What to Do While Engine Out of Car - 1970 Cadillac Convertible

[klinebau]

I have a 1970 convertible and I am in the process of prepping the engine for removal.  The engine has about 100k on it and it runs nicely.  The main reason for pulling it is that it leaks a little and I want to clean up the engine and engine bay.  I am trying to define to scope of things I want to do while it is out and am having a hard time on where to draw the line.  This is not a show car, but would like to eventually have a nice driver.

These are the items I am pretty sure about

• Replace timing gear/chain.  This has been done prior to my ownership, but I suspect low quality parts were used
• Replace gaskets associated with timing gear change (oil pan, timing cover, etc.)
• Replace rear main seal
• Have transmission rebuilt.  There is nothing wrong with it, but it has never been overhauled to my knowledge.
• Replace brake lines.  Might also replace brake booster
• Clean up engine bay.  What have others done for prep and paint?

I've been thinking about these items but am looking for some advice.

• Remove heads and have valve train overhauled including installation of positive valve seals and maybe new valve seats. Since the engine doesn't have any running problems, is this just opening up a can of worms (broken exhaust manifold bolts, head bolts, etc.) or will it give me a significantly better running engine?  In other words, does the effort/cost exceed any benefits I am likely to see?
• I want to paint the engine, but even after prep, there will be some rusty areas and some painted areas.  I doubt I will be able to get to clean metal everywhere without major disassembly.  I know most recommend Bill Hirsch blue, but will I be able to adequately prep given that the engine won't be fully disassembled?

[dogbergs]

Hi there Kurt,

I always think you should do whatever you want with your car.

In this particular case, thats a LOT of time and money for a car that maybe don't need it?
If I choose to comment on some of your "to do's

Rebuild a 100k miles transmission when it shows no need for it?
I now ask you to look back at my first point here.

Go for the leakage if it's bad, a small leakage is only a small leakage?
Maybe heads w valves and be able to some touch up paint job too?

I see this, "Since the engine doesn't have any running problems..
"In other words, does the effort/cost exceed any benefits I am likely to see?..

Have a good day

Johan / Sweden

[James Landi]

I urge you to thoroughly test the engine's health BEFORE you're convinced to embark on the "might as wells." How's the compression?  What does an upper end leak down test tell you about the valves. What does a vacuum test reveal?  Is the engine's oil pressure within "specs?"  Alas, it's not uncommon for a rebuild to go sideways, and your "new engine" has a fatal flaw in the rebuild.  Yes: have the main and connecting rods checked, yes: have the timing chain set replaced, yes: main seals, yes: have the heads and intake re torqued, yes: have new valve guides and valve springs installed. Yes: the water pump and engine accessories replaced, and yes: have the engine's cooling system flushed and de scaled.  All this is to say that a well running engine that meets all of the original vital sign checks is better left alone. An entirely rebuilt engine may not run any better than yours runs now.  James   

[Lexi]

Jame's comment about testing the engine thoroughly before a tear down makes sense to me. As the saying goes, "If it ain't broke don't fix it". If you are planning on keeping this car for many years to come, I might consider buying a rebuild kit and/or other related replacement parts as back up while they are still available. Clay/Lexi

[Jeff Rosansky CLC #28373]

My opinion;
All I see there is money spent that doesn't need to be. These engines and transmissions could still pull a house off its foundation even with 150k on them.
But, I admit that I am of the if it ain't broke camp.
What I would do, however, is do the checks mentioned above. If she is solid, then break all the exhaust manifold bolts loose while it's out and you have access. I would also look at the freeze plugs. Drop the pan and be sure everything is clean in there. If so, clean it, paint it (engine and engine bay), and put it back in--- Done. Oh, replace the motor mounts.
However it's your car, and your wallet.
Just remember that these are heavy.
Keep us updated on your progress.

[tcom2027]

Jeff nailed it. Easy operations, not expensive and will yield good results. Excellent idea about removing the exhaust manifold and replacing the the fasteners, NeverSeezing them and new gaskets. Beware as the the manifolds may be not seal when being reinstalled and need resurfacing. Maybe a leak down test if you run out of things to do. 

Amen on the freeze plugs, replace them especially if the car has lived in iron worm country.

If it's shifting well, just drop the pan, clean it out and replace the filter. New good quality oil, and button it up. Make sure all the linkages are smooth running and adjusted correctly.

Don't keep fixing it until it's really broke.

tony

[bcroe]

My opinion.  I pull a trans apart and throw in a
$40 seal kit, reuse ALL the hard parts if not worn. 
Better to reuse factory parts, than replacements
from across the Pacific.  New clutch piston seals
could avoid a serious (and expensive) overhaul
later, any that old could be very hard.  Maybe a
shop would agree to this? 

Brakes, I have been replacing EVERYTHING that
touches brake fluid on my 70s cars here, the only
way to avoid failures and keep new performance. 
Lines from Stainless or copper-nickel should last
forever, hoses, calipers, and cylinders I do every
couple dozen years (more than once on many cars
here). 

