to get the torque up you need to have bored and stroked motor with higher compression. Or… build a diesel. Diesel compression can be a lot higher than gas but I can’t remember why. My brain has shut down after a 14hr shift today.

i know the feeling....
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Diesel is a compression ignition design. It always takes a full measure of air every stroke...it has no butterfly restrictor. The throttle controls how much diesel is injected on every combustion event. Diesel compression ranges from 14 to 21 to 1.

Diesel is ingnited by heat, vs a spark for gas.

Cool thread. My passion has always been in NA power, but the problem is its just more reliable to have a low boost FI engine over a strung out NA engine. I know that's not what this thread is about and its like beating a dead horse.

This whole theoretical engine is going to have an expensive rotating assembly, a lot of money in heads and valvetrain, and a wad put into the induction.....so the stock 502 block is hanging me up. Spend the $3500 on a good block and push the displacement. If you don't get to the power with displacement then the only other option is to get there with RPM.

Makes total sense DRAG...thanks for the input! That's a lot of the reason I started this...to get the info out there and see what is absolutely needed or not at a said expected power level. So glad this thread took off the way it did!

4.25" 1 piece BBC stroker forged cranks.

What are the reasonable options? Made in USA.

The GM forged 4" 1 piece forged from the marine 454 an 502....what are they good for reliable power?

This is an interesting topic about various piston wear, CH, CD, ring wear, rod angle combinations, etc.

In the Fall of 2003, I had a friend take my engines out of State to what I thought was a legit shop down in NC. Long story, but anyway, one of the many things they told me was that I should mill the decks for better "squish"... but we later discovered when they mill cut the decks they actually carelessly "whacked" the decks of my blocks with a very rough cut that leaked, etc.

We also found many other problems so we completely disassembled the engines and had to start from scratch from a machining and assembly perspective. We had to re-mill/cut the decks of my blocks in hope that we could salvage them and not ruin them beyond usage.

Thankfully, we were able to save them and the piston just peeked over the tops of the decks and able to squeak by at .003" and were able to find/use a thick enough of a head gasket to avoid any piston to head clearance issues, etc. This is before Cometic/MLS gaskets were invented.

All the above being said, I began to rebuild the engines again in the Fall of 2004 and after a few years later of 220 hours of use (2008), I had my old 9.8" deck, 565cid NA engines completely disassembled in 2021 after sitting for many years (Stroke 4.25", Rod 6.385", Bore 4.600").Everything in the engines looked great upon disassembly...just new springs, lifters, and complete refresh/rebuild.

I had originally bought brand new Merlin II blocks back in 2002 (high nickel content) and I had the edges of the bottom of the cylinder bores de-burred by the guys at Performance Engineering in Jenison, Michigan so that it wouldn't rub/wear the pistons skirts.

After cleaning and prepping my pistons, the guys at that shop commented that my pistons (JE forged Flat Top (w/Intk valve relief) looked like they barely had any type of wear and looked almost brand new after 220 hours.

I told them that for this rebuild that I would like to have them sent out for a "coated" ceramic anti-wear treatment on the skirts and a different type of coating for heat/reduction, etc on the crown of the pistons. The shop recommended the people at Swain Tech somewhere over in the Detroit area. They came back looking great and are ready for assembly.

Yeah, deck and head surfacing finish it important for sure. Good machine shops are getting scarce.
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I'm not big on removing any material off the decks, but making them true, and getting a good quench are worth it.

220hrs and the JE pistons look new...great news. Sounds like the rod/stroke angle worked out.

I've always been interested in coatings. What risk factor is there for the skirt coating?

I can't remember what the pros/cons are on the coatings stuff---maybe articSmitty can comment on it. And, you're right, I do not like cutting it too close with taking too much material off a block's deck...just got to try and find the correct tolerance for the application for the right quench/squish.

I wanted to post my previous comment because I had always wondered about the 4.250" stroke combination in a 9.80" block with the rod angel/side loading of the piston, etc. especially in light of Keith Eickert's comment that he won't build them that way, but rather using a tall deck 10.2" deck block for that combination. Plus the fact that we just able to squeak by with my deck height with the pistons stick out .003" and piston rock at TDC made me a little nervous. But I tried to use all good parts and good machine work after the original out of State shop disaster.

