View Full Version : GMC Big Strait 6; 426,477,503,707?


BlackCherryImpala
08-02-2008, 01:55 AM
Gmc built some very large displacement gasoline straight six cylinders before 1954 including a 360, 426, 477, 503 and 707. These engines were in the large trucks starting at the 620 series and going up to the very large 970 series. Has anyone ever built one of these heavy big boys for a hot rod? I know the 302 straight 6 ran like stink in the early 50's with the Wayne head and other mods, in fact, i believe the "Bustle Bomb" car equipped with a 302 held some kind of speed record at the time.
BlackCherry

fiftyv8
08-02-2008, 07:06 AM
I dont know much about these engines but I did see one installed in about a 1946 Chevy coupe in Longmont CO about 2 months ago and it looked real sweet, complete with a nicely built set of big pipe extractors.
I dare say it would produce plenty of torque but these days the gas consumption would be something chronic.
I hope you get some more posts on this thread, as I would like to know more about these big suckers.

Dolmetsch
08-02-2008, 09:56 AM
But it would be fun!
I often thought about the international 450 as well It was a hot motor in its day and I did many heads for the trucking industry for them when I worked in the machine shop . The guys used to love driving them.
Probably wouldnt need a trans , just a clutch and a jack shaft with a bearing support bolted where the trans should be. torque would be gruesome! RPM . might get to 4000 who knows with a reground cam and some pirated valve springs. No speed equipment? How wonderful! Then you can make anything you want. A blower set up even. It would be big loud different and fun The crowds would love it.
For what it is worth I would encourage you in your quest. Maybe a new class. HAMB TRK rail. 6 cyl Truck motors only. I would drive a lot of miles to see something like that run! Or maybe a truck cab rat rod with a huge truck gas 6 up front. I wonder how big an exhaust pipe you can buy?

roddinron
08-02-2008, 10:25 AM
Or maybe a truck cab rat rod with a huge truck gas 6 up front. I wonder how big an exhaust pipe you can buy?
Awwww,you said rat rod!:eek:
Seriously though, I hope this thread goes somewhere, I'd like to see more of these motors too, I'm sure the right guy with the right tools/expense account could build something awesome out of one. Torque is a wonderful thing.

Ole don
08-02-2008, 10:40 AM
I have never heard of building one bigger than the 302 for performance work. If you want an International motor that could make a ten wheel dump truck fly, look for a 549 V 8. In a light car that motor with the right trans could put you in orbt.

OLD HEMI
08-02-2008, 10:58 AM
In the 40,s@50,s manufactures built gas eng. up to 1090 cu. in. ( Hall- Scott) the engine put out 400hp. @2600 rpm and 1400 lbs. ft. of torque at 1200 rpm. But it weighs about 1200 to 1400 lbs.

OLD HEMI

Hot Rod Packard..
08-02-2008, 11:14 AM
I want one!!! If any thing just so ia can say I have it. Parts can be made to hop one up.

RichFox
08-02-2008, 11:22 AM
I know where there is a Roline 805 inch V8 sitting in a field. OHV with the intake and exhaust on top. 8 coils and 8 sets of points, no distributer. Pretty heavy, but they do sound neat.

RichFox
08-02-2008, 11:55 AM
I've seen a few 16:92 GM diesels at Bonneville that ran pretty good. Near 300 in a '47 or so GMC ton and a half. Thats 1472 cubic inches of really heavy truck (Tug boat?) motor. Who knows what you can do as long as you don't know you can't?

RileyRacing
08-02-2008, 12:50 PM
They also had some monster big V6's back in the 50's/60's also. The farmer I worked for in high school had an "eyebrow" GMC with a monster V6... it was sweet. Aren't they the ones with the "plaid" valve cover paint too?
And wasn't it MR 42 here on the HAMB that made the tank engined thing... basically a sweet ass V12 and a frame with wheels? That was cool!

Jay

Dolmetsch
08-02-2008, 01:10 PM
High gear is normally direct drive so no trans required. top speed limeted by rear end ratio and tire size.
I am thinking a old pre 53 truck cab a square tubing frame and a 450 intenational . Striaght axle from a 1 ton truck and a good stout diff . Hopefuly no muffler just a big long pipe running down one side like an old indy car. Lowered even, channeled over the frame with the valve cover level withthe top of the grill shel. An old cab over would be great for such a project. Just move the grill shell 4 feet forward on the chassis. Talk about a rat rod. A gas rail would be even simpler.
We forget that tractor puller guys modify similar type engines all the time. And then there are the boat guys. How about a Kermath Sea Wolfe. 622 cubes ovehead cam ,triple carbs . Tis exciting just to think about the sound. Hope there would be some smoke as well.

