383 Build questions

[dewsky]

Ok Guys....I want some honest opinions. Recently read an old article ( http://www.hotrod.com/articles/mopp-0209-383-engine-restore/ ) on a stock 383 being reworked and taking it to over 450 HP with just a few bolt on mods. I know that this article is old, but the last thing they did was change the camshaft and valve springs to get the final jump of 50 HP.
My question to you guys is..... if a fella was to do a little porting work to the heads (lets say they are 906's), would you not expect the same kind of HP jump from the increased flow?
I am planning a build of a 383 to vindicate all the mistakes I made building one in my youth. I am just in the planning stages at the moment, but would really like a bit of input.
Plan on the engine being a street engine and hope to put it in a "B" body later on.

 

[Steve009]

im currently doing a little work to my 383 similar to this article. The guys im working on it with and I think it will be in the 400-410 HP range. im not porting the heads but the general consensus seems to be that the 906 can flow really well and make a huge difference with some simple at home porting work. here is my combo for the street. I REALLY doubt I will be anywhere near 450 without porting.

holley 650 DP
Edelbrock Perf RPM intake
906 heads
Mancini electronic ignition
Comp Xtreme Energy XE274H cam
dougs 1 3/4 long tube headers with cutouts
stock rebuilt bottom end (~10:1 CR)

I think with some porting work I could get that extra boost to get close to their 450 HP mark. If you do before an after pulls with the 906 to see HP difference I would be super interested to hear more because that may be my next step.

 

[super-bee_ski]

Well,
First off:
After reading the article, I see some discrepancies
1. "Original Dyno run at Westech read: "After the customary break-in cycle, we let the 383 fly. The readout at the end of the pull showed 335.2 hp at 5,000 rpm"
NOTE to article author: THIS IS NOT LETTING A 383 FLY... Perhaps 5,650 RPM?
Then after headers they check at 5,400 RPM, but why not BACK to original 5,000 RPM?
(The article is definitely emphasizing maximum HP for minimum Modifications)
Any Engineer would know NEVER to perform "tests" like this, always use the same parameters, baselines)
2. The 383 definitely thought so, posting 358.3 hp at 5,400 rpm, and 413.7 lb-ft at 3,500 rpm. The headers added a solid 15-25 lb-ft of torque

Thirdly, be careful here, the article simply states: "HIGH RPM SCREAMER"
Who wants that?
Article states: "Since we eventually intend to create a high-rpm screamer from our 383, we opted for a single-plane intake.

In my opinion, a typical "Hot Rod magazine article"
Read between the lines...

So: I had my 1970 Original Superbee 383 906 heads professionally mild ported and I installed TTI headers
I did notice a improvement.

So; yes, the article is confusing, different RPM runs for the same tests, etc but all in all YES, you can get good improvement with Headers, Carb and mild port work on your 906s

 

[PRND21]

If you're asking if port work is more beneficial than a cam change, I would say that you could make ports big enough to throw a football through, but if you only have .400 valve lift, that limits what air you can flow. The easiest way to make power is cubic inches. My .030 over 383 has a 3.9 inch stroke crank, makes all the power I need.

 

[dewsky]

Everything in that article basically had to do with improving flow into the heads, either intake or exhaust, and also improving the fuel intake with a new carb. I am wondering if the heads being improved before the cam install, if that would accomplish about the same kind of improvement. How much HP would a porting job give you? I know that the cam gives a huge difference, but did they get to the old cams top potential before they changed it out?

 

[moper]

There are a few things with 383s that are problems if your goal is a strong street engine with good manners. It starts with parts availability... Pistons primarily. There are no pistons on the market that will yield 10:1 in a stock open chamber build without some serious machining of the heads and block and a bit of attention to detail. Next is the 906 heads. While a great head, it's iron, heavy, open chamber, and worn. So you will spend to get everything into good order, and pay more to have them ported. I'd advise replacing them. In the long run you'll be way ahead: closed chamber (best for quench and good static ratio), lighter by a lot, ports that will be as good as full porting from an average shop, and they look like the factory heads when painted. The cam has to match the heads and intended use. And be honest with yourself. If you're not going to like running premium fuel, a big cam, a slippery convertor, and low rear gearing you're not interested in a big horsepower 383.

 

[rumblefish360]

Well,
First off:
After reading the article, I see some discrepancies
1. "Original Dyno run at Westech read: "After the customary break-in cycle, we let the 383 fly. The readout at the end of the pull showed 335.2 hp at 5,000 rpm"
NOTE to article author: THIS IS NOT LETTING A 383 FLY... Perhaps 5,650 RPM?
Then after headers they check at 5,400 RPM, but why not BACK to original 5,000 RPM?
(The article is definitely emphasizing maximum HP for minimum Modifications)
Any Engineer would know NEVER to perform "tests" like this, always use the same parameters, baselines)
2. The 383 definitely thought so, posting 358.3 hp at 5,400 rpm, and 413.7 lb-ft at 3,500 rpm. The headers added a solid 15-25 lb-ft of torque

Thirdly, be careful here, the article simply states: "HIGH RPM SCREAMER"
Who wants that?
Article states: "Since we eventually intend to create a high-rpm screamer from our 383, we opted for a single-plane intake.

In my opinion, a typical "Hot Rod magazine article"
Read between the lines...

So: I had my 1970 Original Superbee 383 906 heads professionally mild ported and I installed TTI headers
I did notice a improvement.

So; yes, the article is confusing, different RPM runs for the same tests, etc but all in all YES, you can get good improvement with Headers, Carb and mild port work on your 906s

Perhaps that is where they found leak power and it makes no sense to spin the engine higher if it is not making power and I wouldn't bother reporting it in the article. I'd do like they did and just tell you where it made the best/most power & call it a day in that one and move on.

Who wants a high rpm screamer? Dang! A lot of people I know. Also, IMO, 6500 is NOT a high rpm. No way no how.

 

[niteshift70]

Square decking the block and using thinner head gaskets (MLS), along with a box stock set of 440 source "Stealth" closed chamber heads will give you a significant bump in compression with the stock piston. The new stealth heads will be cheaper than just refurbishing the old heads much less the port work. Just be mindful of your quench height and valve to piston clearances. If you add a modern cam grind similar to the 440 magnum cam, like a comp xe hi-lift, hughes, howards, or lunati voodoo with long tube headers, an rpm intake, and a 750 dp should put you at 400+, at the crank.

 

[fishmens67]

Square decking the block and using thinner head gaskets (MLS), along with a box stock set of 440 source "Stealth" closed chamber heads will give you a significant bump in compression with the stock piston. The new stealth heads will be cheaper than just refurbishing the old heads much less the port work. Just be mindful of your quench height and valve to piston clearances. If you add a modern cam grind similar to the 440 magnum cam, like a comp xe hi-lift, hughes, howards, or lunati voodoo with long tube headers, an rpm intake, and a 750 dp should put you at 400+, at the crank.

This, only I would use a flat top with reliefs , a closed chamber stealth cc'd to 75 -78 with a custom cometic mls for no more than .035 quench. zero deck can be achieved with the proper piston and deck surfacing