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Unread 03-05-2007, 09:14 AM   #1
atomicmoose
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Want to build a low cost stroker...looking for input.

So, my current 4.2L is giving me signs of possible valve train problems and I am thinking that instead of putting money into it, I am going to use the good parts of it to build a stroker. A buddy of mine has a 89 4.0L motor from a Comanche that he is willing to give me. I was thinking I could build this:
  • Jeep 4.2L 3.895" stroke crank
  • Jeep 4.2L 5.875" rods
  • Sealed Power 677CP standard bore pistons
  • 9.2:1 CR
  • Stock 4.0 camshaft
  • Ported HO 1.91"/1.50" cylinder head
  • Mopar/Victor 0.045" head gasket
  • 0.090" quench height
  • Ford 24lb/hr injectors with stock 39psi FPR for '87-'95 engines, stock injectors with stock 49psi FPR for '96 and later engines
  • 247hp @ 4900rpm, 300lbft @ 3500rpm

Source: http://www.jeep4.0performance.4mg.com/stroker.html

So, I have a few questions for you all.

1: I have a line on a intake manifold off of a ’98 4.0L. with sensors, throttle body, fuel rail, and injectors. Can I use this with that 4.0L motor? Would the current injectors work? I would like to ditch the Renix FI that is currently on the motor, but I don't have cash for a high dollar MPI system.

2: Where can I source the pistons from? Links preferable.

3: I know that a high pressure fuel delivery system would have to be installed. The vehicle this would be for is an 88 YJ and the pump only delivers ~8 PSI. What is involved with rectifying this? I'm talking from conception to birth, what would I need to do?

4: Can I use my current HEI setup with this?

I am still in the exploring stage of this project and need pointers. What am I getting myself into? Any estimated costs?

TIA.

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Unread 03-05-2007, 12:03 PM   #2
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I just got a 4.0 this weekend with a frame I picked up. I made the purchase for the frame but now have this spare 4.0 with wiring harness and ECU, so I am thinking maybe I should build that up. So I am interested too.

Everything I read says that with the 4.0L HO you don't need alot more than a 4.2L crank and rods and then use 4.0L pistons. Shorten the snout on the crank and use the rest of the stuff right from the 4.0. This is of course simplified but as far as parts being swapped out it's mostly just that stuff and maybe injectors. Anyone on the board have experience with this?

I am wondering how much a machine shop would charge for this?
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Unread 03-05-2007, 01:09 PM   #3
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The best place to start is with the rebuild kit for the 258 from Promar engines on Ebay. Brian's a great help and a couple of us have parts from him. Just do an ebay search on Promar engines.

As far as using the newer intake on the older engine - no problem as long as you have the ECU. I don't think the Renix is compatible with the newer stuff at all.

For parts - figure about $400 or so in new parts (Pistons, rods, crank, cam, gaskets, etc.) and another $300 to $400 for engine machining.

I'm just getting started on my engine but I'm going up to 4.7L (.060 over bore.) and basically just using a stock 4.0L block, ported & polished head, and a 258 rebuild kit with .060 oversized pistons. I'm going to stuff the engine myself, but machining quotes I got were in the $350 range.
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Unread 03-05-2007, 01:29 PM   #4
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Quote:
Originally Posted by BNovak
The best place to start is with the rebuild kit for the 258 from Promar engines on Ebay. Brian's a great help and a couple of us have parts from him. Just do an ebay search on Promar engines.
Looking now. Thanks for the tip. Seems like a nice all inclusive kit. Some parts I have...(see below)
Quote:
Originally Posted by BNovak

As far as using the newer intake on the older engine - no problem as long as you have the ECU. I don't think the Renix is compatible with the newer stuff at all.
I am sure it's not. I am going to have to source an ECU and wiring for this motor as my buddy doesn't have it anymore. I think he sold it.
Quote:
Originally Posted by BNovak

For parts - figure about $400 or so in new parts (Pistons, rods, crank, cam, gaskets, etc.) and another $300 to $400 for engine machining.
I would like to reuse the rods and crankshaft from my 4.2L if possible. I have a line on a new cam shaft for a 4.0L from a member on this board for a reasonable price. So I think I have that covered as well. I don't want to have too many duplicate parts laying around... Now all I need to do is fine a reputable machine shop around here in South Jersey.
Quote:
Originally Posted by BNovak

