I've replaced everything that could leak oil, but the leak remains....so....I can get someone to remove the transaxle and find out if the leak is a badmain seal or a crack in the block at thecam-boss. If seal, I'm ok. Ifablock crack: I can get a good 4.9 block and have been told all the parts from my 4.1 will bolt to the 4.9. I have a concern about the 4.1 heads on the bigger-bore block, but don't know if is a valid concern or not?
Does this block-swap project make sense? Anyone have any experience with the operation? Thank you for any advice/info. I appreciate the help!

 

the 4900 engines has a darn good reputation, but I dont expect that the transplant will go easy or well when it all said and done.

There are a whole lot of Allantes in Austin going to the crusher wearing their iron clad high performance 4100 engines. I say grab one of those ..



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Thanks for the idea Stomper. Did those Allante 4100s have the same block-crack problems the other 4100 had? I don't mean the cooling system problems, that was mostly a maintenance issue.I mean the cam-boss crackingtendency.I wonder if the block-crack issue was taken care of in the 4.5 or 4.9 engines?

 

9 years with Cadillac as a service advisor during this cars era, NEVER saw a cracked cam boss. Saw many seaping coolant blocks that were repaired with JB weld tho. You need a second opinion on this oil leak. Have you done the oil dye with a black light yet?? This fuel system is dependant on engine size. The fuel delivery is based on cubic inches so I would be concerned about proper amount of fuel for the extra bore size. But, I've never had first hand knowledge regarding the swap.

 

I had a suggestion to try and find an HT4100 from an Allante. That design 'fixed' the crack issue. Some time ago I talked with a man who rebuilds these engines and he told mehe's scrapped many 4100blocks because of cracks at the cam location. There are also posts dealing with that same subject. Hopefully that is Not the problem I'm experiencing, but the diagnosis has to be done with the transaxle removed. If it's the seal, I'm good, ifa crack,I'm sc'wd. The leak can only be the seal or a crack. I've changed everything else it could have been. I have to pay to get the ta removed and may need a replacementengine once it is off. Can't afford to have the ta taken off/on more than once.
Thanks Carnut, I appreciate your help!

 

Is this leak severe or just a couple of drops? Careful what you say to the shop. If you say remove my transaxle to fix my leak they will do just that and hopefully thats where it is. Say diagnose my leak and if you have to pull the trans, thats OK.

 

Brand-new Pennzoilleaks from the flywheel cover weep-hole. For years, the leak was more of a nuisance, but it has gotten to near a 1/2qt in 100miles. Thanks for the shop-talk advice, that's a good tip!

 

Whatever the shortcomings of the 4100 engines were, they were corrected by the time the 1st Allante rolled off the line with the HT4100 in late 1986 as the 1987 Allante.

Aside that, the HT4100 also has a few "upgrades" that boost its power curve a few ponies.

IF it was me, with a older Cadillac 4100 facing an engine transplant, I be searching for a HT4100.
They can be had for around $100 - $200, with around 90,000 to 110.000 miles.





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I putan add on the Austin Craigslist looking for an Allante HT4100 engine. I've never seen one so,how is an HT4100 identified if someone has oneout ofthe car? Please excuse my ignorance but: I've seen an HT4100 and an HO4100 talked about/advertised. What does HT stand for? High-?(torque?) HO=High-Output? Same/differant engines? Thanks

 

I would change it from:

Looking for a good/reliable HT4100 Allante engine.

To:

Looking for a 1987 or 1988 ALLANTE HT4100 engine in good condition.


not sure how one would tell them apart if the engine is striped of accessories unless you have the part number .. i lost that info. With the accessories on it, simply compare pics to a 1987 / 1988 car on ebay.

When you find it, it will most likely still be in the car, most of them never get pulled and get crushed, not much demand for them, so they go cheap, mostly the cost of pulling it out.

Do a compression test, although I have not heard of any under 150,000 mile engine fail the test.
If the engine is still in the car, check the coolant, hopefully its looking good and you are probably all set.
Then get it home and put new bottom end gaskets, an easy thing to do when it is sitting on the floor.

IMO, the inners should be left alone, no new rings, no new bearing, no nothing. These HT4100 are showing potential lives ranging into the 300,000 miles with proper maintenance.
A new timing chain, water pump, serpentine, rubber hoses, sure.

Contact the salvage yards, there are several Allantes in the local Austin yards, and you also have a couple of cars parted on Craigs. I would stay away from a Bob Hardman, a deceit artist out of Houston dealing Allante cars and parts.




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