Jitters

Hey Gents,

Just recieved a little bad news from my mechanic. Says that 2 of my pistons are no good. I'll be stopping by tomorrow to take a look.

Anyone have a recommendation on what would be a good replacement kit for the PCAR. My mechanic is recommending Mahle Pistons as a good replacement. Currently, I have 98mm cylinders.

Also, can anyone advise as to what the average cost is on these kits?

Thanks,

Jitters

Mark Houghton

Damn Jitters, that's not good news! Is your engine torn down? if not, how does your "wrench-man" come up with the bad piston(s) diagnosis? Mahle are probably the way to go, but others here certainly know much better than I (since I haven't yet had the good fortune to go there yet).

Geoffrey

yep, the Mahle 98mm are the way to go.

Jitters

Hey Mark,

Yes! The engine has been torn down. I'm going by the shop tomorrow to meet with my mechanic to take a look at what he's talking about.

What he is stating is that although only 2 of the pistons are bad, he can only order the complete kit.

Unfortunately, I'm not sure of what other alternatives I have...

Would appreciate any and all feedback at this point...

Ciao,

Jitters

Jitters

Hey Geoffrey, thanks for the feedback...

Jitters

jimculp

Stephen from IA would recommend the long sleeve Mahle's I figure. I have the short skirt "Ruf" versions and they work fine, but are loud as hell at higher revs.

onboost

I've used Mahle P/Cs in several builds and have had no issues.

Some people are very satisfied with JE as an alternative to Mahle. I personally have not used them but plan to in the future.

Jitters

Hey Jim,

Do you know what the difference is between the two? (short vs long). If I'm not mistaken, the previous owner installed the RUF versions as well. But not sure if they are long or short. How can I tell?

Thanks,

Jitters

Jitters

Hey Geoffrey,

This is off topic, what type of headlights are you running on the PCAR? I have been interested in replacing my lights with the yellow but understand that they don't come in H5's.

Thanks,

Jitters

Geoffrey

The RUF and Mahle 98mm have the same net dome volume which results in a compression ratio in the 7.2:1 range, not the 7.5:1 as advertised. There is a small difference in skirt size (I can't find my picture at the moment). In general, the shorter the skirt, the more wear of the skirt and cylinder due to the short rod to stroke ration and the rocking of the piston that occurs. They may even tend to be noisy when the engine is cold due to the slapping of the skirt on the cylinder. It is more an annoyance than anything. Both of these pistons are better than the JE alternative.

My headlights are H4s and I replaced the clear glass lense with a lexan formed yellow lense. It wouldn't be appropriate for the street as the beam dispersion isn't correct and the lenses have deformed slightly due to the heat from the lights being on. I believe you can get glass yellow lenses for H4s which were used in French delivered cars.

Jitters

Hey Geoffrey,

Thanks so much for the info...truly appreciated.

So, if I understand correctly, the longer skirt would be a better option than the short skirt? Is there any difference in performance?

Also, I've seen the glass lenses, which I absolutely love. Is changing to H4's a simple swap?

Jitters

Jitters

Thanks onboost for the feedback, truly appreciated.

Jitters

onboost

Geoffrey, What's the deal with the JE pistons? Some people seem to hate them while others seem to swear by them. Obviously you've had some experience with them and Mahle.. so what's the deal or your opinion?

Thanks

Geoffrey

Anytime you run aftermarket pistons in a cylinder you need to be sure you understand the engineering involved. You cannot run the same clearances as the Mahles or the piston will stick due to the 2618 piston material compared to the Mahle cylinder material. The JE clearances are 2-3x what the Mahles are. Further, the Perfect bore cylinders that JE sells are not IN MY OPINION high tolerance items. The ones I have measured vary in bore size more than I am comfortable with and they varied from cylinder to cylinder. Further, their honing process causes the rings to scrape the nikasal off the cylinder walls and it get embedded in the rings and makes a mess. The JE piston blanks are weak and expand too much compared to other 2618 piston designs. Other manufacturer's pistons work much better, expand less, and are stronger and lighter than JE. The dome of a JE piston in a N/A configuration is crude and does not have a proper squish area the hemi cylinder head requries. Basically, JE is low quality IN MY OPINION. I am aware that they have a new blank available when they acquired another piston manufacturer and that looks to be better.

So, if you are and engineer and have experience in desigining engines, then you can probably make JE pistons work, however, I still think there are much better alternatives available out there. For the average guy who wants to rebuild their 930 engine, the Mahle 3.4l kit is probably the most reliable option out there.

onboost

Wow, interesting stuff... My question stemmed from the fact that I have a spare set of very low mile 3.4 Mahle cylinders which I was going to use along with spec'd JE pistons for an EFI 930 build coming down the road.
Of course now, considering the info you've provided.. along with some from other threads, I'm now re-thinking the use of the JEs.

Thanks,