TaKtIcAl

Basically whats involved with doing this? Also if I use a 78cc head with stock flat top pistons this will yeild a 9.5:1 compression ratio..correct. I want to do this build but would like any input from those who have done this or someone who has a little info about it.

Polecat

You will need a good 350 crank, and the spacers for the mains. You can get them out of Jeg's.
But a 377 is a great upper RPM motor, and I would hate to see you hold it back with stock heads.Most stock heads are in the 76cc area and will give you low compression, and not offer much in flowing capabilities.
If you decide to destroke the 400, I would seriously look at a better set of Sportsman II's or Dart Iron Eagles.

happy building.

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350 4 bolt main, Speed-O-Motive 383 stroker kit, re-sized rods ground for clearance,TRW Forged pistons,10.7:1 compression,HPC Coated RPM intake, Speed Demon 750 cfm carb,World Products Sportsman II heads,2.02/1.60 valves, Comp Cam 1.6 roller rockers, Comp Xtreme 284 cam,240/246@.050 with .540 lift,Crane pushrods,ATI damper,Proform HEI and MSD6A box,HPC coated 1 5/8 headers, 2.5" exhaust with 40 series mufflers,TH350 with B&M 3000 stall, Powertrax NoSlip Locker, 4.11 gears.

Hurtin4Hp

I think it was Car Craft that did an article on a 377 a few months ago. Actually they were comparing a stroked 350 (383) to a destroked 400 (377). You might try to dig up that article for some tips.
If you can't find it I probably can so let me know.

The ODB

polecat is right about the heads.
The destroked 377 is a low piston-speed/low-velocity engine and will only come into it's own at higher RPM's. That means you will need great heads to make it shine. 9.5 compression is very low for a high RPM engine. You'll want some aluminum heads with 64cc or less chambers.

In all it will cost more and be more of a pain (with a street setup) to go with the destroked 400 than it would be to build a stroker 350/377.

The only major advantages to the de-stroke combo is that you can run longer rods, and you can get steel cranks much cheaper.

ODB

TaKtIcAl

Didnt GM plan to do a production engine like this at one time? Also, the 383 is a torque monster, but built properly wouldnt I get decent torque out of the 377 to0, coupled with the horsepower?

The ODB

Yes you can, but that works both ways. I get great torque and horsepower from my stroker 383 & shift at 6300. I consider my engine a low-rpm torque engine.
To take full advantage of a short stroke you want to spin up closer to 8000 rpm.
Either way the cubes are there and both can be made into super street engines. I just personally prefer the extra leverage the stroker offers along with high flow velocity. Higer piston speeds let the engine make maximum power at a lower RPM.
For example, my stroker 383 would flow more CFM and build more cylinder pressure at 3000 rpm than an equally built destroked engine at the same 3000 rpm.
On the other hand, making torque at a higher RPM automatically means higher horsepower numbers. There are other headaches & costs that come from high RPM operation though.

ODB

GOLD85

Chevy High Performance had an artical comparing the 377 to 383.i see the point of building a 377. i mean a happy reving motor with a big bore to unshroud the valves but dont see the point of building a 383. i mean i wanted to build one for a while but my buddie convinced me to build a 400. i mean its the same stroke so the torque numbers would be the same between a 383 and a 400. but as i said befor the 400 block hase a bigger bore to unshroud the valves therefor giving more HP and more than likeley some torque. can some one explan to me why they would build a 383? ODB purhapes. If i was building a 377 i wouldnt reduce its air suply whit crapy stock smoger heads. get some AFRs or TrickFlows or somethin

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when the green flag drops the bull$hit stops

Curent: 350,performer RPM intake ,650dp, 700r4, headers, 3inch exhast
Spring 01: 406, Comp 282 solid cam, 2400 stall converter, every thing else the same.

R.I.P #3

[This message has been edited by GOLD85 (edited February 20, 2001).]

TaKtIcAl

Well its an oddball motor, not many resources on the net either, however, I think it has the potential to be a good motor given that its built right. Using longer rods would slow the pistons a bit. What kinda cam do you think would go good in a buildup like this?

burnoutrpm

why a 377?? on the street you really cant tak full advantage of the winding rpms possible on that engine!!! THERES NO REPLACEMENT FOR DISPLACEMENT keep the 400 crank you'll build wayyyyy more power and tq!! also the setup you mentioned isnt enough for a 377 wont even touch the surface of the engines possiblities!! as for a cam for the engine man the one you would get the most results with wont even run decent on a street engine! if you do bulid it just make about 10:1 compression, and put a decent carb, cam, and intake on it. also add some sportsman2 or afr's to it for heads the smogers suck trust me!!!