I'm just getting started on my engine but I'm going up to 4.7L (.060 over bore.) and basically just using a stock 4.0L block, ported & polished head, and a 258 rebuild kit with .060 oversized pistons. I'm going to stuff the engine myself, but machining quotes I got were in the $350 range.
I would like to do all the assembly myself and I need to keep this project as inexpensive as possible.
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Unread 03-05-2007, 02:22 PM   #5
BNovak
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Doh! I didn't realize you already had a 258. That's going to change things around a bit.

Building a stroker for your engine is a litle more difficult than starting with a 242 (4.0L) like most of us are.

Usually you take a 4.0L block and add the rods, crank and pistons from the 258 which gives you something like 4.5L's. When you start going into oversized pistons you start adding more displacement - .030 = about 4.6L, .060 = about 4.7L but again that's starting from a 4.0L block.

The only way you are going to get any increased displacement is by boring your cylinders so all you would really need is overzised pistons and rings and re-use your stock internals. You can get oversized pistons from Autozone, NAPA, etc - just make sure they are matched.

As for a cam - be careful - a lot of guys are having problems with the Crane Cams right now for some reason. I have a stock 4.0L cam also if you need one.

I have a guy locally that might still have a complete ECU and wiring harness - I'll see if I can find any details for you. Look around in the for sale section also.
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Unread 03-05-2007, 02:25 PM   #6
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Yeah, I have a 4.2L in my YJ currently and a buddy is willing to give me a 4.0L. So I have the parts for a home-brew stroker. I want to stroke the 4.0L block, BTW...

Sorry if I wasn't clear before.
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Unread 03-05-2007, 02:37 PM   #7
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Quote:
Originally Posted by atomicmoose
Yeah, I have a 4.2L in my YJ currently and a buddy is willing to give me a 4.0L. So I have the parts for a home-brew stroker. I want to stroke the 4.0L block, BTW...

Sorry if I wasn't clear before.
Ok - If I where you, I'd ditch the idea of re-using anything from your current engine. When you have the engine machined you are going to need all new bearings, gaskets, etc and by the time you buy all those parts, you might as well just get one of the ProMar kit's and stuff new parts in there. No sense in putting old parts in a (basically) new engine.

Also, with the Promar kit, you get a new high pressure oil pump and cam and matched pistons. The prices I got on oversized pistons alone where about half of the Promar kit.

Basically, the Promar kit pays for the pistons and gaskets, and you get everything else for free.

Might as well build your stroker over time and do it right than tearing a part a perfectly good (and running) rig. I got lucky too and got a 4.0L complete engine for $50.... I can build and wheel!
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Unread 03-05-2007, 02:45 PM   #8
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Call promar. I have four pistons at my house that are .030 over. If you can get two more, I'll sell you those four and the camshaft for a cheap cheap price. Go to your local jeep store and get a mopar performance head gasket - 28 dollars, part number - P4529242.

PLEASE PLEASE PLEASE MAKE CERTAIN that you have the STOCK THERMOSTAT. I can explain why in a later post. Pick up some RED RTV for the oil pan, you'll want to make sure you get a good seal on the timing end, and this stuff is a good way to do so. For the crank, do as I did. Take a washer that fits over it, and cut out the keyway. I used three washers and have had NO problems.

I have a set of 24# injectors I got from SVTPERFORMANCE.COM/FORUM where I'm a member and got them for 85 dollars shipped to my house.

Make an adjustable MAP sensor and set it at 5.05 and you'll be good.

At the machine shop I have to recommend that you have them press new freeze plugs, and cam bearings in, as well as hot tank it for cracks. The shop will also have to press the pistons onto the rods. My 12ton press wouldn't touch em!

