[656566gto]

I'm switching out an expired 389/TH400 over to a 400 stroker and M-20 in my 65 GTO. The car was originally a M-20, but the original engine and tranny were long gone before I bought it. So...the engine is new to the car and the M-20 is new to the car...as you can imagine, there are lots of issues that need to be worked though as I make this swap.

The problem I'm stuck on now is with respect to clearance between the oil plan and the center link. There is almost no clearance between the two. I can slide a piece of paper between them, but that's it. I've taken a picture to show how just how close they are. The oil pan is a new 6-quart baffled plan (don't know manufacturer, I had Butler build the engine). The pan of the 389 was so badly dented it wasn't worth saving. However, the 389 pan looks like it's about 1/2 shorter in the front. I installed new motor mounts (Anchor), and the frame-engine mounts are correct.

From other threads, I know some people advocate just "dimpling" the pan. Before I do this, though, I wonder if the crossmember/tranny mounts are off. I think the tranny mount is originally from the car (it came with a huge pile of parts). I bought a repo one, but it was actually slightly taller than the original. Still, I don't know that the crossmember wasn't altered in some form by a previous owner.

So to rule out the simple problems first, can anyone tell me how much clearance should exist between the top of the tail-end of the M-20 and the floorpan tunnel? I've posted pictures of how much clearance I have now--does this look about right? To me it looks awfully close. I've also posted a picture of the space between the crossmember and floorpan, in case that looks suspect.

If the tranny could drop even a little, it would probably provide enough room for the the oil pan to clear the center link.

Thanks in advance for help with the first of many more questions to come...

[klunker]

Had same problem, I replaced the new trans mount with a new one I made that was shorter, that fixed the problem.
I think that the new trans mounts are too tall for some applications, it seems to be the right combination of things will give you this.

[Doug]

Centerlink clearance?

I think your centerlink clearance may be too close. I don't know how much, if any, the link can move in an up-down motion when your suspension works on the road. Have you checked the clearance when you turn the steering wheel through max range?

I had a 62 Catalina centerlink start rubbing the oil pan after wear on the suspension parts.

[656566gto]

When the car is jacked up and no weight is on the suspension, it keeps the same "clearance" as you turn the wheels, but it stays really close. When the weight is on the suspension, it rubs in some spots.

I'll try shortening the transmission mount slightly...the trick is to balance clearance in the front with clearance for the headers. From other posts it sounds like it is typical for the transmission yoke to have little clearance.

[chrisp]

It is hard to tell but looks like the cross-member is almost touching the floor , is the cross-member arced up ? I would try another one , i know the energy suspension urethane trans mounts are thinner . As far as the center-link , pan could be the problem .

[656566gto]

That's my concern--that the tail of the transmission is sitting too high. There is no visible sign that the transmission crossmember is arched up, but it is hard for me to be sure without comparing to another that is known to be correct. I don't remember the crossmember sitting that close to the floorpan on my 66, but that was several years ago.

The guy who owned the car before me had a TH400 in it, so he may have "rearched it" (but I think the TH400 would need more clearance, not less).

[geeteeohguy]

My '65 has an M20 and a 389 with the stock pan, and it's close, but not as close as yours. Your trans is too high, causing the engine to tilt towards the drag link. Get a stock trans mount, and make sure your cross member mounts are positioned properly. If you leave it as is, your front universal will knock against the tunnel,too.

[656566gto]

OK, had a chance to check a few more clearance areas. With the driveshaft on, there is just under 1/2 inch of clearance between the transmission yoke and the tunnel. I know the space is tight, but that seems way too tight.

I've also posted some new pics of the crossmember...there is not much bend to it. I don't have a point of comparison to know whether this correct.

Can anyone provide a measurement from the top end tail of their Muncie to the floorpan? Similar to the pics I posted earlier? I think it's the most accurate measurement to confirm whether the rear of the tranny is too high.

I'm a bit hesitant to just drop the rear of the tranny 1/2 to 1 inch because I don't want to throw off the pinion angle.

[Pontirag]

Pontiacs used a tranny cross member that had an insulator at each end, A chevelle crosmember had no insulator and bolted directly to the frame mounts. Locating a chevelle crosmember might be your solution plus the crossmember bolting directly to the frame gives you a bit more structural rigidity but at the expense of more noise and vibration comming up through the shifter.