Bigblock351w
08-02-2008, 01:58 PM
im going to help ALL of you out.
http://www.6066gmcguy.org

go there... NO dont argue or hesitate... just... go there.. and look through everything... then you can make educated opinions instead of hearsay ones.

and no im not insulting you.. yes im harsh..i know this... now shut you yaps and check it the hell out!

thrasher
08-02-2008, 02:15 PM
he is asking about pre 54 gmc INLINE 6 engines, not the large displacement v6 from the 60s. completely different thing.


im going to help ALL of you out.
http://www.6066gmcguy.org

go there... NO dont argue or hesitate... just... go there.. and look through everything... then you can make educated opinions instead of hearsay ones.

and no im not insulting you.. yes im harsh..i know this... now shut you yaps and check it the hell out!

fiftyv8
08-02-2008, 04:11 PM
Anybody out there got some pic's of engines we are talking about, I know Povertyflats had a big GMC six for sale about year back and that thing looked real neat has big engines go.

fiftyv8
08-02-2008, 07:09 PM
Now wouldnt this sucker look something in the right engine bay!!!
I beleive it is the GMC engine that Povertyflats once owned.

I am open to correction if I am wrong.
Id like to see if anybody else a better pic of this or any other!

What diff ratio do you suggest this would need in a painted ratrod.

JohnEvans
08-02-2008, 07:48 PM
Now wouldnt this sucker look something in the right engine bay!!!
I beleive it is the GMC engine that Povertyflats once owned.

I am open to correction if I am wrong.
Id like to see if anybody else a better pic of this or any other!

What diff ratio do you suggest this would need in a painted ratrod.
That is a 702 CID GMC twin six, famous for passing everything but a gas station ,in truck use 2-3 MPG. Rear ratio 2-1 but ya still need a couple of gears to get it moving. Red line on them things was about 3600.
As a aside a Hall-Scott weighs more like 2500 ready to run. Buddy of mine has one sitting in his back yard,still in the remains of a fire truck, good runner though. Also a fuel sucker at 2 MPG.

Zerk
08-02-2008, 07:50 PM
I understand Dodge used a 413 cube INLINE at one time.

The era of gas-powered over-the-road trucks fascinates the hell out of me. I'm sure economics has buried most of the survivors, and diesel repowers buried the rest.

Zig Zag Wanderer
08-02-2008, 11:16 PM
Nope, you don't need a transmission if one of these things is true:
1. top speed is 30
2. you don't mind slipping the clutch for the first 1,000 yards

Try moving a big truck from stop using high gear.
Big trucks use FAR, FAR higher total gear multiplication than anything else that travels on public roads.

the trucks these came in have a GVW of 10 times what a rod that he's talking about would have. that's why they have that gear multiplication. direct drive would be perfect in a light car with torque being that abundant. super low-revving, extra large displacement single and two-seaters are perhaps the oldest and truest forms of automotive hot rodding; the ford 999 and John Parry-Thomas' aero-engined "Babs" spring to mind instantly. they were fast, and because (comparatively) they did not have a lot of vehicle weight to haul around with it they could be geared very high (numerically low). if he wants to build one for a rod, i applaud him for wanting something outside the box; but christ panic, do you have to work so hard at trying to talk him out of it for no real good reason other than YOU think its a bad idea?

roddinron
08-03-2008, 12:12 AM
the trucks these came in have a GVW of 10 times what a rod that he's talking about would have. that's why they have that gear multiplication. direct drive would be perfect in a light car with torque being that abundant. super low-revving, extra large displacement single and two-seaters are perhaps the oldest and truest forms of automotive hot rodding; the ford 999 and John Parry-Thomas' aero-engined "Babs" spring to mind instantly. they were fast, and because (comparatively) they did not have a lot of vehicle weight to haul around with it they could be geared very high (numerically low). if he wants to build one for a rod, i applaud him for wanting something outside the box; but christ panic, do you have to work so hard at trying to talk him out of it for no real good reason other than YOU think its a bad idea?
I like that.

