Possible 4.8L Build

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Muad'Dib
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Possible 4.8L Build

Post by Muad'Dib »

Here is what i was thinking about doing. Your input would be greatly appreciated:
My only real drawback to the build is that it has to run on pump gas.. Whether it be regular, mid-grade or premium... doesnt matter.

Jeep 4.2L crank
Jeep 4.2L 5.875" rods bushed for 0.912" floating pin
Small Block Ford (302) KB364 22cc hypereutectic pistons (dished to 25cc's if possible)
CompCams #68-235-4 camshaft 254 Advertised Intake Duration 111 LSA
Mill block deck to 0.005
Mopar/Victor Reinz 0.043" head gasket

This should get me (if i can dish the pistons to 25cc's):

9.64 SCR
8.13 DCR
0.048 Quench

What say you?
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Re: Possible 4.8L Build

Post by Mgardiner1 »

I say get the block to a machinist and have him sonic test the cylinder walls, and get his recommendation on going with the size bore you are interested in
oletshot wrote:....and silvolites are only cast not hypericantspellits. :-)
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Muad'Dib
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Re: Possible 4.8L Build

Post by Muad'Dib »

How do the numbers look though?

Also what is the consensious on cylinder sleeving?
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Re: Possible 4.8L Build

Post by Muad'Dib »

No one? Is a 4.8 build really out of the question in everyones eyes?
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Re: Possible 4.8L Build

Post by IH 392 »

Muad'Dib wrote:Also what is the consensious on cylinder sleeving?
I wouldn't sleave a block that you actually intend to have that much of an over bore in, the integrity of the block isn't there, sleaves are to repair cylinders.
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Re: Possible 4.8L Build

Post by Plechtan »

You never state the diameter of the pistons, I assume around 4" Sonic testing will tell you where you are. it is best to stay in the .100-.090 minimum cylinder wall thickness. People have gone down to .075 or less. The jeep block is usually only thin on the front and back of the cylinders, so you will have thin spots. The entire cylinder will not be thin.
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Muad'Dib
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Re: Possible 4.8L Build

Post by Muad'Dib »

Plechtan wrote:You never state the diameter of the pistons, I assume around 4" Sonic testing will tell you where you are. it is best to stay in the .100-.090 minimum cylinder wall thickness. People have gone down to .075 or less. The jeep block is usually only thin on the front and back of the cylinders, so you will have thin spots. The entire cylinder will not be thin.

How big are you going with your build?
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Re: Possible 4.8L Build

Post by Plechtan »

Look near the bottom of this page http://www.jeepstrokers.com/forum/viewt ... r&start=15

This shows the cylinder wall thickness from the sonic tests on my block. Rember you will be taking about .060 from each side of the cylinder, so take the measuremnt -.060 to come up with your final wall thickness. This assumes a stock bore size. if you block is worn or has been bored already, then you have to take 4" - the current bore size /2 to come up with how much you will be taking off each side of the cylinder.

I went with a 4" bore
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Re: Possible 4.8L Build

Post by Muad'Dib »

So i guess i need to take the block i decide to use (which will probably be a RENIX block) and get it sonic checked. Hopefully it can be bored to 4" but if not then i guess a 4.7 will have to do ;)
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Re: Possible 4.8L Build

Post by oletshot »

The dish shape on the jeep piston matches the head (somewhat anyway) and that's where you get a lot of the quench. By switching to the ford piston, you may lose some of your quench, as the flat surface on the head may not/won't match the piston. Remember, quench is effective because of the air movement from the flat surfaces of the head and piston coming close to one another and squishing the air in between out.
Performance wise, I think you'd be better off going 4.7L with zero deck, with the better quench you could run higher compression than the 4.8L and get better performance. You also can save the money on having the block tested and wrist pins changed and could use it else where on the build.

That being said, I haven't looked at the ford piston, so I don't actually know how well the dish matches the combustion chamber on the head. If your looking to do something a little more unique, then the 4.8 beats the 4.7 all day long.
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Re: Possible 4.8L Build

Post by Muad'Dib »

I am looking for the uniqueness factor .. but im also looking for the best bang for my buck. Its actually a cheaper build going with a 4.8 as the pistons are way cheaper than kb944's.

kb944 = 607.99
kb364 = 336.39

Arent the 944's just a standard "D" dish? cause its the same on the fords...

So you think i could get better performance with a 4.7L build? Even running on pump gas (premium is fine)? That may be the determining factor then ...
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Re: Possible 4.8L Build

Post by oletshot »

Well, like I said unique=4.8L.
To me the best reason to use the kb944's is to use the longer 4.0 rods. Since the ford pistons need the 4.2 rods, it's no different than a budget stroker that uses off the shelf replacement pistons. So you say the fords are half the price of the kb944's and that may be true, but you can pick up a set of silvolite 3241 hypereutectic pistons on ebay for $135 with free shipping. That's less than half the price of the ford pistons, and they go on the 4.2 rods with no mods. You're already $200 ahead on the pistons plus no wrist pin mods to pay for or sonic testing. Bang for your buck = 4.7L. I'm not trying to talk you out of it, just my opinion.
Last edited by oletshot on March 20th, 2009, 8:55 pm, edited 1 time in total.
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Re: Possible 4.8L Build

Post by oletshot »

Is that the best price you could find on the 944's? At that price you could probably almost buy a custom set. I thought they would go for about $400, at least at that price with the offset of not needing 4.2 rods you almost break even with a budget stroker.
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Muad'Dib
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Re: Possible 4.8L Build

Post by Muad'Dib »

Thats just the only price i saw honestly ... i really havent seen them listed anywhere but summit racing.

I may just decide to go with a 4.7 build ... i have alot to ponder.

How much is sonic checking anyway?

The hardest part is going to be finding a decent machine shop around here... the only one anyone that i know even knows of is napas machine shop .. im not sure how comfortable i am with that.

Im thinking ill just get the block im going to use sonic checked. If i can bore it to 4" ill highly consider custom pistons so i can use the 4.0 rods. If not, then ill definetly build a 4.7 with 944's. Its kinda looking like it might be the same approx cost either way... Im not even sure what to ask for in a custom piston.. lol!

I dont mind spending more to do it right .. as long as i can take my time with it. My current 4.0 still has plenty of power getting ready to roll over to 200,000.... just gotta do the exhaust manifold again.
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Re: Possible 4.8L Build

Post by PolloLoco »

KB944 vs. KB945

Y'all are talking about the 944, but I was suggested to use either one:
viewtopic.php?f=15&t=820

What are the differences and which would be the preferred piston for _x_ application?
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