Jeep Strokers

John wrote:By the way he didn't destroke it as all 199's had a 3 inch stroke, but he did reduce bore diameter.
John

so why did he reduce the bore?????? trying to make a specify CID?????

I can see the 3.00" stroke, but why the small bore .............a larger bore would have had a much better...............Well there wouldn't have had to be valve relieves cut into the bore and it would (in my opinion) breathed a lot better with less shrouding of the valves.......aspesialy the exh. valve.



Flash

"I can see the 3.00" stroke, but why the small bore .............a larger bore would have had a much better...............Well there wouldn't have had to be valve relieves cut into the bore and it would (in my opinion) breathed a lot better with less shrouding of the valves.......aspesialy the exh. valve."

Actually those cuts were to unshroud the valves and improve flow.
John

John wrote:"I can see the 3.00" stroke, but why the small bore .............a larger bore would have had a much better...............Well there wouldn't have had to be valve relieves cut into the bore and it would (in my opinion) breathed a lot better with less shrouding of the valves.......aspesialy the exh. valve."

Actually those cuts were to unshroud the valves and improve flow.
John

Thats my point........they had to put a sleave in it to accommodate the smaller bore.

Why not punch it out so that you could put, say.......a 4.00" bore in it. There would be no reason for cylinder valve pocket in that one

If i was going to the expense of sleeve, that's the direction I would have gone.

Was there a cubic inch limit???????? I just don't get the small bore


Flash

Yes 3000 CC with supercharger.
John

John wrote:Yes 3000 CC with supercharger.
John

Aaaaaaa that make sence then



Flash

Phenolic is a urea formula "epoxy" saturating a fabric matrix, which when cured with heat, creates a high density material with good heat resistance, strength, and acceptable machining tolerances. It was manufactured by Westinghouse in the day for high dielectric strength parts for electric switchgear. Custom knife makers discovered it and still use it extensively for its near indestructability for handle scales.

Summit, Jegs, etc offer it as carb and TB insulating spacers for racing on V8's - it should be just fine on the 4.0, if someone actually offered them. You can get the stuff at local industrial and plastic supply houses in various size sheets and thicknesses. The stuff is tough enough you almost need machine tools to work it. Not sure it would be needed on a MPFI '99 intake - more plenum and insulation for the TB isn't a problem, insulating the intake from the exhaust looks more necessary.

I just picked up the latest Pop Rod "Engine Masters" magazine, it has a lot of good teardown info. Lots of the trick stuff isn't in the crank and rods so much - in fact these guys are buying off the shelf to cut costs. Apparently the devil is in the details - using heavier forged nitro pistons, combustion chamber porting, optimizing carb tuning, 1.9 ratio rocker arms with flat tappets and almost stock springs, or completely massaged intakes with matched spacers. Lots of extensive dyno time.

351W w/ 3v heads, 400M Fords, and 400 Chevies were dominant - nothing real special there - with an couple of well done alternatives - like a 331 Hemi from the '50s. Great insights on what to do for a buildup.

tirod wrote: I just picked up the latest Pop Rod "Engine Masters" magazine, it has a lot of good teardown info. Lots of the trick stuff isn't in the crank and rods so much - in fact these guys are buying off the shelf to cut costs. Apparently the devil is in the details - using heavier forged nitro pistons, combustion chamber porting, optimizing carb tuning, 1.9 ratio rocker arms with flat tappets and almost stock springs, or completely massaged intakes with matched spacers. Lots of extensive dyno time.

Yeah I love that stuff, like I was saying if those guys can get 500-600hp and 400 to 600 pound feet from 300 to 400 CI engines we should be able to coax out way more than the 250-260 we are. The breathing mods porting and intake modification are indeed some of the more visible things.

The key really though is to think of it as a system, They do knife edge and smooth the crank. And they hand mirror polish journals etc.

However there's a lot to be gained from tight oil tolerances, and near Perfect bores, (within .02" roundness) and tight oil clearances makes power by reducing bearing friction. Boring and honing with a torque plate is the only way to get the bore so close to perfect. These guys are getting power from building to extremely demanding tolerances as well.

I was reading my newly acquired "Mopar Jeep Engines" book which is purely about race modifying Jeep engines, over one third of the book is straight 6 (mostly 4.0 with some 4.2). There's a lot of stuff in this book that is not commonly talked about around here.

For example Mopar says you will make more power with a block that actually HAS some core shift, if it makes the cylinder walls thicker on the passenger side (tested by sonic checking) and thinner on the driver side of the block. Apparently this is due to the passenger side taking the brunt of the force. The thicker wall on this side will cause less deformation (flex) of the bore meaning rounder walls during the power stroke, which means less friction. A block with no core shift has more uniform wall thickness but less meat on the passenger side. Meaning it will actually deform more on the power stroke than a block that has core shift favoring that side.

I have a thumb worn 3rd edition of the Jeep Motor book that I would hate to be without. Those motors are built with attention to all details, details well pointed out in that book. $30 well spent.
John

got my off Ebay for $10 3rd edition as well I waited 3 or 4 months for it to pop up at a bargain price <insert even more geeky smilie>.

If I had nutty cash for a completely race built stroker I would love to see what BES racing could do with a 4.0 stroker

That core shift comment almost sounds like Smokey Yunick talking. Always looking for the better thing.

Looks like I need to put the Mopar book on my "get list."