Projects 1954 GMC Series 1

Late last summer I finally drug home mymown project again. It's a 54 GMC 100 Series 1. As you can tell it's a definite project. I picked it up from a friend, that lost it's storage place, and was under the understanding that everything was supposedly in good shape. The last month or so I've been able to start tinkering. So this is a rundown of the last few months.

He had already swapped out the transmission and rear end to get an open driveline. Trans is a Muncie 318 non Syncro and rear end was a 55T. After a few days of sitting in the neighbors barn I am borrowing a nice puddle of gear oil appeared under the rear end. Oh just needs a new seal. And since we are already dropping the suspension a bit the rear end had to come out anyway. Popped it open to find a brand new Yukon 3.88 gear set in it. But sadly the spiders were heavily pitted and edges very sharp. New ring would of been toast in no time. Found out very little exists for the 55T so into the scrap / swap meet pile it went.

I hunted around and came across a 9" out of a 80 Bronco. Got it cheap with 3.50s in it. Went thru it new seals, bearings, crush sleeve and had the axles redrilled to 6 lug and a set of hub rings to keep the load on the axle centers. And by the way in the process I found it to be a Big Axle 31 spline Big Bearing 4 spider (6 in total 2 axle gears and 4 spiders) so essentially bulletproof.

After seeing the mess the rear end was since it is oy 4 bolts, out came the Muncie. Popped the side cover off and my heart sank. Chipped teeth and the slider scored heavily and the OEM magnet was still inside and coated with a thick layer of fuzz. So.its now in the swap meet pile, as well as the late 60s Sag 3 speed that was with the truck as the retainer won't fit the bell housing.

So I figured what the heck know a guy with a S10 T5. Mine for a few Benjamin's and supposedly only has 30k miles on it.

So the carnage continues! The motor did run but it had a funny knock in it I assumed was just the open split manifold. But have borescope will travel. Pulled the plugs out and stuck the camera in #1 and once againy heart sank. At first all I see is deep gouges on the cylinder wall. A definite carbon ridge at the top of the cylinder wall, lots of.rust and pitting. But the heavy layer of carbon on top of the piston tells me this is a tired old motor. Holes 2,4,5,6 all were the same. Rust, vertical scrapes and rust and lots of carbon. 3 looked really good but was super wet inside. All the plugs were black and cokey. 2 of the literally looked like they were dropped on the ground strap and had almost zero gap the other 4 had decent gap but still super tight. Prob 20 thou if that gap.

So since I had done one in the past for a customer my brain was going to a V8 swap. Found Williams makes a exhaust manifold to solve the steering box clearance. The one I did in the past he wanted power steering sonit got a FJ power.steering box and a custom pitman arm and still had to reverse the drag link. This was on a 2 ton 51 GMC Wrecker. It got a V8 swap and still had to move throtpr to the pass side using block hugger headers. Not something I really wanted to do again and these Williams solved that.

Called a good friend to tell him to stick his parts finder "Bird Dog" to get busy and find me a V8 and an auto. He's like hey I happen to have one! Come get it for $$$. I run over to have a look, find he didn't have a transmission sonhendropped the price and we went back and forth but couldn't get the new price where I wanted to be.

But low and behold he's got the 270 sitting in the corner I dropped it in, a few years ago from the wrecker. He saw my eyes latch and laughed. So we made a deal for the 270 trans (Granny low first) and I have a motor again. It's supposedly a low mile motor. I drove the wrecker and it drove great with it, customer just wanted a V8 swap in it.

So now I'll have a 270 but going to get that S10 T5 to run behind it. Just need to sort out the clutch part of it, build a cross member and will have a solid runner for a fraction of cost and headache of a V8 swap and I have. A bunch of bolt ons already, Clifford 6=8 intake and headers, a nice new 390 CFM Holley Performance double pumper. And the nice linkage. And if I can find a source get a bumpy cam to toss in it. And if that 147 HP can break that 9" I have bigger issues. Lol!

