Medium Truck 366/427

[1969 GMC]

I have been thinking about the possibility of my orig. 350 dying, and it scares me...but anyways, has anyone put a med. truck 427 into their truck? Being for medium duty trucks, I'd think that they would have ok HP but great torque. I believe there was also a truck 366 that is a de-stroked? version of the 427, it applies to that too. Any pros/cons to this swap? Would it mate up to my sm465? Is there any aftermarket support for these?
My reasoning for this is, I have seen plenty of GM medium duty trucks with 366/427 in junkyards, and low-milers at that. I can't really afford a new crate motor. Plus, a 366 or 427 would be unusual in a pickup. any info would be appreciated, thanks

[Mike76251]

I myself love the old 427s.
It would be waay cool to see one in a truck
I bought a tall deck 427 off of eBay for cheap.
It came out of a old Chevy truck.

The only drawback to Big-Blocks is the cost of the parts versus Small-Block parts prices.

[1969 GMC]

another thing...what are the differences between truck/car 427's? thanks

[Mike C]

The tall deck motors are not a good choice for a light duty truck. The reason they went to tall deck on the 366/427 is to add a 4th piston ring. This increases friction, but allows the engine to be operated at continuous WOT in the large trucks it was designed for. The taller deck also moves the exhuast manifolds up and out causing frame interference in some cases. Also requires a special intake or adapter spacers to run a conventional BBC intake.

The cylinder heads on these trucks are small port for high velocity at low engine speeds and use larger stemmed valves with small heads. These larger stems allow more contact with the guide in order to better shed combustion heat, once again, for continuous WOT operation. The drawback is the larger stems are heavier reducing RPM before valve float and they reduce bowl volume and restrict flow.

Dollar per dollar, a 402 or 454 would be a better place to spend your money. The 402 crank combined with the 454 block gives you a standard deck height 427. Just make sure and have it balanced as the 402 crank counterweights are designed for the lighter 402 piston.

[SuperStock46872]

I believe that it all depends on what you want. If you want a high rpm screamer, then ditch the tall deck. But if you can get one cheap and would be happy leaving it bone stock, then they are not too bad of a deal. The tall decks will bolt in fine, there will be a few querks I am sure but that is with any engine swap. One area of concern would be the brakets, there are usually HUGE on these trucks, but you could figure some thing out. In stock form these motors are real torque monsters, but they fall flat on thier face at about 3500-4000. A lot of old grain truck jockeys swear a 366 will pass a 427 uphill anyday. But hey what ever floats you boat.

the best thing about these baby's is that you can find them all over out in the sticks, and most of them are original and untouched.

[Tom]

The bore and stroke of the truck and car 427's are the same, 4.25" bore and 3.76" stroke. The 366 is a smaller bore version [less then a 4" bore, on a big block! ]
THe tall deck motors are great if you want a stock motor with no mods thats normally governd to like 3500rpm OR if you want to make a massive stroker these blocks can handle it.

[1969 GMC]

Originally posted by Mike C
\ This increases friction, but allows the engine to be operated at continuous WOT in the large trucks it was designed for.

once again, for continuous WOT operation.

Dollar per dollar, a 402 or 454 would be a better place to spend your money. The 402 crank combined with the 454 block gives you a standard deck height 427. Just make sure and have it balanced as the 402 crank counterweights are designed for the lighter 402 piston.

Maybe I'm missing something, but what does WOT stand for?

Also, thanks for the info on making my own 427 w/ 402 and 454 parts, but 454's are almost nonexistent around here. If my engine ever goes out, I would like a cheap replacement. I suppose I could do a Caddy BB, but they seem to be all the rage now. Also, thanks for the replies.

[lukecp]

WOT= Wide Open Throttle, or when the engine is running at it's max RPM for a long time. Unless you are planning on racing the truck, and you can't find a 454, i don't think a 427 would be too bad of an idea. Since the truck is a 4x4, the gobs of low end torque should move you around just fine.

[1FaastC10]

also, you could ditch those 4 ring pistons for some with only 3 rings and use a longer rod. long rods are good.

[1969 GMC]

this swap is starting to sound more and more interesting...does anyone have any HP/torque specs for 366/427? thanks

[lukecp]

According to my '72 Chevy Resto pack, the 427 had these power4 numbers:

Gross HP: 260 @ 4000rpm Gross TQ: 405 @ 2600
SAE Net HP: 230 @ 4000rpm Net Torque: 360 @ 2600 rpm

So, the HP actually isn't that bad. Your stock 350 should have about:

SAE Net HP: 175 @ 4000rpm, SAE Net Torque: 290 @ 2400rpm

So, you should be picking up about 55hp and 70 ft. lbs. or torque. That should make your truck quite a bit faster. Also, all of those numbers were for trucks with points and restrictive exhaust manifolds. A good set of headers, HEI, and a good carb/intake should bump you up even more. Good luck!

[Mike76251]

Good thread indeed.....
I got that Tall Deck 427 to play around with it.
I really have no use for it.

The plan is a stroker with real long rods (to reduce side loading of the piston).
High-pin JE pistons is what I will "stuff" the holes with.
It should put out tons of torque.

I don't care how high it winds 'cause my tranny holds the engine under 5000 rpm anyway.

Eldebrock makes a nice intake for the 427 Tall.

I know the mounts were huge but standard BB mounts should work out nicely. I have a tig machine if they don't. HeHe

[1969 GMC]

Just curious, what ya gonna slap that 427 in Mike? Sounds like you are ready to have fun...I am just planning for the future, cuz the 350 is still runnin strong. But if somethin were to ever happen to it...hehe

[Mike76251]

Tough Question.............
I don't really know.

I have a bad disease, It has no name but the symptoms include wanting to build engines with no clear reason for doing so.
I am taking shots now. LOL

This '84 Silverado will not break down enough to keep me busy so I have to "import" projects like that.

I could hook it up to a Freon Compresser......... I think it would put out enough power to really get "things" cold in a Icebox.

I guess if I ever did anything with it I would put it in my Chevy Truck but I lapsed back into that "disease" late last winter and built a 383 Mouse Motor that goes in there first.

[Super Chevy]

i know were two 366's are, on in a 67 c60 and one in a 73+ c60 or 70

i could probly get the whole 67 cheap, has a eaton two speed rear, but no air guage or tach

i was thinking of putting that 366 in my 72

[1FaastC10]

SuperChevy, i think you'd be better off with a 350 or something different. that 366's small bores will shroud the valves a whole bunch, which is no good for any kind of performance.

[sbc350gearhead]

How much taller is a "tall deck" block....are there any other differences than deck height.....could it be milled to standard height? Just curious.

[Mike76251]

Originally posted by sbc350gearhead
How much taller is a "tall deck" block....are there any other differences than deck height.....could it be milled to standard height? Just curious.

I don't know about milling one down. It might leave you with too thin a head surface.
There is no real reason to mill anyway.
I like the tall deck for one reason.....It lets me use longer rods and that will decrease ring wear on the walls.
To make it short...the engine will last longer.

It takes a different intake for a tall deck block over a standard deck (or you could use spacers-but I wouldn't)
Some tall deck engines need a longer timing chain but there are several to choose from.

One thing about all this "non-standard" stuff on engines;
It all costs more.
If you have a set budget, do a 383.

If you like it different....like me....one call to Crower or ten other places will get you a complete bottom end for a tall deck block.
Not cheap by any means...but it can be had.

[jeffspower]

9.8" & 10.2"- For a difference of 400 thousandths. For a hard runnin motor for cheap, use the tall deck 427 (all of which I have seen are 4-bolt), a 454 crank, along with some .400 longer rods (6.535) that you can get new reasonably priced. This combo will use a standard out-of-box 454 piston of your choice. At standard bore you have a long rod tall deck 454- something GM should have built but didn't. I prefer long rod motors for torque & durability.

But hey, I am a Caddy 500 guy at heart, they have a taller deck than any automotive engine I know of, & a 6.752 rod. They easily take a 7" rod without putting the pin anywhere even close to the oil ring!

[Super73Cheyenne]

Can I use regular passenger pistons on my 427td? I'm using 6.535 rod but I want a piston that will give me the highest compression ratio available while still using 781 heads. Later I will change the heads. So how do I find out what the max dome I can use without doing the Plato or plastigauge trick. Isn't there a formula? Grumpys garage forum is to informative with to much opinion. I get list trying to find what I'm looking for. I'm building a simple 427 TD with 550 cam. So no opinions please. I got told by comp cams that by running a 850 double pump it'll bog on take off. I'm not running stock pistons. K.i.s.s. what are the piston specs I can use on my engine using 781 heads but keep in mind I'm trying to raise compression (if possible) so I don't have piston to valve interference?

[b454rat]

You can use regular car 427 pistons but not with stock rods. Use the longer rods and it will work. Would be a long rod 427. Never mind, thought 6.5 was stock...only had couple sips of coffee....

[Captainfab]

To use a car piston in a tall deck block, you will need rods that are .400" longer than the stock truck rods. I honestly don't know the exact length of the truck rods, but you will need a longer set to compensate for the extra deck height with the shorter car piston.

[b454rat]

All big blocks used the same size rods....just different sized ends and bolts.

[toolboxchev]

I too have found this thread interesting. If I could pick one up on the cheap with the other stuff you find in a med. truck it would be a go.

What the heck, When I did my SBC 7 years ago, someone asked who does those anymore?

I smiled...

[hans2]

7 years ago this thread was already 8 years old. They'd probably say the same thing about a TD motor now.