XXO/BVGC '38 Chevy Coupe Build

[Freud]

Back to blown Cad flatheads!

Rex


What a marvelous destination. My experience in Cad flatheads goes back to 1947.

My Dad loved those monsters.

FREUD

[38flattie]

I've just returned from 5 days In California, on a quest for more HP in the flathead- wow, did I ever get my arse kicked! More on that later!

Tuesday morning, I met Rex Schimmer for breakfast, then we headed over to Dema Elgins, and spoke with him about a cam. Rex, thanks for taking the time to meet with me-it was good to see you again! Tony, time was short, but we'll catch up next time, okay?

From Dema's I headed down to Rich Fox's, to pick up a tranny he loaned me. Always good to see you Rich!

Then, on to Don's place, where I picked up the test chambers he cut, so that I could modify them, instead of our real heads. Don's always on top of this stuff!

Tuesday night I was in Arroyo Grande , having supper with Garry Odbert. Garry was an immense help on everything- he even had his test block there, so we could compare the porting to his. Garry runs the Retarded Spark Special, a record setting Caddy flathead powered roadster. Thanks Garry!

Wednesday morning, Garry and I headed over to Race Engine systems, in Santa Maria, owned by Craig Gerfen. Craig was Alan Johnson's top fuel port and flow guy for 8 years, and had also ported Garry's Caddy flathead.

Here is where the arse kicking started! I'm not going to post every number, test, and dye test we did, but I'll tell you what we found out. Plain and simply put, the ports are too large, therefore velocity suffers, and they don't flow as well as they could. Across the board, we're down about 20 CFM from Garry's. We flowed my engine, then Garry's, back to mine, etc', so the data was current and reliable.

After, trying everything to increase flow- different valve angles, different valves, different chamber designs, blending the valve guides, etc., to no avail, we tried a different approach. We added material around the short side radius. BAM- an instant 10 CFM gain! We played with this for a while, and determined we need to add material back to the ports, then do another port job. We also played with the relieved block, but that only reinforced my previous belief, and that belief is that it is a waste of time.

So, I called Frank Morris with the Salt Cat guys, to find out what epoxy they had used on the Buick engine. Frank and Doug are great guys! Frank gave me the info I needed, sold me a set of 29" tires, so it was a win/win conversation for me! Thank's Frank!

So, it can't get any worse, right? Wrong!  We flowed the exhaust, and they sure do flow- too Dodge much! The exhaust out flow the intakes, and that is not good! That correction will come with the cam choice- my guess is we'll end up with a dual pattern cam.

We did a couple of dye tests, to see what was going on in the chambers. With our current setup, the A/F mixture swirls around in the chamber, running back into itself- basically creates a traffic jam in the chamber. We took the angled ramp out, and straightened that transfer area out. On my engine, we see a small inrease on flow, but a lot better flow pattern out of the dye.

At the end of the day, the stock block, ported, with a stock 106 CC Caddy head, flows better than the FlatCad head and either of the 2 mods I made, better than Edmunds, and better than Cyclone! The stock head has several complex contours and ramps in it, and flows well- it appears the Caddy engineers really knew their stuff!

So, to gain the CFM I went to California for, we need to add material to the ports, re-port the block, and change our chamber design. Here are numbers from the #8 cylinder, which is the best flowing cylinder on Garry's car- he flows 200 CFM on the intake side.  Our best cylinder was # 3


                         #8 intake                                   #3 intake                                       #8 exhaust


.100 lift                 69                                              64                                                    73

.200                     121                                           118                                                  120

.300                     154                                           157                                                  145

.400                     175                                           173                                                  165

.500                     173                                           180                                                  174

.525                     173                                           179                                                  176        


Here is what is typicle of our worst ports, intake only  


                        #5 intake                                    #5 intake modified with clay


.100 lift                 63                                             60

.200                     114                                           110

.300                     150                                           151

.400                     162                                           169

.500                     163                                           174

.525                     163                                           174




At this point, I had the knowledge I had came for, and I loaded up and headed back to Don's place to spend the night. After a nice dinner, Don and I retired to the garage, to smoke, joke, and bench race. Don, as usual, it was great seeing you and Dar- many thanks!

