RPM Machine Stroker Kit Questions?

[xjmyway]

First off, has anybody dealt with this kit? the price is not too bad, so that's why I have this question to begin with. I also noticed that their kit says it's at 9:1 and "high Compression" upgrade at 9.25:1. I know I've seen many people running much higher than this, do they do this because of detontion issues? and how much performance would you lose at 9.25:1? I've read posts about piecing it all together for more hours than I can recall...this seems a bit more straightforward if everything checks out.

 

[CanMan]

First off, has anybody dealt with this kit? the price is not too bad, so that's why I have this question to begin with. I also noticed that their kit says it's at 9:1 and "high Compression" upgrade at 9.25:1. I know I've seen many people running much higher than this, do they do this because of detontion issues? and how much performance would you lose at 9.25:1? I've read posts about piecing it all together for more hours than I can recall...this seems a bit more straightforward if everything checks out.

Don't know about the kit, but more compression=more power. Although it is only .25:1 more than the standard kit, you may get 5-10 hp best out of it. Detonation shouldn't be an issue. I would just run 92, instead of 87 octane. An aluminum head can take more compression than a iron one, due to the fact it can dispurse heat better. Hell, the new C6 Z06 Corvettes run 11.0:1, and they reccomend 92 or better. Just my .02.

 

[Kittrell]

http://www.rpmmachine.com/amc-stroker-kit-4l.shtml

 

[Dr. Dyno]

It's a carbon copy of Speedomotive's stroker kit:

http://www.speedomotive.com/ps-147-15-jeep-40l-to-45l-stroker-crank-kit.aspx

 

[philip_g]

It's a carbon copy of Speedomotive's stroker kit:

http://www.speedomotive.com/ps-147-15-jeep-40l-to-45l-stroker-crank-kit.aspx

Doesn't sound like a bad deal considering the difficulty I'm having finding a crank at a reasonable price. I'm looking at 200 bucks delivered for a good crank and that one has already been turned down.

 

[xjmyway]

That;a kind of what I was thinking. I talked to the guys there and they say that the "high compression" pistons are designed to give the 9.25:1 at zero deck, and if I decked .010 it would be around 9.5. Does that sound right? Granted it's a bit higher priced than cherry picking, it's there with no searching.

 

[philip_g]

That;a kind of what I was thinking. I talked to the guys there and they say that the "high compression" pistons are designed to give the 9.25:1 at zero deck, and if I decked .010 it would be around 9.5. Does that sound right? Granted it's a bit higher priced than cherry picking, it's there with no searching.

And you know what you've got...

 

[amishxj]

hey im new here and am planning a stroker kit aswell, i have crank and connecting rods from a 4.2 but need to know what main bearings to get, whether i need bearings from a 4.0 or a 4.2?

 

[Dr. Dyno]

hey im new here and am planning a stroker kit aswell, i have crank and connecting rods from a 4.2 but need to know what main bearings to get, whether i need bearings from a 4.0 or a 4.2?

It depends on the year of 4.0 block that you're using. The '87-'90 Renix 4.0 blocks use the same main bearings as the 4.2 blocks (tangs are offset to the side, Clevite part no. MS-704P), but you'll need different main bearings for the '91+ HO blocks with the tangs in the center (Clevite part no. MS-1947P).

 

[Bouncy]

Which block is better to use...A renix block or an HO block?

And what the hell are tangs??

 

[streetpirate]

later ho blocks had extra ribbing in the block for support, as part of the NVH (noise vibration harshnes) reduction.

renix blocks have a high nickel content and are considered tougher metal.

 

[JohnX]

...give the 9.25:1 at zero deck, and if I decked .010 it would be around 9.5. Does that sound right?

I get what you meant...but it should be considered "stock" deck height, not "zero". Zero implies that the piston is even with the deck at TDC. .010 means it sits .010 below the deck at TDC. Stock on most engines can be from .020-.100 below deck surface at TDC.