RichFox
08-03-2008, 06:32 AM
When I was a Moter pool mechanic for my uncle we had Reo and Studebaker trucks with 331 cubic inch Reo Gold Comet inline sixes in them. OHV and pretty neat. The truck I drove, the wrecker, had a 606 inch Continantal OHV 6 in it. The next bigger truck had the 805 Roline V8. Reo also made a 440inch V8. They were pretty cool motors I thought.

Dolmetsch
08-03-2008, 07:38 AM
Well go ahead and put a trans in. I wont be using one. and i wont be slipping the clutch either. With that much torque and that big a flywheel and the LIGHT car (I will weigh about a 5th to a 10th of a truck,) it wont even know thw clutch is out. I might rework an old Dp rear end from a 2 1/2 ton but that would be all. And it will go considereaabley more than 30mph btw. depends on engine rpm. diff gears and tires size TRucks are direct in high too or at least where back in the day. How would i know that? Because i was the truck guy for a few years at the local Ford Superduty dealer and a have had several apart for complete overhauls. The rear reduces the speed not increases it . Ratios in the fives and sixes are not uncommon.
I have driven a 92 viper by the way and they are only 488cubes but will pull away in 6th gear without slipping the cutch becaue of their huge torque. Compared to a truck engine torque wise they are just a baby. The viper owner told me to try it and i was surprised. It was smooth and no jerking . Anyway doesnt matter. You can do whatever you wish.
There is a 707 V12 near by.belngs to John Ryan and is sitting back the lane on his farm. I have seen them on tractor puller modifieds. (Maurice Cuyer of Otttawa area used one, probably still does. Worked absolutey wonderful. GM guys insist Gm quit making them because they never broke down. Those are their words not mine. . I am just repeating what they told me.
The international engine is known as a RED motor and was built from 372 to 501 cubes although around here the 450 was the most popluar. Bore is 4.375 and stroke 5 inches i think. Ford had a bunch too but they were V8s. 401 477 and 534. I have had about 30 or so of these apart in my career as when i started in the trade diesels were few and far between. These big Fords are kind of a different engine and remind you of a huge version of a 409 chevy. International had a 549 that was very similar inside. I dug out my old spec books from my machine shop and was looking through it To me the RED intenational is the best choice for a huge gasoline six cylinder. From my perspective anyway. Thanks forstarting the thread. It is an intersting subject and a good idea. I am going to see fi i can find an old cab cheap and build a rat rod with a red 450 . I believe i know where i can get an engine.

Truckedup
08-03-2008, 08:04 AM
The 707 engine is not GMC,Mack had a 707 OHV inline 6 gas engine in the 50's.Extremely heavy engine.I think the largest GMC built inline is a 502.
Mopar never made a 413 inline,but the 413 B block V-8 were used in their own trucks and some Macks

FiddyFour
08-03-2008, 08:19 AM
Try moving a big truck from stop using high gear.


thats easy. i do it EVERY DAY. i can leave a stoplite in high range pulling an empty trailer simply by letting the clutch out a lil slow. maybe for the first 10 feet and then away i go. with the kinda weight he's talkin? easy as hell

panic
08-03-2008, 10:19 AM
There are reasons why a transmission is needed, but I've rather lost interest in explaining why the sun is hot, don't poke yourself in the eye with a sharp stick, etc.
You don't have to take my word for it.
I suggest a refresher course in mechanical engineering.
Oh, and engines.

JohnEvans
08-03-2008, 10:39 AM
The 707 engine is not GMC,Mack had a 707 OHV inline 6 gas engine in the 50's.Extremely heavy engine.I think the largest GMC built inline is a 502.
Mopar never made a 413 inline,but the 413 B block V-8 were used in their own trucks and some Macks
Ah Contrair !! GMC DID have a 707 way back in the 30s and in the early 50s Dodge truck had a 413 inline 6 with 2 carbs.
Ah Contrair !! Back in the 30s GMC had a 707 six. Also Dodge trucks in the early 50s used a 413 SIX with 2 carbs.

Truckedup
08-03-2008, 11:53 AM
John,you are correct............I checked it out

Dolmetsch
08-03-2008, 12:48 PM
Why the sun is hot.
I am just gonna forget it. Hopeless.

