64 conversion from 300 HP to 340 HP car

[Duke W.]

Re: 64 conversion from 300 HP to 340 HP car

It's not that hard to get "more power" without changing external parts, messing with the stamp pad, or screwing up the low speed idle and high low end torque of the 300 HP engine.

See my first post in this thread.

Duke

[Duke W.]

Re: 64 conversion from 300 HP to 340 HP car

Great article Duke. I considered that myself. But at the end of the article you considered the experiment a failure. Do you still recommend those cam profiles? I read the article in increments. I must have missed something.

I've heard similar comments a number of times, now, and I think a lot of guys need to reread the article- if they're really interested. Granted, it's not light reading like a romance novel - or Chevy High Performance magazine. It's technical, and it goes into considerable detail, but there was no other way to do it. You have to read it like a textbook, and it may require several readings for all of it to be absorbed.

Reading it once in increments probably won't get you a passing grade. Come-on, it's only 6300 words and a handful of tables and graphs! If you want light reading, try a newspaper. If you want to understand what makes good road engine performance...

Perhaps I am too tough on myself, but I don't try to sugar coat expectations that aren't quite fulfilled. Read the conclusions three times in a row.

John McRae's Special 300 HP engine with the Special 300 HP camshaft idles just like a stock 300 HP engine, makes at least 90 percent of peak torque at 2000 just like a 300 HP engine, and has no external visual clues that it is anything other than a mundane Flint-built 327/300, but it makes as much top end power as a Flint-built L-79 and is still pulling strong at 6500.

Is that a failure?

In a relative sense, yes, because EA predicted more. Was it an absolute failure? That's for everyone to decide for themselves.

Now read the article straight through three more times. Make a photo copy and use a yellow highlighter to mark important information - like information that is new to you or you didn't understand before.

Test results for the camshaft I designed for Mike McCagh indicated that it may produce both more low end torque and more peak power in a 327/300 than the Special 300 HP Camshaft in John's engine, but because of Mike's stroker FI configuration with small port heads and lab dyno test, it will take a real 327/300 with the McCaw Special camshaft on a chassis dyno to see if this is true, and a 1964 327/300 is in the works.

It's now basically a contest between the two, but until I get chassis dyno results for a 327/300 with the McCagh Special camshaft, it's still a horserace.

The guys who put their engines on the line to participate in this project - Dennis, John, and Mike knew there was some risk. The Special 300 HP camshaft produces very good absolute results albeit somewhat short of what EA predicted, but just try to pry those engines away from them.

Mike's engine made in the ballpark of what EA predicted, and he's clearly stated his opinion - something about not prying that cam away from him until he's deep underground.

Duke

[Domenic T.]

Re: 64 conversion from 300 HP to 340 HP car

You know it's not hard to get more HP out of the 300/327 without changing a # or the outward appearance. You can do it with a hydraulic cam also.

Some on this board went the other way, and reduced their HP to burn the fuel we have today. They reduced compression, changed timing, cam, and maybee lost 25% HP. They are as fake then as the guy that puts larger valves, higher compression, larger cam and still keep the same #s on the pad.
Make it more HP and keep the same #'s. That's the easy way.
Who knows it might be 330 HP, 355,hp or whatever in a 300 block.

This was done in the old drag racing days. One would protest and demand a teardown in a stock class if he suspected things were changed.
I did a few things to my engine that increased it's HP,
The 461 castings work really good with the large valves and port reliefs and matching just to mention one thing.

DOM

[Duke W.]

Re: 64 conversion from 300 HP to 340 HP car

I guess you didn't read and/or understand the article or understand the objectives and constraints of this project, either.

There were significant boundary conditions.

The engines had to idle exactly like an OE 300 HP engine - butter smooth, 500 RPM at about 18" manifold vacuum with little or no loss of OE low end torque, so lumpy-idling OE or aftermarket high overlap cams were not an option.

