Stroker Build

[Patman]

Hey folks, newest member of the broken skirt club. 1999 Wrangler Sport with 250K miles couldn't handle it's first Colorado winter. So I'm looking at least rebuild, probably go stroker. Here are my thoughts so far, please correct me if I'm wrong or using outdated information.

For my daily driver/weekend warrior...

Scat 4.2L crank
Scat forged 4.0L rods 6.125"
KB421 Hypereutectic Pistons -27.5cc

cleggengine.com offers this as a package for a great deal, w/ clevite bearings, moly rings, and balancing. It would be several $100 more to go Hesco crank, scat forged rods, and Russ's no need to deck pistons, is it worth it? Latter scenario also requires finding a shop to balance rotating assembly. Does Russ sell balanced rotating assemblies? (I'll be PMing him after this post)

I like the idea of the lower piston to wall clearance with the hypereutectic pistons. This should reduce piston slap/wear, especially during cold weather startup when clearances are at their largest. I'm not looking to make huge horsepower so I don't think the disadvantages of forged pistons are worth it.

I'll have the block cleaned, magnafluxed, line honed, cylinders bored/honed, and milled for 0.000" deck height. What's your favorite shop near Denver?

I'm hoping my stock 0630 head is good. I'll have a shop clean and check it. If so, I'll do a little gasket matching and chamber work to reduce detonation possibilities. Because my 99 has EFI, the only factory spring compatible choice for cam is Russ's custom (low lift) grind based on comp cams 68-232-4? I'm hoping this comes in the thrust plate flavor. If not, I only need older style timing set and the bolt w/ spring & pin?

If my head is shot, I'm thinking stage 2 from 505 performance (nice price again) and then I could use whatever camshaft, but probably want the 68-232-4 (standard full lift version) because I need to pass emissions and want strong and stable idle vacuum . Even if my head is good now, I'll likely do this in the following couple years.

This should work out to static CR 9.1:1 with dynamic CR 7.77:1 (6.63:1 in Denver altitude) with quench 0.043". I'm hoping to stay 87 octane, reasonable?

Since the hyper pistons reflect more heat into the head, I'll add a Hesco high flow water pump. Hopefully that and the Mishimoto aluminum radiator will keep head temperatures in check.

Thanks for checking out my plans, I look forward to hearing from you.

[SkylinesSuck]

Russ can set you up with springs that will handle whatever lift and talk to your machine shop to get the head set up for them. I would run far, far away from 505. They have a terrible rep.

[Russ Pottenger]

Chris is correct. I'll be able to set you up with a valve train package or a complete cylinder head if you would like.

Stay away from that 421 hypereutectic piston.
The compression height is wrong, and running a full circular dish is a torque killer.

My 1.385 CD pin height with speced out reverse mirror dish piston with bushed steel rod is a hard package to beat for quality and price.

No reason to run a static compression ratio as low as you're planning on running other than to compensate for an inferior piston design.

For just a aditional $120.00 i'll upgrade you to a full balanced rotating assembly

Feel free to shoot me a call and I'll be happy to go over this in greater detail.

Russ Pottenger
Bishop-Buehl Racing Engines
531 N. Lyall Avenue
West Covina, California 91790
Work (626) 967-1000
Cell (626) 673-2203
Email/PayPal: [email protected]

[MunkMaster]

Listen to that guy. I just bought my pistons, rods and some other goodies from him. Top notch.

[jsawduste]

Since the hyper pistons reflect more heat into the head, I'll add a Hesco high flow water pump. Hopefully that and the Mishimoto aluminum radiator will keep head temperatures in check.


This is the first I`ve ever heard of a piston "reflecting" more heat into the head.

There are many variables on what constitutes combustion temperature and pressure. Piston reflection based on material and the manufacturing process is a new one. Please show us some tech to support that claim.

The stock cooling system is fine. While the water pump is a nice but un-needed addition I`d be critical of that radiator. Them factory engineers are pretty smart. Corporate spent a lot of money engineering a cooling system that works in Alaska to the Desert States.
Just spending money hoping to make an improvement is likely going to backfire.

[Patman]

Hey everyone, thanks for stopping by.

I'll give you a call soon Russ, thanks!

Appreciate the advice guys. I'm trying to learn as I go and enjoy talking with anyone about these things. Please correct me if/when I'm wrong

I should have said Since the hyper pistons reflect more heat into the head, and I'm increasing compression, and I want to run cheap gas...

The reflectance claim is directly from the manufacturer. I don't have the link atm. But with a phd in physics, I can say the heat reflectance is most certainly a property of the material and geometry through fluid dynamics within the chamber, so I believed them. It's supposedly small, a couple percent. But considering I'm pushing the CR and hoping to stay with 87 gas, this little change could be enough to make the difference. I understand detonation (specifically pre-ignition) to be more probable with higher chamber temperatures.

I never had a problem with the cooling capability of the stock system, only it's ability to actually hold the coolant...damn thing was always leaking Stock system was fine stuck in traffic for an hour in the middle of Houston everyday. Mishimoto held temperatures a little lower and more stable, thus it's clearly more efficient and it doesn't leak! In cold weather the thermo limits flow to the radiator, so over efficiency is not a worry either.

A thermostat only works at the thermostat so the temperature elsewhere is not guaranteed at all. The only guarantee is to ensure the coolant is mixed thoroughly via high flow. None of these pumps are capable of flow high enough to cause the hydrodynamics problems people worry about online. Heat transfer is only increased with greater flow under these first order conditions. Most high flow pumps are simply designed to improve low RPM flow for low speed, high load crawling and return to normal at higher rpm. The hesco pump is nice because their impeller design reduces drag within the coolant and therefore is easier to turn, wasting less engine power. I like efficiency, if it saves me a couple gallons a gas of month for the next 10 years, i'm down and it will pay for itself.

In the end I expect more uniform temperatures throughout the water jackets of the block and head thus reducing the chance for hotspots and locally induced pre-ignition. Is it overkill, quite possibly, but if not I'll be kicking myself hard. I know I'll be creating more heat, could calculate it and be all precise but that's my day job lol I'd rather just have the beefiest jeep possible and not worry about shit on the trail...see ya out there

[Patman]

Got the head off, thoughts on what you see? 250k miles

[MunkMaster]

For 250k its not terrible. The head gasket looks suspect between 2-3, 3-4, 4-5 but between 3-4 looks the worse. Until the surface of the block is cleaned up a little bit you can really tell whats going on. The machine shop would probably do a skim cut just to get a good surface.