: 425 Runs pretty good, but is it good enough...

07-28-12, 12:40 PM
My 425 Runs pretty good. Always starts, 15 MPG average consistently, decent power. I'm planning to rebuild the carb, and I wanna do the keyed timing chain to advance the cam, and play with the ignition timing as well.

But then, my heads are caked up with sludge pretty bad, I have some lifter ticking, and it burns more oil than I would like. It's at about 160k. I don't really want to spend $1,300 or so on a premium rebuild kit right now, so what would you guys recommend?

The Ape Man
07-29-12, 01:53 AM
Put out feelers for a good 500.

07-29-12, 11:22 AM
Because you are aware the heads have sludge, I conclude you have had the valve covers off. Which lifter was ticking or multiple lifters? Run the engine with the cover removed and push down on the lifters one at a time to find the guilty lifter. Push on the heel of the rocker. If the clacking stops and there is little lift, you may have a problem lifter. If there is a lot of resistance and you still have lift, you may have an oiling problem. Check that you have oil coming to the rockers. No oil to the rockers, serious problem.
Remove the rocker shaft ( make sure to keep track which bolt came out of each bolt hole ) and turn it over. Check the rockers for wear. Gouges on the valve side of the rocker mean oil isn't lubing the toe. If the top of the valve stem is rough and shaved, means the valve isn't rotating.
Several lifters rattling? Does the ticking go away with increased RPM? Your oil pressure could be suffering. And the problem could be that the teeth of the timing set have broken off and clogged the pick-up screen. They don't always come out when you drain the oil. They can get past the pick-up and through the tube to the pump.
Pull your oil filter and cut it open to see if there are any pieces of plastic in it.
I'll stop here, as the next step is up to you, but I have personally done all this, to analyse and repair these engines. Yes U can drop the oil pan in the car.

The Ape Man
07-29-12, 11:39 AM
So the plastic gears make it through the pump to the filter???

07-30-12, 10:25 AM
They can if the engine sits and the screen fails.

The Ape Man
07-30-12, 10:47 AM
How about the pump gears?

07-31-12, 09:23 AM
He is doing the timing set and will have to open the pump to remove the pump shaft and driven gear. Time to inspect the pump and gears.

08-02-12, 04:58 PM
Would just rebuilding the top end be a bad idea? Seems like I could go with a cam, all new lifters, oversize valves, a little milling for compression, and new springs, and just leave the block in the car, but maybe by that time it's just a might as well situation. And am I correct in assuming it would be pointless to just pull the heads to clean the sludge out and inspect them, since it might just build up again if I have any of the aforementioned problems?

08-03-12, 08:22 AM
Rebuilding the top end of an engine and increasing compression without at least checking the bottom end is a bad idea. The 425 engine uses aluminum insert bearings and the condition and clearances should be checked out before icreasing pressures at the top end

The Ape Man
08-04-12, 02:27 AM
The bottom end wears out faster than cams and heads on these powerplants.

I used to take high miles engines and just replace main and rod bearings. Good for another 125k.
U can flip the engine over on an engine stand and carefully remove the crankshaft.

Any mention of sludge/deposits usually means severe neglect in the past. Sludge in a Cadillac engine of this vintage is not normal.

08-05-12, 02:54 PM
Yeah, there's a lot of it on there too. When I had taken the valve covers off, I could barely see the springs. I've always changed the oil pretty regularly and stuff though, so it wasn't from me.

Anyway, I don't know if it really has much lifter sound. Sometimes I think I hear some, and other times I can't hear any, but yeah, usually it's more when idling, and on cold starts, especially if it's been a few days, you'll hear it more and then it goes away gradually over like a minute or so. It's been like that for the 10 years that I've owned it and never gotten any worse.

When I did the valve cover gaskets, I called a few shops and posted on here, and most people said just leave it alone. They said if I tried to clean it off, I might end up blocking an oil passage. But couldn't that happen anyway if some of it decided to just come loose on it's own? Is there a safe way I could just pour something in there (seafoam?) and just clean it out?

The other day I replaced the EGR TVS, and managed to move the distributor while I was doing it. I got a timing light and redid the timing. First I went for the factory 23 @ 1600 (with the EGR and VA disconnected and hoses plugged of course). Mech advance seems to be working for the most part, but it seems like I'm only getting another 12 out of it. After reading more on here that I should really set it to about 10-13 @ idle, and then try to make sure it hits 33 or so around 2,500, I tried, but it won't go past 24. I went in and inspected the weights, and there is a bit of red iron dust, but they moved fine. Sprayed some lithium grease and wd-40 just for the heck of it, but I still only seem to go be able to get up to 24. With the vacuum hooked up it goes way up, probably in the high 30s somewhere, I didn't bother to adjust my light, but it looked about that.

08-05-12, 04:30 PM
Actually, for an iron engine with aluminum bearing inserts you're past due for major overhaul. Everything is creaky, including the cam and lifters.

Haven't checked, but look in the PAW (Performance Automotive Warehouse, Chatsworth, CA) for overhaul kits. You could have the block, heads and crank machined and DIY all the rest.

(For grins and kicks I build Olds 455's for work and racing boats)(albums in my profile)

08-06-12, 08:10 AM
Pennsylvania oils are high in parafin content and are prone to sludge build up. If the engine does not reach operating temperature during the couse of it's use and the oil starts to break down from enriched cold starts, ring blow-by or prolonged change intervals, the parafin separates and will build on anything it sets on. This is good for cold starts when the oil clings to the crank and rods, but when it builds at the top of the engine you will get the sludge you described.