Do you have 383 or 406 proven parts combo?

[Low76K5]

Hello,

I am ready to upgrade the 350 in my 2WD Blazer. I want as much torque and HP as possible but with good vacuum and easy driveability. The budget is $3k for motor alone.
I like the extra cubes of the 400 but the siamese bores seem a risk. I have estimates from two solid local shops on the two sizes and they are about the same cost.
I am leaning towards my block with a scat 383 crank, a Lunati Truck Avenger Cam/Vortec heads or a Trick Flow 350h/400t top end combo, 9:1 comp, Hedmann 14G thermal coat headers, Edlebrock Performer, and my original Q-Jet.
Anyone have any experience with something like this in 4000 lb hot rod or do you have a combo that worked well for you?



Thanks,
Scott

 

[skelly1]

Make sure you have a good going through of your quadrojet. That motor will flow well and you don't want to hold it back because of air/fuel flow. I'd go with the 383. The 400 has some funky flywheel and or balancing or something that makes it's weird. I'm not sure if the performer manifold is the best choice, but it's definitely a popular mod to the SBC.

 

[b454rat]

This is the combo that i used in my old truck with TBI. .030 400, 5.7" rods, KB hypereuctic pistons, IIRC 22cc dish, Comp Cams Xtrme Energy 268 cam, STOCK TBI heads, stock everything else. Balancer/flexplate was new, rotating assembly balanced. Truck had headers and single into duals. Heads were stock, just rebuilt. Motor with the cam and being TBI, didnt set any codes or lights, had a sweet idle, little choppy. This thing would pull like a freight train, in any gear, at any RPM. Would smolder the tires and a dead stop till I let off. Kepting pulling till i ran out of room. With a 700R4, 3.08s and 275/60s, speedo went to 85, then would start over, I was at 30 MPH in third gear, and still pulling. I bet if I hooked this truck to my current truck with a Vortec 454, it would pull it across the parking lot, if it could get traction. I just got another 400 for my 62 burban to build identical to that motor, just with the Vortec heads. It wont be awhile for that, so I'm thinking about selling the heads.

 

[rjfguitar]

I'd go with the 383. The 400 has some funky flywheel and or balancing or something that makes it's weird.

Since a 383 uses a 400 crank, they both then share the same "funky" balancing issue, which isn't funky at all. The 400 is just externally balanced, where all the other SBC's are internally balanced.


Original Poster,

Good luck finding an original bore 2 bolt main 400 block. They are getting pretty darned rare, I got lucky with mine.

I love my 406, it makes the torque of a 383 but revs faster since it uses a larger bore. What I don't like is my running temperature. When I put the motor in I was positive I could make a 400 run 185* like I wanted. After a new big 4 core and powerfull dual electric fans, it still runs 200-210* at normal temp and load. If it is very hot outside with the A/C on it will easily climb to 220*. I finally got tired of fighting it and just let it run that warm, screw it. i just change the oil slightly sooner than I would if I had a 350.

I spent about $3K myself on my 406. I have a stock rotating assembly and stock 400 1.96" heads. Edelbrock performer intake, HEI with a hotter coil, 9.2:1 compression, Comp 268H cam, Hooker headers, and edelbrock performer Qjet.

I ran mine on the roller dyno and put out about 200HP and 300ft lbs to the ground at the wheels. That is about 315HP, and around 425ft lbs of torque at the flywheel. I have a th700R4 behind it, hence the large parasetic drag loss.

What adds so much to the cost of a 400 conversion is that you have to buy a block (you already have your 350 so thats no added cost when redoing a 350) and the new balancer and flexplate that is 400 only stuff due to it being an externally balanced engine.

 

[retroblazer]

I have a 406 in my race Blazer and a 383 in my 94 Sub. Both built by D&L Automotive in State College, PA. Dennis Chencharick is the guy to talk to. I have no cooling issues with the 406. www.rafforacing.com

 

[yoshisv]

I would probably just build a 350. Put some airflow research heads and one of their port matched intakes, And a good cam like a comp xe270 along with headers and good carb. Should be a good combo.

 

[Shawn]

I'd STRONGLY suggest comparing real world dyno's. This is a build that I'd love to do and put in my K5 (formally 496ci).

http://www.chevyhiperformance.com/techarticles/148_0401_imp/

Here's the same engine with Vortec heads:
http://chevyhiperformance.com/techarticles/148_0306_406/

 

[Moody]

I'm doing this exact buildup for for 1970 K5 using the vortec heads. So far, minus carb and intake I'm right at 2,000. I'm using Keith black 30cc dished pistons to put me right at 9 to 1 compression. I'm using a comp cams XE268 that has slightly less duration at .050 compared to .230/.230 and .480 lift in the lunati cam that chp used. I had my heads modifed to accept 3/8" screw in studs so I if want a little more cam in the future I'll upgrade to 1.6 rockers.
I haven't decided which carb/intake setup to use probably air gap and a SMI q-jet. Oh yea, make sure you have the steam holes drilled in your heads if you go with the vortecs

Not to hijack the thread... but b454rat I would be interested in how you ran your old TBI setup. I want to run TBI but was told that the duration on the XE268 was too much and the 110 lobe center would not run enough manifold pressure. Sounds like my setup would be the same as yours just with vortecs instead of stock heads. I have also heard that TPI/TBI on this motor will not flow enough air?

