Vacuum on 1968 GTS 340 4 spd.

[nm9stheham]

Do you remember which KB pistons? Stock 360 bobweights are already 150-160 grams than the stock 340 bobweights..... the stock 360 pistons are mucho lighter than the 340 pistons ever were. So, I bet that 360 weight change simply was not all that much... though enough to put a 4500 RPM limit on it.

 

[Kendog 170]

Pulled the pan last night and found sludge on bottom of pan. I hope it's not babbit or lifter , cam wearing . Haven't had time yet to investigate. This is the break in oil. Car was only driven a couple of miles for an alignment but started and ran quite a bit .No metal chunks but I haven't stained it yet. Not normal right ? Never dropped a pan right after break in .

 

[scatpackbee]

Pulled the pan last night and found sludge on bottom of pan. I hope it's not babbit or lifter , cam wearing . Haven't had time yet to investigate. This is the break in oil. Car was only driven a couple of miles for an alignment but started and ran quite a bit .No metal chunks but I haven't stained it yet. Not normal right ? Never dropped a pan right after break in .View attachment 1715295230

It might be moly and zinc which is I believe brake in oil is heavy in.

I would cut the oil filter with a large pipe cutter or chain cutter and look in the filter pleats.

The oil flows from the outside of the filter towards the center.

 

[Kendog 170]

Yes, I will check it out. Can't get back to it for a few days. Just too busy.

 

[nm9stheham]

Check for fine metal particles. But as above, could be some sort of assembly lube.

The old Kendall oils were green like that back in the day.

 

[scatpackbee]

Yes, I will check it out. Can't get back to it for a few days. Just too busy.

What brand of brake-in oil did you use?

If it's Joe Gibbs BR oil, I would call Lake Speed Jr. (Chef Tribologist at Joe Gibbs Driven Oils) directly and ask him what he thinks of the color of the oil.

He's an awesome guy to talk to and extremely knowledgeable on everything oil related.

Here's a great article on modern oil and about 3/4 of the way down he talks about wear during break in. He says 4 times the amount of wear metals are created at break -in.

All about oil: Lake Speed Jr breaks it down

 

[Kendog 170]

Lucas break in oil
Lucas Engine Break-In Oil 10631-1

 

[Kendog 170]

Ok, so I never took just the crank out with heads on but i feel I should remove rockers and push rods so valves are all shut for when I leave all the pistons up in the cylinders.

 

[nm9stheham]

It won't matter. Engine is on engine stand, right?

FWIW my son reminded me that the Joe Gibbs oil is green....which makes sense, as it comes from the old Kendall product line.

 

[Kendog 170]

That's good news . I thought pushing each rod out of the way may hit the valves?

 

[Kendog 170]

Oh, and yes it's on a stand

 

[Kendog 170]

Ok the crank is out. The main bearings look good but the piston side of the rod bearings are showing wear. Probably from the balance issue. I will get some pics.

 

[MopaR&D]

Ok the crank is out. The main bearings look good but the piston side of the rod bearings are showing wear. Probably from the balance issue. I will get some pics.

That's usually caused by detonation and/or heavy loading (towing etc) at lower RPM. When the cylinder pressures get too high the oil gets "squished" out the sides of the rod bearing which causes it to wear. My last 360 had serious long-term pinging issues and the rod bearings had copper on the upper shells, same with this high-mileage 5.9 Mag I pulled out of a big 3/4-ton Ram truck though not quite as bad.

 

[nm9stheham]

So the plan is to re-balance the crank to the lower nominal bobweight?

 

[Kendog 170]

Yes lower bob weight.

 

[Kendog 170]

Few more.

 

[Kendog 170]

One other question. Is this rear main seal install correctly? I had a rope seal previously. I thought it could be leaking but I found the back cam plug is leaking. I guess I didn't use enough sealant when installing it. The new rear main seal wasn't very clear to me so I want another opinion .
Thanks

 

[Kendog 170]

I used Sealed power no groove rod bearings. Do you think I should go with the Clevitt full groove this time around ?
Clevite P-Series Rod Bearings CB481P

 

[nm9stheham]

Down load the Clevite-Mahle catalog and read through all the application info in the front section; it's good info and will help you with this decision. Personally, those marks look typical to me. I'd go to synthetic oil long before a bearing change.

 

[Kendog 170]

You think the rod bearing are ok ? Leave them alone ?

 

[512Stroker]

The motor ran good before the rebuild. The dist. is the same along with the orange box ignition. I did inspect when this began . Bought new cap rotor and wires. Same coil. I can say I've proven intake but my vacuum gauge was messed up. My gut tells me intake. I might pull it and go from there or I might register it and bring it somewhere just not sure yet.

Does your orange box have a good ground? I believe it gets ground thru the mounting screws.
Someone correct me if I am wrong.

 

[nm9stheham]

You think the rod bearing are ok ? Leave them alone ?

Others may want to chime, but nothing looks deep or out of the ordinary to me. Make sure you prime the oil system when you reassembly this.

 

[512Stroker]

Others may want to chime, but nothing looks deep or out of the ordinary to me. Make sure you prime the oil system when you reassembly this.

Nothing looked all that bad to me.
I am still trying to figure out why he tore into the bottom of the engine for low vacuum?

 

[nm9stheham]

Lots of water under the bridge in this thread..... Turns out the pistons were changed to some with quite different weight and no re-balance work done. Vibrations......

 

[Kendog 170]

So the Machine shop that wants $450 for total balancing wants $350 for just doing the crank. I found another shop that says they can do it but owner won't be back from Vacation Until Wednesday to shoot me a price. They do charge $375 for a complete balance job. I'm hoping he'll do it for $200.