So yes, I was very happy with how everything looked after 220 hours---especially with how the pistons looked. The longest time I ran my engines was for about 7 minutes at WOT while a 36' stepped hull Apache with a pair of 540cid Vortec superchargers making 800+hp and was very happy with how all my internals looked on a NA 565" 4.250" stroke 9.80" deck engine after we tore them down and could have even reused the bearings for this next rebuild---that's how good they looked and ring wear looked normal---not excessive. And I thought it would be good news for guys who want to get away with using a short 9,80" deck block w/4.250" stroke....at least that's what I found on my 565" short deck block engines.

Also used Jesel Sportsman's shaft-mount roller rocker arms, good tool room valve springs, AFR 315cc, Cnc ported baby heads and just some baby hydraulic roller cams (.601"/.619" Lift) that only made power at only 5100rpm on the dyno, abput 670-lbs of Torque @4200-4400rpm, but peaked at 5600rpm in my boat w/30" 5-bladed props or 32" -4-blades. Cruised mostly at about 3800rpm in my 32' AT w/Stellings extension boxes and IMCO -2" shorties----boat was runner!.

Zero deck height is a very common blueprinting block prep goal. Certainly 0.003" out the hole is no big deal.

It's more about choosing what gasket to use, and compressed thickness...that will be available in the future etc. The right quench 0.035- 0.040" is one of the foundations of wedge head engines. Grumpy Jenkins' perspective was to only use enough quench as is necessary. There may be pimping losses to push up to the tighter quenches...and also the piston pulling away. Lots of good BBC head gaskets with .040" and 0.43" compressed thickness.

400 SBCs with stock 5.56 rods had rod ratios of 1.48. The 4.25" stroke with 6.385" rods gives a 1.50 rod ratio. Not the 2.0 Smokey suggests...but were (most of us) not running too much past 5500.

Long (vs short) piston skirts will help here...along with the proper piston to wall clearance for the specific piston and application. Proper cylinder wall finish, break in procedures, and of course oils.

Keith can't control the operating environment of his engines once they leave the shop...so maybe he doesn't want bad press from failed low rod ratio engines that were used beyond their intended rpm and use.

Piston tech has come a long way with metallurgy and production methods. Oval piston shape with the piston to wall clearance at the thrust side on the skirts. The rest of the piston is designed to have clearances to support the rings etc. Larger dia pistons require more clearance than smaller ones, due to expansion factor.

One of the larger issues for auto makers...was the forged piston noise at startup. Not something we would be concerned about...it's an accepted and understood factor. Many probably enjoy the sound.

One of the benefits the guys told me at Performance Engineering was that the coating on the sides/skirts of the pistons will really help protect the pistons especially during a COLD start up

Well, if Smokey Yunick (spelling?) didn't like anything under a 2.0 rod ratio along with Keith Eickert leaning in the same direction--- I would still think keeping the RPM's of a BBC at 5500-6000rpm's should be okay---but I am NOT a BBC expert, so I am mostly speculating.

I am only a witness as to how my experimental 565" low deck 9.8" blocks, pistons, and other internals looked after a 220 hour tear down---and as you were saying, technology with much improved parts and components has certainly come along way since my engines were built in 2005.

I also forgot to mention that even though my piston skirts, ring-lands/grooves, etc looked barely used with very minute wear along with normal ring wear. Based on the Performance Engineering guys inspection, they told me the rings were only approaching about half their life yet and that going by the way they looked that I could probably go at another 250 hours or so on them yet.

So it was a good tear down/experimental analysis of my 565" engines with still about 50% more life in them yet. It's just that they have been sitting still since 2008 and I wanted just take a peek and do a refresh.

I am retired and kinda bored and don't always have much to do so, sorry about my redundant superfluous rant, but it keeps my mind busy---so thanks for your interaction and willing ness to engage.