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Why would anyone build a 377?

112K views 121 replies 51 participants last post by  Aml383 
#1 ·
Just curious as to why anyone would take a sbc 400 and throw a 350 crank into it...

Is there a benefit here reducing torque this much or does it make for a high performance combo elsewhere?

What am I missing here?


Thanks guys!:)
 
#3 ·
my wifes Nova has a 377, you'd be surprised that you don't have to spin it all that high to make power. Two benefits to a stock block 377, first the stroke you removed will exponentially add to the life if the block when your in the 600 to 650 hp range. 2nd, the added bore helps unshroud the intake valve and improve air flow into the cylinder.

In an attempt to slow my wifes nova down to keep it out of the 9's we incrementally lowered the shift points 200 rpms at a time from 7400 to 6500. The car went faster each time. She now shifts 6500 goes through the traps at a tick over 7500 on a 9.9x pass at 134-135.

I guess you ask why would anyone build a 377, i ask why would anyone build an underperforming 500 plus inch big block. I guess it comes down to personal preference. Personally i like when my small block junk doggs on a big block car, let alone a big inch big block....
 
#54 ·
my wifes Nova has a 377, you'd be surprised that you don't have to spin it all that high to make power. Two benefits to a stock block 377, first the stroke you removed will exponentially add to the life if the block when your in the 600 to 650 hp range. 2nd, the added bore helps unshroud the intake valve and improve air flow into the cylinder.

In an attempt to slow my wifes nova down to keep it out of the 9's we incrementally lowered the shift points 200 rpms at a time from 7400 to 6500. The car went faster each time. She now shifts 6500 goes through the traps at a tick over 7500 on a 9.9x pass at 134-135.

I guess you ask why would anyone build a 377, i ask why would anyone build an underperforming 500 plus inch big block. I guess it comes down to personal preference. Personally i like when my small block junk doggs on a big block car, let alone a big inch big block....
I have seen some stout running 377's, but haven't seen too many naturaly aspirated daily driven pump gas 377's run down my underperforming 505's @ similar weight. Maybe in a light car, race gas, boost, or n20 but not Na, pump gas 377 vs 500'' NA BB pump gas at 3600+ lbs no exotic parts.
 
#117 ·
yes They were all the rage in the late 70's and 80's. with steel caps and crank you could rev them to 7000 rpm all day. i just bought a barn find 68 tubbed el camino with a 93 octane 377 nitrous motor. no nitrous on a chassis dino made 358 hp @ 3200-7000 rpm and torque was modest with a solid roller and 230 cc brodix heads.some one put about 9-10,000 $ in this sb.i am going to pull it for 406 blown sb. also a 93 oct. motor. i love brutal tork but hearing this 377 scream when you play is awesome. after i get it on a stand and see whats its make up is i believe its going in my 1800 lb. monza with a blower and hydraulic roller cam for street toy
 
#5 ·
My uncle raced dirt track in the early 90s and used 377s because he was told (and felt it afer he used them) that they were high revving and good torque in the high RPMs when taking turns in dirt tracks since you stay in the throttle taking turns alot.

The only thing he did not like was the extra parts needed..oversized bearings and the weight on the back of the crank.
 
#6 ·
I did that for somebody once, for a dirt track car actually. Couldn't talk him out of it.

He basically spent extra monay to take power away from his 400. He figured that out when he got beat consistently by 400s. He ESPECIALLY got beat coming out of the corner. Running the high line to keep the RPMs up wasn't always the fast way around, and he would get beat coming off, every time. He told me later that he regretted not listening when I warned him that would happen. Common sense should have told him that 7% less power, at maybe 200 RPM higher, doesn't somehow make a winner.

The only time I can see that it makes sense is if you are CID-limited by class rules or some similar circumstance. As far as I've been able to tell there is no advantage whatsoever otherwise. For most people who do that, they are merely using their own money as the weapon to shoot themselves in the foot with.
 
#20 ·
And its a bolt budget together...You can use off the shelf 400 pistons, 5.7 SBC rods, and all you need special are bearing spacers.
I think 377's are a throw back to the days when there weren't readily available after market heads for the SBC that would really support the flow requirements of a 400+ SBC in the upper RPM band or the bottom end parts needed to make a long stroke SBC live a long happy life.
Its a throw back from the 1980's to the early 1990's.
Yeah, back in the "pre-aftermarket" days, it might have made some degree of sense.
But, whatever reason there might used to have been back in the days of our near-forgotten youth, there's not much reason to build one now. ;)
I agree. Once upon a time, there wasn't a lot of "institutional knowledge" about how to build a 383. A 377 was nearly the same displacement.
 
