Walked 7bolt 2.4 Results

[Raptor]

Okay, finally Chris's walked 7 bolt 2.4 is torn down and the reasons for it's problems can be assessed. All the bearings in this engine look like new with the obvious exception of the thrust bearing. The block is perfect and suffered no damage as the bearing still had adequate material on both sides to protect it. The remaining thrust surface on both upper and lower shells are exactly the same thickness which means that they were not out of alignment in any way. There is no difference in dimension from side to side thickness meaning they were not cocked to one direction or the other and when assembled without the bearings, the thrust surfaces on the block and the cap line up perfectly with very little movement possible due to the CRCO bushings. Now what caused it to wear? Well, as said before, the rest of the bearings are in perfect shape so there could not have been oiling issues at least in the main galley. The only thing somewhat obvious is the wear on the crank itself and the bearing. The bearing should have worn much furthur than the crank but it doesn't look to be the case. The crank has a fair amount of wear for the amount of damage to the bearing. That does support the case that the 7 bolts have looser/weeker grain structure in both the block and the crank and are most likely more effected by the heavy clutch pressures than the 6 bolt blocks/cranks. I would hope the cranks are nitrided equally on the thrust surfaces, but maybe they are not.

We are going to try using H rated bearings and having the crank repaired if possible. The clutch is being replaced with a twin disc and I am hoping that that solves any furthur issues with crankwalk on this engine at least.

Any useful input is welcome. Any stupid input will be dealt with accordingly.

[Enes]

stupid coment insert here...

I hope this engine is salvagable..
do you guys know what year this engine was from? because suposedly 99's had some changes done to them?

-E

[Raptor]

The engine itself is fine, the crank however is not without a rediculous amount of money. We did find a reasonable one already though so it's all good. I have not done any searching on what the factory does for nitriding on the 7 bolt 2.4's, would anyone happen to know off hand?

[Enes]

so basicly the passenger side of the crank inner bearing was getting worn out?

[JET]

There was talk of crank differences on NABR. It looks as if the 7 bolt cranks may not be nitrided at all! This isn't a very scientific test, but if a 7 bolt crank is left outside for any length of time, it will rust. You can leave a 6 bolt crank outside for years and it looks like new.

Allan was supposed to take my 6 bolt crank that walked several months ago. It sat ouside for about 6 weeks. It looks like new except for the surfaces that were damaged from the crank walk. So there is definately a coating on the 6 bolt cranks.

Also not totally related to this situation, but another data point to look at. When my engine crank walked it wore much worse on one side than the other. The bearing was still about 3/4 original thickness on one side, but wore into the block a good .030" on the other side.

I am thinking you should have the new crank sent out and nitride coated, because the 7 bolt crank is either not coated or it has a substandard coating that is causing a problem. This is just my 2 cents, YMMV.

JET

[Enes]

i tought your crankwalking issue was a trany install problem?

-E

[LightningGSX]

So the H rated bearings are just a harder material right?

[Raptor]

Yep Eric, they are a higher load bearing, originally designed for use in Nascar. There is info on several bearing manufacurer sites. Worth reading. The bearings we are going to order are ACL's from Austrailia.

JET, I don't doubt that what you say is true, I believe it has a lot of merit. The wear on the crank is pretty extreme for the damage to the bearing. The crank is pretty soft is the only conclusion I can make based on what I saw. The thrust surfaces on the crank were in very nice shape when it was put together. I have a place to do the nitriding and then it will be sent to gopher to polish all the surfaces including the thrust areas. It is pretty normal for the bearing to wear on one side(flywheel side) more than the other with a heavy pressure plate which is the case here as well.

And Enes, you are a gutsy Bosnian bringing that up again :stick:

[Goat Blower]

Well, being that bearings are pretty soft, I'd say the 7-bolt crank is awfully soft if it has a lot of wear on it. Nitriding was about $180 when I had it done, but that's a deal compared to completely switching motors. Make sure you throw away the oil cooler if it's an external.

[slowbubblecar]

Originally posted by Raptor@Oct 4 2004, 08:33 PM
It is pretty normal for the bearing to wear on one side(flywheel side) more than the other with a heavy pressure plate which is the case here as well.
Mine wore about the same way as this with the stock clutch and pressure plate. They were all worn but that end was a lot worse. I am sure mine wasn't from the pressure plate though. I also had a bad ring and lost the #1 cyl rod bearing also. I wonfer what other reasons there are for that end being worse.