building 383 for my '70, need help

[Brian J.]

I am going to build a 383 for my 70. I am interested in a street engine RPM range to 5500. I have 186 heads 2.02/1.60 valve, so far.
1) should I go with a steel or cast crank(leaning toward forged steel)?
2) should I have rotating assembly balanced? I've noticed most cast assemblys are externally balanced.
3) are these heads good or the smaller valve ones better for street?
4) what size connecting rods would be best 5.7" or 6.0"?
Brian

[Wayne P.]

Re: building 383 for my '70, need help

Buy the GM crate engine. 36 month warranty.

[Joe R.]

Re: building 383 for my '70, need help

Brian,

Glad you posted this cause I want to see what all these experts will recommend.

For me:

1. Heads can be purchased from Jegs or Summit for less than it will take in machine work to make the 186 heads work.

2. Forged Steel

3. Balance it without a doubt

4. You are limiting your engine to 5500 so the 6.0 are not necessary and will cost you additional to have the block machined for the 6.0 rods. You may also have to purchase an after market pan for the 6.0 rods.

My 383 was made from a 010 block 0.060 over with 6.0 rods. I purchased my crank and rods from Kryptonite with pistons from BRC. Difference was that I wanted 7500 rpm from my engine. Had to use a roller along with some of those 55cc Air Flow Research heads that flowed 240. Worked quite well with a six speed and 4.09 rear.

Regards,

JR

[Brian J.]

Re: building 383 for my '70, need help

I have the 010 4 bolt block and 186 2.02/1.86 heads, hoping these will work. NO crate engine for me, gotta start somewhere. This wil be my !st. non stock build.
Brian

[Scott Marzahl]

Re: building 383 for my '70, need help

Since you are not looking for a high RPM motor I would use a nodular iron cast crank, SCAT makes a nice one you can probably buy for less than turning down a chevy 400 and nitriding it. I used to run a 400 crank with 400 rods and ran nitrous. I ran it hard and often up to 6,500 RPM. I would also buy the AFR heads, I used an old set of Brownfields I had however the AFR's are some of the best out there for the money. YES, you need to balance this assembly it is also externally balanced.

[Dick W.]

Re: building 383 for my '70, need help

I think that the 6.0 rods would make a good addition. It totally changes the "personality" of the engine, especially if you are running a cam with a lot of duration. The engine is streetable. Someone with more knowledge and memory will have to explain why. I have built several engines with 6.0 and 6.050 rods, cams with LOTS of duration, and they were streetable.

[Mike Cobine]

Re: building 383 for my '70, need help

Longer rods tend to improve torque, due to things like vector angles of forces. For a simple example, do some push ups with your hands straight down below you and then some with them further out. As you go even further out, the effort is much harder, because the force you exert is being wasted into not just downward force but sideways force.

Just as importantly is that having less sideways force on the piston means having less friction, which doesn't waste power (and cylinder walls).

2.02 is the minimum in valve size. Remeber 383 cid is big block territory and they range much larger. Spring for 2.05 valves if you can.

[Patrick H.]

Re: building 383 for my '70, need help

Even if you don't think about the more expensive Airflow, Edelbrock or Dart heads I would at least consider Vortec heads from GM if you don't mind using a Vortec intake. At $250+/- street price each, they're cheaper than re-doing your 186's. The only kicker is that I don't recall off hand their flow rate and valve size - that may be the limiting factor.

If it was me, I'd use aluminum heads.

Patrick

[Clem Z.]

Re: building 383 for my '70, need help

remember some rods require the bolt heads to be clearanced to clear the cam lobes unless you buy the correct rods. that is why it is best to buy a complete rotating assy that comes already balanced and with the proper rods.

[Mark #28455]

Re: vortec heads

At most tracks that limit "stock" classes to a factory cast iron head, they have all but stopped using the "fuelie" heads and switched to the vortec heads - they flow that much better even with the smaller valves.
Even Chevrolet claims they outflow the cast iron bowtie heads as cast with the smaller valves.