Matt Sheppard

I pulled apart my 2.7 this weekend. These are the pistons I pulled out of the motor and they have "ROSS XL400" debossed.

<img src="http://boards.rennlist.com/upload/rosspist.jpg" alt=" - " />

Doesn't JE forge their own blanks? Do they buy from a manufacturer (Ross) and machine them to specs? Supposedly these were speced by Garrity before he closed and invoiced as JE pistons.

Help

TT

Ouch. Looks like you were had. Ross is the "lean and mean" manufacturer of pistons (less $ than JE). Give them a call and see what you have there and compare it to what JE would have provided.

aka 951

Garrity used Ross pistons AFAIK. Don't know why it would have said JE on the invoice. He also used Pauter rods, rather than Carrilo.

fast951

On some engines Garrity used Ross. I believe the XL400 is the part#..

So why did you pull the engine apart?

Matt Sheppard

No Kidding. . .? Bummer. The ARP rod bolts listed weren't in this motor either. Not Garrity's fault, this was the piston set he supplied, but it's the P.O. who said they were JE's and that the ARP's were there. I guess it's easy to lie about what you can't see in an engine. Sometime I'll make a list.

Yo, live and learn . . . some people take the low road and sell it to you afterward. . .

<img src="http://boards.rennlist.com/upload/pistcompare.jpg" alt=" - " />

Look at how little skirt area is on these pistons compared to a stock 951 piston. That and the .0052 min cyl. to pist. skirt clearance (as near as I can tell w/ tele gauge) made this one loose engine. Also notice the cheap spray-on, bake-in-you-oven coating on the skirts, well that stuff that is missing from the skirt is on the cyl walls as well. There was a coating on the piston tops also that flaked off in areas. The rod bushing to pin clearance was so large that I can rock the big end of the rod back and forth laterally about 1/4" without moving the small end of the rod on the pin itself. All in all, this thing is 10x as worn out as the 260K stock engine I tore down last week. This engine builder is going to hear it from me.

For those interested, it was built by a shop called Eurosport in Manhatten Beach.

TT

XL400 is the forging, you can see the etched part number on the bottom.

Matt Sheppard

Fast951:

I pulled it apart because it had what seemed to be a rod knock at low RPM's or piston slap, turns out it was piston slap - loud enough to cause some real concern. Well, I'm considering sending the pistons off to Swain and have them build up the skirts .004" or just start over w/ some new pistons. The skirt design bugs me. If I get new pistons, that will add $800 - $1000 to my proposed rebuild budget so I might just shelve this engine and build my stocker for the time being.

What is your opinion of Ross Pistons. I assume "lean and mean" denotes remove as much material as conceivable and dont bother with the details.

m42racer

You problems are not Pistons. If all 4 Pistons look like the one in the pic, your in good shape. The problem is with the clearance put into the block. I don't know what clearance is required with Ross Pistons, but typically JE, Wisco, and maybe Ross need from 0.003 - 0.006 clearance, depending on your use. Piston noise is normal with JE Pistons. As for the Pin clearance, you should have 0.0008 -0.0012, again depending on use. Remember you get what you pay for. If you want a quite engine cold, you must run tighter clearances. Most US made Pistons will not allow you to run at the lower end because of expansion.

Do not build up the skirts. That would be bush engineering at its best. As for the skirt design, very typical of US Pistons for the aftermarket. Again its the choice of whoever spec'ed out the Pistons. You have not been done wrong here. It appears all you have is some excessive Pin clearances. If there is as much as you say there is, then the Pin bushing will shows signs of been hammered under compression. As for the Piston clearance, if all you have is a little noise, this is a trade off for less friction.

Maybe you should measure the Piston bores and the bores in the small end of the Rod. Then do some math and see just where you are. You may not be that from wrong, and the worst that has happened is that you torn down a perfectly good engine.

m42racer

And by the way, "as near as I can tell". What the hell does that mean, when talking about clearances in an engine. Either it is or it is not. Where are you measuring the Piston diameter. I do not know where Ross spec this to be done, but I think JE and Wisco say to do it at Pin height or maybe 0.500 below the Pin. You should ask Ross where they want this done, or maybe someone here might know. I'm no engine builder, but it sounds like your not one either.

m42racer

And one more thing, if you have the amount of Pin to Piston clearance, then maybe this was the noise, not the slap?

fast951

I would contact Ross to find their recommended clearance. Sleeved blocks with JE or similar pistons tend to be noisy when cold.

Some people tend to run the piston/wall clearances very loose.. Have a machinist check the sleeves to make sure they didn't move...
I'm a bit concerned about the coating sticking to the wall or getting in the oil. Let me guess, the top coating is goldish/yellow??

I'll post a picture on how they look like when new. I've had a set for 3 years now, and still in the box.

Matt Sheppard

The engine wasn't just noisy when cold, it was noisy always and had 107 PSI compression in all cyl. when warm. I checked w/ two different gauges, one brand new, at two seperate times. I just didn't want to beleive what I was seeing.