#39 ·
And its a bolt budget together...You can use off the shelf 400 pistons, 5.7 SBC rods, and all you need special are bearing spacers, about $70.....My budget 377 with a flat tappet .550/.570 solid cam and Dart Pro 1 215 went 10.80's all day at 3200 lbs...

Steve O.
The math doesn't work out on stock 400 pistons, 5.7 rods and 3.48 stroke with out decking the block over 1/4", .275+ to be exact. Decking the block that much would structurally weaken cylinder deck. Using a 6" rod would be quite feasable though. Especially when you look at the desirable attributes a longer rod brings into the equation.

9.025 Deck height
-1.740 1/2 of stroke (3.48)
-5.700 Rod Length
1.585 Piston Comp Height
 
#11 ·
It's amazing how many folks believe that the 1/4" shorter stroke somehow makes this a rev queen. I don't know that I've met anyone that took out a 377 and replaced it with a similarly built 400 and didn't go faster, spinning it to about the same revs. Build ia 400 like a truck motor and it will act like a truck motor, build it like a race engine and it'll act like one.
 
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#12 ·
a friend of mine used to run stroked 400's up to 430 cid or so. He would have to grind the block to accept the crank, cut the skirts to accept the rods and then shave the rods to accept the cam.

He was running a big fogger system on top and was running high 9s at altitude, (4500) feet. The block would get 50 to 80 passes and then have to be torn down.

It was fun to watch the process of putting the 400 together. He runs BBC's now, pretty much put together the same way. He moved to Washington and runs in the 7s and 8s now. I wish I still had a picture of his 68 camaro
 
#13 ·
destroked 400's used to be the ticket for the 3/8 mile high banked clay oval "dirt" track at east alabama motor speedway in phenix city al. some folks would even put sleeves in the blocks for smaller pistons. those motors got plum angry out of the corners !! they did used to have problems clearing tech afterwards on some of them though. am sure they would get a big body heavy chevelle moving pretty quick too sans tech inspection. now a days those good ol boys run the gm crate motors for the most part.
 
#119 ·
It goes back farther than that, to 1962&3 in the Corvette GS's with the 377 engines in Nassau - then 1967 with the Z/28's in SCCA in Trans Am Racing & NASCAR in it Baby Grand National Regulations! Been Using destroyed engines most of my life, since 1968 until now and I'm 72 (73 next month) albeit I don't Drag Race - I prefer Road Racing like Watkins Glen and Oval Tracks, where a Light Vehicles With High RPM's prevail! I may be a Dinosaur but I have raced against some of the best and always did well doing it!
 
#14 ·
The only time that I would ever de-stroke an engine would be if I were running a weight per cubic inch class. You can get a higher horsepower per cubic inch with a big bore, short stroke engine. Other than that, I just like to build them big.
 
#27 ·
We've built and run 383" and 377" small blocks and, IMO, most of the generic statements made about the two combinations are misleading. I quoted several statements below that are valid based on our experiences running both combinations.
If you look at strict lbs/ci classes, they tend to be dominated by small ci engines, because you can make more hp/ci on small engines than on big ones.

... Build a 400 like a truck motor and it will act like a truck motor, build it like a race engine and it'll act like one.
This tends to be true regardless of the engine size. Our last 383" (4.030" x 3.750") launched at 7000 and shifted at 8200.

...The only time I can see that it makes sense is if you are CID-limited by class rules or some similar circumstance...
For some of us, it's an ego thing.:D

...the added bore helps unshroud the intake valve and improve air flow into the cylinder....
This is the primary advantage to using the big bore/short stroke combination vs the small bore/long stroke. For example, the 2.180" intake valves in our AllPro 245RR heads on our 381" (4.165" x 3.500") engine require at least a 4.125" bore to achieve the flow (and consequently the hp) that the heads are capable of.
 
#15 ·
I think 377's are a throw back to the days when there weren't readily available after market heads for the SBC that would really support the flow requirements of a 400+ SBC in the upper RPM band or the bottom end parts needed to make a long stroke SBC live a long happy life.

Now days, there are heads and bottom end parts to support lots of cubes in a small block and toi make it live a long happy life. IMO there is no need to give up cubes to go with a 377 unless there is a class rule or restriction on heads or blocks.
 
#16 ·
Its a throw back from the 1980's to the early 1990's. I remember it was common practace to de-stroke 400's and 350's for higher RPM but it's not something done today. Heck you could buy a 377 from PAW at one time; I don't think they sell them anymore.
 