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1989 firebird formula

Mods: converted from T.B.I. to a carburator 305 to a 350. Flowmater exhaust,hedman shortie hedders,202 160 (882) heads,.447/.447 lift 222@.050 duration speed pro 327/350hp cam 350 .40 over (356) edlebrock performer rpm intake and a 600 edlebrock manual choke (1405) Proform H.O. distributor slightly revised 700r-4

Future mods comp extreme energy roller cam, world products sportsman 2 heads, msd 6al ignition, billet distributor, blaster 2 coil and a 406 engine is in the works soon!!!!

BadSS

Not being confrontational here. I've been building engines for years and I've yet to understand why someone would want to destroke a 400,, unless the 3.75 crank was fried,,, and you had a 3.48 crank laying around. I mean I've used a 3.25" crank in a 400 block for cube limited circle track class. Maybe if I was running in a cube to weight class I'd run a "destroked" 377. It's just,, I can see stroking a 350 for added cubes,,, I just have a hard time understanding why someone would want to drop 30 cubic inches and LOSE the torque "destroking",, if they didn't have to.

TaKtIcAl

So is there anything good to say about this motor? Any benifits to it?

Polecat

Well, I think the benefits are mentioned. It's a high revving motor. And yes it does make good low end, but not as much as a 383 or 400.If you have all the parts for a 400, by all means build it. But 400 blocks are getting harder to find. That's why 383's are getting so popular.Get as many cubes out of the motor you have.
That's why I chose the 383 route. To buy a good 4 bolt main 350 was cheaper than a ratted 400. So for the extra money between the two, I spent it elsewhere on the motor.

If you have a light weight car, or like and S10. I would see the 377. Because it's not heavy, so you can rap it up pretty quick. On a heavier car, go cubes.

Happy building.

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350 4 bolt main, Speed-O-Motive 383 stroker kit, re-sized rods ground for clearance,TRW Forged pistons,10.7:1 compression,HPC Coated RPM intake, Speed Demon 750 cfm carb,World Products Sportsman II heads,2.02/1.60 valves, Comp Cam 1.6 roller rockers, Comp Xtreme 284 cam,240/246@.050 with .540 lift,Crane pushrods,ATI damper,Proform HEI and MSD6A box,HPC coated 1 5/8 headers, 2.5" exhaust with 40 series mufflers,TH350 with B&M 3000 stall, Powertrax NoSlip Locker, 4.11 gears.

Box of Rocks

Tactical Warfare,

I'm in agreement with BadSS here - why build a 377 instead of a 406 ?

In terms of streetcar performance (say, 6,500 rpm), all it does is knock off 30-35 LB. FT. torque.

That's exactly what you don't want to do in a street car. If you can find a 400 block, have it sonic tested, bore it .020 over, stab in a good roller cam with heads, and boogie.

If you're on a budget, use a 4-bolt 350 block to build a 383. Scat crank, 4340 rods, good cam and heads = 520 HP.

What else do you need? The 377 makes sense to me only for restrictions in class racing, where you're limited by displacement, or for super-high RPM application.

Neither of these scenarios applies to street cars. Just my opinion.

BOR

Grim Reaper

Add my vote to NOT destroking a 400 to a 377 unless there is a reason that you HAVE to.

In that Car Craft article, there really wasn't that much difference between the two motors as they were built virtually identically (same heads, cam and rods).

The 383 definitely made more torque and much lower than the 377. The 377 didn't even catch up to the 383 until around 5,500 rpm and even then it did not produce a LOT of HP more than the 383. Maybe 10-15 HP if I recall correctly.

Now, I will also say that this comparison was not totally fair. While the setup may have been nearly optimal for a good street 383, it was not optimal for a 377; thus the nearly identical power of the two engines.

What would have been fairer is to build BOTH engines to their optimal potential and then I think the 377 would have shown more of its high rpm stuff. But now, we are into the basic issue: do you want a street engine or a strip engine?

So, between the two (383 vs 377) for the street, I lean to the 383. For an all out strip engine where you want a gazillion rpm, 377.

But, the winner "take all" between both will still be the 400.

406 S10 Man

iTrader: (1)

none of you guys have mentioned that the 383 beat the 377 in the drag test by 3 tenths. the extra low end of the 383 more than makes up for its high end loss. if you have a 400 block, but no crank, buy an aftermarket one from eagle. the cast steel ones are 300 bucks in summit and jegs. i considered a 377 for about ten minutes because i thought it would be cool, but i'm glad i went with the 406. cubes rule

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88 S10
Dropped 3/4
18" Boyd Coddington Timeless 5s
Dart equipped 406
12.20 @ 115.25 mph

Guido

A man who knows what he is talking about!




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-86 IROC
Vortech Supercharged 406
-=ICON Motorsports=-

82camaro

The 377 has it's place, just not in a street car. It will produce more power than a 350 and last longer than a stroker/400 in high rpm endurance applications(circle track).

