The Stovebolt Site Forums The Shop Area Engine Shop New project ....270/302 rebuild ....

Just acquired what looks like a 270 or 302 engine with 4 speed Muncie M420 with PTO attached. Allegedly came from a "Canadian" GMC COE 1958.....tranny is dated 1959 on the casting......

As of yet not been able to find anything similar to GMC engines that would compare with "The Stovebolt Forum and the identification of GMC engines is a nightmare compared to Stovebolts.

Long term plans are to assess condition and possible "fire up" while bolted to a spare engine stand made from a GM Frame...... I have exhausted the U tube video posting with some good information accumulated... I am very reassured that there has been some earlier postings on the ENGINE section pertaining to the GMC inline engine.

Eventually the GMC engine/tranny will be shoehorned into a 1940/45 Canadian Military Pattern 4x4 right hand drive frame....externally plain jane but with more hummmph....... My current restored 1940 Chev was upgraded with a stock 261 and runs like a charm......

My first question is.... Is there a particular GMC site/forum that would help me identify the serial number....I have been "told" it reads 232-4004 which does not make sense...... the engine/tranny will be home by the weekend. I will need all the help I can get being born and raised with Chev engines...... I do have a stored/spare 248 and a 228 to compare and learn from.....

will document our progress on Stovebolt for future references

Thanks for all the future assistance.

Bob C.

Unless Canadian rigs have a different numbering sequence, the displacement of the GMC engines will be included in the stamped (not cast) number on a machined pad beside the distributor. 228, 248, 256, 270, 302, etc. The 256 was used in some WW II era Canadian military vehicles- - - -very scarce down south! I have bore and stroke information and engine bearing specifications in a couple of old Federal-Mogul shop specification catalogs. There are a couple of other Stovebolters who are very well versed in GMC-speak, also!
Jerry

For specific GMC info, try this.

Same guy runs a GMC specific forum here, but it has much less traffic than the StoveBolt site. Also, you need to join to access.

I don't have a lot of Canadian GMC info, but what I have shows either Chevy (6 cylinder) or Buick (V8) engines in the late 50s.

As Jerry says. the GMC engine size is the first 3 digits of the engine serial number located as shown in the attached picture.

Hy RAC1812 and guys, for some unknown reason none of my Canadian GMC 248 engines have their serial numbers stamped the way their American cousins are, mine are stamped with letters at the beginning of the number, always a G first letter but different second letter and no reference to the engine's internal size in the number used. The 302 engines I have are stamped the same way their American cousins are.

The old gmc site has all the info you will need in the search area. Your 232-4004 block is a 302 from 55-62.

Thanks for all the info guys....... I now realize that there is a vacuum out there when it comes to GMC 302......nothing matches the breadth of experience on Stovebolt.

Well we got the "beast" home along with two Muncies tranny...... one that fits the 1958 block with the bellhousing and the burnt clutch..... one of the Muncie is longer with an aluminum top cover but hat is a different topic for now..

Apparently the engine ran before it was removed and didnot smoke....... the PO purchased the 1958 GMC just for the cab that he has since dropped on a Cummings powered Ram frame...

Immediate plans are build a proper engine stand using the front and rear enginemount on the Bell housing.....do some cleanup.....possibly a compression check....remove and clean the pan, valve covers and side cover. Then with clean plugs, clean up the dizzy (points. cap, rotor, condenser) and a temporary radiator fire it up to see how it sounds. Based on our findings decide whether we fit it to a front section of a frame on trailer wheels and tear in to it for a full or partial rebuild. It will eventually reside in a 1940 CMP right hand drive vehicle....so some fabrication will be in order. The final vehicle will replicate the "UMBAU_WAGON" that the German army made using all the left over Chev/Ford trucks after the hasty retreat from Europe in Summer of 1940 and leaving behind tons of brand new Chevs and Ford 4X$ in various format..... the German used the vehicles in the Russian front mud and as rough terrain officers staff cars. They mainly kept the front cab/sheet metal and added a van type steel body tot h4 rear with two extra pass. doors and a canvass roof covering...... and were highly regarded by the Germans. Since they were adapted by the German army it gives me some poetic license as to what was original or modified and should make a good 4x4 to drive on the abandoned logging trails of Western Quebec...that with the extra hummmmpphh of the 302 and the synchro Muncie should a blast.

