Old cylinders compatible with new pistons

[joetiii]

I am preparing to modify my stock '82 3.0SC to a hot street engine (some Auto X). The PO rebuilt it to stock specs 5 years ago. It has PMOs and elctromotive crankfire. When he rebuilt, he replaced with stock CIS nikasil P&Cs. I would like to upgrade the cam to higher lift, narrower LSA cam similar to Camgrinders Mod S cam. I know there are clearance issues with CIS pistons so I'm looking at JE 9.5 or 10:5 pistons.

My question is can I use the old Nikasil cylinders with new JEs? Will 10.5:1 require dual plug?

Other consideratons?

[Henry Schmidt]

If the cylinders are in good condition there is no reason not to use them.
That said, the issue will be fitment. Cylinder to piston clearance.
The are 4 different diameter specs for 95 mm cylinders.
0-3
If you buy a "shelf" JE piston you will get a piston that will most likely fit a 0 or 1 cylinder.
If you have a 0 or 1 you win. If you have a 2 or 3 cylinder you may end up with a larger than desirable piston clearance.

Check the cylinder for ovality and surface condition. When you measure for ovality, you should know you diameter and that will allow you to order a JE to fit your application.

You might also concider machining your Mahles for valve pockets. It will only slightly reduce completion and substancialy improve you wallet thickness.

10.5 is pushing the envelope for single plug engines, race fuel is required.

[joetiii]

Originally posted by Henry Schmidt


You might also concider machining your Mahles for valve pockets. It will only slightly reduce completion and substancialy improve you wallet thickness.

Not sure why I didn't think of machining the pistons first. Maybe that is because I was planning on a higher compression setup. JE's 9.5:1 isn't much different than stock 9.3:1 as I do want to stay on pump gas. So what does it typically cost to machine the piston tops for valve clearance?

Another thing I'm thinking.... does the case need to be split to get this work done?

[Eagledriver]

I'm sure many shops can do this. The thing you need to know is how much to take off. I use German Precision for this but he won't know how much to take off unless you tell him. You could assemble the engine and measure how much you need to take off during the valve timing process. Maybe Henry can give you a number.

-Andy

[Porschekid962]

You dont have to split the case to replace pistons although depending on mileage you might as well replace the rod and main bearings and possibly upgrade your rod bolts. Other than that if your cylinders spec out you can go off the shelf mahle, off the shelf JE or custom JE.

[joetiii]

Originally posted by Porschekid962
You dont have to split the case to replace pistons although depending on mileage you might as well replace the rod and main bearings and possibly upgrade your rod bolts. Other than that if your cylinders spec out you can go off the shelf mahle, off the shelf JE or custom JE.

Well the case was split on the last complete rebuild 5k ago. I was thinking about doing the rod bolts as insurance. Would I need to split for that?

[Henry Schmidt]

Rod bolts are not an issue on 3.0 engines. With mod "S" cams you power band is all in by 6800 and at that rpm stock rod bolts are more than good enough. In fact, Verbus 10mm rod bolt are adequate all the way to 7600 with complete confidence.
Given your engine specs and recent rebuild, there is nothing to gain by splitting the cases, unless you have some reason to question the last engine builder.

[78P930]

10.5 is pushing the envelope for single plug engines, race fuel is required. [/B][/QUOTE]

Henry, Do recommend race fuel for the higher compression Euro engines?
Thanks,
Pat
Sorry about the highjack

[Henry Schmidt]

Race fuel is required when condition warrant it.
Ignition timing, compression, dome configuration, mixture and air density. Operating temperature can be added to that list if high temperatures are encountered.
I lean towards less compression whenever fuel quality is in question.