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82 camaro--original steering wheel, brake/gas pedals, seats--everything else modified
82camaro

humble

93 third gen mazda RX7 R1,377 sb,modified mazda 5 speed mt,4.10 rear gear,AFR 210,efi controlled, 280 mph speedo 11:1 cr,255 zr 18 fr-295 zr 18 rear.2780 LBS weight 207mph not flat out on the highway. Great cruiser & GOES WHEN CALLED ON. ENGINE IS GREAT AT 1500,8500 & INBETWEEN.advice :build your engine to suit your vehicle.yes it's a dailey driver

built91Z28

Wow, a 9 year old thread to tell us about a car thats not even a third gen?

shanep1991

its a third gen mazda....

cIaRmOaCrZo

iv never built a 377 before, but i was talking to one of my local engines&transmissions machine shop (amazing reputation btw) and at one point i had asked about a destroked 400, and he said that EVERY single one he has HEARD of, FIXED for, and TESTED, have ALLL broken the crankshafts. he has had so many people in his 40ish some years of experience try to destroke a 400 and ended up with broken cranks. and these are some hes never touched.

i dont understand why. but its convinsing enough to me to just let that idea of a destroking a 400 go. lol

cIaRmOaCrZo

oh and most of the people he was mentioning were circle track racers lol.

humble

find out from the guy what type of cranks thet were running,if oem or aftermarket. look for a pattern. if you do intend to build a 377 or any engine ,pay attention to the fine details.at that rpm if there is unbalance in the rotating assemble,improper machining,the weak link will fail.i use a scat rotating assembly #1-41010BI, no problems.remember to build engine vehicle specific.weight of car -3000 lbs + automatic, go with cubes,you will be happier.my car is not a drag car, it & i love to corner, up shift,down shift & allow the rpm to take over.its a lot of fun for me.try to make the right choices because it's your money being spent & HAVE FUN DRIVING YOUR CAR !

five7kid

iTrader: (14)

So, humble one, to whom exactly are you offering this advice?

humble

to whomever needs it. everybody needs good advice but most don't know what advice to use.it is agreed that everyone should compile all the advice given and then make a decision on how best to move forward.i'm trying to encourage, but to whoever it concerns they may or may not come up with the right decision. trial & error works too.

humble

ben franklin:i can show you 1 way to build a light bulb & 1000 ways not to.

five7kid

iTrader: (14)

Just wondering why you were responding to a 9 year old thread. There have been many such threads over the years, and if someone is interested, a simple will turn up the information.

five7kid

iTrader: (14)

That would be Thomas Alva Edison. And what he actually said was, “We now know a thousand ways not to build a light bulb.”

Or, on another occasion, "I have not failed. I've just found 10,000 ways that won't work."

ASE doc

My Two Cents, My Next engine will be a 377. My machinist and I have planned one that will make 650hp. The 377 is a circle track motor. The key idea behind it is stability. By using the shorter stroke with taller deck, we are able to use longer rods to get closer to 2:1 rod to stroke ratio. I dont hear many people talk about R/S ratio. I guess with all the stroker street motors out there today, its not a popular subject. But just for information sake, 2:1 R/S is ideal. A 383, even with 6" rods, is a long way from 2:1. A 377, which can run 6.125" rods gets alot closer. This makes an engine that can run at high revs all day long and not be stressed.

One point to mention though is the use of a factory 400 block. This is not recommended for a serious 377 build. The crank spacers prevent good heat transfer and can cause bearing heat failure. The best route is to use a good aftermarket block. There are several choices available that can take 4.165 bore and accept 2.45 main bearings.

Lightweight cranks, rods and pistons can make a 383 fairly durable, even at high revs, a 406 is a little better as the taller deck 400 block allows for longer rods. But for all out durability, the 377 is king. It also leads in horsepower production since it can rev higher and the 4.165 bore allows for big valves.

humble

looking for wedsite on chevy high performance street fighter 377.anyone?

humble

thanks for the correction got my history mixed up.as you say plenty info out there, just got to look for it. correct on r/s ratio.

Blue377Camaro

Wow, how old is this thread now? 20 years? Any of the original posters still on here. I just built a 377 from a Brodix block and Scat Ultralight rotating assembly with Brodix IK 200 heads and the Brodix 1000 intake. love the power it makes and I don't have to worry about over revving it. It is built to handle 8000 rpms and I'll rarely take it past 7500. Smooth and no vibrations. One of my main priorities was to build a motor that you can run for a couple hours on back roads and be reliable. I hopefully have achieved that.

Rodek rodent

Personal combo rodek 400 aluminum 4 bolt block custom cnc moly crank moly rods forged 13to 1pistons afr cnc ported heads full roller engine rev kit stud girdles not even stressed at 580hp it should go 680 + with a cam and head change its in holden commodore brock hdt ex police interceptor the only one ever built to chase high powered american imports

BadSS

Still around and replied to my twenty year old post - nothing has changed. That said, build what you want and I'm sure you'll be happy unless you run across some one that builds the same combo with more cubes.