MikeM

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

Seems like you diminish other's postings in favor of whatever you have to say.

427 Hotrod showed 500 or so horsepower with the reworked 270 dual quads and you haven't commented one word on that. I believe many posts back, you said it's probably useless to use that intake setup?

Just another "deplorable" trying to make some sense out of your posts.

68hemi

Sure it is not going to be the best flow but more cubic inches are hard to beat for additional power and torque. I find it strange that no one ever mentions the fact that the original 270 h.p. engines were giving the small 283 over 700 cfms? Certainly regardless of flow the 383 will take those cfms better than the 283.

Accelo

You have to remember the compression will be high, very high.
I used 4.30 bore and a 3.75 stroke and standard gasket thickens and Combustion Chamber Volume of 60 CCs and calculated you would have a 13.96 Compression Ratio.
The 2 bbl head for 57 is almost 70 CC. That comes out to 12.32 CR.
I'm am not sure you want to go there. You could us dished pistons but quickly run into other issues with quench. You certainly will end up with a dog because of quench and airflow issues. It could be done but without the budget of a major race team, I would look elsewhere for the look.
I like the adapter idea more and more.
Rick in WA State

SWCDuke

You're making and apples to oranges comparison. Neither the "327 LT-1" configuration nor the "Special 300 HP" configuration were about extracting maximum power out of the engine at any cost.

The second sentence of the article applies equally to both configurations.

"The owners wished to maximize power without affecting normal operating behavior or original visual appearance."

That means the engines had to go through Flight judging with minimal engine and operating behavior deductions and pass the NCRS Performance Verification test to qualify for a Duntov award.

An important part of "operating behavior" is idle behavior. The Special 300 HP configuration had to have the same idle characteristics as base cam engines - butter smooth at 500 RPM in neutral for a manual transmission and butter smooth at 450 in Drive with Powerglide. Also, no significant loss or low end torque was a requirement, so the above two precluded the use of a long duration high overlap cam.

The requirement for using all major OE components precluded the use of aftermarket heads, headers, inlet manifolds, carburetor(s), or FI and larger than OE exhaust pipes.

There was no specific top end power requirement, but simulations indicated at least ten percent greater peak power, and, more importantly, extending the peak power "sweet spot" by up to 1000 revs, which would yield base engine idle behavior and low end torque with L-79 top end power and revs. This objective was met, too.

Most guys see engines as one-dimensional as represented by peak power, but in normal road driving engines spend 99.9+ percent of the time under 4000. Often no consideration is given to maintaining normal engine operating characteristics like idle behavior, good low end torque, fuel economy, or original major engine components.

Within the established boundary conditions all objectives were met and the second design camshaft, the "McCagh Special" provided better all around performance within the constraints than the "Special 300 HP" camshaft, which was the first design.

Regarding maintaining CR within an acceptable range for pump gas - say 10-10.5:1, Keith Black offers a sufficient range of off-the-shelf pistons in most cases, but in some cases a semi-custom piston may be required.

Quench clearance is only a consideration on a racing engine where you want to maximize the CR that can be tolerated with legal fuel. As-built OE engine quench clearance ranged from about .040-.060", primarily because (small block) deck heights were typically higher than the nominal 9.025" spec, likely due to broach wear.

I'll also add, as I've said before, that Taylor states that increased detonation resistance does not occur until quench clearance is less than .005 times bore diameter, which would be .020" with a four inch bore, which is less than Chevrolet's .035" spec, but plenty of racing engines have been built with less.

When customers complained about detonation on '62 340/360 HP engines Chevrolet's solution was to double gasket these engine both in the field and at the plant beginning about midway through '62 production, and this continued through the end of '63 production. Double gasketing increased the as-built quench clearance range stated above by .018", but detonation complaints stopped because the second gasket dropped as-built CR by about half a point.

Duke

MikeM

Lest we forget where this thread got derailed..........

The issue was heads and intake manifold. Then you hi-jacked the thread and started talking about camshafts and "data" and misguided advice.

Nobody said anything about "road engine".

The OP said he wanted a much bigger look alike 270/283. That was the issue. I know the 283 manifold will work well on the bigger heads. I've done it and you haven't so I'm done here.

PS. Since you brought it up, how many 300 Specials have you sold? Second call.

jimh_1962

Got to love it!

My friend gave me a set of heads which were on his 59 corvette back in the 70s. These were 461x heads which were ported plus larger valves. The double humps were shaved off. Someone added bondo where the double humps were located to fake the the cast look. Someone welded and tapped screw holes for staggered bolt pattern valve covers. The welds are underneath the valve covers and very crude.

Long story why I am using them. It was a gift and I gave him my word I would put them to use.

Right now, the heads are on my 327. I am not using the staggered valve covers.

The only thing extra I did was a paid for valve job, cleaned up the shoddy porting, added screw in studs and guide plates. I get questions about the heads like "No fuelie heads?". I simply say "yep!".

SWCDuke

The OP stated that he wanted a large displacement engine using as many original components as possible that appeared and behaved like a 270, which is in line with what I did with the "327 LT-1" and "Special 300 HP" configs. His objectives were clearly for a road engine, not a racing engine, which are two completely different animals.