Friday I headed for the house, but stopped in Salt Lake City to visit Kenny Kloth, as I had some specific questions for him about roller lifters and his chamber design. Kenny is a great guy, and a wealth of knowledge, He was very helpful, and informative. I stayed a couple of hours, but easily could have stayed several days, had time permitted.


So, the HP quest continues!

[38flattie]

A few more pics.

[Glen]

Very interesting stuff Buddy. looks like you have a few days of work ahead.

[Jack Gifford]

Are you certain that exhaust can flow "too much" on a forced induction engine? My limited experience (eleven full seasons of heads-up pulling competition) indicates otherwise. When Mickey designed the heads (Pontiac hemi) he went overboard on exhaust valve size and port CSA (recent flow-testing showed that exhaust flow would almost support a modern top fuel engine). Rather than downsize them for my small (370 c.i.) alky engine, I left them alone (2.03" valves, same as my intakes), and built 2.375" I.D. zoomies to match the port-exit area. Toward the end of my campaign, it was making a little over 900 HP (at no more than 13 PSIG in the manifold) and was "happy" at 9,000 RPM throughout most runs. So I'm not convinced that blower engine exhaust can breathe "too well".

[Rex Schimmer]

Buddy,
I think that I have to agree with Jack, when the differential pressure between the inlet manifold and the cylinder is jacked up by a blower the flow past the valves is probably considerably different than when the differential pressure is only atmospheric. It is one thing to check the port flow at a max potential differential pressure of 14.7 psid and another when you add 17 lbs of boost and the differential potential is 32.7 psid. Using some basic flow through an orifice calcualtions the flow difference between 14.7 psid and 32.7 psid is about a 50% flow increase which also means the velocity of the incoming air is also increased by 50%. Any chance of testing your ports with additional inlet pressure?

Great seeing you and going to Dema's place.

Rex

[SPARKY]

I am a rookie with no blower experience but lots of research and questions--many of  the WWII aircraft engs. had almost identical ports and valves .

I talked with the eng on the Blown Ecotech---my question was "At higher boost levels is moving the exhaust port and exhaust valve larger the correct way to go?  He replied "VERY"

[BoredAndStroked]

There are many opinions on this - with some saying that our current exhaust flow is too much and this is a problem.   That is exactly what Buddy heard in his flow-bench work . . . makes it hard to know what to do???

FWIW: Before I ported the block and selected valve sizes I talked with Jeff Fowler at length . . . his comment was basically that with an all-out competition blown engine, you need to pay particular attention to the exhaust and you just about can't get it out fast enough.   His comments were that 'big flow' is usually better with this style of engine.   That is the reason we have 1.78" exhaust valves and extensive port work - I went for as much flow as I could get.   I also asked about things like putting port dividers in the center exhaust port (big Siamese port on the FlatCad) - he said it wouldn't make any appreciable difference on this engine.  I also asked about tuned-length headers - he said that won't make much difference either - which is why you see zoomies on all the top-end blown motors.   Is he correct?   Guess I was willing to bet my porting time and efforts on him.  In retrospect, we made some big HP on the dyno, so at least we have some results/statistics to work from.

So - who knows who is 'right' on this - but I trusted my instincts and the advice of somebody who has been building very high horsepower blown/competition engines for 30 years.  His engines are the most frequent winners in the unlimited tractor pull events - with the guys running 5 or 6 of them at a time.    Given the level of money and competition in his world, he has to be making very big horsepower for these folks to be running his stuff . . . and consistently winning.   Look up the 'Black Widow' tractor pulling operation - all the engines are Jeff's.

So - I only wish I had the time, energy and a personal dyno to test some of these competing theories and come to some concrete conclusions.   Until then, we'll try a few different things, see what the engine and great-white dyno tell us . . . hopefully we'll learn something.  I'm sure the debate will rage on - seems to be how it always is.  

Thanks for all the comments and advice - we're just rookies trying to go faster!   The more we hear from you guys, the better.  

I'm going to continue to look into 'all things flathead' - as I believe there is a LOT more to learn.