That's why I had to design camshafts myself, and they feature modest duration and low overlap with a very late phased inlet event so compression can be high - close to 10.5:1 true, which is higher than OE regardless of what GM claimed. There are no off-the-shelf cams that would achieve the objectives within the established constraints.

In addition, all judged engine components had to be OE correct and the engine must pass a PV without question. A high overlap cam in a 300 HP engine would likely not even make it off the judging field before it was failed.

Sure, you can massage the heads and install a SHP or aftermarket high overlap cam that won't pass a PV or make 90 percent of peak torque at 2000, but that was not the point of this project.

I'm beginning to wonder if anyone other than the participants understand what this project was about and what was accomplished.

Duke

[Robert K.]

Re: 64 conversion from 300 HP to 340 HP car

It's not that hard to get "more power" without changing external parts, messing with the stamp pad, or screwing up the low speed idle and high low end torque of the 300 HP engine.

See my first post in this thread.

Duke

Duke, could you or have you done the same for a 340 hp engine?

[Duke W.]

Re: 64 conversion from 300 HP to 340 HP car

Yes, I system engineered a configuration I call "327 LT-1" that has the same boundary conditions - all OE parts and pass a PV. Neither ever went through a PV, but one got a Top Flight. The configuration is applicable to any SHP/FI 327. It's a 7000+ rev screamer with decent low end torque.

Look at this thread:

https://www.forums.ncrs.org/showthre...-1%22&uid=5531

It discusses the second 327 LT-1 that was built and tested on a chassis dyno.

Then follow the link in the above thread to The Corvette Forum for a lengthy discussion and dyno sheets.

The first 327 LT-1 was tested on a lab dyno and the results are here:

http://forums.corvetteforum.com/c1-a...o-results.html

Duke

[Robert K.]

Re: 64 conversion from 300 HP to 340 HP car

Good stuff!

Duke,
Question, The Duntov cam (097) had a noticable idle, due in part to the Degrees of Lobe Separation @ 110.5, but the LT1 cam has 116 degrees. Won't this cause a smother idle than the 340 hp had. Could the LT1 cam have the LS be tightened to 110 to provide the same idle? Would the cam still retain the desirable torque numbers? If so, what would you move Intake, Exhaust or both?

I eliminated the 30-30 cam early in my research due to it's lack of torque, even though I like it in my Z28.

Thanks,
Bob

[Robert K.]

Re: 64 conversion from 300 HP to 340 HP car

Duke,
Crane has a cam IO(14), IC(48), max lift (107) duration (242) @.050 and
EO(64), EC(19), max lift (117) duration (254) @ .050 for a lobe separation (112)

Would this provide the idle like the Dontov and keep the performance of the LT1? Should the tighting in the lobe profiles take a different form?

Bob

[Duke W.]

Re: 64 conversion from 300 HP to 340 HP car

Good stuff!

Duke,
Question, The Duntov cam (097) had a noticable idle, due in part to the Degrees of Lobe Separation @ 110.5, but the LT1 cam has 116 degrees. Won't this cause a smother idle than the 340 hp had. Could the LT1 cam have the LS be tightened to 110 to provide the same idle? Would the cam still retain the desirable torque numbers? If so, what would you move Intake, Exhaust or both?

I eliminated the 30-30 cam early in my research due to it's lack of torque, even though I like it in my Z28.

Thanks,
Bob

Using LSAs to compare overlap is only valid if the cams have equal duration. What counts is effective overlap measured in sq-in-deg. Look at the last issue of The Corvette Restorer. The L-79 cam has only two more degrees LSA than the base cam, but nearly five times the effective overlap!

Despite a wider LSA, the LT-1 cam has about the same effective overlap as the Duntov, which is more than the L-79 cam, but less than the 30-30.

Idle behavior is highly dependent on overlap. Both the Duntov and LT-1 cams pull about 12" manifold vacuum at 900, the 30-30 only 10".

