427 tall deck in a '70 C20

[Ol'Blue70]

I recently acquired my grandfather's 1970 Chevy C20. This truck originally came equipped with a 250, 4 speed, and a coil spring rear axle. I am wanting to modify the truck to make it more heavy duty (I'm wanting a truck I can pull a flatbed trailer with). I am planning on swapping out the rear coil springs with leaves.
I have found a good deal on a 427 medium duty truck engine. It comes with a good 4 speed. I know this isn't usually what people use when wanting to re-power these trucks, but I thought this would be a unique, high torque solution to fit my needs.

My question is: what all is required to perform this type of swap? Since these engines weren't offered in pickups, I know I'm going to have to fabricate some motor mounts. How about the clutch linkage? Another option would be to use an automatic. I know where I can get a TH400 for a good price, but I doubt it would bolt directly to the 427?

Thank you in advance for your ideas!

[LockDoc]

-
Welcome to the board from another Iowa boy.... I have never looked into this but I'm sure it is doable. If you want to read some threads on it type "427 tall deck" into the Google search box above, click on the circle in front of "67-72chevytrucks.com", and click on the Google button. Quite a few threads on the subject.

LockDoc

[El Dorado Jim]

sub'd

[Mike C]

Motor mounts same spot as a regular big block. The issue is exhaust. Less so if you run iron manifolds, but the higher deck moves the heads up and up completely changing relationship of manifolds to chassis.

In addition to the big block motor mounts, all of the clutch linkage is different for the big block manual trans truck and you need a high hump for the cab.

You should have no trouble pulling a flatbed with the coil springs. That's a lot of extra work.

[100%Chevy]

Recently traded my t.d.427.
It's the same install as any big block Chevy except for the extra block height of .40"
You can't use certain big truck exhausts on it with side mounts,but you may need to clearance the frame for the extra hieght.
It's an internally balanced engine,so any trans/flexplate.flywheel that fits a 350,396,427,etc. will fit just fine.454 and sb 400 flexplate/flywheels won't work because of balancing weights.Same with the harmonic ballancer.
It's a torque engine and that means it's not a high rpm engine.So you have to keep the rpm's down under 5000 rpm or it will blow!Most have a governor under the carb for this reason.
It will pull,but you're gonna go slow!
Mike.

[68is4me]

I don't see why it wouldn't be a problem some challenges might come up. The gm 572 motors are tall decks and plenty of people running them. I am not sure what would be different about the old td vs the new ones. Maybe different accessory mounting holes?

[Ol'Blue70]

Thanks guys!

I've set up a time to go look at it this weekend. It's been sitting for a few years, but the seller said he's kept a cover over it. If it turns over and there's no evidence of rodent infestation, I'll probably end up getting it.

What would be the best way to deal with the clutch linkage situation?

I'm hoping that the transmission mount location will be the same so I can use the stock driveshaft. My truck's original transmission was an SM465. Is that what this one will be?

[Mike C]

No difference between old tall deck and the 572. If you have $15,000 to spend on a motor, $1000 headers probably does't bother you. But if you are trying to swap a junkyard 4 ring piston 427 because it's a good deal, you probably do care.

I have a .070 over 4.25" stroke 427 I am putting in my Camaro. I too got a "deal" on it and wish it was a low deck but beggars can't be choosers. But I'm struggling to drop a grand on headers, but I will at the last minute before I swap the motor in.

[68Gold/white]

I will tell you all, what I know about this potential swap situation...
I had a 366 I got for free, it has the tall deck also, was going to swap it into my 67 C-10...decided not to...too much work.

1. The intakes are all Holley 4 Barrel intakes, unless you find a later 427/366 that's throttle body injected. Not sure on how big of a carb you can install on the stock intake, I never measured the throttle bore openings on one of the intakes. The intake has like a 1-1/2" bypass opening at the front of the intake.
That bypass is a problem... There's 2 types of water pumps for these tall deck blocks. The most common one I've seen is the "high" fan model. The center of the fan/water pump shaft is approximately on the same plane as the carb mounting surface. You couldn't run this deal on a normal vehicle, fan blade would stick above the hood about a foot. The high fan pump is common on school buses, for some reason.
The low fan water pump has the fan in the standard location as a normal pickup or car engine, no biggee, BUT, BUT there is a special adapter between the water pump and the intake for the bypass hook up. I've seen the low fan engines in dump trucks, not sure what else they might have some in.
You can use a regular car/pickup water pump on these engines. A friend did this, for a customer, but adapting the bypass to the intake was VERY ugly!!!

