1964 FI Roadster

[Duke W.]

Re: 1964 FI Roadster

If I wasn't such a terrible writer, I might consider that, but not sure if any of my chapters would be interested. I am having mine tuned on a chassis dyno, and I will be very disappointed if it is less than 310 HP at the rear wheels. If you are using an engine dyno (which it sounds like you are), I would expect north of 350 HP if your engine gets the best tune on the FI unit and is stock configuration. That's my guess.

You have to be careful as there are several different ways to measure horsepower. In my experience, a "stock rebuild" will be about 10 percent short of the advertised SAE gross horsepower/torque at about 10 percent less revs. Massaging the heads will get pretty close to the OE SAE gross numbers. SAE gross uses the "standard temperature/pressure (STP)air density correction factor, which is 29.92" Hg, 59F, zero humidity and is the defacto air density correction method for aftermarket lab dyno tests.

Various correction factors can be applied... DIN, JIS... but current SAE net correction uses lower temperature/pressure than STP, which reduces torque /power data by about 4.5 percent compared to STP. SAE net should also be applied to RWHP test data.

Another issue is headers versus manifolds. If you plan to run manifolds on the car, use manifolds for the lab dyno test. One lab test session I have where both headers and OE manifolds were used showed about 8 percent more peak torque, but only about 3 percent more top end power, and, of course, that would be with no mufflers on either. With the OE exhaust system the differences will be less.

I have yet to see a SHP/FI 327 make over 300 SAE corrected RWHP, but with massaged heads they come close. Peak power is usually at about 6500 with a little rolloff to 7000+.

You need to let these short stroke engines rev, which is why I say you are nuts if using OE connecting rods, especially the pre-'66 versions that are decidedly weak at the bolts seats and have destroyed many blocks when they let go over the years.

During a chassis dyno test you need to ensure that the fan clutch does not tighten, which can cost up to about 10 lb-ft and 15 horsepower... best to test on a cool day, make sure the shop has good external cooling fans, and bring a garden sprayer to spritz down the radiator between pulls. If you post data, please provide full context like correction factor type, headers or manifolds, and whether an electric or mechanically engine water pump was used. It's usually assumed that no mufflers are installed in the lab exhaust evacuation system.

I have a written chassis dyno test plan. If anyone is interested, contact with via email through the TDB.



Duke

[Duke W.]

Re: 1964 FI Roadster

My '65 made around 330 with the dyno exhaust. 294 with the sidepipes installed. Of course, using different dynos means the numbers cannot be compared.

George- I have your dyno test data sheets and my understanding is that it was a lab dyno test with STP correction with both manifolds and headers through the dyno cell exhaust system with no mufflers, and the 30-over 327/375 HP FI engine has OE replacement pistons with no head massaging. Where did "sidepipes" enter the equation?

Why don't you post the sheets, provide complete data on the engine configuation and we can discuss. For sure some power was left on the table due to insufficient total WOT spark advance with both manifolds and headers and WAAAAAAY too rich a mixture with manifolds, but I question the data because it is too consistent.

A lot of guys are disappointed after dyno runs, typically because their expectations are too high, and they don't understand that the advertised SAE gross numbers from the era was just a pipe dream..

The key to being satisfied is having realistic expectations.

Dyno test data is comparable from different dynos, dyno types, and different times if full context including correction type (if any) is included, but it's usually not. Guys just throw numbers around and don't really understand how they were derived or what they mean.

Duke

[Michael G.]

Re: 1964 FI Roadster

Slightly off topic I know, but curious as to how the 365 HP carbureted engine compares in a real world dyno test situation against the 375 HP rated FI mill. I would be interested to know the actual difference between the two, versus a theoretical 10 HP.

Duke, is there any such data in your archives?

[Duke W.]

Re: 1964 FI Roadster

I don't have any actual data, but I can give you some insight. With both the 365 and 375 HP engines the limit on top end power with the OE heads is head flow. The FI single plane "tunnel ram" manifold is more efficient at high revs than the 365 HP dual plane manifold, but the FI manifold doesn't help much because of the head flow restriction, so the modest (less than three percent) higher FI rating is probably justified.

But things change when you massage the heads. With massaged head the 365 HP manifold becomes the major restriction, but not the FI manifold, so with massaged heads the FI system should make about 4-7 percent more top end power and add another few hundred useable revs, maybe up to 7500, but the valve train limiting speed with OE springs is about 7200, and beyond that I get concerned about the OE wet sump oiling system being able to keep up with demand.

At very high revs there is at least 3 quarts of oil up in the engine, and the higher the revs, the harder it is for the oil to get back into the pan and keep the oil pump immersed in oil. At very high revs it only takes a couple of seconds of oil starvation to seize bearings and possibly break a rod.

