300k mile 4.0 to 4.6 stroker

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JDB636
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300k mile 4.0 to 4.6 stroker

Post by JDB636 »

New to this particular forum so I'll start out by saying hello! I am in the middle of a full frame off restoration on my 1999 TJ 4.0. I don't want to throw a 300k tired but otherwise healthy engine back into my fully restored TJ but don't have much room left in my budget. I am considering doing a "poor mans stroker" but need some questions answered first. With 300k on the clock am I correct in assuming that the block will need to be bored decked cam bearings replaced and mains line bored along with some head work (I know the cylinders will need bored due to oversized pistons for a 4.6) and what costs can I expect at a machine shop? I want to reuse as many parts as possible but with 300k are my 4.0 rods going to be any good still? Also what is a good place to source a good 258 crank and is $500 the going rate (price I found online) it also seems that with a 258 crank and 4.0 rods I need custom pistons, where are people getting these from and how much do they typically cost? I don't mind running 91 octane if it'll yield me more low end power running something like 10:1 though I will admit that I do need to do more research to fully understand how everything relates to each other in respect to compression ratios. Thanks guys I'm looking forward to hearing from you!!!
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Re: 300k mile 4.0 to 4.6 stroker

Post by Cheromaniac »

I'm sure Russ Pottenger will chime in and offer a 4.6/4.7L stroker kit that'll suit your needs. If that's beyond your budget, you could build a 4.2L mini-stroker using a 232 crank, your existing 4.0L rods, and Silvolite 2229 pistons.
Your engine will likely need all of the machine shop work you've mentioned.
1992 XJ 4.6 I6 - 5MT - Stroker build-up, Stroker "recipes" Sold
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JDB636
Posts: 7
Joined: August 30th, 2017, 2:13 pm
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Vehicle Model: Wrangler

Re: 300k mile 4.0 to 4.6 stroker

Post by JDB636 »

After thinking this over I think it would be in my best interest to reuse my 300k 4.0 motor in my project as my budget does not support a rebuild or swap at this time. The 4.0 runs good but the lifters are pretty noise until it warms up. Since the motor is already out and on a stand I am wondering if there is anything against me pulling the head to remove clean and reinstall the factory lifters then resealing the head with a fresh head gasket. I'm hoping that this will at least buy me some time until I can spend some money. Alternatively I guess I could do a handful of 500 mile interval oil changes running a qt. of MMO or similar with each change for the next 3000 miles or so?
Russ Pottenger
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Re: 300k mile 4.0 to 4.6 stroker

Post by Russ Pottenger »

Something to consider. If the engine is out on a stand and your plans are to pull the head and replace the lifters, you're not that far away in time and money to send your cylinder head out for a valve job and bottlebrush your cylinders and install new rings, bearings, oil pump, brass freeze plugs, and rear main seal.

All of this will turn the clock back on your engine and reseal it and should cost you less than $500.00

I'd be happy to price out and give you a cost breakdown on a kit if you'd like

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JDB636
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Joined: August 30th, 2017, 2:13 pm
Vehicle Year: 1999
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Re: 300k mile 4.0 to 4.6 stroker

Post by JDB636 »

I would love to be able to do what you just suggested, I was under the impression that throwing in new main and rod bearings without the supporting machine shop work could cause the new bearings to fail due to worn or out of round rods/caps, I was also worried about new rings in a 300k bore with a light hone not seating properly. Am I just being over cautious?
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Re: 300k mile 4.0 to 4.6 stroker

Post by Russ Pottenger »

A piston ring set with a Molly Top ring likes a fairly fine finish (400 grit) so a few passes with a bottlebrush hone to break the glaze the Molly rings come in really easy.

Chances are a new set of Clevite rod and main bearings will be better than hey set of factory bearings that have gone through 300k miles.

It's just a suggestion while you have it out of the Jeep.
If it's like most Jeeps at 300k it most likely has some oil leaks. A fresh rear main seal, replacing the oil filter adapter O rings might not be a bad idea at the very least
JDB636
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Re: 300k mile 4.0 to 4.6 stroker

Post by JDB636 »

Thank you for the advice I think I'll do exactly as you recommended. I already planned on doing the rear main seal along with valve cover and oil pan gaskets, never heard of the oil filter adaptor O-rings so I'll definitely look into that. Thank you so much for steering me in the right direction!
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Cheromaniac
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Re: 300k mile 4.0 to 4.6 stroker

Post by Cheromaniac »

JDB636 wrote:After thinking this over I think it would be in my best interest to reuse my 300k 4.0 motor in my project as my budget does not support a rebuild or swap at this time. The 4.0 runs good but the lifters are pretty noise until it warms up. Since the motor is already out and on a stand I am wondering if there is anything against me pulling the head to remove clean and reinstall the factory lifters then resealing the head with a fresh head gasket. I'm hoping that this will at least buy me some time until I can spend some money.
Russ has made a very good recommendation. Your best solution, if your limited budget will allow for it, is to refresh the motor completely since it's already out and on a stand rather than merely trying to patch it up. You'll spend the money now but save a whole lot more in the long run.
Parts you'll need:

Main/rod/cam bearings, piston rings, ARP rod bolts, ARP head bolts, oil pump, timing set, lifters, pushrods, upper/lower gasket sets, oil filter adapter o-rings (if not included in lower gasket set), brass freeze plugs, and possibly valves (if existing units are too worn or tuliped).

Machine shop work:

Hone cylinders, mill cylinder head flat, valve lapping (re-cut seats if necessary).

This way you'll end up with a solid, reliable motor that should last you at least another 100k miles.
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