SWCDuke

What you're trying to do is the same as Mike McCagh's objective and results as documented in the "Tale of Two Camshafts" article. Since you plan on running the 283 2 x 4 manifold larger port heads may be of limited value because that manifold has small ports that cannot be opened up all the way to equal the cross section of later big port heads. If you put a 1.5" restrictor in a 2" pipe, it will flow like a 1.5" pipe.

283 heads can be massaged for better flow efficiency and the inlet valve seat can be opened up to accept the 305 CID 1.84" valve. That's what Mike did and you can see the flow and dyno data in the article. If you want to simulate a 270 with a hydraulic cam use the L-46/82 cam.

I highly recommend against trying to stroke an early small bearing 327 block. As I said before, a '67 ...657 block that has the rear crankcase ventilation port is a much better candidate for stroking, and get a hold of Joe Randolph. There's no need to reinvent the wheel. Joe has a 383 based on a ...657 block and has thoroughly documented what it takes to make it work.

What you're trying to do has been done before with proven documented results. Look at Mike's lab dyno results in the article. With a longer stroke (Mike's 283/250 FI "cheater motor" has a 3.48" stroke.) top end power will be about the same at slightly lower revs with the McCagh Special cam (Taylor's Rule), but with greater average power through the useable rev range due to the greater average torque. The L-46 cam will trade some low end torque for more top end power and useable revs and have idle behavior somewhat like a Duntov cam, but not quite as lopey due to the lower effective overlap.

Also, such a torquey engine will work very well with a taller axle ratio, like a 3.08, as long as you don't live in very hilly country, and you could also swap out the OE CR transmission for one with wider ratios that will work very well with an engine that has such a high and flat torque curve.

You're currently in the "system engineering" phase, and it's important that you establish a set of objectives and select complimentary components that will work together to meet your objectives while controlling cost. A lot of guys screw up this phase, if they do it at all, and it's easy to end up with an expensive kluge.

As is usual with the CF the advise you're getting is all over the map, often not well thought out, and not backed up with real test data.

Duke

MikeM

I assume you have test data to show that manifold won't be beneficial with bigger ports and valves? And I'm sure you have tested/simulated (or otherwise) running 283 size heads vs bigger port/valve heads on a 383? Or, are you just assuming?

Some of us just may have found that 2X4 set up very satisfactory with the big port heads. No scientific data of course.

DZAUTO

One thing Duke mentioned, and I fully intended to mention it earlier, is that with an engine which produces a lot more torque than a 283, is rearend gearing. More torque, ESPECIALLY with a well built 383, will easily pull a 3.08 with ZERO effort. That's what I have in the 56 behind the FI 406 SB and wide ratio Muncie. And if need be, I can destroy the rear tires. One thing I really like about a higher rear gear ratio, is that you can wind the engine much longer and achieve higher speeds in each gear than can be done with something like a 4.11 or 3.70. And a 3.08 is really nice on the Interstate. And if the 3.08 is too much for cruising around town, an easy fix is to drop it into 3rd or 2nd gear--------------------that's what 4spds are for!

SWCDuke

It's basic fluid dynamics, accepted science for at least 150 years. You didn't include with what you quoted from me, so I'll repeat, put a 1.5" restrictor in a 2" pipe and it will flow like a 1.5" pipe.

It would be easy to take Mike's configuration in EA increase the stroke, change the induction system and cam to get performance predictions including comparing any heads for which reliable flow data is available. Mike's lab dyno test made within one percent of predicted maximum SAE gross HP. As is usual with EA, peak torque was a few percent lower than predicted, but low end torque was significantly greater.

I bet you never read the "Tale of Two Camshafts" article, and maybe you shouldn't because, heaven forbid, you might actually learn something!

Duke

MikeM

I didn't think you had any real data.

No, I haven't read your book. I am far too old to worry about learning anything new. Nothing there for me I don't set my valves on my 30-30 cam at your recommended setting either. As it did with others, it destroyed the low end on my Z 28 about 35 years ago. Long before your paper on the issue. That's was enough theory for me. I also tried the LT 1 cam years ago. Not for me either.

