[goatman1970]

I have a couple questions. I bought a '70 GTO and was told it had a rebuilt, non-matching '70 400 in it. I pulled the motor after I got it, and the date codes (block=B139, Left Head=B129, Right Head=B189) indicate a '69 motor. The engine id behind the distributor appears to be 9790078, which I cannot find listed anywhere. The last number, 8, looks like it may be doctored (it is not a regular shape like the other numbers), and if it was originally 9790079, then it is actually a '69 350. It runs strong enough that it may have been turned into a 400, I was told the original 400 heads were reused, but the date codes don't back that up. Any ideas about what I have?

Second question is about the motor/frame mounts. I just re-installed the motor and replaced the trans mount. Felt a vibration under driver's seat on de-rev and driveshaft thumped in forward gear. The new trans mount had a spacer plate, once removed the thumping & vibration problem cleared.

The driver's side header still just barely clears the underside of body. I am beginning to deduce it requires an adapter or something. The driver's side of motor sits 1"-2" higher than passenger side (the driver's side frame mount sits a good 1"-2" higher than the passenger side frame mount), and the motor sits tilted toward the passenger side because of that. This causes fan to sit off-center in the shroud, had to put a smaller fan in to prevent shroud from being damaged (put in new fan shroud because old one was torn up in same spot). I'm guessing that the mounts are different setup between 69-70.

Can the existing motor mount setup be properly modified or adjusted, or do I need an adapter kit? It appears that if I can get the driver's side of the motor lowered 1"-2", the driver's side header will properly clear the underside of the body, and the fan will properly re-center so I can put the correct (and larger) thermostatic clutch fan back in.

[goatman1970]

I have a couple questions. I bought a '70 GTO and was told it had a rebuilt, non-matching '70 400 in it. I pulled the motor after I got it, and the date codes (block=B139, Left Head=B129, Right Head=B189) indicate a '69 motor. The engine id behind the distributor appears to be 9790078, which I cannot find listed anywhere. The last number, 8, looks like it may be doctored (it is not a regular shape like the other numbers), and if it was originally 9790079, then it is actually a '69 350. It runs strong enough that it may have been turned into a 400, I was told the original 400 heads were reused, but the date codes don't back that up. Any ideas about what I have?

Second question is about the motor/frame mounts. I just re-installed the motor and replaced the trans mount. Felt a vibration under driver's seat on de-rev and driveshaft thumped in forward gear. The new trans mount had a spacer plate, once removed the thumping & vibration problem cleared.

The driver's side header still just barely clears the underside of body. I am beginning to deduce it requires an adapter or something. The driver's side of motor sits 1"-2" higher than passenger side (the driver's side frame mount sits a good 1"-2" higher than the passenger side frame mount), and the motor sits tilted toward the passenger side because of that. This causes fan to sit off-center in the shroud, had to put a smaller fan in to prevent shroud from being damaged (put in new fan shroud because old one was torn up in same spot). I'm guessing that the mounts are different setup between 69-70.

Can the existing motor mount setup be properly modified or adjusted, or do I need an adapter kit? It appears that if I can get the driver's side of the motor lowered 1"-2", the driver's side header will properly clear the underside of the body, and the fan will properly re-center so I can put the correct (and larger) thermostatic clutch fan back in.

[stephen]

1968 to 1972 the mounting systems for all A-body pontiac 350, 400,and 455 are the same, so that is not the problem. Did you replace the motor mounts, or are they the ones that came in the car? It may have a crushed mount on the right side. Just for giggles what are the first 3 number of the vin.
stephen

[goatman1970]

For sure it is a GTO (VIN 242370R140533). The motor mounts and frame mounts are correct for the 1970 GTO (verified by ordering motor mounts and checking frame mounts on two GTOs in junkyard). The issue seems to be that a 69 motor may need an adapter to sit level in a 70 car? See posting:
motor mount post

So, do I need adapters and if so where do I find them, and if not how do I get the motor to sit level? And is the engine casting number legitimate or a fraud? I was actually told that the motor came from a Corvette, but the numbers are Pontiac, not Chevy.