Engine, I would not touch the rotating parts if
compression is good with no noises.  Clean out
the pan, gasket refresh is OK, check timing
chain slack, OEM must be replaced.  A high
volume oil pump with stronger shaft might extend
life by keeping pressure up even at idle with
some wear.  These are available for the Seville
O block, maybe not for the 70.  Check harmonic
balancer for slipped ring, I have replaced all
these with FluiDampers.  good luck,
Bruce Roe

[TJ Hopland]

I too would do the transmission, if its been 20+ years its not gonna be working as good as it should which will start damaging hard parts.  So far I have not heard bad things about the quality of soft replacement parts and there still seems to be transmission shops especially for something like a THM400.

Engine,  compression test is a good idea to just see if there are any cylinders that stand out. If they are all fairly close I would not mess with the heads.  Pull the intake and have a look at the intake ports and valves, if its reasonably clean that would confirm leaving the heads alone.  If they are badly gunked up then pull em and get your credit card ready because its probably gonna get expensive.

One problem with doing engine work these days is finding quality parts and a big problem is finding a machine shop with good people that are willing to work on something a bit odd that may require different tooling or fixtures.  Even working on common stuff like a classic Chev can be a problem today.  IF you do find some place how long will it take?  The few good shops that are still around seem to have a several month backlog. 

How bad are the leaks?  Is it the kind of thing that just leaves a few spots where its normally parked?  I would call that normal for an old car.  Or is it leaving spots anywhere you park even if its just for a couple hours?  I did my engine around 15 years ago because I knew it needed a timing chain and I thought it was leaking bad.  I think at the time I spent almost $4k and that was no labor other than machine shops which were still easy to find at the time.  Lots of stuff I did or friends or trades. 

I actually got to do it again after 1000 miles because the made in usa oil pump sized onto its shaft.  I think 2 or so years had passed between when I bought the bearings the first time and when I had to re buy them and the price more than doubled.  I'm not sure if doing it twice caused things not to seal up as good or that I bought a stupid new stainless bolt set that doesn't stay tight but especially as time went by the leaks are at least as bad as when it was a 30 year old engine.

I fairly recently blew up the engine in my Suburban that had 280k on it so not totally unexpected.  I had a good running used engine out of another rig that was badly rusted before I crashed it.  It really only needed a water pump but 'they' said while it was out re seal everything freeze plugs ect.  I wish I would have left it alone because it leaks worse now that I fixed it.  Some of it was maybe my workmanship but I think a lot of it is poor quality parts. 

Annoying stuff like the crank seals are leaking. They didn't leak before, there are no grooves you can feel with a fingernail on the crank or hub, new felpro once piece seals.  Timing cover is the same one I took off and has pins so its not like I could have got it in the wrong spot. I even tried the trick I saw online where you pack some grease inside the seal so the spring can't pop off when you are pounding it in. Basically wasted time and money.

If I knew nothing about the engine that would be a little different but this had been mine for several years so I knew it was a solid runner.

[klinebau]

 have had this car for a while and have already done quite a bit to keep it up to date and reliable.  The compression is good and is between 170 and 180 on all cylindares.  The vacuum gauge shows 18-19 in/hg with a steady needle.  I don't have a leakdown tester so that has never been done.

I have previously replaced intake manifold gasket due to a leak and valve cover gaskets.  The valve seals were also replaced with new stock replacements (I don't really like the stock system) and there doesn't seem to be oil consumption problems (other than some leaks).  The area under the valve covers is clean so I don't think there are sludge issues.  When the car is parked for an extended period, there are some oil spots in the garage.  I see oil drips coming from the oil pan and trans inspection cover.  This is why I want to reseal oil pan and rear main seal.  I also want to check for timing gear bits in the sump/pickup.  Motor mounts and trans mount were done previously.  When I had the intake manifold off, I had a look at the timing gear/chain so I know it is not the original.  Based on other "new" parts that were installed prior to my ownership, I am suspicious as to the quality of the timing gear parts, however.

So it seems that I will probably not do much with the engine internals other than timing chain/gears and various gaskets.  I forgot about freeze plugs.  I don't have any leaks, but they are steel.  New brass plugs are cheap, but they look difficult to replace.  I will try to remove exhaust manifolds and get new bolts.

I have heard that the soft parts in the 54-year-old trans should be replaced to prevent bigger problems.  Does it make sense to only do those and I can I do those myself?

What is the best way to strip and clean the engine before paint?  I am thinking some sort of chemical stripper.

[tcom2027]

I think you've answered most of your questions. From your description everything is is good shape. There are a lot of owners would like to have a drive train in as good condition as you say yours is, Don't over think it. I'd replace the front cover gasket and seal if it's leaking, the same for the oil pan, and remember there is a difference between a leak and seepage. If you feel the timing chain needs replacement, do it if for no other reason your timing will actually be right on.

If, or when you replace the freeze plugs (they are not freeze plugs they are there to make it easier to remove the green sand from the casting,) use #2 Permatex around the sealing surfaces and then epoxy around the lip. It doesn't have to be slathered all over the plug just around the edges, a belt/suspenders thing.