Zig Zag Wanderer
08-03-2008, 09:54 PM
There are reasons why a transmission is needed, but I've rather lost interest in explaining why the sun is hot, don't poke yourself in the eye with a sharp stick, etc.
You don't have to take my word for it.
I suggest a refresher course in mechanical engineering.
Oh, and engines.

ok, let's put this in hard numbers, like engineers do, since you are suggesting we all need a refresher course.....

a 1958 503 c.i. GMC produces 217 hp and 455 ft/lbs of torque bone stock.

an Ellis dual-carb intake, mild cam regrind, "borrowed" valvesprings as suggested above and some home-built headers could net us an easy 5% gain in hp and torque giving us and 228 hp and 478 ft/lbs; but we will plug in the stock numbers just for sake of argument.

our "control" will also be a bone stock, but HAMB-friendly 59AB flathead making 90 hp at 3600 rpm, and 72 ft/lbs of torque at 2000 rpm.

drive wheel torque = flywheel torque x first gear ratio x final drive ratio x .85 (a constant of parasitic loss of drivetrain friction and mass)

in the case of the GMC will use a first gear ratio value of 1.00 since we are proposing direct drive.

for the 59AB we will use the standard ford toploader with a 2.99 first gear

in high gear all things would be equal since high gear in the ford box is 1:1
but that does not enter the equation in either case...

i just thought i'd remind everyone:rolleyes:

in either case we will use a 3.54 ratio rear axle.

the drive wheel maximum torque value on our 59AB comes out like this...
72 x 2.99 = 215.28 x 3.54 = 762.09 x .85 = 647.77

we also know that in an a-v8 with a bone stock flattie, you don't need to bring the engine clear into it's torque peak to accelerate the vehicle away from a stop. it only requires a slight rise in rpm.

the GMC also has the added benefit of producing it's peak torque and hp at roughly 300 to 400 rpm lower than the flattie

now let's do the numbers on the GMC....

455 x 1.00 = 455 x 3.54 = 1610.07 x .85 = 1369.10

ok, that's maximum...but that's not what we use to accelerate from a stop; it's actually a lot less, so....

now, let's say we let the clutch out on the 59AB 1000 rpm. our available flywheel torque according to ford's power curve sheet is 67 ft lbs at 1000 rpm.

let's do the numbers on the 59AB again at 1000 rpm...

67 x 2.99 = 200.33 x 3.54 = 709.17 x .85 = 602.79

our torque at 1000 rpm is around 90% of peak torque, whether at the flywheel or at the rear wheel...

now let's say we let the clutch out at the same 1000 rpm on the GMC; calculating the same 90% of availability of peak torque available at the lower rpm (even though this engine's torque curve probably peaks out at around 1750 or so)...

409.50 x 1.00 = 409.50 x 3.54 = 1449.63 x .85 = 1232.19

twice as much available rear wheel torque for accelerating the car from a stop...without benefit of a transmission for torque multiplication.

BTW, i'm a parts man, not an engineer, but i invite comment from any engineers on my math here.

fiftyv8
08-03-2008, 10:30 PM
How about some pic's of these amazing monsters?

BlackCherryImpala
08-03-2008, 11:10 PM
The 707 engine is not GMC,Mack had a 707 OHV inline 6 gas engine in the 50's.Extremely heavy engine.I think the largest GMC built inline is a 502.
Mopar never made a 413 inline,but the 413 B block V-8 were used in their own trucks and some Macks
The info I had as for the 707 cubic inch along with the other large sizes came straight out of a GMC book I saw at the bookstore and i believe the book to be accurate. Thanks for all the info guys and keep it coming. I'm enjoying the heck out of it.
BlackCherry

Dolmetsch
08-04-2008, 08:48 AM
off to see if the big int 6 is still available.
BTW nice math. Good work and excelant explanation. Impresssive to say the least

BlackCherryImpala
08-04-2008, 10:18 AM
off to see if the big int 6 is still available.
BTW nice math. Good work and excelant explanation. Impresssive to say the least
I'm working on the purchase of a 33 International 1 1/2 ton. Wouldn't that be really cool with one of the big IH sixes. I salivate at the thought.
BlackCherry

no bux rod
08-04-2008, 12:03 PM
Let's see some photos, I'm drooling....a really big 6 in a T-bucket with the needed reinforcements sounds cool.