2. OK, you say you can buy adapter plates to use a car intake on the tall deck engines, YES, many folks make the adapter plates. BUT, BUT you will still have to adapt the water pump bypass deal, AND using the spacers means you will have to modify the distributor "stop", because the distributor sits quite a bit higher!!! Again, many folks make a slip ring to pit on a distributor for this purpose, I know Moroso does.

3. If you use headers, as mentioned above, the heads set .400 high on the block that a standard big block. You may have to grind on the frame for clearance, then you'd need to know where the collector's and the ends of the primary tubes end up on the particular headers you use. Many here say that headers design for pickup hang too far under the engine, and some have used car headers to remedy this ordeal. If that is true, pickup headers may do OK, I just don't know which ones would work.

4. If you can use a factory type water pump, you will need to likely use that monster big honk'n harmonic balancer, You'd have to make sure you had room for the pulley setup on the end of it. The factory water pump and thermostat housing use much bigger hoses, also. you have to have adapters made to get that to work. There's no choice on a different thermostat housing. The factory piece uses 2 thermostats and is pretty much a one and only part.

4. The oil pans I've seen on 366/427's were all either 7 or 10 quart pans. The 7 quart MIGHT fit in a pickup, the 10 quart sump is nearly as long as the crankshaft, it will not fit a pickup with a conventional cross member. I saved one I will try on my 396, when that day comes. A standard 5 quart pickup or car pan will bolt directly to the engine, you just need the appropriate oil pump and oil pump pickup assy.

As mentioned above the bell housing bolt patter and motor mount holes are same as car blocks, 366, 396, 427's were all internally balanced. Some of the later fuel injected 366's were not internally balanced, beware, not sure about injected 427's. So an internally balanced engine could use a balancer and flywheel/flex plate off of a car/pickup engine.

The 572 is a different deal. It has an intake made with a single thermostat. Not sure if a special distributor is needed, I'd think NOT, after all we are talking about a Chevrolet engine, not a stink'n ford or dodge...LOL There may be parts from the 572 engine family that could make this swap easier, question is how much $$$?

When the racing folks started making bigger cube engines, that tall deck 427's were in demand. The taller deck allowed longer stroke cranks much easier. Same deal could be done now...only takes $$$.

You are likely like me, hoping to make a go of it with stock type parts. It's tough, but can be done.
The factory cast iron intake doesn't look too spiffy, but it's a good piece. Might support 400 HP in stock form, more with some modifications
366 and 427's were built heavy duty with steel cranks and such so they could endure 4000-4500 engine speeds going down the road with a load on. They had to spin them that high to make the power.
This is most of what I know on this deal....

[Ol'Blue70]

Thank you guys for your help!

The issue with the clutch linkage bothers me somewhat, and I hadn't thought of the clearance issues with the fan (makes sense though). I'm kinda leaning towards not buying the 427.

As much as I'd rather not, I'm thinking the most economical thing would be to revive the 250 that's in it now. It had a very cheap rebuild a few years ago (reusing everything that wasn't completely wore out), but it was never started. It was kept un-covered in a shed until I brought the truck to my house. Now it's sitting in my garage waiting for me to decide what to do with it.

[68Gold/white]

Originally Posted by Ol'Blue70

Thank you guys for your help!

The issue with the clutch linkage bothers me somewhat, and I hadn't thought of the clearance issues with the fan (makes sense though). I'm kinda leaning towards not buying the 427.

As much as I'd rather not, I'm thinking the most economical thing would be to revive the 250 that's in it now. It had a very cheap rebuild a few years ago (reusing everything that wasn't completely wore out), but it was never started. It was kept un-covered in a shed until I brought the truck to my house. Now it's sitting in my garage waiting for me to decide what to do with it.

The 250 having never been started is a very good thing. You could (need to) take it apart, make sure nothing is in it that you were not planning on, such as dirt, mice, etc...go from there.
I have no interest in 6 bangers, as I assume you don't either, but a running pickup is a way better thing than one that's just a sitter...get it running make new and better plans. Neither my 67 or 68 have been running in years, that's NOT a good thing, the 67 is getting much closer though!!!!

What part of Iowa???