#17 ·
I built a 377 back in 1972 for my '70 El Camino. It was hard to get stock 400 rod bolts to live and there weren't a lot of aftermarket cranks then. I sent my steel 350 crank with a spun bearing to Reath Automotive and had them weld it to fit the 400 mains. When I got it back it was a work of art that would have looked good on the mantle. I used stock 12.5-1 (64cc heads) 400 pistons with 5.7 rods and 77cc heads that work reworked by Booth-Arons. It had an actual 10.2 compression and needed Super Shell or Sunoco 260 to run without knocking. It was the hot setup in 1972. We had a brand new extension of a super highway here and we snuck on before it was open. I hit 6200 rpms with a 3.08 gear. Somewhere around 150 mph, not bad for a 2 ton+ truck.
I think there are much better combos now but in 1972 it ran!:thumbsup:
 
#18 ·
Yeah, back in the "pre-aftermarket" days, it might have made some degree of sense; in which case the OP's question would have been something like "why did people used to build a 377?"

But, whatever reason there might used to have been back in the days of our near-forgotten youth, there's not much reason to build one now. ;)
 
#21 ·
Instructions in the Chevy "Green Sheet" manual suggested building a 365 CI engine with 4.125" bore and 3.4" specially made crank. Rational thinking would normally move this recommendation to use a stock 350 crank and find some way to put that crank in a 400 block. Once that problem was solved, it seemed like a good choice to add 27 cubes to a 350 with better breathing and have the advantages of a forged, nitrided $70 crank.

I've always been at a loss to understand the logic behind the 377, at least with the availability of parts today. Why not get about 10% more torque for the same money? That's like getting the torque advantage of a solid roller for free.
 
#22 ·
We were using them for circle track cars for a couple of reasons. On a tight corner track we would get allot of tire spin coming off the corners. With a 377 we would give up a little torque to help the tire spin and hope that we could pull them down the straights.

Also there are 400 blocks with the same number of freeze plugs as a 350 block. So looking at the motor in the car people would think it was a 350. Yes we cheated a little with the cubic inches.

In my chevelle I run a 377. I like this combination for its fun factor. Drive it like you stole it.
 
#24 ·
On problem is you have 20 plus replies but only 3 people have personally run a 377, the rest either heard of someone, or are going off what they read. Your poll would reflect opinion, not real world experience....


377's are still being built with aftermarket blocks and cranks, especially in Turbo applications where a larger bore but shorter stroke is beneficial. My friend who own a well know cylinder head shop has built a 15 degree 377 with a single 106mm turbo that has been in the 6's at over 200 in a 10.5 S10 pickup.
 
#25 ·
I built a 377. Started with a bare 400 block, so my engine builder suggested why not try it. The crank cost the same as the 400 would have, but I got it with 400 mains, so no bearing spacers. Personally I look at it as more of a big bore 350.
 
#26 ·
I built one back in the day for two reasons

1 I had a good 350 crank and a 400 block

2 It was going in a 89 camaro with a 5 speed and I didn't have a 400 flywheel.

So took what I had and made it work. btw I had a buddy build a 383 with same cam and intake and carb in about the same year camaro his was a auto we raced alot it was who ever got hooked up first that would win.
 
#28 ·
I have a 377 with vortec heads and a 256 @ 0.050 SFT cam. It runs 12.0 at 110. Nothing spectacular about that. Other than I built the short block in 1996 and the oil pan hasn't been off since. So I think that debunks any worries about the bearing spacers.

Mine has TRW forged FT pistons that are super heavy, like 630 grams IIRC. So the high revving notion with this combo comes at a price of having heavy pistons. There are lighter pistons today I'm sure, but like the OP asked....why????

PS - I built mine to reduce the low end torque so I could have a better chance to launch my truck (69/31 weight bias). I now have Cal Tracs bars that hook awesome (1.63 60') and I wish I had the 3.75" stroke now.
 
#29 ·
Short stroke big bore engines behind a stick are a blast. Built one of these with a set of track 1's many years ago and put in a 67 Nova SS. 2nd gear would kill you, 3rd you $hit your pants, and 4th was just FUN... The Chevy 302 by some is said to be the funniest engine GM ever made...
 
#31 ·
You all forgot about the other 377. Stock bore 350 with a 400 crank... 4.00 + 3.75 = 377ci.
 
#36 ·
Now this is a combo that has a place.

I have made 900 rear wheel horsepower (that is over 1,000 at the flywheel) with a 4.00 x 3.75 stroke combo. The smaller 4.00" bore when using an aftermarket block leaves a really thick cylinder wall that seals up a lot of boost real well.
 
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