Okay, this summer I am going to pull my angine and erbuild it, so is it worth it to de-stroke it to a 377? I am on a budget, so I don't have alot to spend. Can i just use a stock 350 crank and stock 350 rods? I know I would have to get it custom balanced, how much would that cost? Also, how high can a 377 rev?

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1983 Firebird
TH700R4 Auto
Small Block 400
LG4 ECM, Intake, Carb, Distributor, etc.
Soon to be non-computer.
Clarion Head Unit 45X4
2 Pioneer 400W 12" Subs
Third Gen Performance
"A four cylinder is half an engine."

 

If you're on a budget then just rebuild the 400.

You can use the stock 350 crank and rods but you need special bearing spacers since the mains on the 350 crank are smaller than the ones on a 400.

Anytime you use different cranks, rods or pistons you should get everything balanced.

377's can usually to around 7000 rpm if properly built. A local racer here has one in a T-Altered, 650cfm carb and runs high 9's. Car only weighs 1200 pounds.

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Follow my racing progress on Stephen's racing page
and check out the race car

87 IROC-Z Pro ET Bracket Race Car
383 stroker (carbed) with double hump cast iron heads and pump gas
461 Big Block installed and ready for the 2001 racing season

Best results before the 383 blew up
Best ET on a time slip: 11.857 altitude corrected to 11.163
Best MPH on a time slip: 117.87 altitude corrected to 126.10
Altitude corrected rear wheel HP based on power to weight ratio: 476.5
Best 60 foot: 1.662

Racing at 3500 feet elevation but most race days it's over 5000 feet density altitude!
Member of the Calgary Drag Racing Association

87 IROC bracket car, 91 454SS daily driver, 95 Homebuilt Harley

 

I aplod you! destroking rocks!
I beleive that you can use the 350's stock parts in your 400, but i think you might want to check the length of the rods i dont think that 400 rods are the same lengh as 350's it might not work to well "very low compression if what im thinking is correct.
"Ive never had the privlage of messing with a 400 " But to destroke it correctly i think you need 400 rods bolted to the 350 crank.
Any good crank service can custom ballance almost anything dont know how nuch it would cost a standard serive on my 350 cost 100$ so i might say no more than 300 for your job.
Now the fun part, Ive heard people say that thevy had destroked 350's reving to 11K makes me droll if its true so a ds 400 would be wicked

 

Aww crap i forgot about the rod length difference. Although i thought 350 rods were longer? they are 5.7" and i believe 400 rods are 5.625" or maybe 5.565". Can't freeking remember now...my head hurts.. :P

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1983 Firebird
TH700R4 Auto
Small Block 400
LG4 ECM, Intake, Carb, Distributor, etc.
Soon to be non-computer.
Clarion Head Unit 45X4
2 Pioneer 400W 12" Subs
Third Gen Performance
"A four cylinder is half an engine."

 

I belive the stock rods on a 400 are 6.0 ?

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BigBlockJason
85 Z28 T-Tops
http://communities.msn.com/JasonsStuff/homepage

 

No, Ward is right. Stock rods on a 350 is 5.7" and for a 400 5.565".

 

The compression height of 400 pistons and 350 pistons is the same. The sum of ½ the stroke plus the rod length for each of the motors is also the same (7.44" is the magic number: 1.875" + 5.565" for the 400, 1.74" + 5.7" for the 350). So, all you have to do is use a 350 crank, 350 rods, 400 pistons, and the spacer bearings. Comp sells them which is about the easiest way to get them.

You should always get your rotating assembly balanced, no matter what combination you're building.

I fail to see where there's any significant money savings.

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"So many Mustangs, so little time..."
ICON Motorsports

 

Okay, I'm seriously considering doing this over the summer. Will stock heads with 2.02/1.6 valves and mild porting feed it? Also, what has to be balanced? just the crank and harmonic balancer? And you guys really think it'll hold to like 7000 rpm? Thats the only thing I don't like about my 400, it doesnt rev high at all. All its power is below 3500.

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1983 Firebird
TH700R4 Auto
Small Block 400
LG4 ECM, Intake, Carb, Distributor, etc.
Soon to be non-computer.
Clarion Head Unit 45X4
2 Pioneer 400W 12" Subs
Third Gen Performance
"A four cylinder is half an engine."

 

anybody that thinks a small block anything turns 11K and makes hp up there needs a new tach. Considering there are no heads and intake that are designed to move that much air (unless this is some type of custom job), it is very unlikely. Have them change gears and I bet the car will go faster.