"decking" the block is surfacing the top to lower you overall deck height (distance from Crank center to the deck). If stock were around .050, you "decked" it .040, that would leave you with .010 clearance not counting the gasket.

Just FYI

 

[xjmyway]

Yeah, I guess "stock" deck height sounds better, but you know what I mean...

 

[offroading]

I purchased the jeep stroker kit from RPM Machine that uses the 6.123 long rod forged piston combination. I called and talked to them about it first and they explained that while it was a little more money for the forged set up I would be buying a piston that was actually set up for this application that has an adjusted compression height so that it is not off so far. When I got it built we cleaned up the deck .010 and the piston came out exactly .015 in the hole.

 

[markaboo929]

Those are the ICON 944 pistons...which are the 9.6:1 comp ratio.The ICON 945 piston are the higher compression....both are off the shelf piston.I installed the 944"s and decked the block AKA..milled .020 and they are .0015 in the hole.
My build...
4.6L low-buck stroker

Jeep 4.2L 3.895" stroke crank
Jeep 4.0L 6.125" rods
Keith Black UEM-IC944-030 pistons
9.6:1 CR
CompCams 68-231-4 206/214 degree camshaft
Ported HO 1.91"/1.50" cylinder head
Mill block deck 0.020"
Mopar/Victor 0.043" head gasket
0.050" quench height
Ford 24lb/hr injectors with adjustable FPR or MAP adjuster for '87-'95 engines, Ford 24lb/hr injectors for '96-'04 engines, '99-'00 Chevy LS1 26.2lb/hr injectors for '05-'06 engines
264hp @ 4900rpm, 324lbft @ 3500rpm

Here is stock deck...

CYLINDER BLOCK​

Deck Height 240.03 to 240.18 mm
(9.450 to 9.456 in.)
Deck Clearance (Below
Block)​

0.546 mm (0.0215 in.)
.0215 - .020 = .0015

 

[XJEEPER]

264hp @ 4900rpm, 324lbft @ 3500rpm

Measured at the crank via engine dyno or estimated?

 

[markaboo929]

Dr. DYNO...dyno.Believed to be estimated at the crank on desk top dyno.Results will very...like if you use an actual dyno---you wont get good results with a 35 " tire with 3.07 gears...4.88's with 35's here.Still awaiting for the cyl head to return from shop.
http://www.jeep4.0performance.4mg.com/stroker.html
Credit goes to Dino...THE stroker guru.
http://www.angelfire.com/my/fan/stroker.html

 

[Dr. Dyno]

Believed to be estimated at the crank on desk top dyno. Results will very...like if you use an actual dyno---you wont get good results with a 35 " tire with 3.07 gears...4.88's with 35's here.

Correct. Indeed those are simulated numbers on a desktop dyno, and they're very close to the actual engine dyno numbers Golen got from their Insane Inline stroker so I've got them down to a fine art.
If you put your Jeep on the chassis dyno, you'll get much lower numbers especially if you have an AW4 and big tires. It's best if you do a baseline dyno with the stock engine, and then go back to the same dyno with the stroker built and dialed in. To make the comparison scientific you need to keep the same tires/gearing and run it in similar weather conditions.

 

[CobraMarty]

4.6L low-buck stroker

Jeep 4.2L 3.895" stroke crank
Jeep 4.0L 6.125" rods
Keith Black UEM-IC944-030 pistons
9.6:1 CR
CompCams 68-231-4 206/214 degree camshaft
Ported HO 1.91"/1.50" cylinder head
Mill block deck 0.020"
Mopar/Victor 0.043" head gasket
0.050" quench height

264hp @ 4900rpm, 324lbft @ 3500rpm

Hey Dr. Dyno,
With your desktop dyno program, how would this engine be with a different intake manifold. In particular a short runner-3", large plenum, bored TB-62-63mm. Would it raise the HP and rpm and knock a little TQ off? Any predicted numbers? How about a big valve ported head? Thanks.

 

[markaboo929]

Thank you Dino...:wantyou: