OT--Has anyone built a 377 sbc

I am wanting to find some one who knows about building a 377 sbc. 400 block 350 crank. Is there machine work neccessary? Is it just clearancing for rods? Do you use 400 rods or 350 rods? I know about main journals being different. I am not looking for an argument, just the facts. I could not locate this info after a search on here.

 

No tricky machine work is needed. The 350 stroke is shorter than the 400 stroke so it and the rods go into the block without a clearance issue. You just need the spacer main bearings. I think the most common piston has the pin location for the 350 rods. Check Speed Pro, Pro Tru,SRP, for piston info.
Smokey

 

Check with Speedway. They have complete kits with the correct rod bearings.

 

The spacer bearings come in couple different ways.
Some have just a spacer that goes into the block so you can use regular 350 main bearings. So there is four pieces on each journal
Some are a special thick main bearing. So there is just two pieces per journal.
Smokey

 

PAW used to sell 377 kits back in the day, and I believe Powerhouse can hook you up as well. I actually think this combo makes much more sense than the 383 motors most folks fool with...you get a big bore with a shorter stroke...essentially a "scaled-up" 327 (almost)!! Bearing spacers and "377" pistons are required, but aside from thet, they build up like any other small block.

(Just be sure to use 400 sbc heads, or heads with the 400 sbc "steam holes" drilled in them. The large bore 400 block will support oversized intake valves if you really wanna get radical, too!!)

 

I built one years ago ... some 400 blocks only have 2 freeze plugs instead of the normal 3 ... I used a 2 freeze plug block ... bored it .030 and installed a good set of heads ( for the time ) I used the factory #140 off road solid lifter camshaft. It sounded NASTY and really pulled hard ... from 3500 rpms on.

 

thanks, for the info. I have the block, a 350 steel crank, i beam rods and after market pistons, don't know about the brand names right now. Just wondering if I need to plan on buying rods, since obviously new pistons are in order.

 

If you're doing it just because you need a new crank in the 400, the main spacers/bearings will set you back more $ than a new 400 crank.

 

My 400 crank is good, my 350 block is good, just got a project and always wanted to build a motor that cranked some serious R's. What do the spacers cost? My mental plan is to go with a solid roller cam and roller rockers, which i have. I have a set of 202 double hump that have been ported, but need new vavles and seats. Thinking about getting those fixed or looking for some good breathing after market heads.

 

i've known 2 people qith 377s that they raced. Both of them ahd some problem with it burning a hole between two cylinders at the head gasket.. I have no clue why, but only saw it happen with those two 377s

 

The 377 is my favorite motor, I had one when I raced stock cars. I started out with a good two bolt (817) block and had splayed mains installed, found a good crank, j&e pistons, eagle H beam rods and an extremely worked over set of double hump heads. I also added a rev kit to the full roller top end. This motor was a screamer!! I turned about 7800 nightly with it. I eventually swapped the heads out for some brodix units and switched to alky which was good for 8500 nightly, probably ran that motor for 5 seasons or so (long time for stock car motor) until I switched to latemodels and got an aluminium 415 and 430. I ran the bearing spacers for what its worth, never had a problem with them. I think we quit running that motor cause we eventually just wore it out!! I think we ended up with a 60 over bore and sonic tested it and found it was too thin to continue to run. Good luck with the build, its a fun motor if ya like holding your foot way down!!!

 

Go with aftermarket heads if it's in your budget to do so. Dart (World Products) makes some good ones, or you can jump to Brodix and run a set of their 200cc aluminum heads...which would beat the pants off the old factory "double hump" heads! (Just drill the steam holes using a 400 sbc head gasket as a template).

Ask when you buy the heads, though....most major aftermarket companies will sell you the heads with the holes drilled already.

 

That is some very helpful info Fat Hack, so should i****semble with 400 head gaskets for correct cylinder size;

 

Yes...you need to use 400 sbc head gaskets on a 400 block...for bore size and for the "steam holes".

 

RHS is now offering the old Pro Topline castings again, they're a good set of aftermarkets also. I've got a set we had to fly from New Zealand because no one in the states knew who they were at that time. Enjoy that 377, they scream!

 

The 377 is a good combination just make sure you check your bearing clearance when putting it together. You should have the block line honed to make sure the mains are round and same size. With a thick brg you never know what your going to get for brg clearace. Also dont use main studs they*****ing*****.

-Eric

 

I have built a few. The easiest way to do it is with:

-400 block
-400 piston with a 1.560" compression height (stock height)
-350- 3.48" stroke crank
-5.7" Chevy or aftermarket rod
-bearing spacers or spacer bearings
-6" or longer rods will require a piston with the correct compression height.

I have run them on my IMCA modified because the 3.48" stroke is far easier on the tires on dry slick tracks. The whole steam hole thing has been beat to death, and in my opinion is does not matter what you do with them as I have run them open, and plugged them and it didn't change anything as far as cooling goes. It is worth building, but an .080" over 350 comes close without all the drama of the 400 block.

 

Drive em has it right..
400 stock pistons, 5.7 rod, 350 crank and spacers w/ 350 bearings.
My favorite combo with factory sizes.
personal favorite w/ non factory sizes = 454 small block ( big $s ! )
Dave

 

377's rock. I run one in my Late Model Stockcar.
My teammate is a machine shop owner.... an awesome shop all in his garage!!

We built the 377 in my car out of a bunch of pieces we had laying around.
Since we are "poor boys" we made our own bearing spacers.
We used a CNC block machining center to line bore the block std 400 size, then we instaled .040"(?) main bearings, and re-line bored the main line to std 350 size,with the bearings installed...notched them for bearing tangs. and its good to go. I got 4 races on our "experiment",
If you got the $$ to spend,I know that***** and EAGLE both make 377 cranks w/ the 400 main sizes to eliminate the need for bearing spacers.

 

Like Driv Em said; the compression height for 400 and 350 are the same, they just used a shorter rod with the longer stroke.

When drilling steam holes in heads please note; the outboard holes are drilled at an angle to catch the coolant by the plug. failure to do so will result in,,,,uh,,,,er,,,,Failure!

 

I knew a builder that wanted to build me one but my block was hurt so I moved on. He used 6 inch rods and said the engine had a long flat torque curve.
I too am still of the oversquare short stroke engine thought that was prevelant in the muscle car era.
I had a few Olds 400s back then and a short stroke 400 would stomp the***** out of the later long stroke engine.
Arguably the hottest thing on the street, the Buick stage 3, was hugely over square.

 

we have run a couple of them ,high rpm ,drag race application. You can use stock bearings with the tabs cut off for spacers and save some $$$.You do need good heads.

 

Ahh the 377. Not my favorite choice,just because of the 400 block dilema,although a good combo for an all around hot-rod. Here are the findings from my engine shop.The first pic is of the space saver bearing that will ride in the main saddles of the block. The second pic is the actual bearing that the crank will spin in. The 3rd pic is the two bearings as installed in the block. Notice that the imprint from the #2 bearing has etched a imprint into the #1 bearing. This tells me that using a soft**** bearing for a spacer is a bad idea. This type of spacer is a short term deal. We have made the spacers out of steel but that is not cost effective. If you choose to build a 377 I would recomend to use a 3.48 stroke crank with 400 mains. This is just my opinion and results from what we see in the shop. I hope it will help>>>>.

 

I just buy the thick bearings....work better in my opinion.

 

The 377 is also my favorite race engine.I've been running this setup imy front engine dragster for YEARS!7.90's on injected alky.7.20's on nitro.I can't kill it no matterd I try.Don't think you can go wrong with this set-up.

 

thanks for all the good and helpful tips on main bearings, thats the info i was looking for. I've found other people that have these questions, but usually everyone wants to tell you what to do. These are the answers i needed, before continuing.

 

Okay, dumb question...

Were the 377's in the Grand Sport Corvettes overbored 350's, or 400 blocks?

 

I don't know about the grand sports but in my race engine shop I build a 3-5/8th stroke 4" bore engine that hauls serious****. When bored 4.060 on the 5/8th stroke the magic # is 377. It's just another way to build one and it is my favorite combo>>>>.

 

does that have the same effect as destroking the 400 block, lots of r's?

 

I have better luck with the 5/8th stroke engines in 350 blocks. I've got them running on dirt tracks turning 8300-8400 RPMs nightly. And around here they will outrun the 377 on the 3.48 stoke. Some of these engines have run 28 shows a year and they are having there 5th season birthdays. I would say lots of power and plenty of reliability. Long and the short is they haul**** and there easy on parts. I sale the cranks out my shop>>>>.