Get a HAYNES MANUAL and read up. If you have any questions feel free to ask in here. I'm workin on a write up of the stroker build with pictures, but I'm currently fixing a 94 cavy and lifting my yj
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Unread 03-06-2007, 07:40 AM   #9
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Quote:
Originally Posted by BNovak
Ok - If I where you, I'd ditch the idea of re-using anything from your current engine. When you have the engine machined you are going to need all new bearings, gaskets, etc and by the time you buy all those parts, you might as well just get one of the ProMar kit's and stuff new parts in there. No sense in putting old parts in a (basically) new engine.
Ok, makes sense...Since the motor I am going to use is is older, is it an HO? Can I even use this motor?
Quote:
Originally Posted by BNovak

Also, with the Promar kit, you get a new high pressure oil pump and cam and matched pistons. The prices I got on oversized pistons alone where about half of the Promar kit.
I want to stay with standard sized pistons if at all possible. I guess I shouldn't buy the kit until after I have the block machined just in case it "needs" to be bored???
Quote:
Originally Posted by BNovak

Basically, the Promar kit pays for the pistons and gaskets, and you get everything else for free.

Might as well build your stroker over time and do it right than tearing a part a perfectly good (and running) rig. I got lucky too and got a 4.0L complete engine for $50.... I can build and wheel!
I would tend to agree here. Thanks for the suggestions.
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Unread 03-06-2007, 07:42 AM   #10
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Quote:
Originally Posted by heywaitfourme
Call promar. I have four pistons at my house that are .030 over. If you can get two more, I'll sell you those four and the camshaft for a cheap cheap price. Go to your local jeep store and get a mopar performance head gasket - 28 dollars, part number - P4529242.

PLEASE PLEASE PLEASE MAKE CERTAIN that you have the STOCK THERMOSTAT. I can explain why in a later post. Pick up some RED RTV for the oil pan, you'll want to make sure you get a good seal on the timing end, and this stuff is a good way to do so. For the crank, do as I did. Take a washer that fits over it, and cut out the keyway. I used three washers and have had NO problems.

I have a set of 24# injectors I got from SVTPERFORMANCE.COM/FORUM where I'm a member and got them for 85 dollars shipped to my house.

Make an adjustable MAP sensor and set it at 5.05 and you'll be good.

At the machine shop I have to recommend that you have them press new freeze plugs, and cam bearings in, as well as hot tank it for cracks. The shop will also have to press the pistons onto the rods. My 12ton press wouldn't touch em!

Get a HAYNES MANUAL and read up. If you have any questions feel free to ask in here. I'm workin on a write up of the stroker build with pictures, but I'm currently fixing a 94 cavy and lifting my yj
All good suggestions, thank you.
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Unread 03-06-2007, 11:16 AM   #11
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One thing to remember. If your block does need a bore, it is a VERY SMART thing to have the pistons there with the shop when they bore it over. It's kind of like an insurance policy. This way they can double check, the bore and the ring clearance, one less thing you will have to do. I've done 9 motors so far, and I've had my pistons with the block every time, except the first when I didn't know. I ended up having to take the block back for them to hone it out .001 more. Needless to say, after that I got a new shop to work with.

Just don't rush and take your time.

You can also use any 4.0 block, HO or not. I would use the heads and intake from an H.O. motor though, as that is the main difference. Also, since you're doing this, port match your intake, and port and polish the exhaust, but DO NOT PORT MATCH IT. You want the exhaust to be slightly smaller on the head side than the manifold side. This keeps the exhaust from entering back into the motor and causing a serious problem. If you want, I can try and copy a few pages out of one of my build books that explains the principle and theory behind this.

Cheapest place for pushrods is at napa! Don't forget to pump up the lifters with either oil or diesel fuel before installing. Prime the oil pump, if you can. If you can't....rotate the motor over by hand atleast 4 complete rotations to help ensure a safer start. I watched someone dry start a BRAND NEW MOTOR because they didn't WANT to prime the oil pump first....pump was air locked somehow and seized his 5K motor.

Also, you should add a ZINC additive into the oil before you start the motor. There is not enough zinc in todays oil for proper break in of cams/bearings/piston rings. I got mine at a local mitsubishi dealer per recommendations of my machine shop. Also, be sure to cover the cam REAL good with the provided grease/lubricant. I am pretty sure a white lithium will suit if you were not provided any, but you may want to double check that.