The reason 400s dont turn high rpm is they don't need to. It's the torque. I would not try to do it with stock heads. Save some money and put it in the heads. all the rpm in the world does not make a bit of difference if you are not moving enough air and there is no stock head that can feed a 350 at more than 6000 rpm

Don't worry about how high you can spin it. gear the car accordingly to put the engine just past the peak hp in the top gear at max speed.


[This message has been edited by jcb999 (edited May 02, 2001).]

 

"Stock heads"... do you have any idea how may different possibilities that phrase has?

A 400 should easily be able to produce meaningful power at more than 3500 RPM. If it doesn't, the problem is almost certainly one of flow. What heads have you got on it (casting # would be ideal)? What exhaust?

I would suspect that if you'd get the rest of the LG4 crap out of the way, you might be surprised at how good a 400 can run. Mine doesn't have any trouble winding up, and it's all stock in the bottom end.

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"So many Mustangs, so little time..."
ICON Motorsports

 

Amen brother

 

destroking is great for a circle track engine, but totally against the point for street or drag use. better off using long rods and alot of compression in the 406. (assuming you bore it)

 

I can't guarantee it hasn't been rebuilt already. Its a 73 block so hopefully its been rebuilt and bored AT LEAST once. Okay, so maybe I will keep it a 400. I am not actually sure what all LG4 parts are on it. I know it has an LG4 intake, carb, distributor, and computer. Please god I hope LG4 manifolds won't fit it, because im wondering if I have LG4 manifolds. Oh well, headers ar ecoming soon. BTW, the manifolds do have the AIR injection... Oh god I hope I don't have 305 heads...

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1983 Firebird
TH700R4 Auto
Small Block 400
LG4 ECM, Intake, Carb, Distributor, etc.
Soon to be non-computer.
Clarion Head Unit 45X4
2 Pioneer 400W 12" Subs
Third Gen Performance
"A four cylinder is half an engine."

 

I thought that the 377s had to have special pistons b/c of a difference in compression height. For your case, though, Ward, I would say to keep the stock stroke and focus on the flow going in and out of the engine. But, then again, being different from the rest is kind of cool.

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'86 G-body Cutlass
Olds 307/TH350
Soon to be 377/700R4
To Beer or, not to Beer...

 

"RB" is right on the money. In my SS I had a stock bottom end 406 (5.565 rods arp bolts), TRW pistons, CNC ported heads and roller set up that I shifted at 6800 rpm,, spraying the house down making a 3750lb car w/driver run traction limited 10.40's all day long. Now I'm running Eagle 5.7 rods and 3.75" 4340 crank,, and more nitrous twisting it to 7100 rpm.

IMO,, "destroking" is just giving away cheap and easy power. About the only time I could ever see me building one for myself (I've built a couple for other folks) is if I was racing in a limited cid class or a weight to cid class and I could run nitrous (and more of it to make up the cid difference).

edit - However,, I admit if someone came to me and said "You have to build me an engne to run 9,000 rpm,, or I'll die",,, I'd build them a 6" rod 377.

[This message has been edited by BadSS (edited May 03, 2001).]

 

I would make it a 377, a 400 is a hard engine to feed unless you have lots of money, which you stated you don't. You will have more of an high RPM motor with the 377 as opposed to a 383 or 400, but you may loose some low end power.

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1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission
Borg Warner 7.75" 9 Bolt Rear End

Current Mods: LT4 HOT Cam, Comp Cams 1.52:1 Roller Rocker Arms, Edelbrock TES 1 5/8" Headers, Hooker 3" Aerochamber Cat-Back System, Performance Resource Chip, Accel Ignition Coil, Cap, Rotor, 8.8mm Wires, K&N Filters, JET TPI Air Foil, All Free Mods, Falken ZIEX Z-Rated Tires.

Best ET (w/o LT4 cam): 14.32 @ 97.7mph
(corrected for elevation)

Soon to Come: 7.625" 10 Bolt with 3.42s and Accel TPI Intake Base

 

Personally, Presented with your situation, I would build a 377 Just to be Differnt.

But then again, Im the guy building a Turbo 200 I6.


Im holding onto My 305 Till I find a 400(To destrok), 327, or 302 ( yeah, right ) For My camaro.


But Im weird.



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60 Ranchero - Project ( Money Hole )
85 Sport Coupe LG4 - Daily Driver
Reader's ride -> My Ride

Just another Hot Rod kid, or thats what they all tell me.
Livin' the Stereotype