47-55.1 GMC w/orginal engine and Mustang II?

[mphudak]

I'm building up a chassis for my 55.1 Suburban and have installed a mustang II. All along my plan was to put in a 283 but am toying w/the idea of keeping it all GMC and going w/a 270 instead. I've been seaching but can't come up with anything on a 47-55.1 GMC that has a mustang II and is still running an original engine (228-302 GMC). My concern is the oil pan clearance to the crossmember since a GMC isn't notched like a chevy inline.

[mphudak]

I went ahead and reached out to Speedway Motors since I used one of their crossmembers. It's a no-go for just dropping in an original GMC motor. As i was suspecting, the oil pan needs the same real estate that the crossmember is taking up. It is possible to do it, just will some extensive mods to the center of the crossmember. If end up going w/a 270 I'll do a write up on the install.

[Jemezcrusher]

So, are you an original 6 would not fit with an aftermarket crossmember (IFS). I plan to keep my 235 in the 50 but had not considered the crossmember being a problem with oil pan clearance

[Katrina/10]

I think it's a great idea, and should work if you can get the right dimensions on the crossmember.

[Coach529]

How much interference between the crossmember and the oil pan?

[mphudak]

Chevy motor will fit w/no problem, but w/the GMC the oil pan is pretty flat front to rear. If it all has to do w/the location of the oil pump/tubing being different from a Chevy to a GMC. I don't have the 270 yet, still working trying to see if i can work out a deal.

I"m thinking i can cut out the middle of the crossmember and drop it or cap then ends and make a tubular crossmember/cradle that has a drop in it. Before i finalize any of the plans I'd have to try and mock up the 270.

Chevy vs GMC engine/oil pan

Chevy


GMC

[Coach529]

Wow. I did not realize there was such a difference between pans.

[joedoh]

Originally Posted by Coach529

Wow. I did not realize there was such a difference between pans.

the GMC motor is bigger in every dimension, like 5 inches longer, at least an inch taller, they are beasts. I have the crossmember from my gmc frame saved because you never know when someone will need one.

[mphudak]

Good save on the crossmember, someone will need it. I looked for quit a while to find a gmc suburban hydramatic chassis with no luck...then figured I would settle for a gmc chassis, again no luck. Gave up any hope for a hydramatic chassis and ended up with a standard chevy chassis. It took me a while to locate a gmc crossmember for it. We won't even discuss how long it took to find the suburban body mounts or the hydramatic crossmember.

[Coach529]

Originally Posted by joedoh

the GMC motor is bigger in every dimension, like 5 inches longer, at least an inch taller, they are beasts. I have the crossmember from my gmc frame saved because you never know when someone will need one.

That is good info to know. Thanks!!

[mphudak]

I was able to work out a deal on the 270, so looks like this project is moving forward. Downside is that the engine is 5-6hrs away so it might be a couple weeks before i can pick it up.

Thx to amazon, I'll be getting a couple GMC/Inline 6 hop up books today and can start deciding how to build it. Not shooting for high HP just a fun streetable motor. The big hp 270/302's make the power in the high RPM range and not realistic for the street. Initial thoughts will to convert the head to sbc valves, bump the compression (pistons/head work), either 4 barrel or multi carb set up and headers. Building an GMC, or any inline for that matter, isn't cheap. Once you get past the basics items the cost get's astronomic.

The seller did tell me that he has a rear sump 302 oil pan he'll throw in w/the 270. Not sure all 302's had rear sump or just some (note that there 2 different 302's, a civilian block and a military block.) Still looking for a pic of what is considered a rear sump pan.

[mr48chev]

Red engine with the 3 carbs is in a chassis with a MII I did a search for 302 GMC If you open the link it goes to a lowrider page that just shows links for adds and no script or photos. Closed forum me thinks. The photos can be expanded and studied though.

https://www.google.com/search?q=302+...sAQIHA#imgrc=_

[mphudak]

Thx! Looks like that is the other oil pan..fingers crossed i won't have a ton of fab work in it to make it fit.

[mphudak]

I'll be picking up the 270 this weekend and plan to run a tape measure on the chassis/engine to get an idea of what i'm working with by the end of the weekend and mock everything up in the coming weeks.

Taking another look at the 302 link Mr48chev posted it appears the MII crossmember was spaced down a few inches since there was no notch for the rack/pinion in the frame. With my crossmember there is no way i can pull off the steering w/out the notch. I have some better pics of 3 of the oil pans offered that I will post later this week. There were 2 10 quart pans and at least 1 one lower profile 8 quart pan.

