Visit The Dirt Forum for More Information

Author Topic:   how do you build a 377 ?
m33mcg
Member
posted November 22, 2004 05:15 PM
I have a couple of question about building a 377. I just purchase a chevy 400 engine. I took the heads off and noticed it had .30 piston, there was little to no cylinder ridge. How far can a 400 be bored? is .40 too much? If I can go .40 over how long of rods can I go with, or is 6" rod the way to go. what piston should I use flat top or dome? would like to get arould 12.5 to 13.5 :1
Thanks for all the help, Mike


engineman
Member
posted November 23, 2004 02:06 AM
quote:
Originally posted by m33mcg:
I have a couple of question about building a 377. I just purchase a chevy 400 engine. I took the heads off and noticed it had .30 piston, there was little to no cylinder ridge. How far can a 400 be bored? is .40 too much? If I can go .40 over how long of rods can I go with, or is 6" rod the way to go. what piston should I use flat top or dome? would like to get arould 12.5 to 13.5 :1
Thanks for all the help, Mike


ok, you left this wide open, but to answer some of the basics…..here we go.....

First, it is my opinion that if an engine has ANY wear on it, I go to the next size so I can get the cylinders round. In your case...on a small block 400...yes you can safely go to a .040, and if it's a .030 now...have a good machine shop put the torque plates (or plate) on it and hone it to a .040.

as far as rods go....again..in my opinion, I would use the longest rod you can afford to put in the engine.
A 6" rod would be the easiest "long rod" to get in it because pistons for a 4.165 bore,3.48 stroke,6" rod combo are sold everywhere!

As far as pistons go, depending on the heads you use.....well... I would lean towards flat-tops....if you can get the compression out of them you need.
Flat tops work better for reasons I would need this whole web-site to explain, but if you need more compression than flat tops offer, go with the shortest dome you can to get the compression you want.

NOW here's my question.....why build a 377 if you have a 400 crank and block? just wondering...I hate giving up cubes

Maybe this will get you started in the right direction

------------------
Mark's Racing Engines

(903)883-0196

www.northtexasracing.com

engineman@northtexasracing.com


m33mcg
Member
posted November 23, 2004 06:06 AM
Engineman, thanks for the input. Our track turns dryslick very quick and I have been told that the 377 would work great, do to its shorter stoke. I beleive I can run a taller gear with the 377 which will help get out of the corners.

What would be your opinion regarding a 408 over the 377. I understand engines but I am no expert in these matters. I would rather build chassis and drive.

Thanks again, Mike

stockcar5
Member
posted November 23, 2004 11:00 AM
i love the 377 on a dry track...the 406 is good for big tacky tracks. all depends on the driver i guess.

------------------
www.geocities.com/dirtstockcar5


21racer
Member
posted November 23, 2004 08:27 PM
i have 377 and 400 both good motors 400 makes more torque i can tell by driving them i also have a dyno program on my computer i ran both a 377 and 406 and found both to have the same hp with the same parts the 406 made more torque about 40 lbs more


engineman
Member
posted November 24, 2004 02:28 AM
quote:
Originally posted by m33mcg:
Engineman, thanks for the input. Our track turns dryslick very quick and I have been told that the 377 would work great, do to its shorter stoke. I beleive I can run a taller gear with the 377 which will help get out of the corners.

What would be your opinion regarding a 408 over the 377. I understand engines but I am no expert in these matters. I would rather build chassis and drive.

Thanks again, Mike


OH BOY..Here we go AGAIN with the Torque vs. HP argument

so I will give you my thoughts and you can take them for what their worth.

first, understand that there are sooooo many variables left out here that it would be impossible to give you a solid answer.
Track length, track condition, car weight, tire size & compound, gear ratio, engine RPM range, driving style,ect... all influence the answer to this question.

BUT in GENERAL if the track is real dry and you cant hook it up, the torque from a longer stroke (3.750) might hurt you by blowing the tires off. In this case the shorter stroke of a 377 might help if you were running the same gear for both engines.

However...you can also run an engine with more torque (tha 400) and adjust the gear ratio to match (I.E. higher gear). This is what I like to do for short tracks. This will keep the tire spin to a MIN and pull real hard down the straights without a bunch of unnecessary RPM.
I'm NOT saying you should gear the car so that it "lugs",just gear it so it don’t "buzz" the tires every time you "stomp" the throttle.

Now understand...this doesn’t apply to everything, I'm just trying to give you some things to "ponder" over.

Good luck!

------------------
Mark's Racing Engines

(903)883-0196

www.northtexasracing.com

engineman@northtexasracing.com


modfan
Member
posted November 24, 2004 10:41 AM
Its kinda funny this torque vs horsepower arguement. Considering your not comparing apples to apples. Torque is actully a veriable of horsepower along with speed. the formula for horsepower is torque X RPM/5252. The way I look at is I want all the torque I can get then adjust my gearing according to the track


engineman
Member
posted November 24, 2004 12:28 PM
quote:
Originally posted by modfan:
Its kinda funny this torque vs horsepower arguement. Considering your not comparing apples to apples. Torque is actully a veriable of horsepower along with speed. the formula for horsepower is torque X RPM/5252. The way I look at is I want all the torque I can get then adjust my gearing according to the track


you are exactly right...(and so is your math )
And that’s basically what I'm saying...assume the 377 and the 400 are similarly built , the 400 is going to have more torque in a lower rpm range than a 377...simply put, you will have to twist the 377 to a higher rpm to get the same amount of "work", and "theoretically" the 400 should make more torque AND HP throughout the entire RPM range.

I'm with you modfan, I like all the torque I can get, and gear the car accordingly.


------------------
Mark's Racing Engines
(903)883-0196
www.northtexasracing.com
engineman@northtexasracing.com

[This message has been edited by engineman (edited November 25, 2004).]

dirtbuster
Member
posted November 24, 2004 02:06 PM
Hp is a function of torque. When you dyno an engine you dont actually measure HP you are measuring the torque produced and then you calculate HP. Therefore the more torque produced at a given rpm the more HP at that rpm. That is why a 406 and 377 may make the same HP even though the 406 is producing way more torque, the torque comes at a lower rpm, whereas the 377 may not make as much torque but it is offset with more rpm it makes the same HP. As the 406 turns more rpm it runs out of airflow and torque really starts to drop off which then means less HP. If the 406 doesnt run out of airflow then yes theoretically it would make more HP all across at all rpm ranges, but more often than not the 377 will breathe better at high rpms possibly making more torque and also turning more rpms. That is what contributes to its ablility to make the same HP, but be down on peak or midrange torque.

In the end you still have to gear the car to your engine, no matter what it is. There are advantages both ways, just depends on what you want to do with your money.

modfan
Member
posted November 24, 2004 07:19 PM
The only things that will affect air flow are the cyl. dia, piston speed, cam profile, head ports, and intake ports. This being said if both motors are identicle except stroke and you could keep the bottom end together. The 406 will make more hp and torque to whatever RPM you turn it to. The difficult part is keeping the bottom end together at the higher RPM. After the cam reaches peak efficiency both motors will taper off in power.