[JC455]

UGHHHH!!! During my filming/measuring for roller lifters, I found this mess in my cam tunnel.
Background: 75 455. Came out of a jet boat. Freshwater boat.
Any thoughts?

[steve25]

Not too uncommon as I have seen that in high mileage motors.

Did you build the short block, or just buy it this way?

The answer kinda does not matter at this point because those bearings need to come out and the Cam bore needs to get checked out in the same way the motors main bore would get checked.

The beating that a motor gets in a Boat due to airated oil from poor oil control is the likely main cause of this issue.

How do the bearings look in the front 4 rods and number 1 and 2 mains?

If the Cam bore checks out out of whack, then I bet the main bore is out a bit also unfortunately!

[lust4speed]

I would say that the damage was from the builder forcing the cam into place. Not unusual to have the cam bore out of line. Figure the number of main journals that have to be line bored at the time of the rebuild and seems that many builders ignore a tight cam fit and just wedge the cam in place hoping the cam will self clearance after being fired up. I guess in a way it does clearance itself, but you can see a ridge at the outside edge of the bearing in the photos 1 & 2 along with the missing Babbitt from the extreme heat generated as the cam heats and moves the Babbitt out of the way.

[Cliff R]

I have a commercial cam bearing driving tool here with adjustable collets and woln't use it on Pontiac engines. Decades ago I had a machine shop make a custom cam bearing driving tool specific for Pontiac V-8 engines. The custom made tool is more precise than the "universal" tool.

Since doing this zero issues in that area. I'm not exactly sure why but these blocks are somewhat sensitive when it comes to cam bearings and can be hard on them.

With the commercial tool most went in fine but too often for my liking we'd get a "tight" spot in one. With the custom machined tool they are dead nuts on center and every cam I've installed after switching to that tool turns with two fingers. Beats having to buy several sets of bearings and/or having to open any of they up slightly to get rid of the tight spots.

I made the mistake ONCE of going ahead and putting one of these engines in service after relieving the tight spots and ended up with cam bearings that had material come off of them and require replacement.....FWIW......Cliff

[MarkS57]

I'm going through something similar now, see attached. In my case, I believe it was the cam, I do not believe it was the bearings as they lived just fine with the previous CC 280M & Melling 068 cams. It wasn't until I went to the VooDoo 703 and then didn't like the cruise noise it made- that I decided to step to something less aggressive. Upon pulling the 703 I saw the carnage to bearings 1 through 4. The #5 rear bearing was completely unaffected. Forensics on the oil filter showed I got lucky with bearing debris not inundating the oil system. I plan on evaluating the 703 for straightness; I don't recall the 703 being high spotted on install but will for sure check the new cam upon installation.

["QUICK-SILVER"]

Pic #1 is why I run straight 40wt or 50wt oil in my jet boats. While engine temps stay cool... Oil temps run high. Average jet boat could easily require 10 X the horse power to cruise 55 mph, compared to a car cruising 55 mph.

10W?? dino oils can get worn slap out, in a few hours of playing, from polymers getting crushed and burnt from the continuos heavy loads and high temps.

BTW Might be interested in engine plates, mounting hardware and possibly other items if the boat got scrapped or re-fitted with a different engine
Clay

[PAUL K]

Paul Sandoval covers the Pontiac cam tunnel issue in his book... At least I was told that.

[tom s]

My machine shop is seeing more cam tunnel issues with 455 blocks?Tom

[steve25]

Don't forget that with some of the thin aftermarket valley pans out there and having to use different hold down bolts that you can pinch in those bearings that have those bosses above them since they are drilled all the way thru if the bolts are too long.

[Bill Eveland]

I had to have my 455 cam tunnel line honed. Couldn't hardly get a cam in without scraping the bearings. Rick Johnson honed out to max spec to still use standard bearings.