I referred the OP to the "Tale of Two Camshafts" article and Joe Randolph to give him an idea of what is involved and what is possible. Since he stated he wanted 270 type behavior with a hydraulic camshaft, I recommended the L-46 cam, but since the McCagh Special camshaft makes about the same top end power, other things equal, as the OE SHP hydraulic cams, the OP can get an idea of what is possible within his constraints of using as many OE components as possible. Had he wanted to replicate a 245 I would have recommended the McCagh Special camshaft.

Two Special 300 HP camshafts were manufactured by Crane, but since the McCagh Special provided better overall performance, I only recommend the McCagh Special for those who want to pursue the Special 300 HP type config.

I don't sell the McCagh Special camshaft. It's manufactured and sold by Crane, and I receive no financial benefit from those transactions. I don't have a current count on how many have been sold, but it's less than a dozen.

Your posts remind me of the "fake news" promulgated by the mainstream media. You have taken this thread way off topic with your ranting and "fake posts" about what my research and development has accomplished by misrepresenting and disrespecting my automotive engineering background and virtually everything I have contributed to preserving vintage Corvettes while improving their performance without any detectable modifications, which has benefited many vintage Corvette owners.

I could ask you how many camshafts you have designed and sold that meet all performance objectives, how many papers you have published in print or on line reporting the results of your R & D projects, but never mind. I know the answer is zero!

Duke

AZDoug

We need a purse fight emoticon option in the Smilies selection.

Doug

jimh_1962

65tripleblack

The flow coefficient of a device is a relative measure of its efficiency at allowing fluid flow. It describes the relationship between the pressure drop across an orifice, valve or other assembly and the corresponding flow rate.
Mathematically the flow coefficient Cv (or flow capacity rating of valve) can be expressed as:
C v = Q S G Δ P {\displaystyle C_{v}=Q{\sqrt {\dfrac {SG}{\Delta P}}}} where:

• Q is the rate of flow (expressed in US gallons per minute);
• SG is the specific gravity of the fluid (for water = 1);
• ΔP is the pressure drop across the valve (expressed in psi).

Moderate porting, which goes beyond cleaning up the valve bowls, of 461 heads yields results somewhat better than 250/.05-.06 and 195/.05; 200/.06 @ 28 in-hg drop without adding material or relocating the pushrod centerlines.

The results have been quantified in both Engine Analyzer 3.5 and the chassis dtnomometer.

68hemi

For you two guys that are arguing throughout this post let me clear up a few things about my intent.
I want this engine to LOOK as much like an original 270 h.p. engine as possible but I don't care what the cam sounds like. I want a hydraulic cam that will red line around 5800 as I don't want to take the chance of blowing up the engine so I want to keep it under 6000 rpms.
I will have what ever is possible done with the original 2x4 intake to "try" to port match to the bigger heads I put on it. This engine will look very close to and original 270 h.p. engine unless someone spots the 2 1/2" manifolds or looks at the casting number on the block which is not easy to see with the ignition shielding on.

jimh_1962

definitely doable!

Plus, definitely cool!

MikeM

Be sure and have the engine internally balanced or you'll have another identity problem with the large balancer and the different timing cover.

I wasn't the one that started talking about camshafts but you need one with a little rumplety bump to it to mimic the 270 cam. The L 79 cam has always worked well for me for that purpose,

65tripleblack

Be sure and have the engine internally balanced or you'll have another identity problem with the large balancer and the different timing cover.

I wasn't the one that started talking about camshafts but you need one with a little rumplety bump to it to mimic the 270 cam. The L 79 cam has always worked well for me for that purpose,[/QUOTE]



You are getting some bad information here.

If you build your engine as you intend to then it will begin to "lay down" after 4000-4500 RPM. See my earlier post.

If you want your engine to idle like the 283/270, then the 151 cam won't work. You'll need a solid lifter cam and one with more overlap than the Duntov had because overlap is masked as displacement increases.

68hemi

I have had a lot of engines built over the years and you can rest assured that this one will be blueprinted as well as balanced.

MikeM

Be sure and have the engine internally balanced or you'll have another identity problem with the large, lopsided external balancer and the different timing cover.

I wasn't the one that started talking about camshafts but you need one with a little rumplety bump to it to mimic the 270 cam. The L 79 cam has always worked well for me for that purpose,

65tripleblack

I see you opened that dual quad intake quite a bit.

427Hotrod

Here's a video of the 400" we did.

500 HP with the WCFB's....540HP with an air gap style dual plane and 750 Holley. 555HP with a team G single plane and same carb.




JIM

427Hotrod

It has a 248* solid roller cam. Had to weld about a 1/4" on top of each port set to cover the ports in the Dart heads. Took some work to get the "patina" to blend but no-one has ever noticed. Probably should have completely opened plenum but it was getting pretty light and was getting concerned it might crack. It's been running for years now with no issues. He's got a TKO 5 speed and 3.08 gears. It's a big surprise for the Viper guys from a roll!

JIM

AZDoug

What SCR you running in that?

Which Dart heads?

Engine dyno setup with open exhaust?

Thanks,
Doug