I have not looked at my rear tranny clearance yet and will post pictures when I do but I recall they are very close. So close in fact that there was a dealer alert about the sheet metal dust cover that fastens to the floor around the shifter on early models. Its fastening screws would sometimes contact the drive shaft and score the tube. The corrective action was to replace the offending screw with a shorter one, So just a heads up on that.

as for the contact between the oil pan and the center link. If the problem did not exist previously then I would suspect the oil pan...unless you replaced the motor mounts as well and they sag under the weight of the engine. Not to say your engine is heavy but who is to say about the rubber used in current motor mounts or thier dimentional integrity.

[mrtonegto]

I had an clearance issue with my M20 after doing my engine swap - the front universal would rub anytime I had two or more people in the car.

Didn't make sense since the engine and trans. mounts were not changed in the swap.

I found that we must have put a hydraulic jack under the trans. w/o unbolting the trans. mount completely. This bent the "ears" that fit into the rubber insulators downward.

What worked for me was to bend them back until I had enough clearance.

My point is that you might try bending yours a bit too - doesn't take much.

[Pontirag]

check out these pics from the little square boss on the top of my tranny tail housing to the sheetmetal tunnel is just under one inch. Looking back towards the u joint the clearance is even less. closer to .5 inches

[656566gto]

Thanks!!! These pictures are extremely helpful.

[chrisp]

Did you ever get this figured out ?

[656566gto]

kinda-sorta. I initially thought the transmission sat too high, pushing the oil pan into the centerlink. However, after reviewing the pictures posted earlier, and reading the websites (shown below) to check the driveshaft angle, it was clear that the transmission was sitting right where it should.

http://www.hurst-drivelines.com/file...roc_111606.pdf

http://prostreetcamaro.com/dshaft.shtml

http://www.markwilliams.com/driveshafttech.aspx

I had purchased new motor mounts and reused the old tranmission mount. Still no clearance. So...I manned up, got a hammer and dimpled my brand new oil pan just slightly to clear the centerlink. I did a little research into this and it appears that most of the aftermarket pans are deeper in the front than the 65 pans. For example, on Ames' website or catalog, they now say clearance is tight and the pan may need to be dimpled.

Why can't someone just make a pan that fits (or maybe someone does...)?

And since we're on the subject of parts that ain't quite right, the fuel filter for the 65 GTO (tripower) from Ames is printed incorrectly. The arrow points the wrong direction (see https://secure.amesperf.com/qilan/De...part_num=N131A).

I could write a book about parts that fit/don't quite fit as I've gone through this engine/transmission swap (389/TH400 to a 462/M-20)...I may post these "lessons learned" when it's done.

[chrisp]

I am right behind you on parts that they sell that do not fit properly , i got a box full of new repo. Asian junk . seems like the Chevy parts fit great . As far as your trans. mount is it thicker than original ? Some vendors sell different thickness trans. mounts . You could always put some thick washers between the engine and the mount to raise the engine .

[656566gto]

I reused what i think is the original trans mount. So far, after dimpling the pan, things look to be working ok. One could probably raise the engine just slightly using washers, but then there might be issues with driveshaft/pinion angle.

If I had to do this again, I'd spend some time looking for a 65 pan.

[geeteeohguy]

656566GTO, I've been involved with this hobby for a long time, and have been involved in antique cars as well. Virtually none of the reproduction parts for my Model T Ford fit correctly or were workable. I ended up junking them and scrounging good original used parts over a few years. Amazing how well a 95 year old part can function, but a 6-month old one fails due to poor workmanship and materials. The other option, besides poor quality repro parts is NO repro parts. We are lucky to have available what we do that DOES work. These cars were a lot harder to fix up 30 years ago with only junkyard parts available, believe me. It's a two-edged sword, indeed!!! As demand for quality increases, I think the the quality (and price) will rise to the occasion.

[656566gto]

I think you hit the nail on the head--it's an issue of supply, demand, and cost. Don't get me wrong, frustrating as they can be, I'm glad we have the repro parts that we do. Sometimes there's no choice (due to availability or cost).

[Tom Vaught]

The Trans Mounts that were made in India for a while and probably now China as usually about 3/8" taller vs the old American factory NOS trans mounts. 3/8" is enough to get into clearance issues.

You can take a poly trans mount and mill off about 3/8" of the poly/ steel insert and still have plenty of thread engagement for the trans bolts to the cross member.

Cut slowly on the part and you will have no issues. Run a tap through the threads after the milling operation.

The Poly part is a better part for support but poorer for NVH

Tom Vaught

[goatman65]

Check the engine mount frame brackets,the ones bolted to the frame.One is,should be 'taller' than the other.Could be yours are on the wrong sides or maybe both are the shorter one and needs to be swapped for a correct 'tall' one.This may/may not cause the engine to sit too low.