377 chevy small block?

[450rboy]

ok in my truck i want to change my 400 to a 377. well the thing is someone told me summit racing has kit but i can seem to find it on there web site. but if anyone knows of a kit that changes a 400 to a 377. could you please tell what it is. i want to do to my engine cause i am pretty sure that engine needs a rebuild on it badly and because it will make my engine more reliable after i make it a 377. so anyone can help me please do.

thanks bye

[lorenjr83]

find a 350 crank buy 400 and 350 rod bearings, install both into the 400 rods and bolt them to the 350 crank! there you have it a destroked 400 or a 377

[Moded86R]

So you already have a 400 and you want to build a 377?

I don't know why you would want to lose that stroke and give up the torque.The reason why 377's are built is guys like the short stroke of a 350 with the big bore of the 400 for breathing reason's.There good motors to rev high.

You will need a 350 crank with special main bearing spacers.They do make a crank to do this with also.The 400 has a bigger main bearing than the 350.


If it was me I would leave the stock stroke 400 crank in it.More torque is always a good thing.

[450rboy]

yea you might have a high reving motor but lets say your stuck in a mud hole with a 400 and you just keep on reving reving and reving that 400. well you will probably just rev that thing till it blows up. a 377 though i shouldn't be losing any torqe. i might be loosing horse power but not much. the engine will be more reliable after i do this. and when i destroke it to a 377 i should be gaining more low end and it might make it torgier i aint sure yet.

but does summit have a kit?

[Moded86R]

I am not trying to be rude but your wrong.


A 400 has a stroke of 3.75 inch's.A 350 has a stroke of 3.48 inch's.The longer the stroke the more leverage the engine has on the crank and creates more torque.

Circle track guys and drag races run a 377 because the 400 has a larger bore and can breath better than the smaller bore of the 350.There are a few reasons they put the 350 crank in it.And none of them are to create more torque.

I think you should stay with the 400.I have a 400 I am putting in a 1970 nova.It has vortec heads and alot of stuff done to it and should be putting out around 400hp.


As far as I know there is no kit that you can buy.There are cranks made just for this.As well as pistons.You will have to pay more for the pistons and also have the entire rotating assembly balanced if you want to spin it to hard.

[chris46250r]

In a 4x4 truck I would take the 400 anyday over the 377. Take the 400 and punch it out to a 406 and put it back in.

[lorenjr83]

377's are torque monsters.

[bossman525]

Originally posted by lorenjr83
377's are torque monsters.
377's are not torque monsters. shorter the stroke, the more it will rev. 383 stroker is a good torque motor, but not the 377.

[lorenjr83]

they will put out almost the same torque, built right it can have more torque then a 383. but much faster revving then a 383. would be better for race car engines then a daily driver

[blasterfreak99]

Originally posted by 450rboy
ok in my truck i want to change my 400 to a 377. well the thing is someone told me summit racing has kit but i can seem to find it on there web site. but if anyone knows of a kit that changes a 400 to a 377. could you please tell what it is. i want to do to my engine cause i am pretty sure that engine needs a rebuild on it badly and because it will make my engine more reliable after i make it a 377. so anyone can help me please do.

thanks bye

so what exactly makes you think it will be more reliable??

[Rich250RRacer]

Originally posted by bossman525
377's are not torque monsters. shorter the stroke, the more it will rev. 383 stroker is a good torque motor, but not the 377.

Nobody mentions that a 377 can be built two ways. One as mentioned above, as a destroked 400. Two as a standard bore 350 with the 400 crank, you don't get a 383 until you bore the 350 .030 over.

[450rboy]

Well i have ran a 377 and a 400. the 377 had a lil more low end than that 400. yea but i am looking for a more reliable engine than an engine that i have a better chance of blowing up. the 377 wont rev like the 400 and too me thats a good thing cause you can just rev those to much and blow them up and the with a 377 it won't rev a high. i got a better chance of it not blowing up. and summit has that kit i found it. but it cost like 1000 dollars. i mean i could make it so that 400 wouldn't blow up on me for sure but you might spend like 4000 dollars. you would deffinatly need a stronger crank. to switch it over you need the 350 crack, bearings, spacers too, and connecting rods and a few other things too.

and i am looking for a reliable engine. well i know at a demo derbie i see 307s being used a lot and they are a 327 with a 283 crank in they and i have a 307 too and it probably has like over 200 hundred thousand miles on it and plan how much i beat that truck around.

hopefully you are getting my concept.



Originally posted by Moded86R
I am not trying to be rude but your wrong.


A 400 has a stroke of 3.75 inch's.A 350 has a stroke of 3.48 inch's.The longer the stroke the more leverage the engine has on the crank and creates more torque.

Circle track guys and drag races run a 377 because the 400 has a larger bore and can breath better than the smaller bore of the 350.There are a few reasons they put the 350 crank in it.And none of them are to create more torque.

I think you should stay with the 400.I have a 400 I am putting in a 1970 nova.It has vortec heads and alot of stuff done to it and should be putting out around 400hp.


As far as I know there is no kit that you can buy.There are cranks made just for this.As well as pistons.You will have to pay more for the pistons and also have the entire rotating assembly balanced if you want to spin it to hard.

[450rboy]

Originally posted by Rich250RRacer
Nobody mentions that a 377 can be built two ways. One as mentioned above, as a destroked 400. Two as a standard bore 350 with the 400 crank, you don't get a 383 until you bore the 350 .030 over.

wait a sec couldn't you bore it after you destroke it and then bore it out to a 383? ain't sure on this though

[Moded86R]

I don't understand why you think the 400 is gonna blow up.It doesn't matter what kinda motor it is.If it has junk parts in it then it's not gonna be reliable.


Alot of people think the 400 has overheating issue's.Mainly because they don't use the correct style head with the steam holes.Even though you don't have to have them if the motor is going to be run hard most of the time.

I know of guys that plug the steam holes and run without them and have no troubles.Those steam holes create a thin spot between the cylinder's compared to other small block blocks.But these are motor's in roundy round cars and strip only.

The 377 you "Ran"Was probably put togother better than the 400.Better matched parts.Also maybe it was put togother to make torque.If you built both engine's with similar parts the 400 would make torque lower in the RPM range.You don't have to spin it as hard and therefore it's easier on the engine.


If you want to build a 383 out of your 400.You would need to put the 350 crank in it.The bore it .030.Then you would have a 383.

I played with a 307 in my 69 truck.Pretty much a stock engine except a Comp 270h cam,Performer RPM intake,Performer 600cfm carb,HEI and exhaust.I used to spin that motor 7000RPM.Eventually it started burning oil and I exploded the clutch racing a hemi.I was winning though,