 

Brings back memories. I bought a '54 Hydromatic 100 when I was 18. It had a 1970 300 hp 350 somebody shoehorned in it. Looking back, I really believe it was a 551st. I wish I still had that beat up truck.
You scrap pile sounds like my stuff.

 

A small update. Found a T5 that has low miles on a complete rebuild. Did the Jeep 10 spline input shaft swap, it had a few oozy seams so I split the cases, inspected, learned a few new cuss words, sealed it back up with ultra black, then cleaned it up and bombed some cast grey on it. (Had an awful flaky bug bomb black paint over everything) Oddly the cast didn't flatten out like the third member did but still looks crispy. Plan on running the stock shifter arm so I was advised to get a shift stop kit for it to prevent bending 3/4 up. Found a member on here selling nice ones and sent a message. Hopefully have the 248 yarded out soon and get the ball rolling on getting the 270 slammed in.

 

Oh and it's always nice to get a grin out of old Buffalo when you stop by and tell him your plans. He did give me some solid advice on my Clifford 6=8 intake to pressure test the water floor as they were notorious to leak. Mines actually been repaired before right under the carb. But it held 30 psi for over an hour. I think it's good.

May also pick up a set of his headers and ditch the Clifford header's see how much I can make selling all.tbr 248 stuff at the Monroe swap meet in may.

 

It sounds like that is going to be a pretty nice truck when you get it all squared away.
Your story sounds like some of my trials and tribulatrions 50 years ago when I was putting my 48 together to go to the Street rod Nationals in Tulsa while living in McGregor Texas.

 

I grew up building cars with the old man. He's having a hard time helping me as this onesy project and my actual first that has gone anywhere. We started a 65 VW together but the end goal was unobtainable of keeping it under $10k and the motor would eat half that. So it got sold and the guy who bought it has over $30k in finishing it. Lol.

My old man, He's always had a soft spot for 5 windows. The biggest argument right now is front suspension. Ready dropped the rear. Front needs down now as well. I'd honestly do a mustang Ii but again money $$$. So I probably do a Sids drop axle old man thinks springs and notching the pan will be better. I'm holding my guns for a Sids kit as at least I'll have the same pan to axle clearance and Sids kit is cheaper. Still gotta redo all the steering control arms.

We will see it thru. I've got my ideas what I want in the end, a truck I can drive down the freeway and attend my first national event at the good guys in Puyallup. If I figured gearing right I should be able to run 65 no problem with 3.50 gears, .85 overdrive and 30" tires.

Old man just wants to get it together and sadly he's never been known to cut corners. But he's got his ideas as well and given me a firm NO on a few of my ideas. (no tail pipe flame throwers, rats) but he is funding most of it. I bought all the new power train but he still holds the checkbook. Lol.

 

Ah you are over there in Wolley, Years ago I took summer classes for vocational teachers with a gent who taught auto mechanics at the high school there who also ran sprint cars.

It looks like if you have a .7 overdrive you will be running at about 1784 rpm at 65.
Calculate RPM for Given Speed(MPH), Rear Gear Ratio, and Trans Gear Ratio (purperformance.com)

If you don't know the ratios this list by trans number off the tag tells the ratios. Identification Key to Borg-Warner T5 transmission ID Tags (britishv8.org)

 

Sad with the layer of black paint it had and being rebuilt at some point the tags were gone or unreadable. It's a 91 NWC T5 and I believe it has the .86 OD in it so just a few more RPM at 2200 at 65.
I lived in Yakima for a few years going to JM Perry in the HVAC program 20 years ago. Amazing how different the school is now. Still got friends out in T Heights as well. I be passing thru this summer on the Hog on the way to Idaho for a our postponed HS Reunion. Camping at Hells Gate Park.

 

Other thing I have to sort is I have a Brand new Holley 390 CFM that was on the 248. Looking online it "should" no okay for the 270. But talking to Buffalo he said putna 650 on it and be done with the big Clifford intake and headers. That Holley is worth some $$$ maybe find someone to.swap for a 650 real Carter AFB or something. Or sell it and buy a AFB clone.