B&S

[SPARKY]

It occurred to me that the reason the exhaust on a turbo eng needs to be big-- the duration is usually less and you are not using "draw through" as much

[Koncretekid]

I don't know much about supercharged motors, but I know one thing - - if you make more than one significant change between runs (dyno or actual) you probably won't know which change made the difference, if any.  So if you've found something that seems to improve the intake flow, and you change the exhaust flow at the same time,  you may not learn anything.
Tom

[38flattie]

Jack, Rex, Sparky, - you guys may well be right. Using best/known proven practices are our best bet in my mind. Even top fuelers only run about 90% exhaust to intake ratio, but that is not to say what we have won't work, and work well. At the end of the day, Dema will grind the cam based on the numbers, and his experience, and we'll go back to the dyno.

Tom, you're absolutely right! Unfortunately, time and money dictate one trip to the dyno, so we'll have to see if we made gains on the entire 'package'!

Dale, you and I have sent numerous emails back and forth, and pretty well kicked this dead horse to pieces! Lol! So, one more time

Fowler builds high end tractor pulling engines-yes, I realize he does other stuff too, but his reputation is built on the pulling engines. I'm guessing that they have a huge amount of torque, and HP to waste. WE DO NOT! Simply charging more for the work he does, does not make his opinion more valuable either!

One of the conversations you and I keep having concerns flow. You feel the blower probably compensates for bad/lack of flow, and just 'stuffs' the air into/out of the engine.

I believe air flow is air flow- if you have problems flowing N/A, then the flow issue is compounded when you add boost. A traffic jam is a traffic jam at any pressure. I believe the same about exhaust. It is well proven that tuned headers increase power on the dyno. Why would that not hold true on a supercharged engine? We don't have a 8000HP top fuel engine, where creating headers might cause too much heat or restriction. We have a 570 HP engine, when running headers on the dyno! I'll bet we don't have that HP with the short, straight pipes we are running. Next dyno session, we will dyno with the headers going onto the car, so at least we know what we have.

We cannot dyno every time we want to test a new idea- time and money will simply not allow it. Therefore, we will follow simple 'rules' for tweaking the engine- getting better flow N/A, headers, special cam, etc.

[BoredAndStroked]

As you can all tell - Buddy and I don't agree on everything . . . and that is perfectly okay!   We're kind of a constant check and balance system for one another.   He is entitled to his opinions -- me to mine.   The dyno and the salt will settle some of our differences.   

My one comment to the above is this:

IMHO:  I don't believe that anybody who is a constant winner looks at their engines with an attitude of "I have horsepower to waste" -- quite the opposite.  If they're willing to give up horsepower, their competitor probably isn't -- so they will be losers with that attitude.  In all forms of highly competitive racing, even incremental increases in horsepower can make the difference in who wins and who loses.   The only time I've seen folks knowingly give up horsepower is for consistency and/or reliability . . .  and exhaust design probably doesn't fall into those categories.   And they won't usually do it for long - as somebody else will solve the 'reliability' issue and kick their butts.


With the above said - we are all learning along the way, we'll continue to experiment where we can and over time (hopefully!), we'll figure out what this particular engine design likes best and how to make the most horsepower possible . . . and MAYBE we'll keep it together in the process!   

Keep the conversations alive and the debates active - it is how we all learn . . .

B&S

[38flattie]

As you can all tell - Buddy and I don't agree on everything . . . and that is perfectly okay!   We're kind of a constant check and balance system for one another.   He is entitled to his opinions -- me to mine.   The dyno and the salt will settle some of our differences.   
B&S

 

[SPARKY]

" The only time I've seen folks knowingly give up horsepower is for consistency and/or reliability ."

AERO     

[38flattie]

Haha! Sparky, I'm on that track too!

I feel that while we can eek out a little more HP from the engine, aero is our biggest bang for the buck. The few HP we can add will help, but the big difference in speed will undoubtedly come from a sleeker, better flowing aero design!

Oh, and Don is starting work with some of the parts you loaned me, for the next phase of the project! I'll post pics as progress is made!