Atached some info to the grade's

 

If I get the pistons from AVOS, I want to buy the matching sleeves and all.

Thanks amigo.

 

My block says *22222222*

JJB

 

Hello, so if my block is *22222222*, and I use pistons type 2 , they be a perfect match?
Thanks

 

Indeed, that was the intention of noting the numbers on the block.

 

In theory the Pistons will be a match to the cylinder bores. Depending on the mileage on the engine and how hard it was ran, the rings will wear the upper part of the cylinder to a larger diameter. (Cylinder taper) Your shop needs to measure each cylinder and determine if any of the bores are outside the 86.000mm to 86.010 specification. (They can measure the actual bore and the ring gap) If it is out of specification, then this is when the machine shop would hone the cylinders to the next larger size.

Can you feel or see a small lip between the very top of the bore down to where the rings hit top-dead-center? If you can feel or see a lip, then chances are you will need to have the cylinders honed. If not, yours rings will start out with less pressure on them and the engine will age a lot faster.

Read this link for a better understanding of what the shop will do.

Piston Ring End Gap Recommendations

If you have a good engine rebuild shop, they should be able to explain this to you. If not, and they just want to slap the engine together, then you better find another shop.

One other comment. There is the posability that most of your pistons are still good. If the skirts don't have contact marks on them and there is not apparent wear on the tops or ring grooves, it is possible to just replace the rings.

 

Any thoughts on picking up a clean low mileage 4.2L N/A AJ-V8, and swappiong over all the peripherals, blower, manifolds, sensors, fueling, etc, from one's existing 4.2L SC, onto the 4.2L N/A long block?

Compensate for the slightly higher compression ratio with meth injection/tuning...?

 

You will miss the oil squirters under the pistons, though that could be retrofitted with some work. Not sure if the valve clearance will be enough that must be checked.

Although Water Meth would help with the (big) difference in compression ratio, I would find it risky to have to rely on it to always work.

 

Hi!
Will you tell me please, after Basic rebuild and Stock cast crank re-ground, whether crancshaft strength is broken?

Thank you!

 

Hi Pai Mai
I have quoted this for you from the link below. The discussion describes engine rebuild principles in general not specific to Jaguar. But thought you might like to read it.


“You can grind a crankshaft, camshaft, or any shaft to make it round again when it's worn out. You replace the bearings with thicker/oversize ones, so the crankshaft fits nicely in its bearings again. The shaft becomes a little weaker, but only marginal. It doesn't really compromise safety or strength. It is done with crankshafts, camshafts, cylinders(although naming is a bit different here) and much more.”


If you have specific questions you are better off creating a new thread to get the attention you need.

https://mechanics.stackexchange.com/...why-is-it-done

Paul

 

Last time I looked, undersized crank and rod bearings were not available to jaguar 4.2 engines. (Do you have a source?)
Standard Jaguar 4.2 engine bearings were available only in letter indicated sizes intended to account for standard journal size variations.

4 choices were possible last time I looked into this.
1. Have the crank journals spray welded and ground back to standard size, then straightened and heat treated.
2. Have a custom bearing set manufactured. (Often long lead times - 8 to 16 weeks)
3. Find a new or used crankshaft with the journals in spec. (I have read that OEM 4.2L spare cranks are gone worldwide, but some jaguar dealers have sources for refurbished cranks.)
4. Pony up $3.5 to $4K and have a billet crank machined to replace the stock crank.

Let us know what you end up doing.

 

Any updates on this thread? I’ve been doing some mods to my STR and have been wanting to throw some money at building the motor.