 

I like your project!! My son and I are building a 1950 3100. We are using a 1964 Chevy 230 and a Saginaw SM-326 transmission, but I am undecided on the rear axle. How well did your Bronco 9” fit? Was the width ok without having to narrow it? What wheels and backspace did you use? I’m watching your thread, thanks for posting.

 

Bronco rear end is about an inch wider both sides. But it still allows stock wheels to fit almost nicely. I don't know how wide the stock rear end was but the 55T looked super narrow under there. Fills the fenders a bit better. Haven't figured out what wheels I'm running yet or have the stockers widened and offset set up.

 

That 390 cfm will be fine on there.

 

That is fantastic!! Thanks for the good news!

 

Got the 248 out today and the carnage continues! Was told he put a new clutch in. Yeah a disk. Didn’t even machine the flywheel or replace the pressure plate. Flywheel has heat scoring and major cracks. Hopefully the one in the 270 is savable. One thing i found surprising is the pilot bushing is a Bearing! And its fried as well. Rear main leaking so the bell housing is a mess. Sadly i am done taking anything he said as done right. He was learning but darn man. Stainless bolts into cast iron. Those green coated bolts holding the clutch together and honestly nothing not even the flywheel was correctly tightened or torqued.

Now the big decision. Sids axle up front and deal with the mess redoing the steering arms. Or bite the bullet and dip into my reserves and put IFS up front. I put my foot down and no to the lowering springs up front as ive heard nightmarish results and having to notch the pan or have no front suspension travel. Current springs are sagged without the sheet metal on i could hardly get 3 fingers between the bump stop and frame. I already have 3” drop springs with the 9” swap in the rear.

I also ordered a new vin plate for it today so it matches the title. What was Washington thinking using the motor number for the vin!?! Lol

oh are the Big Truck and half ton bell housings the same? The half ton the bell housings have the angle where the bolts go in and the 270 came out of a 2 ton and the mounting pads are flat but haven’t seen if they just bolt on as the motor is still at my buddies.

 

You’ll lose the charm of driving the truck if you go IFS, besides it not being HAMB friendly.
I’ve a ‘36 Ford PU I put a Heidts IFS in. It’s taken apart waiting it’s turn to be put back together on a “regular” chassis I have. At the time it was going to be my “commute” and I lived about 95 miles from work. I got layed off and took it apart again.

 

As future info a 54 did not have a 1st or 2nd series. 55 did.
Your 248 bellhousing should be fine. I’ve been using them on 302’s for years. The crank bearings were open and I install a sealed one. I take the inside seal out an add some grease. The 270’s 4” stroke will give you plenty of torque.
Which head does the 270 have? Small ports of the last ones with the small combustion chamber work fantastic on the street with a larger port intake blending the first 3/8-1/2” of the head pot to match the intake manifold. Goodluck with your fun project.

 

@jimmy six the pilot bearing caught me off guard. All the kits and references all said it would be a brass bushing. So when i saw a bearing i was like

 

All GMC cranks I’ve had bearings. I see both are available in places like Rock Auto. I was able to use an electric motor bearing after a little research. I’m sure either would be fine.

 

Got both the 248 (one on floor) and the replacement 270 to the home shop today. Nicest day of the year so far, should of been on the Harley nope playing with greasy metal. Got the 270 on the stand so i can start prepping it for the proper color, chevy orange isnt working for me. Lol. I was told this motor was very low mile and after pulling the plugs looking inside revealed a slight ring of light carbon at top of thr cylinder. The valve cove looked brand new. Tops of pistons still fairly clean and Cross Hatching! Very visible. Pulled the valve cover and its spotless under there. Pulling the pan for a new gasket tomorrow hopefully the bottom end is as clean as the top. Got plenty to go with me to Monroe Swap in a few weeks.

note the old school dual exhaust mod on the 270. Should make for a neat wall hanger.