All of these cams really have too much overlap. I did design a mechanical lifter cam based on the 0.8 E/I flow ratio of massaged heads. It had the 30-30 lobe on the inlet side and the Duntov lobe on the exhaust side with less effective overlap than any of the OE mechanical lifter cams. With massaged heads, simulations showed a little more low end torque than the LT-1 cam with about the same top end power as the LT-1 cam.

But the lobe phasing was so far out from normal that there wasn't enough material on the cam blank for Crane to grind it, so I abandoned the idea. The increase in low end torque was pretty modest, so given the accuracy of simulations, maybe it was just as well.

The '65 L-76 owner who rebuilt his engine to "327 LT-1" spec had some concern that the engine would not have the "30-30 cam idle", but once the engine was done he said the idle sounded about the same, and he really appreciated the substantially better low end torque along with the greater top end power and rev range compared to his original Flint-built 365 HP engine.

The bottom line is that all three OE SB mechanical lifter cams have a very similar idle quality. Some say they can tell the difference. I just laugh.

If anything the Duntov cam may have slightly more valve train noise even with the clearances set to my recommendations. That's because the Duntov lobes have peak jerk just above the tops of the clearance ramps, which is one reason why I don't like the design.

Despite the less than ideal dynamics, the Duntov cam is still a decent choice for a 283 restoration, but it has too much overlap for this short stroke engine. In the past I've recommended to 283 owners to have Crane grind the cam on a 114 degree LSA with a 110 deg. ATDC inlet POML, but I don't think anyone has ever done this.

The above specs would tame the idle somewhat, but improve low end torque.

The best thing to do to the DZ engine is install a 350 crank and pistons along with the LT-1 cam. That would effectively make it the same as the 70 LT-1 engine, and because of the significantly greater low end torque, you could run a 3.31 gear to make highway cruising more relaxed and have better low end acceleration than the 302 with the standard 3.77 - maybe even the 4.10 - and no one would ever know unless you told them.

Duke

[Duke W.]

Re: 64 conversion from 300 HP to 340 HP car

Duke,
Crane has a cam IO(14), IC(48), max lift (107) duration (242) @.050 and
EO(64), EC(19), max lift (117) duration (254) @ .050 for a lobe separation (112)

Would this provide the idle like the Dontov and keep the performance of the LT1? Should the tighting in the lobe profiles take a different form?

Bob

Way too much effective overlap for the duration.

Here's a story. A stroker L-71 owner was not happy with bottom end torque of his engine. He thought the idle was too lumpy, and it ran hot. Imagine that - a 496 CID big block with not enough low-rev grunt!

The engine had a Crane cam and massaged heads, but was all OE in external appearance. The cam had about the same duration as the OE cam, but the LSA was 110 rather than 114, so the Crane had a lot more effective overlap.

I recommended than he install an OE cam, but retard it six degrees because of the longer stroke.

He did chassis dyno pulls before and after the cam change. The OE cam retarded six degrees made more bottom end torque and more top end power. The engine has so much torque that nailing the throttle at nearly any speed in the first two gears breaks the wheels loose, but his likes it that way.

In normal driving, he says it's very docile, and it idles like an L-71 should.

He also modified the center carbuetor to yield full time vacuum advance with no external visual evidence of the change, and it doesn't run hot anymore.

Duke

[Jack H.]

Re: 64 conversion from 300 HP to 340 HP car

Yep, nothing wrong with wanting more power/higher performance, EXCEPT how you go about doing it...

The new NCRS rules on counterfeiting, morals and ethics embodied in the 8th Edition of the Corvette Judging Reference Manual can be construed to apply IF the 'upgraded' motor's stamp pad is altered to agree with the new higher HP configuration of the engine.

Penalties for doing this include NCRS membership suspension and the car being declared 'counterfeit' in our judging data base! Plus, there are corrolary provisions for any/all who 'abbet' the act by either judging the car or failing to report its configuration change. Hence, some may be hesitant to join in this thread...