4.5l stroker build advice.

[4.0l sahara]

Well to start out nice forum for just jeep strokers. I'm 16 and go to a tech school and take auto. Always loved cars and always working on them but I really like jeeps. I have a 99 tj with a 4.0,ax15,np231,d30,d35 But with all thew other mods like axles gears tire and lots more I would like to do a stroker. I was thinking 4.5l. I have the better intake on a 99 right? I want to do new rod bearings,cam bearings,mainbearings and all the stuff that goes with a rebuild. I will have the cylinders checked and if good honed. Also will check block and head for flattnes and hope that it doesn't need a rebuild. Also get the head rebuilt. I will get a cam crane,comp? I need a 4.2l crank. I would like to run this on regular gas to help keep coast down. So to do that I need to keep the compression ratio down but would like to keep the QUENCH good or better than stock. So I need a piston with a dish and if I do that do I use the 4.0 rods? What size dish would I need to get a close to or little higher than stock compression ratio? So I really just need help on all the details.

thanks.

[seanyb505]

Yes you have the better style intake on the 99.

With all new bearings and such, it sounds pretty much like a rebuild to me.

Which cam to go with was my million dollar question in research. I finally went with the Isky 133125/26, for better than stock but not extreme lifts, and a dual pattern that flowed more on the exhaust side. I cant say how it performs yet as I havent put it all together yet.

You will need custom or Diamond ($$) pistons to reuse the 4.0 rods. UNLESS, the KB piston we keep hearing so much about has the right pin height to use the 4.0 rods. If your using the 4.0 rods you will need a 1.380" pin height I believe. If you use the 4.2 rods you can get Silv-o-lite 2229 pistons like me, and have them dished up 30cc. Using this combo and decking the block a bunch (Ill be taking .045 off) will result in a relatively low CR with a good quench, depending on which head gasket you use. Using the stroker calculator (top of page) my engine should have 9.13 CR and .0475 quench if I go with column IV.

[oletshot]

From what I know the silvolites are the only aftermarket pistons that are thick enough to add more dish. If you use them and don't deck the block your quench will be worse than stock. If you deck the block to get quench back to or better than stock, you'll need to shim the rockers. The only recipe using 4.2 rods that has quench and compression the same as stock without decking the block is this:

4.0 block
4.2 crank
4.2 rods
4.0 stock pistons dished to 20+ cc's (I dished standard pistons, yours are metric. I'm not sure if the casting is the same, with different machined ring lands or different casting entirely).
Victor Reinz 5713 head gasket (.043 thick).

With this recipe quench and compression match stock 4.0. The only problem is you need a lower mileage 4.0 so that pistons and bore are still usable. Even then you are doing a rebuild/refresh with used parts, not everybody's prefered method.

[4.0l sahara]

I thought since it has 108k I might as well do all new bearings and such. I will need to measure the bore and see what the condition of it is.

[oletshot]

The used parts I was refering to was the block (no new bore) and pistons. I would agree, new main and rod bearings even if you don't have the crank ground.

[4.0l sahara]

The pistons I want new. For the bore I will measure and check out of round and if it's good I'll just have it honed out. If it's to worn I'll bore it .30 over.

[4.0l sahara]

Could I have a custom pistons made that I could use with the 4.0l rods and have a good QUENCH and have a close to stock compression ratio? Where is a good palce for custom pistons and what do you think they will run me? Also what does a good QUENCH do for you? Why is a smaller QUENCH better?

[oletshot]

You can have pistons made that will give you zero deck height or flush to the top of the block at top dead center. Your quench would then be whatever gasket thickness you use, i.e. .043" or .051". The price I have heard for said pistons is about $600 a set. Places to check are Diamond, Ross, or Venoila (not sure if this is spelled correctly). The other advantages are the are forged so they are stronger, plus I believe you can spec. how much dish you'd like. The down side I've already listed ($600).
Quench is an important factor in controlling ping. It is the air turbulence caused by the piston coming up to TDC. The closer the piston comes to the bottom of the head (without hitting of course) the more turbulence is created. The air movement has a cooling effect in the combustion chamber which reduces pinging. With proper quench, you are able to run a higher compression ratio without pinging, which gives you more power.

[4.0l sahara]

600$ isn't to bad. So that way I could have a zero deck high,good quench and a big enoughf dish to run regular. Another ? is would it be worth porting my head or is the head on a 99 better than others? What heads are the best? Could I port it my self with a dremel?

[mecompco]

After reading about all the issues and challenges getting a good quence and CR able to run on regular gas, it seems like custom pistons might very well end up being the more economical choice. Say off-the-shelf pistons are $200 (guessing) and customs are $600 for a $400 difference. If that means you can run regular instead of super, and there is a .50 per gallon difference, the custom pistons would be paid for in about a year (13K miles, assuming 350 miles on a 20 gal tank, which is about what I get with my slightly tired 4.0).

I think it makes much sense to spend a little more up front and avoid higher costs and headaches down the road. Any counter-points?

[dwg86]

If you can wait a little longer, the kieth black stroker pistons should be available within the next month,according to the email I got sent from their tech dept. I don't know what they are going to cost. I think they are going to be forged(I know we all wanted hypereutectic). I also don't know what comp ratio, but the feedback they were getting was around 9:1. Supposed to be correct quench with using the 4.0 rod.

[aaronkeiser]

As for porting your own head...yes it's worth it, even if its not full on ported. Obviously it will flow better but one of the main reasons I ported my head and smoothed everything out was so the exhaust runners and combustion chambers wouldn't have soot buildup later on. When I took apart my junkyard head it was really clogged in all the exhaust runners and it had 230,000 miles on it. As for doing it with a Dremel...totally possibly...thats what I used. I went through 4 grinding stones and I didn't really port...more like cleaned up everything and made it smooth (Intake runners, Exhaust runners, Valve seats, combustion chambers). Make sure you wear a face mask and goggles...you will be blowing black snot out of your noes for weeks not to mention all the stuff you inhale and get in you eye. You can buy a porting kit that comes with all you need which is probably a good idea since if you port your own head with the Dremel with griding stones, it will cost 5$ for each griding stone. Read up on the head porting topic on hear, it will show you what not to do. This the page where my head is pictured...its about half way down.

viewtopic.php?f=5&t=84&st=0&sk=t&sd=a&start=10

[4.0l sahara]

So it looks like you don't want to open up the middle of the prts much as it will lower the velocity on the intake side. But to feather the ports so they match the size of the gasket. Is it also good to smooth out around the valve guids. Open around the valve seats. Also smoothe out the combustion chamber. Thats all that I need to do?

[John]

Smoothing is really what you should be thinking unless you have a flow bench. Cleaning casting marks rough areas, a little material removed to match (gasket match) ports. most improvement is made in the bowl area, also the area easiest to screw up. If you are removing lots of material, you are likely doing something wrong, don't attempt to remove the texture from the intake side. If you want to clean up the combustion chamber, again smooth rough areas is your goal, I finish combustion chambers to 80 grit only.
John

[seanyb505]

Ive calculated 9.13 CR and .0475 quench for my motor, I think I should be able to get away with mid grade, which is what I use anyway. I will not be using custom pistons; 2229s dished to 30cc, decking the block and using a .043" head gasket.