 

So far im stoked pulling the 70 down for clean and paint. Debating whether to have the side cover chromed or take it and the timing cover to my powder coater and put cast grey on it. Motor will be GMC Red.

but the cam lobes look brand new thru the fuel pump hole. Valve train is spotless and whoever’s set the valves needs a lesson waay loose.

Then got the new suspension pins installed. I bought a set of pins off Jegs and they were Posies Inc what I thought was quality. Put 2 new in the back a week later one broke right where the grease groove is. Talked to Posies said give Jegs this number and they will send you a new set. Well while doing the front another broke and one of the new ones on the back broke so 3 out of 4 new had broke right at the hole. Posies apologized and since i got them thru Jegs i had to get them to refund. Call them up sorry man 90 days no refund. Get Posies to sent you another set and you are probably over tightening them. Nope i am not torqued to spec.

So a call to General Spring and i got 4 from them made in India. So hopefully these don’t break.

now to figure out and get a Sids axle coming.

 

@jimmy six

head is a 2194819 same as the one i have on the outgoing 248. Glad the 48 had the intake rings. Pulled the manifolds off and about a tubes worth of orange RTV to not have them installed.

 

Going to need a speedie sleeve on the harmonic balancer its got a very wide worn groove in the sealing surface.

Plus i need to find a gasket kit for the motor. Ebay wants $$$ for it and cant find kits anywhere else.

also looking at the cam lobe does it look stock? Or do i have my dream lumpy cam. I keep finding more and more surprises. No history on the motor other its a low mile rebuild. Wish i could measure bore thru a plug hole. Lol. Would be awesome of it was a 292 bore.

 

Best are the best gaskets you can buy especially for the cylinder head.
292 is an odd bore for the 270. If done a long time ago and if it’s been bored I’m guessing standard bore sizes over stock because of ring widths and availablity.
If the cam has been made bigger on a regrind it will be marked. I can give you standard cam lift if you need it. Larger diameter push rods (5/16”) are a dead giveaway for a performance cam.
Sound crazy but a good crank grinder can put a new key groove 180* out and you can find TDC on your own and tape the balancer.
On my last GMC street build I bought a Tom Langdon late 292 converted balancer for the 3/8” belt.

 

A look inside now with all the tins off. Bottom end is phenomenal. Wish i could know how far its been punched out. Hard to measure from below. Pistons have a casting number of 2341508. That edge is getting fairly thin at the bottom of the bore.

Have a look at them can lobes. Hardly many miles o suspect. Still has that dull grey on the outside edges.


bores still have nice crisp cross hatching
4 and 5 have an oddity. Its below the top land so maybe some surface corrision from fuel or water? Motor has sat a few years. Why im resealing it all.

 

While I had my scope out and working again, i popped back into the 248 to get a better look at how tired it is. The one pic with the vertical heavy black line? Best I can tell its either a crack or a massive gouge.

 

The black line looks wide enough to be a witness mark for an oil ring. If it’s low in the cylinder it’s not normally a problem as that ring is for spreading out the oil not for sealing. If the second or top ring goes thru it that can cause wear.

 

Heavy black line looks more like a gouge, or deep scratch. A crack would seem narrower and not as wide.

On the cam, if you can try to measure lobe height vs base circle (sort of 90 degrees apart on same lobe), the lobe lift may give an indicator of the cam being more than stock or not. Or if you are removing the timing cover, might find something stamped on end of cam?

 

^^^ just checked 2 of the stock cams in my stash.. lift on each lobe was .270-.275” with digital dial not mics. The base circle is about the same appearing distance from the casting. Hard to tell on the top of the lobe since there is no good view but the lobe on the right looks pretty close to a stock ramp.

 

Paid a little visit to Buffalo since i was in Stanwood today for a Ham Radio Swap. Came home with one of his last sets of his Repop Nicson Manifolds.