Hello everyone! I recently purchased an Olds Cutlass Cruiser 1979 with a 5,7 350 diesel (D3) with blown headgaskets and broken dieselpump. I have however a 6,2 l diesel engine on hand from a Chevy van that I was thinking about putting in the car as a replacement.. Does anyone here have any experience from a conversion like this, can it easily be done and will the gearbox from the car fit on this engine, if not, what is needed to make it work? I ask as a total novice as this is my first Olds/American car. Appreciate any helpful answer!

 

Unfortunately I don't know anything about the 6.2 or the '79 family of cars, but I can help a little....

The 5.7 is a true Oldsmobile engine. It uses the BOP bellhousing pattern and Olds engine mounts.

The 6.2 will have the Chevy bellhousing pattern and I would expect mounts similar to a big block chevy.

First check the transmission. There are "unibell" transmissions that have both the Chevy and BOP patterns. Look at the back of the engine. The Olds engine block is flat between the top two transmission bell bolts while a Chevy has a peak. If the transmission has a bit peak poking above the block then it has a unibell and will bolt to the 6.2. If the transmission follows the block then it's a BOP transmission and won't bolt up. Many transmissions by '79 were unibell, but not all.

For the mounts, just see if you can find any information on mounting the 6.2 into a similar year GM A body. It *appears* it just uses the same motor mounts and frame pads as the Chevy 454, but I only did a little bit of looking.

 

It seems to me the mounts and trans bell housing bolt pattern are chebby. My old Boss did the opposite, he went from a carbed 454 out of his 80 4x4 to replace the 6.2 in a 93. Pretty sure it bolted right in. He had a heck of a time getting it the 4L60E shift properly, surprised it didn't die like they usually did. It will probably have the clamshell style mounts which should be available aftermarket. As said a lot of transmissions are actually dual pattern, look for two extra sets of bolt holes. I don't blame you on this swap, the 6.2 while also gutless was pretty reliable. The early blocks were supposedly extra heavy duty. You could actually add a turbo and have it live on a 6.2, unlike a 5.7. Good luck.

 

Thank you for the feedback! Im pretty sure the transmission in my Olds is a TH400, thats what I was told anyway, as I havent pulled it out yet. But as I have understood, this trans goes in to several engines so hopefully it will match up with the 6,2

 

Thank you for the feedback aswell! The 6,2 in question is out of a '92 Chevy van, and its the 599 block, wich I have heard is one of the better 6,2 versions. The trans in my Olds is a TH400, and I have so far found this to be a often used gearbox on several engines, among them both Olds and Chevy, so Im hoping it will match up with the 6,2.

 

If it isn't dual pattern, there are adapter plates available. I did this to mate a 4L60E to an Olds 350 in a 94 Z71 pickup. It is about $80 US for a good one.
https://www.summitracing.com/parts/trd-0060

 

They made several different cases for the TH400. You can tell quite quickly if you can get a good look at where the motor and transmission meet, just behind the distributor.

 

Got around to look at the transmission today, and it wasnt a TH400 at all, but a THM200... Just proves its a bad idea to trust what a previous owner says I guess..Is there any adapter plates to make this trans fit a 6,2 Chevy engine? 🤔

 

Got around to check the trans a bit more today, I trusted the previous owner when he said it had a TH400 in there..but in fact it was a THM200.. So I will need to try to find an adapter plate to make it fit the 6,2 Chevy, or I'll just have to try and find an actual TH400 that will fit.. Im totally new in this game, should have checked it sooner but I trusted what I got told haha.

 

I wouldn't suggest using the THM 200 behind the 6.2l Detroit diesel. I have an 86 Ford F250 with the 6.9l IDI and it uses a C6. I'm pretty sure Chevy used the TH 400 behind the Detorit diesels.

Here are good sites to use for parts.

http://www.conestogadiesel.com/

https://oregonfuelinjection.com/

 

I always thought the 5.7 Diesel got the TH350/C for a trans. Yes, that adapter I put a link to will work but get a spare TH350 to have around when it dies. Anytime a car came into the shop I worked at with trans issues, even leaks, if it had the square Metric pan, we went to my bosses yard and pulled a TH250/350 to replace it. They are basically a direct bolt in.

 

Yeah, I think I will be going for a TH400, currently searching for one.. I know of a van nearby that has it but the owner doesent want to sell it in parts, so the search goes on, but shouldnt be too hard to find one, even tho I live in Norway there seem to be quite a few of them around. Thank you for the links, I'll take a look at them!🙂

 

Yeah, it has the square metric pan.. I was really considering getting an adapter plate and throw it in, but I think I'll be going for a TH400 instead. I see them posted for sale quite often, just have to try and find one that isnt too far away. Thank you for the link anyway, really appreciate the help I have recieved from you guys!🙂

 

Be aware that if you find a TH 400 it uses a vacuum modulator. You will need a vacuum pump and Vacuum Regulator Valve on the injection pump to get the transmission to shift properly. The Ford VRV for the C6 in my truck is as rare as hen's teeth. Does the 6.2l diesel you have already have a transmission? If so, you should use that one.

 

Be aware you will need a 32 spline yoke and the drive shaft will need shortening. What rear gear ratio is in this car? A stock TH350 or TH350C, don't get a TH250 or TH250C, look for a stud where the cooler lines goes into the trans or a TH2004R, either trans will live fine behind a 6.2 diesel with minor mods and bolt right in using your current drive shaft. Unless you plan on towing, a TH400 is over kill. Your call but be aware of the drive shaft and yoke issue.

 

I found a TH2004R actually...! So this will work nicely on a 6,2 diesel?

 

No it came without a transmission. But I stumbled over a TH2004R now that Im considering.. I read that it will work on a 6,2 diesel aswell 🤔

 

Yes, it will work, almost all of them are dual pattern. Minor mods help like bigger boost valves or shift kit should help it live. You can also run 3.42 or 3.55 rear gears and still run under 2000 rpm at 100 km/hr.