Good luck, call promar - 1-800-422-6022
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Unread 03-07-2007, 01:11 PM   #12
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Quote:
Originally Posted by heywaitfourme
One thing to remember. If your block does need a bore, it is a VERY SMART thing to have the pistons there with the shop when they bore it over. It's kind of like an insurance policy. This way they can double check, the bore and the ring clearance, one less thing you will have to do. I've done 9 motors so far, and I've had my pistons with the block every time, except the first when I didn't know. I ended up having to take the block back for them to hone it out .001 more. Needless to say, after that I got a new shop to work with.
Perhaps I should just go .030 over and be done with it. How much does boring add to the cost of this project typically?
Quote:
Originally Posted by HWFM

Just don't rush and take your time.

You can also use any 4.0 block, HO or not. I would use the heads and intake from an H.O. motor though, as that is the main difference. Also, since you're doing this, port match your intake, and port and polish the exhaust, but DO NOT PORT MATCH IT. You want the exhaust to be slightly smaller on the head side than the manifold side. This keeps the exhaust from entering back into the motor and causing a serious problem. If you want, I can try and copy a few pages out of one of my build books that explains the principle and theory behind this.
I need some more info on this? What is port matching/polishing? Links to reading are fine. Any info you have, I will take.
Quote:
Originally Posted by HWFM

Cheapest place for pushrods is at Napa! Don't forget to pump up the lifters with either oil or diesel fuel before installing. Prime the oil pump, if you can. If you can't....rotate the motor over by hand atleast 4 complete rotations to help ensure a safer start. I watched someone dry start a BRAND NEW MOTOR because they didn't WANT to prime the oil pump first....pump was air locked somehow and seized his 5K motor.
Ouch. All good tips.

How does one pump up the lifters?
Quote:
Originally Posted by HWFM

Also, you should add a ZINC additive into the oil before you start the motor. There is not enough zinc in todays oil for proper break in of cams/bearings/piston rings. I got mine at a local mitsubishi dealer per recommendations of my machine shop. Also, be sure to cover the cam REAL good with the provided grease/lubricant. I am pretty sure a white lithium will suit if you were not provided any, but you may want to double check that.

Good luck, call promar - 1-800-422-6022
I have been hearing so much about the Zinc additives....why have oil manufactures been removing/lessening it? what does the Zinc do?
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Unread 03-07-2007, 04:35 PM   #13
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any machinist worth a damn will want the pistons with the block before he touches anything. that is the only way to bore/hone it properly. I bought .060" over pistons w/ rings for about $120 online somewhere, nice quality pieces too. dont go cheap on those.
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Unread 03-07-2007, 05:20 PM   #14
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Port matching and polishing can have two different meanings.

Port polishing is always the same though - with an intake port you polish it fairly smooth but so that it has a slight "Wave" texture to it so that the air / fuel mixture swirls a bit before it gets into the cylinder. This increases the atomization of the fuel and causes a better burn. Sometimes you can "swirl" the head to get a similar effect.

Port polishing the exhaust side is basically that - honing the INSIDE of the port so that it's smooth and thus easier for the gases to flow out the port.

Now port MATCHING (can be two different things)

1 - Port mathing the intake and exhaust ports so they are both the same size. This is a good idea on a turbo or supoercharged car, but not so much on an NA engine. This allows the exhaust to free flow and generally spool up the turbo quicker. On an NA there is usually a negative effect though as you get less evacuation of the cylinder after combustion, which causes a pre-ignition.

2 - port matching (what I'm doing) is matching the size of the intake and exhaust port TO THE GASKET AND MANIFOLD. if you take your head off you will most likely notice a dark ring around the outside of the exhaust ports. This is because the holes in the gasket are bigger than the holes in the head. Basically, I'm grinding away those burn marks so that the exhaust port on the head are the same size as the gasket and the manifold. You can do this by taping the gasket to the head and scribing a line around each opening - then grinding away until that line is gone. You can do the same on the manifold. Although it's a tedious and noisy dirty job, you can usually get a couple extra HP out of this, and what the heck - why not.

Make sense?
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Unread 03-07-2007, 07:10 PM   #15
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Quote:
Originally Posted by BNovak
<snip>

Make sense?
Actually, yes...

Thank you for the explanation. I really appreciate it.
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