The "as near as I can tell" part is from using a telescoping gauge and then measuring off my micrometer. I get mixed results using the tele gauge, I really only trust a bore gauge and that requires me taking it to someone with the tool, but I can get within a thousandth variation with the tele. gauge and that still gives me .0045-.0055" which means this thing is the epitomy of "4-banger". The piston I measured (pictured) I measured at different points on the skirt (not many places I can measure there that thing is so minimal). I found the tightest point and took readings off all the skirts there.

So, "How the Hell..." does one explain the 107 PSI compression on a "healthy" engine. #1 Compression rings are gapped well at .016.

M42racer:

For someone who "isn't an engine builder", you sure know a lot of clearances off the top of your head. In fact, the last "engine builder" I got information from told me to throw away a perfectly good set of forged turbo rods . . ., but I digress.

If this information is accurate, this is a real sorry case for american manufacturing/metalurgy if factory forged pistons can run clearance spec of .0008 - .0012" why do these require .003 to .006" (?). That and I can possibly see this engine builder saying this clearance is OK, but the piston pin slop is sooooo bad, there is no way I'd assemble an engine (theoretically, of course - not being an "engine builder myself . . .) with this much play - again it wobbles 1/8 - 1/4" laterally on the pin! There was a stock headgasket in there. . .in an overbored engine. This overhung the cyl wall by 1 mm on every side. This gasket was blown - surprise. The cyl studs backed out almost without having to be doublenutted, only one stud required double-nutting. How did they get a proper head torque? They tried plugging leaks in the oil-pan gasket with clear (!) silicone beads.

I've now torn down (3) 944 engines this month (unemployment has it's privlidges), 2 factory and this one. This one was a very different experiences is about all I can say, again, not being an engine builder - I'm trying though, please keep helping everyone.

This is about 1/2 the things that were wrong with this engine - just what I found out upon teardown of this motor this weekend. Who hear think I have cause to approach Eurosport with just what is mentioned?

Matt Sheppard

Fast951:

Yes, the top coating is goldish colored, what I can see once the carbon is removed and then what is left of it. I'll post a pic later tonight. The cyl wall transfer was slight, but I'm sure more washed off and prob. got into the oil. What ramifications would this have?

m42racer

The compression test does not really tell where the problem was. A leak down could tell if you had lots of blowby. I cannot tell by your pic how the rings have worn. Look to see if there is some non shining parts across the ring face. If there is, then the ring face has some use left.

0.0045- 0.005 ins of clearance will not give an problems. It may make the engine a little noisy when cold, but this will not be aproblem when hot. If what you say is correct, the noise is from the Pin clearance. There should be signs of the Pin bushing been pounded and maybe even a Pin boss cracked in one of your Pistons. This will make a noise all the time.

You have answered your own questions here. If the H/G was blown, then thats why your comp # were probably low. As for the head studs, they should never be installed till they either bottom out or thread end. The propoer way to install studs is to oil them or use an anti friction grease supplied, and install them finger tight only. This will not affect the torque.

AS for the leaks, these are not acceptable peroid. Unfortunatly, if you were not the owner who had this engine built, you really don't have a leg to stand on. You can try, but I'm sure I know what the builder(assembler) will tell you.

Please do yourself good here and get everything checked by someone who knows if you don't. Start with the Block, Pistons, Rods etc
looking for clues for the noise. Have the engine checked for the correct sizes. Your Piston clearances are good. Yes they may be a little noisy cold but will cause no problem.

A little saying of an engine builder I respect is
"every good engine starts with good machining".

Ask Travis from Guru who to get this work done by. He will give good sound advice.

Danno

"I do not know where Ross spec this to be done, but I think JE and Wisco say to do it at Pin height or maybe 0.500 below the Pin."

Where you measure on the piston makes a BIG difference on your clearance specs. You'll notice that the piston is tapered? The difference in diameter at the top and bottom will give you some useful info as well.

" this is a real sorry case for american manufacturing/metalurgy if factory forged pistons can run clearance spec of .0008 - .0012" why do these require .003 to .006" (?). "

That's because the factory pistons are hypereutectic with high silicon-content like the block itself. Hypereutectic alloys do not expand as much as lower silicon-content aluminium alloys. Ross recommends a clearance of 0.004" on their 2618-alloy forged pistons.

"Ask Travis from Guru who to get this work done by. He will give good sound advice. "

We are looking at two configurations for rebuilt 944/951 engines. Both will be sleeved with a high-end option using a foreign-made piston. A lower-cost option will use domestic pistons in SAE sizing. One of the benefits of this is a wide variety of ring selections.

None of which helps you Matt . Your pistons are OK, the clearance is fine for a forged eutectic piston. The knock you were getting is most likely due to the piston-pin clearance. The Ross piston-pins are slightly larger than the 951 pins. Whoever sized the rod-ends for that combination messed up. New bushings on the rods will take care of that.

"the engine wasn't just noisy when cold, it was noisy always and had 107 PSI compression in all cyl. when warm."

How were the ring-gaps lined up? How many miles did you have on the engine? I've seen new engines go from 130psi to 160psi compression in a week as they broke in. But I agree with M42racer, most likely your blown headgasket was the cause of the low-compression. I would at least mill the deck and head flat before re-assembling. <img border="0" alt="[bigbye]" title="" src="graemlins/xyxwave.gif" />