BTW the engine I referred to earlier, started as a '65 L-79, rebuilt 30-iver with OE replacement forged pistons, massaged heads, LT-1 cam, and aftermarket high strength rods made a little over 350 STP corrected HP at 6500 and 332 lb-ft at 4500 on a lab dyno while meeting the design objective of no less than 80 percent of peak torque at 2000.

Another identically configured engine that started out as a '65 365 HP made peak RW torque/power of about 270/275 at the same revs, with 80 percent peak torque at 2000 and 90 percent at 2500,but it was done on a hot day without external cooling fans and the owner reported that the fan was "screaming", so with decent external cooling that would prevent the fan clutch from tightening I think it would have made about 280/290 SAE corrected torque/RWHP. Power fell off a little beyond 6500 and the fall accelerated after 7200 and more at 7250., which was the max test speed.

I recommended a standard redline of 7000 and 7200 for "war emergency power". That was ten years ago and the owner still buzzes it to seven grand at every opportunity.

Duke

[Patrick C.]

Re: 1964 FI Roadster

Gentlemen,

With my comments about expected HP on the dyno and my 326 water pump I did not mean to cause this much of a discussion. I recently retired July 1st as CEO of a large manufacturer of sophisticated full authority electronic engine controls systems. While I am an engineer, I was a poor one, but we ran 12 state of the art AVL 650HP dyno's with dilution tunnels and fully certified emission capability. They were about a $1.0M a piece so I have some familiarity with this type of testing. But I always made sure we hired the best of the best to run them.

But my Corvette is my hobby, not my job. and my bone stock 1964 375HP fuelie, is going to be run on the dyno of my local engine builder K&S. Kent has built many of these engines over the years. He has an older Superflow dyno and we are going to run the engine on his SBC headers without a fan or fan clutch. The engine has stock heads and stock shim head gaskets, its honed .020 over, and has a replacement 30/30 cam. The dyno room is very simple and does not have temperature or humidity controls. We will use some crude correction factors to get a rough idea of the power. I'm guessing about 300HP. My real intention was not to maximize the power but to break in the cam before I put the engine back in the car. I don't want to be pulling it out again. I am just getting it ready to go today see pictures. Any suggestions are welcome.

Regarding the 326 water pump, I can remember numerous times when I was an engineering executive and we had a problem with a mold, a vendor or a part we would pull the next part number on the register and use it if we had a replacement to keep production rolling. Drawings would follow later when we had resources. This was especially true if it was a form fit or function replacement. Just my two cents but you guys have spent much more time researching this issue than me. I am just puzzled why the judging manual does not reflect this? A mistake?

[Ed S.]

Re: 1964 FI Roadster

Duke,

You have mentioned "massaged heads" when discussing SHP SBs numerous times, and on a few occasions you briefly described what does and does not constitute a properly massaged head. Have you ever published a how-to article that included before and after pictures of a massaged SHP double hump head for the Restorer or another publication? Or, can you provide a reference or a link to an article?

Thanks -

[Duke W.]

Re: 1964 FI Roadster

The dyno cell doesn't need to be climate controlled, but it should have pressure, temperature, and humidity measuring devices. You then plug those data recorded during the tests into the software, select STP correction, and you have what is essentially SAE gross.

With OE exhaust manifoldsI would expect something close to 300 honest SAE gross horsepower based on what you have told us about the engine configurations. With headers, a few percent more.

Duke

[Duke W.]

Re: 1964 FI Roadster

Duke,

You have mentioned "massaged heads" when discussing SHP SBs numerous times, and on a few occasions you briefly described what does and does not constitute a properly massaged head. Have you ever published a how-to article that included before and after pictures of a massaged SHP double hump head for the Restorer or another publication? Or, can you provide a reference or a link to an article?

Thanks -

I've attached this before, but here it is again.

Duke

[Patrick C.]

Re: 1964 FI Roadster

He does have temp, humidity and pressure but the calibration and accuracy may leave a little to be desired. Will see.

[George J.]

Re: 1964 FI Roadster

George- I have your dyno test data sheets and my understanding is that it was a lab dyno test with STP correction with both manifolds and headers through the dyno cell exhaust system with no mufflers, and the 30-over 327/375 HP FI engine has OE replacement pistons with no head massaging. Where did "sidepipes" enter the equation?

Why don't you post the sheets, provide complete data on the engine configuation and we can discuss. For sure some power was left on the table due to insufficient total WOT spark advance with both manifolds and headers and WAAAAAAY too rich a mixture with manifolds, but I question the data because it is too consistent.

A lot of guys are disappointed after dyno runs, typically because their expectations are too high, and they don't understand that the advertised SAE gross numbers from the era was just a pipe dream..

The key to being satisfied is having realistic expectations.

Dyno test data is comparable from different dynos, dyno types, and different times if full context including correction type (if any) is included, but it's usually not. Guys just throw numbers around and don't really understand how they were derived or what they mean.