The owner knew very little about the engine serial number BUT it has the "302" CLEARLY STAMPED..... only then did I give him the $$$$$

I now realize that 302 aftermarket parts will require patience and $$$ and have already spent countless hours reading all kinds of web postings but glad to be back to Stovebolt and the familiar advisors.

Will have some "as is" photos soon. Bob C.

That trans with the aluminum top probably isn't a Muncie- - - -more likely it's a New Process 435. Some GMC's came equipped with them, but they were mostly found in Ford and Dodge trucks, with a different input shaft and bellhousing bolt pattern.
Jerry

Thanks Jerry...... I can always use it as potential trading chip!!!!!

...come to think of it we do have a spare Ford CMP frame with a stuck flat head....... it is circa early 40s and was manufactured with GM front and rear axles when Ford ran out of parts and the assembly line was NOT to be shut down...... Ford and Chev had co-designed the CMP vehicles ( government dictated) so parts could interchange except the engine/tranny set up. The original CMP was a British dictated specs that proved to be a pain and when the orders started to come in by the tens of thousands, GM and Ford refused until they could produce them if they were allowed to modify the cab sheet metal design to better match North American standards... then it was game on....mine is an early Sept 1940 and a pain.....

I have a Federal-Mogul shop specification manual that will provide part numbers and dimensions for rod, main, and cam bearings, piston pin bushings, etc. and dimensions once you get deeper into the rebuild. If you can send me a private message with a mailing address I'll be glad to send you some photocopies of the applicable pages of that manual. I've also got AERA machine shop specification manuals that show connecting rod reconditioning specs, etc. Most GMC's run gun-drilled connecting rods that supply pressurized oil to the piston pin bushings. They're MUCH more rebuild-friendly than Chevy engines.
Jerry

Thanks Jerry....... will consider your offer as I get into the deep end of the engine. Meanwhile I am baffled by the vacuum of info/manuals, etc. when it relates to GMC engines. I am getting copies of the military manual engine section but it seems that every book I look at is entitled Chevrolet & GMC trucks and has 90% of content dedicated to the Chev 235/261 and very little on GMC or when I find something it pertains to the V8 GMC not the 302...... I took a chance on a couple of manuals that were on Ebay, which claims to have 302 information. By chance I found in my stash of books a Motors truck repair manual.......which covers 1954 to 59 and has specs of the 302..... talk about luck!!!!!! Now need to read and memorize its 60 or so pages.......

I will return to the Forum as I come up with more intelligent questions ........ There are NO machine shop in Ottawa ( government city) that will tackle an engine rebuild.... bnot enough demand to keep qualified staff on hand.... so everything has to be shipped to Toronto or Montreal at my cost and risk!!!! I have found a shop where the owner is about my age (old) who may guide me to some of the more reputable shops that they send/deal with when they have a farm engine to rebuild job ...... hoping to have a long talk over coffee.

Good Machine shops and older experienced staff is a dying breed!!!!! ..... when you find one they only work on CNC driven machines and are usually younger than my own kids.

I'm making an effort to train my son and my grandson on some of the finer points of automotive machining- - - - -cylinder boring and honing, connecting rod reconditioning, valve and guide work, line boring, cylinder head rebuilding, and crankshaft grinding. I'm also in the process of building fixtures to rough out stroke changes on stovebolt and flathead Ford V8 crankshafts on a lathe, to save wear and tear on crankshaft grinding stones. Those things are E$$$$$PENSIVE! I almost purchased a new-looking Storm Vulcan camshaft grinder for a giveaway price, bus someone on Ebay beat me to it!
Jerry

55.2-59 GMC Maintenance Manual available here. But it is one page at a time and hard to use.