Re: Transmission. Unless you have experience, best to keep your fingers out of them. You don't want to learn on yours. The valve body can be daunting. "Where the hell does the .183" check ball go" or "where the hell did the .183" check ball I dropped go? I don't see it in the manual or parts schematic. Help." 

I have eight years dealership experience, not Cadillac, along with experience with CAT 3406, 3406Bs and 855CI Cummins non electronic engines, my own, and the 346/322s,along with the ubiquitous small block and big block Chevies. I have machine tools in my home shop.

The only time I dove into an automatic trans was my '85 Seville. I disassembled and cleaned the valve body along with replacing the torque converter lock up solenoid. It taught me patience and humility. Never again.

Drop the pan, clean it and replace the filter. Don't forget to tap around the bolt holes with the pan on a true surface. I'm sure over the lifetime of the car the pan has been off and the bolts have been overtightened, distorting area around the bolt holes. Prevents leaks. Use a paper gasket if possible and #2 Permatex or a VERY light coating of blue or black snot. You don't want gobs of it breaking off floating around in the transmission. 

I'd use ZEP or Simple Green concentrate to clean up the block. Wire brush the rusted areas. Prime it if you like, but the factory didn't. You're not going to grind off the casting flash and use two part epoxy paint on it are you?

More than enough for now.

tony



 

 

[bcroe]

I cannot tell if you have a TH425 trans in an Eldo, or a TH400. 
Not everyone is mechanically inclined, but I learned to fix stuff
myself after countless bad (usually inconvenient and expensive)
shop experiences.  By the 80s I was tired of being held hostage
by transmission shops.  I got a couple TH400s from wrecks and
with the factory manual, spent 6 weeks taking them apart and
puttiing them back together.  Then I started driving them. 

Perhaps the TH400 is about the easiest trans to rebuild.  Usually
it shows almost no wear, there is plenty of support, and it might
be the simplest auto 3 speed to rebuild.  It does not have those
break in and usually not rusted bolt problems.  There are a few
tricks and half a dozen tools to ease the reassembly, made many
tools myself.  At first I tried a few after market parts, and in half a
million very hard miles, a few things broke.  Almost all the failures
were swapped out parts, which is why I go with original hard parts
as much as possible. 

With a TH425 (Eldo), the classic leak is from the rear chain cover. 
This is a poor gasket design, usually needs the trans out to fix. 
A lot of us have thrown away the OEM cork gasket, and use a
make-a-gasket to glue the cover on, no more leak.  Like later
valve covers.  It is like a th400, but with the addition of the chain. 

My shop experience with full rebuilt engines has been equally bad. 
good luck, Bruce Roe

[klinebau]

This is a rear-wheel drive Deville, so the transmission is a TH400.

[chrisntam]

While you have access, consider having the steering box rebuilt.  Lots of slop in mine, wish I would have done it back in 2014.  Maybe remove the heater/ac box and replace all the seals.  Clean up the evaporator and maybe have the heater core rebuilt  Pretty easy access now but for the under-dash fasteners.

Ah, the joys of creeping elegance. 

[klinebau]

I had the steering gear rebuilt a while back.  I didn't think it was that difficult to remove and replace even with the engine in the car.

I think it is a good idea to remove the heater/ac box.  I think there is some foam/padding on those mode doors that might be in bad shape. 

I'll post some pictures once I get the engine out.

[The Tassie Devil(le)]

I agree with previous postors in that checking the engine before pulling, through normal testing is far more productive than simply stripping off bits and pieces and changing them because it is easier once out of the car.

Remember that these engines were designed to last a long time, and unless something is wrong, don't mess with it.

With any older engine, once it is internally disturbed, it will never run the same when put back together, as all the parts have worn in together.   Checking things like heads, pistons and bearings, you will end up doing a full rebuild, costing thousands, as it will be found that the amount of wear will require a total rebuild.   Plus, sometimes new parts aren't as good as the original parts, especially stuff from overseas.

I learnt this years ago.   I had an engine that ran well, and decided to "have a look inside".   Put it back together, and it never ran the same.   Ended up doing a rebuild.

Bruce.

[klinebau]

I just removed the three bolts that connect the flex plate to the torque converter.  Are there supposed to be washers in between the flex plate and torque converter?  Two washers for each bolt fell out after I removed them.  I don't see any reference to them in the shop manual.  I suspected that the engine has been out before and it wouldn't surprise me if it was reassembled incorrectly.

I probably won't get a chance to pull the motor this weekend as I have other commitments, but will keep you posted.

[TJ Hopland]

I don't think there would be any reason for a factory to put washers there.  Seems more likely someone was trying to solve some sort of missmash issue.  Were the bolts too long?

[Roger Zimmermann]

Or to solve a vibration?

[jwwseville60]

All the advice from others here is top notch.
But if its leaking just a little....

I would replace that antique, barnacle-strewn cargo ship iron anchor with an all new GM E-Crate EV engine! Just fill the entire trunk with batteries up to the top plus the back seat and use the original tranny. Range will be 90 miles.

Off you go!

[klinebau]

Just fill the entire trunk with batteries up to the top plus the back seat and use the original tranny.

That might need some suspension work as I don't have the factory air ride