowledge is good knowledge!

OK, So a couple questions for a newbie engine builder. What does “bushing the rods” exactly mean?

Also can you explain this sentence in a little more plain English?
“I wanted to push about a 0.035 Quench. but to acheive the compression ratio we were looking for we had to go with the 0.030 instead of the initialy 0.013 deck clearance.”
I guess my real question is exactly what’s quench, and how do you measure it?

Thanks,
Jack

[XtremeOverKill]

I'll try a stab at this...

Chevy pistons 0.927" pin
AMC Piston and Rods are based around the 0.933" Pin

Difference of 0.006" Which for pin to rod clearance is NOT good, but I would venture to guess that 0.005" or better for piston to pin clearnace is good - but dont quote me on that unless someone else backs me up.

Bushing the rod would be like putting a 0.933 Outside diameter pipe, inside the small end of the rod. To then be drilled out to 0.927" to accomodate the Chevy Pin.

6 of these 1/2 Dozen the other when all is said an done.


And then to answer your question on quench:
Quench as I define it is the clearance between the highest spot on the piston to the head when the piston is at TDC.

The idea here being that so long as the laws of physics hold true - no two bodies of mass can occupy the same amout of space at the same time - then you can create an effectively "smaller combustion chamber"

But let me explain a little more as to how. Pushing the piston as close as you can to the head is like putting a book on top of a tube of toothpaste... its gotta go somewhere. The more you squeeze, the more can be pushed out. The same is true with the gasses inside the chamber. They are squeezed between the piston and the head thus creating a rather violent rush of gasses towards the spark plug.

Some people say you start having good quench when you can reach the 0.040 mark. I have not heard anything smaller than 0.028" But it is a close science, because as thermal expansion happens, adn the rod stretches, that 0.0XX can become darn near 0.00X IF the piston kisses the head.... you can kiss your engine good bye. Its a gamble either way. High benefits from tight quench , but DO your homework.

I would feel more comfortable running a tight quench on a low RPM engine, as opposed to one that turns over 6500 Revs.

Rod construction also has an effect on quench. As alumnium rods will expand MORE than steel will. For example: With alumnium Rods AMC engines are encouraged to have at least 0.060" clearance. But say the same engine, same RPMS and everything you could probably push closer to 0.045

Time for class,
-Humbly yours
Mike