N B r

Piper106
08-04-2008, 08:51 PM
Some of the monsters were built as late as the 1970s.
Looked at the 1972 Statistical Issue of Automotive Industries and it lists for gasoline engines;

International
501 cubic inch 6 cylinder 4-1/2 bore x 5-1/4 stroke 215 HP @ 3000 rpm
451 foot lbs torque @ 1600 rpm

Brennan (mostly tractors I think)
620 Cubic inch 6 cylinder 4-1/2 bore x 6-1/2 stroke 250 HP @ 2000 rpm
500 foot lbs torque @ 1200 rpm

Minneapolis-Moline
605 cubic inch 6 cylinder 4-5/8 bore x 6" stroke 177 HP @ 2000 rpm
515 foot lbs torque @ 1000 rpm

also
Minneapolis-Moline
800 cubic inch 6 cylinder 5-5/16 bore x 6" stroke 250 HP @ 2000 rpm
718 foot lbs torque @ 1100 rpm
800 cubic inches is not small; 30" wide 43 -3/4" high, 76-1/2" long

Geared for about 2100 rpm at 70 mph, and multi-disc clutch (I'm thinking maybe from a top fuel car) and one gear would be OK (well maybe a little rough pulling into a parking space at the local A&W for a chili dog).

Piper106

RileyRacing
08-04-2008, 08:59 PM
I went into work today and added a pic of the V12 to my computer to use as my desktop background (not supposed to surf the net on company computers). Anywho, the engineer who sits across from me looked at it and started chuckelling, he worked for a guy who used to run a Kenworth between K-Zoo and Nebraska that had one of them 12's in it... and he said to show it to another engineer who works with us, he's got some good info on them. (I work at Detroit Diesel, these are 30 year + guys).

Any first hand experience on how big the Group I (big big 6's) are compared to the Group II sixes (the 228, etc).? I'd be curious to see if the weight is worth the percieved displacement advantage (power to weight ratio, etc.)

Jay

Zig Zag Wanderer
08-04-2008, 11:26 PM
I went into work today and added a pic of the V12 to my computer to use as my desktop background (not supposed to surf the net on company computers). Anywho, the engineer who sits across from me looked at it and started chuckelling, he worked for a guy who used to run a Kenworth between K-Zoo and Nebraska that had one of them 12's in it... and he said to show it to another engineer who works with us, he's got some good info on them. (I work at Detroit Diesel, these are 30 year + guys).

Any first hand experience on how big the Group I (big big 6's) are compared to the Group II sixes (the 228, etc).? I'd be curious to see if the weight is worth the percieved displacement advantage (power to weight ratio, etc.)

Jay

i don't have dimensions but here is an example of the "big big" GMC six

http://oldgmctrucks.infopop.cc/eve/forums/a/ga/ul/6141070002/inlineimg/Y/teaneck_gmc_rescue_15.jpg

RileyRacing
08-05-2008, 07:36 AM
Or not. :)

Thsnks though!

Jay

fiftyv8
08-05-2008, 07:42 AM
Man I just pic's and torque figures and lots of them.
Come on lay a few down please!!!

Silent_Orchestra
08-07-2008, 05:30 PM
The big sixes are sweet...but more practiacal is the 702 GM V12...here's a couple of examples that have been done...A video of a speedster of sorts with one...sounds sweet...but I like the old hit miss engines poppin' off in the background noise better...
http://www.youtube.com/watch?v=1Fkmfcnt1SM

and the Blastolene B-702...
http://www.youtube.com/watch?v=BX_zDx-aiog

and some pics of the B-702...I think it was in Street Rodder mag too...not sure I'll have to look

BlackCherryImpala
08-12-2008, 10:15 PM
Man I just pic's and torque figures and lots of them.
Come on lay a few down please!!!

I have finally found some more info on the big GMC straight 6 engines. I still have not found any pictures.

707 is actually 706.9 cid
Bore 5.00 x 6.00 Stroke
Torque 630 @ 1200 RPM
HP 225 @ 2200
Truck Series 900 -970 gas

503 is 502.7 cid
Bore 4.56 x 5.12 Stroke
Torque 422 @ 1200 RPM & 455 @ 1000-1600 RPM
HP 200 @ 3000 & 255 @ 3200
Introduced in 1949, discontinued in 1959
Series 740, 750, 850 & 890 gas
(Higher torque and HP figures are from the 1955 and later engine)

477 is 477.1 cid
Bore 4.50 x 5.00 Stroke
Torque 382 @ 1000 RPM
HP 153 1/2 @ 3000
Introduced in 1941
Series 750, 850 & 890 gas

426 is 425.6 cid
Bore 4.25 x 5.00 Stroke
Torque 342 @ 1200 to 1400 RPM
HP 177 @ 3200
Introduced in 1939
Series 640, 640H, 720, 800 & 870 gas