Duke

Duke,
I thought I sent you both sets. For some reason I can't find them on my computer. I knew the people running the dyno were not going to give me the best results, but it was the best I could get at the time. It gave me the ballpark I was looking for. Once I had the original manifolds on and the engine was in the car, I was able to lean out the full throttle a little and pick up some hp. I need to get it on a chasis dyno, but life is just too busy for now.

[Duke W.]

Re: 1964 FI Roadster

I've attached (with permission) three test sheets from George's rebuilt '65 L-84 back in 2001. There are three tests, and the engine is basically a "stock rebuild" - .060" overbore, with OE replacement 30-30 cam and forged, 5.3cc dome pistons. The heads received a valve reseat, but no "massaging" for improved flow, so they are representative of typical Flint-machined heads. Gasket thickness is not verified, but as is typical I am currently assuming that it has a thick composition gasket which would place the CR at something close to 10.25:1 assuming nominal deck heights, which were not measured.

Download the pdf and we can compare. Look at page three, and ignore the data about headers and mufflers. This configuration had the OE manifolds routed into the 3" dyno exhaust system with no mufflers. Correction is STP so this engine is representative of the configuration and SAE gross test procedure that Chevrolet used to establish the advertised SAE gross ratings.

Note that the 321/332 torque/power ratings are 92/89 percent of the advertised 350/375 HP ratings that can also be expressed as actual SAE gross torque/power being 8/11 percent lower than the advertised ratings, which is typical of the era. Sorry guys, that's the way it was back then. Honest ratings did not come into effect until the new SAE net procedures were first implemented in 1971.

Massaging the heads would have improved torque and power by close to ten percent, which would about the achieve the advertised ratings.

Now let's look at the two tests on page 1 and 2. These were back to back tests within about five minutes and the exhaust system consisted of the OE manifolds and full OE sidepipe system that routed to the dyno cell exhaust system with no downstream mufflers.

Sheets 1 and 2 torque/power average about 291/293 or about 91/88 percent of sheet three and the only difference is the addition of the sidepipes, so sidepipes alone knock down torque/power by 9/12 percent.

Now we can get some insight into how restrictive the sidepipe system is compared to the under-the-car exhaust. I have dyno data for two "327 LT-1" configurations, both tested with OE exhaust manifolds and measured CR averaging about 10.4:1. Both have the ...461 OE aluminum manifold, OE Holley, and LT-1 cam with nicely massaged heads. One was tested on a lab dyno at 356 GHP and the other on a chassis dyno with under-the-car exhaust at about 270 with SAE air density correction. Using 0.85 driveline/tire efficiency that would be about 318 SAE net at the flywheel, which yields a 0.89 net/gross conversion factor.

About half of this net-gross difference is the lower air density correction of SAE net compared to STP used for SAE gross, and the rest is the exhaust system and front end accessories. Of the latter, only an alternator and clutch fan that does not tighten absorbs only a couple of horsepower, so from a practical standpoint we can say that half the net/gross difference is air density correction and the other half is exhaust pumping loss.

Given the above the under-the-car exhaust system pumping loss is about 19 HP or about 5.3 percent.

Sidepipes ate up 39 GHP on George's L-84, which is about 11.8 percent, so we can conclude that sidepipes cost about double the parasitic pumping power as the under-the-car system, which is significant!

Duke

[John D.]

Re: 1964 FI Roadster

Slightly off topic I know, but curious as to how the 365 HP carbureted engine compares in a real world dyno test situation against the 375 HP rated FI mill. I would be interested to know the actual difference between the two, versus a theoretical 10 HP.

Duke, is there any such data in your archives?

Michael, Didn't read all the replies here as too many. But here's a story for the gang. You asked the difference between 365 HP and 375 HP on a dyno I believe.
Forget the dyno and lets talk drag racing. My cousin had a 365 with TI brand new. I had a new 365 with a points distributor. Same gears.
He used to beat me all the time because he could out rev me. So I pulled a trick with the points distributor. Put a piece of rubber to keep the points from bouncing.. I got the non TI car up to almost 7000 RPM and it was a dead heat going down the old Lincoln highway one night.
I used to full throttle shift without using clutch pedal. The good old days. JD

[William M.]

Re: 1964 FI Roadster

Re: 3839175 Water Pump
The 3839175 water pump was used on the 1964 Corvettes with the solid lifter 365hp327 and 375hp327 FI engines. Period!!!! The 3859326 water pump was never used as it was cast later after 1964 production. The expert on this is Mike Manson who swears that the 3859326 water pump was never used on any 1964 Corvette and has the Grey Iron Foundry documents to prove this. Over the last 20+ years I have stated this as well along with Mike Hanson(you can put in "3839175" in the Search box in the Technical Discussion Board and bring up the posts as well as in the archives).
You can go to www.mockauto.com and click on the small block chevy water pump link to see pictures of all of the water pumps used on the small block V-8 engines from 1955-1972.
Put this to rest!!!!!!!!!!!!!!
Regards, Bill Mock #93