But I have run the old 270, 2X4 intake system on big port 327 heads. And I have compared the performance of them to a single Holley on aluminum intake.

Bashing other people's opinions here is not really a good idea unless you have done some actual testing or have experience outside of a book or a simulation.

MikeM

Turn it around and tell me why you have 2 1/2 head pipes and 1 7/8's tailpipes. Does that apply here?

AZDoug

Not really.
Exh gases are quite warm coming out of the heads, down the pipe aways, they have cooled and also take up a lot less volume in the cooling process.

Without doing the math, i woudl guess that the velocity in the cooler, smaller tail pipe is similar to what you have in the initial hot, and larger, exh pipe.

PV=nRT

http://www.westfield.ma.edu/cmasi/ge...0law/pvnrt.htm

Doug

MikeM

Yes, now turn that around. Air coming the carb is cool. Heats a little going through the intake manifold and heats a little more passing through the head ports and valves. All the time expanding. How much? I have no idea but still seems it would expand some.

427Hotrod

Might do a search on Wes Mieglietz. He had a stroked 327 and did some back to back Dyno and dragstrip testing in his 62. It was featured in Car Craft. They tested his very nicely ported oem heads against some AFR heads as well as a cam swap. It was good stuff

You can search here or posts by Devildog or me concerning the sneaky 400 we built for his 61

jim.

AZDoug

Not much, but some.

Ambient air in at 80F, heating to maybe 200F at the intake valve is a lot less expansion than exh out at 1100F, cooling to 200F at the tail pipe.

The math is pretty simple.

Here is an online calculator for those who lost their Hewlett Packard.

http://www.chemicool.com/idealgas.html

Ans if you want to figure velocity in the pipe now that you know relative volumes:

http://www.calculatoredge.com/mech/p...20velocity.htm

Doug

68hemi

THANK YOU!!!
I did not know they existed and apparently others here didn't either as some have done some pretty time intensive things to remedy the situation.

MikeM

Searching under your name, it looks like he used a Chevy 2X4 intake with a lot of porting with 461/462 heads that were also ported even bigger. Then switched to AFR 200 heads keeping the same intake?

AZDoug

They sometimes will not work on a C1, depending on the year, as they raise, AND make the valve covers move outboard, which may interfere with either your generator, or expansion tank.

I had to mill the valve cover rails down about 3/8" on the dart Pro 1 CNC heads I have so the valve covers wouldn't hit the exp tank.



Doug

SWCDuke

As I've said repeatedly, head flow test data and engine dyno test data is in the "Tale of Two Camshafts" article. The article is attached to a thread I started and is available to anyone with enough time to spend 30 seconds on a search for threads stated by me. (There aren't many.)

I learned a long time ago that one can never know everything, and you are never too old to learn. Otherwise you become a grouchy curmudgeon stuck in the past.

Duke

68hemi

Good to know so I will deal with it if it is an issue as I just now ordered them. Thanks

AZDoug

Clearance issues with taller heads.
The first pic shows how tight the exp tank it to the valve cover.

The second and third pic show another view of the engine and the tach drive alternator.

Note the custom exp tank quick release lever and cold air intake.

Doug

MikeM

Yes, I converse with John McR and Dave McD.

Yes, I've heard all about your 300 special cam. Don't know where this fits in this discussion. How many have you sold?

Yes, I read Racer Brown's very first tech article on the SBC when it first came out. January, 1955. Hot Rod Magazine. A few months later, Edelbrock got about 300 horsepower out of a 265.

Yes, I have every Chevy Power book Chevrolet published. Read them cover to cover many times.

See posts #25, 32.

GCD1962

He certainly is Mr. Theory. Theory and reality can be two different results

SWCDuke

Clearly, you didn't read the article either.

MikeM

I read it but you have left a number of my question on the table, unanswered.