[stephen]

1968 to 1972 A-Body pontiac frames are the same. it doesn't matter if it is a gto, tempest, or a lemans. If a 69 motor, no matter 350,400,or 455 will not fit straight in a 1970 frame something is realy wrong. and no adapter plate is going to to fix it. the newer motors 74 and up I believe would require the adapters you are talking about. They are pretty easy to identify they have three bolt holes for the motor mounts. Your 69 should have only 2.

First make sure it is indeed a pontiac motor. you mentioned that someone had told you that it might have came out of a vette. To the best of my knoledge pontiac motors were never put in vettes. I believe that to put chevy motors in pontiacs (an act I highly discurage) you may have to change the frame mounts. or someone may have already changed the mounts to the incorect ones already.

eather way verify motor type Pontiac- chevy- olds etc, correct motor mount instalation, and correct frame mounts and thier position on the frame and there is no reason it won't sit strait unless the frame is realy bent.
Good luck Stephen

['ol Pinion head]

Might consider measuring where the frame brackets are located, then compare to another Pontiac A-body frame with the same brackets. For an engine to set that "caddwampus", the frame crossmember has got to have wrong positioned mounts or be majorly twisted. These crossmembers just don't easily twist. Often times, high mile A-body frames will sag, but frame "sagging" will not result in an engine setting like you describe. Just can't see this being the problem, w/o one noticing major damage... evidence of previous repair of majorly twisted frame horns accompanied with the occasional crack behind the lwr passenger side A-frame mount. Most possible, one of the two frame brackets has been installed in a non stock position.

Frames... though the common '64-72 Pontiac 326-350-389-400 frame brackets will bolt up on most any '68-72 frame, there are other differences between A-body frames, so stating the frames are "all the same" is not 100% true.

The 9790xx block should not require any form of motor mount adapters. Motor mount adapters would only be needed in this chassis, if the 400 block was cast after mid '76 (either a late 500557 casting, or a 3 bolt mounting 481988 block from a '78 or '79 W72 400)

Hope this helps.

[stephen]

Ol' pinion head
we agree there should not be a mounting problem that cool, since I would imagine that you have a lot more expierance than me. A- Body frames 68- 72 besides boxed for convertables and the standard for the coupe and hard tops what are some of the differances. They are all I play with and like to know as much as I can.

Thanks Stephen

[goatman1970]

Thanks, guys, for taking the time to respond. I started out believing what you are saying, then wasn't sure, but with your support on the matter I'm convinced this is an issue of jockeying the motor until it settles in.

The thing is (and I've checked out several junkyard cars and they are the same) the frame mount on the driver's side is a good 1"-2" higher than the frame mount on the passenger side. Since the driver's side of the motor sits higher than the passenger side in my GTO (the driver's side header is almost up against the underside, not even 1" of clearance, while the passenger side header sits an easy 2"-3" below the underside), I figured that the motor mount was the problem and an adapter would fix it. Also, the fan sits down in the bottom right-hand part of the fan shroud opening, and I had to replace the regular clutch fan with a smaller one to save the shroud. The car goes straight down the road, so I don't think the frame is bent. I'll try what someone else suggested, loosen all the mounting bolts and try to shake it down and hope it's just cockeyed by accident. I'll post another note on the result.

[goatman1970]

I just realized that I may not have worded the original question or follow-up posts correctly. When I was saying frame mounts, I was talking about the frame part of the motor mounts. It is the frame-side motor mounts on the cross member(whatever they are called) that are of different height and appear to be causing the motor to sit cockeyed, and these are exactly the same as the ones I've seen in junkyard cars.

Even though the car goes straight down the road, I wonder if the frame is a little off and causing the motor to not sit level (like if the left side of the frame is pushed in a little). I'll take it to a frame shop and have it checked.

[boozer]

hello, i have got the motor out of my 70 gto right now. would you like for me to take some good pics and send to you?? email me if so. shawn515@swbell.net later boozer

[goatman1970]

boozer, thanks. Email on the way. New motor mounts and stock frame-side mounts, they look OK. Any help on this is appreciated. JGoat