[mr48chev]

That's the other way to do it if you don't absolutely have to have a ground scraper. There are some MII crossmembers that don't set the truck real low that might give more pan clearance.

They are a bit of a pain in the Keester to install but you could use a "universal" crossmember and cut it to fit to set it lower in the chassis.

I think I would look into modifying a crossmember first though.

[mphudak]

I'm not going for ground scraper or bagged, just a bit of a relaxed stance. I don't want to worry about anything when i'm out driving. Though I do like the look of a low stance, it's just not practical for me to justify the expense.

I agree that i think my best option is modifying the crossmember, especially since it is already welded in the chassis. I have the ability to fab whatever needs to be done, but don't want to get into customizing the oil pan or any other motor part if i don't have to. I like the thought that if something happed to the pan, it's easy enough to grab another one and bolt it in.

Here is a pic of 3 of the available pans. I "think" this is all that was available between the 228-302's. The 228-248 had the 8qt pans and the 270-302's had the 10qt's, and which one just depended on the application/chassis it was in.

From what i have found the oil pumps may have been the same for the 228-302 with the only difference being the pickup plate w/the longer pickup tube that was bolted to the bottom, which do interchange.

[mphudak]

Made the long trip to KY yesterday to pick up the 270 along with some other misc items, which included a small port Edmunds intake and some Carter W-1 carbs and a 302 oil pan. The motor is a 55-59 so I will need to get a 47-55 front engine mount before I can start the mock up.

[mphudak]

Forgot the pics

[mphudak]

A few pics of the guys toys I bought it from. Nicely built 302 in a custom he's building and his 55.1 hydramatic. I didn't get a pic of his 51 (I think) with a built 270 that is gorgous. Thing pulled harder then my mild 350 I have.

[mphudak]

The custom has a LOT of small details done and I think it has a 50 Buick dash that looked factory.

[mphudak]

My folks came to town so dad and I got a bit of time in the garage this afternoon. We were able to get the notch cut for the steering rack and mocked up the engine. I still need to get the 47-55 motor plate but was able to mock it up with the later 55-59 style. Very happy to find it will take minimal fab work to make it all work. I either need to trim an inch off the oil pan or clearance the crossmember an inch. If I notch the crossmember I will need to also drop the rack an inch or so.

[mphudak]

This project is going to take a back seat for a while. I've been having some issues w/my 350 in my suburban and was hoping it was just a bad intake or head gasket. When I checked the plugs, several had oil/carbon build up and one was fouled pretty badly. Once I pulled the manifold I found oil sitting on top of some of the valves and pretty bad carbon/oil build up on several of them. Turns out the valve guides are bad. Pretty disappointing since I just put new Dart SHP heads on it less then a year ago. I did some research and found some discussions on how poor some of the quality control around the time I purchased them (complete heads). Specifically the issues were valve guides were to tight and/or loose and valves were not square to the seats. Unfortunately I purchased them a little over 2 years ago and am out of luck.

All this said I needed a motor now and picked up a sweet little 283 yesterday. I've always had a soft spot for 283's and the nostalgia with them. I will swap out a few things to give it an early 60's vibe.

Upside is that I will be able to finish up the chassis a lot quicker since I don't have much to left to fabricate on the chassis. Downside is i don't know when, or if I'll ever mount the 270 in a chassis w/a MII.

[Highsider]

This is a great thread with lots of twists and turns.
Very entertaining since you are doing the work!
Please keep us updated.

[dsraven]

Would it be possible to install the engine without the panso you could see the actual clearance you need between the oil pump and pickup and the crossmember? Maybe just mo
Reworking the pan would be all that is required. Way back I used to install sbc's into stock vega chassis. I always had to modify the oil pan for clearance. Not that tough to do really. You just need to know what you have for room to work with.

[mphudak]

That was going to be the plan, pull the pan, once I got the proper 47-55.1 engine mount. From what I understand the proper mount is roughly 1" lower then the 55.2-59 mount. Given where the sectioning was needed in the pan it is completely doable without any interference with the oil pump.

I'll probably either rename this thread or start a new one to document the 283 swap and chassis completion. It's bittersweet to move on to the 283 from the 270 plans but I do have a lot of good memories working with my father on 283's. He was actually able to go up to Chattanooga with me to pick up the motor so that adds just one more item to support the decision to keep the suburban running while I restore the chassis I have been working on to swap in. The build for the 270 was going to be $$$ with the head work I wanted and long rod/stroking I had planned. Still will eventually do it, just may not be on my suburban. Honestly I would likely have more fun with the 270 back by a manual transmission vs the original hydramatic I wanted. The 283 will have a th400 for now but will swap the original v8 hydramatic in once I complete the chassis.