360 cid
Bore 4.12 x 4.50 Stroke
Torque 297 @ 1000 to 2000 RPM
HP 155 @ 3200
Introduced in 1939
Series 620, 700 & 770 gas

I must have the 707. If you check, the Torque figures are the same on the GMC Twin Six or V-12 as on the 707 straight 6, 630. I think i will need to find a very old metro bus. What did that GM travelling future bus have in it that sold at Barrett-Jackson a few years back?
BlackCherry

patrick66
08-12-2008, 10:35 PM
Mopar never made a 413 inline, but the 413 B block V-8 were used in their own trucks and some Macks

NOT true! Mopar built an INLINE 413 inch straight Six, that was in Imperials and medium-duty trucks in the late '30s. It was the largest six that Chrysler ever built for road use. This is a great bar bet, BTW, or a rod show trivia question!

From allpar.com:

Larger trucks used another family of in-line flathead six cylinder engines. There was a 331 cubic inch and a mammoth 413 cubic inch lugger was available in the T series and up. There may have been another engine in the 370 CID range, but I am not sure about that. The 331 was highly regarded in trucking circles as a durable, hard working engine. The 413 was equipped with two single barrel carburetors and had a very large appetite for gasoline. It was noted for twisting the drive sprocket off the end of the camshaft.

Silent_Orchestra
08-12-2008, 10:39 PM
I have finally found some more info on the big GMC straight 6 engines. I still have not found any pictures.

707 is actually 706.9 cid
Bore 5.00 x 6.00 Stroke
Torque 630 @ 1200 RPM
HP 225 @ 2200
Truck Series 900 -970 gas

503 is 502.7 cid
Bore 4.56 x 5.12 Stroke
Torque 422 @ 1200 RPM & 455 @ 1000-1600 RPM
HP 200 @ 3000 & 255 @ 3200
Introduced in 1949, discontinued in 1959
Series 740, 750, 850 & 890 gas
(Higher torque and HP figures are from the 1955 and later engine)

477 is 477.1 cid
Bore 4.50 x 5.00 Stroke
Torque 382 @ 1000 RPM
HP 153 1/2 @ 3000
Introduced in 1941
Series 750, 850 & 890 gas

426 is 425.6 cid
Bore 4.25 x 5.00 Stroke
Torque 342 @ 1200 to 1400 RPM
HP 177 @ 3200
Introduced in 1939
Series 640, 640H, 720, 800 & 870 gas

360 cid
Bore 4.12 x 4.50 Stroke
Torque 297 @ 1000 to 2000 RPM
HP 155 @ 3200
Introduced in 1939
Series 620, 700 & 770 gas

I must have the 707. If you check, the Torque figures are the same on the GMC Twin Six or V-12 as on the 707 straight 6, 630. I think i will need to find a very old metro bus. What did that GM travelling future bus have in it that sold at Barrett-Jackson a few years back?
BlackCherry

The Futurliner used the GMC 302 Six, here's a link to the Futurliner site...

www.futurliner.com/index.html (http://www.futurliner.com/index.html)

victorsam
09-04-2008, 12:45 AM
Good day,
I am new here. Recently purchased a 1948 GMC ACR723. Overall it is really good shape and I am going to use it for some sort of project. I do not have all the details worked out yet but I do plan on maintaining the dual tires. I will probably run 22.5 low profile tires and lower the truck.

I am toying with engine choices. Currently it does have a 503 inline 6 that does run but I was considering a big block due to the mass of the tires and wheels. Other than that, there will not be much weight involved.

I stumbled onto this thread and site researching the motor. The guy I bought it from believes he replaced a 426 I6 with the 503, but there is a slight chance it was the other way around.

Is there a simple way to differentiate the 426 from the 503

BlackCherryImpala
09-11-2008, 09:49 AM
I know on the smaller GMC straight sixes there is a stamping next to the distributor with the cubic inches. I don't know about the big boys as I haven't had the opportunity to see on that close.

Fiorano
02-05-2009, 03:01 PM
where do you find these things? tractors or old trucks?
mmmm kinda makes me think of the old aero engined cars....

44todd
02-12-2011, 01:42 PM
Hey all.. I was doing some research on the GMC 477 motor and wound up here.
I bought the inventory of a local shop that opened in the 30s.
Included was an NOS box of Sealed Power brand piston rings marked GMC 39-48 477 motor standard bore. I'd like $75 anyone interested? Todd 218-208-2080