Paper manual reprint available here for $42

Just an quick word to update...... I have now viewed, a few time, KevinB"s video....all very good but too short for me.....

Discovered "nozzles" I had never heard of before and I see from the recent postings that info is available.

Bill H ....thanks for the tip on the manual...... got the military model info and bought one other manual from ebay, which is supposed to contain 302 information, but have not received it yet....if I find it lacking, I will immediately make a run for yours.....

Part of my problem is that I got the 302 removed frm the frame and not even sure of what series or model it came from..... and manuals tend to be focussed on series/ model numbers.... all I know is that the truck came from Saskatchewan out West.......

and this lack of model/series numbers except that it is suppose tobe a 1958........ this all leads to more confusion....for example the Motors Truck Repair manual that I am now using is lisitng the distributor by serial number and not be model/series or engine size..... I know it is a Delco and it shoulf have the part number on the inside plate....but I am not there yet...and thatone is easy.....

My starter motor is missing and again.... the one supplied which looks GM and fits the bell housing mounting bolt pattern has no ID tag..... and my manual list starters by "plate" number...... I know how critical having a matching starter is....got a page full of starter lsiting but not cross refenced to the engine size......blah.....

Will be building and engine stand....... need casters.... and will attach the engine by the existing front engine mount and rear BH mount which will allow me to even go as far as bumping the starter for a run when I figure out the starter issue.

I am learning........ but had to blow snow fro 3 hours today on an open tractor........ Brrr froze my whatoosie!!!!

Bob: Send me a PM with your email address and I'll send you a few files that may help.

PM sent Bill thanks

Well my engine as a clear 302 stamped on the pad.....BUT.... no other number...blank

Looks fairly stock but may be a GMC replacement......

Stock Holley carb 660-1 ....tag still on part number 2328076 checks out......... is it worth rebuilding......??? what else will bolt on the stock 3 bolt manifold???? can't really fit a more modern 4 barrel carb and tube exhaust manifold due to lack of space in the engine compartment...... may change my mind as I progress even if I need to remanufacture a new engine cover. I do have a NOS stcok military Holley carburator for the waterproof GMC....

Dizzy is 1112403 IC8 which is oddly very similar to the 261 when just quickly eye balling.... and I have collected a supply of AC 42 ,43,44,45 and a few 46 and 47 used on fire trucks...when EBay was affordable....common use on the 261/235

Water pump also looks widely similar to the external 216 pump with the adapter plate used on my 261......

The current political storm across our borders MAY cause me some problems or $$$, which is the same. I maintain a mail box service across the border in upper NY State and makes shipping such a pleasure....... time will tell.

At least the forum is available!!!!!

Bob C.

Bob: Check your email

A Thousand Thanks Bill..... it was like Xmas all over again...... printed very thing....used up all my spare cartridges and ordered more........

The 302 is on it own fabricated stand.....tied to the front and rear engine support.... now I can sit at eye level and admire it and list all the dumb questions that come to mind....

My first ???? I am familiar with the by-pass and full flow oil filtarion process on 235/261 and the dowel that you push in..... BUT I keep reading little snippets that the block has to be converted to "fullf'low" My preferred solution is to install a dirt tack dual filter remote aluminum bracket inside the frame that takes stock screw one filters such as the old PH8 filters..... easy to change, cheap, adds to the engine oil volume, helps in cooling the engine............... How do we do this on a 302?????? My 261 truck is running with the big rubber/steel lines and the two filters in the frame...... works great.

Bob C

Check page 30 of the Bill Fisher book I sent you for instructions on adding the full flow filter, although some on this forum swear by the stock bypass filtering system.