 

[88-383]

I've run both 383's and 406 over the years, and now I'm playing with a 355. You can't go wrong either way! Plan on buying some heads, preferably aluminum and set your compression up around 10.0

I ran a 406 with a set Canfields 190's with the XE268 cam. The engine made crazy torque, guessing close to 500lbs. Would have no problem breaking other parts.

I now have a full race 383 in my Vette that uses a set of hand worked AFR 210's and a solid roller cam. A basic 383 with decent heads and cam will put out a solid real world 400-450HP and about as much torque.

I just bought a pair of TF 195's cnc'd heads. You can search under my name and see the pics, cam choice etc... Now keep in mind that all things being equal the 400 will make more power! The slightly bigger bore tends to help aifllow past the valves.

My advice would be to get a set of good heads! then buy a 383 short block somwhere. Make sure you have the rotating assy balanced, then you should be good.

Enjoy!

Kelvin

 

[Shawn]

My advice would be to get a set of good heads!
Kelvin

I totally agree! Its all in the heads. The Vortecs are good but if you want over a certain lift, some machine work has to be done then you need the special intake so that limits you on FI systems for SBC (MPFI, TPI). AFR heads like used in the above dyno seemed the best bang for the buck. Alum also allows you to run more a tad more compression because of the better cooling properties plus you have a less weight. If you can get a 400sbc, then get one. More cubic inches = more torque. I have yet to see cooling issues with a 406 if a larger radiator is used.

 

[b454rat]

Moody, I used the stock computer stuff. It had all new sensor and stuff, new injectors, MSD coil, headers, and think that was it. I did nothing to the computer, chip, etc. Like i said before, never had a light come on, never overheated, never had any problems with it. Wish I would have kept it. I have a set of Vortecs that I think I'm gonna sell, wont be able to do anything for awhile, and I also have a 400 short block for sale, too. It's not a 2 bolt, but it's all stock out of a 70 GMC. I had alot of different SBCs, and I will never run anything but a 400. Not saying that the other motors aren't good, but like the saying goes, no replacement for displacement. What you do to a 350 will work in a 400, and make more power. Get a good set of heads, and on any motor will make it run good.

 

[88-383]

One thing I forgot to mention about the 400 blocks. You need to have a real good look at the deck surface around the steam holes. I've seen plenty that had small cracks extending out from the steam holes.

If you do find a good one, and put heads and cam on it you're in for a real treat with the power it'll have.

KM

 

[Diesel Dan]

I am leaning towards my block with a scat 383 crank, a Lunati Truck Avenger Cam/Vortec heads or a Trick Flow 350h/400t top end combo, 9:1 comp, Hedmann 14G thermal coat headers, Edlebrock Performer, and my original Q-Jet.
Anyone have any experience with something like this in 4000 lb hot rod or do you have a combo that worked well for you?



Thanks,
Scott

Just dyno'ed a setup of what you are looking at.
383, scat crank, scat rods, dished Keith Black pistons, compression ~10:1.
Vortec heads, stock porting, 1.95/1.50 valves
Cam, hydrallic roller .525" lift, duration @.050 218/228, rockers 1.6 roller
Carb: 750 holley, dual feed, vacuum secondaries(box stock)
Intake: RPM air gap
Headers: headman stepped primaries with 3" collectors.
Distributor: GM hi-po HEI, MSD 8MM wires
Honest 375hp/410TQ
Peak HP @ 5400, dropped by 6hp @ 5800, TQ 400lb/ft from 34-4400 rpm. 300 lb/ft came in ~2300. Still making 375 TQ @5200rpm.

Should be a good performer, hasn't been installed yet.

 

[gauder]

Here's a tip that I use on my 350's I've built for street rac... um racing. If you want a little more power but still want to run the gas from the local gas station take a look at pro-topline heads. You can get very small cc combustion chambers which allow you to acheive a higher compression ratio with flat-tops. They will run on 91 octane very well because with a flat top you get a better flame propagation as compared to a domed piston. This means no detonation at the higher cr with the flat-tops on lower octane gas.

I've also run cams with up to 250* duration at 0.050" and using a vacuum canister, had no problems with power accessories. That's a heavy truck and if you really want to go fast.....

edit: I second the edelbrock air-gap rpm intake, but if you look on e-gay, there is a lesser known company that sells similar intake manifolds for lower $ and they are American made still.