Altitude and Carburator size selection and VE

[jimmy six]

A lot of this has a lot to do with manifold design and I'll give 3 different ones on the same engine in the same car. When I first ran my 311" GMC 6 in our roadster with a stock head which has 3 shared intake ports.
   First, I used 3 Holley 2 barrels @ 280 cfm each. The manifold was a Clifford steel with 9" tapered ram tubes with 3/4" equalizing tubes between the rams 1" under the carb mounting plates. Record at 162 mph.
    Second manifold was tubes to a common rectangular box slightly larger than the carb base. Outside ports equal length center one much shorter. All level with cylinder head. 1 single Brazwell Holley 2 barrel which flowed 600+ cfm. Speed 163.. No record.
    Third.  Clifford aluminum intake for a 194-292 GM 6 with extended hours of modifications to fit. 1 single Holley 650 cfm 4 barrel modified by Sean Murphy. Speed 165 and record.
All engines had the identical cam, compression, head porting. A top speed of 171 has been reached with different engine components. Absolutely no dyno results known. My dyno was tires on salt or dirt.. Good Luck.

[Polyhead]

So in other words, manifold design is far more important than carefully chosen carburetion.

[fordboy628]

A lot of this has a lot to do with manifold design and I'll give 3 different ones on the same engine in the same car. When I first ran my 311" GMC 6 in our roadster with a stock head which has 3 shared intake ports.
   First, I used 3 Holley 2 barrels @ 280 cfm each. The manifold was a Clifford steel with 9" tapered ram tubes with 3/4" equalizing tubes between the rams 1" under the carb mounting plates. Record at 162 mph.
    Second manifold was tubes to a common rectangular box slightly larger than the carb base. Outside ports equal length center one much shorter. All level with cylinder head. 1 single Brazwell Holley 2 barrel which flowed 600+ cfm. Speed 163.. No record.
    Third.  Clifford aluminum intake for a 194-292 GM 6 with extended hours of modifications to fit. 1 single Holley 650 cfm 4 barrel modified by Sean Murphy. Speed 165 and record.
All engines had the identical cam, compression, head porting. A top speed of 171 has been reached with different engine components. Absolutely no dyno results known. My dyno was tires on salt or dirt.. Good Luck.

At the risk of oversimplifying:

What matters is the total flow capability of the "individual components" once assembled together on the engine, and how well the "set" of said components might flow.

Ie:
A/  Straight shots of airflow to the valve are usually "good"
2/  90 degree (or more) turns with little to no radius are usually "bad"
d/  A blower is helpful in making "poor flowing" combinations "work"

This topic could be debated endlessly.    For results sooner, go technical.    If the journey is important, stick with cut, fit & try.

Both work.

 
Fordboy

[Polyhead]

A lot of this has a lot to do with manifold design and I'll give 3 different ones on the same engine in the same car. When I first ran my 311" GMC 6 in our roadster with a stock head which has 3 shared intake ports.
   First, I used 3 Holley 2 barrels @ 280 cfm each. The manifold was a Clifford steel with 9" tapered ram tubes with 3/4" equalizing tubes between the rams 1" under the carb mounting plates. Record at 162 mph.
    Second manifold was tubes to a common rectangular box slightly larger than the carb base. Outside ports equal length center one much shorter. All level with cylinder head. 1 single Brazwell Holley 2 barrel which flowed 600+ cfm. Speed 163.. No record.
    Third.  Clifford aluminum intake for a 194-292 GM 6 with extended hours of modifications to fit. 1 single Holley 650 cfm 4 barrel modified by Sean Murphy. Speed 165 and record.
All engines had the identical cam, compression, head porting. A top speed of 171 has been reached with different engine components. Absolutely no dyno results known. My dyno was tires on salt or dirt.. Good Luck.

At the risk of oversimplifying:

What matters is the total flow capability of the "individual components" once assembled together on the engine, and how well the "set" of said components might flow.

Ie:
A/  Straight shots of airflow to the valve are usually "good"
2/  90 degree (or more) turns with little to no radius are usually "bad"
d/  A blower is helpful in making "poor flowing" combinations "work"

This topic could be debated endlessly.    For results sooner, go technical.    If the journey is important, stick with cut, fit & try.

Both work.

 
Fordboy

I would like to know what you think I'm actually looking for as fast as results go.  Doing cut fit and try would have me running a gm small block... But who wants to do that?  Getting your name in a book... That's boring crap.  Trying to coax an engine along into an application it was never designed for, far more entertaining.  Dropping into a distinct and unusual body style is icing on the cake.  It won't be fast but it will be a riot.

[SPARKY]

Boring Crap---just try running over 2 at EL M late in the meet when about the time you can see the balloons it looks and feels like you are running through a plowed field 

there maybe crap involved----- but its far from boring to most

[RichFox]

I think what you could read into JDs post is that he "Cut and tried" until he found an intake he liked. I don't expect your car to be fast. I didn't expect my Packard to go fast. Yes the idea was to go faster with an unconventional engine. Cause I wanted to. There was a thread on here about cutting up Studebaker heads and altering them to flow more air. If you can find it it might demonstrate some ways you can use your machinist skills to help your project along. You did mention running on the long course.  If you are going to limit yourself to bought items, I think the 130 club might be a stretch.

[wobblywalrus]

Are two pistons at BDC on a bank of that polyhead at the same time the other two other pistons are at TDC?

[ronnieroadster]

 Why not take the time to contact carb building specialist. I as well as a number of other LSR racers have had great success using Quickfuel Technology for the proper size carb. Their tech guy not only sized the proper carb he also included the jet size based on location be it on the runways or on the Salt. Thier custom built carb is actually less money than an off the shelf carb from any mail order speed parts merchant.
  Save your self time and money why waste a good poly with the wrong carbie size when the experts in the filed can size what works.  

[panic]

Are two pistons at BDC on a bank of that polyhead at the same time the other two other pistons are at TDC?

Not without a new crank and cam, it's a conventional Chrysler V8 same as every other.

[Polyhead]

Are two pistons at BDC on a bank of that polyhead at the same time the other two other pistons are at TDC?

Nope... It's the same as any small block chrysler v8.   Same as the big block mopar as well.  All stock chrysler v8's are cross plane engines.

[Polyhead]

Why not take the time to contact carb building specialist. I as well as a number of other LSR racers have had great success using Quickfuel Technology for the proper size carb. Their tech guy not only sized the proper carb he also included the jet size based on location be it on the runways or on the Salt. Thier custom built carb is actually less money than an off the shelf carb from any mail order speed parts merchant.
  Save your self time and money why waste a good poly with the wrong carbie size when the experts in the filed can size what works.  

Why?  Because I've never heard of 'em.  Having someone else do it for me seems like taking the easy way out.

I dunno.  I'm pretty set on starting off with anything made by carter that I can score cheap, but preferably a Thermoquad, just because everyone will HATE that choice.  Besides Moroso make a pretty great 2" tall square bore to spread bore adapter.  It's one of those situations I think on a small engine, I can have my cake and eat it too.  I'll have plenty of throttle authority so that getting the car rolling on the little 1" primaries won't be a hassle, and those big 2 1/4" secondaries will take over and flow plenty of fuel to get the engine to peak power. They are complicated to tune, they are difficult to get tuning parts for, but jets... that's what drills and silver solder are for!  I've got every number drill you can get, every letter drill you can get, and every fractional drill you can get up to 1".  The advantages of being a job shop machinist for 15 years!

Failing finding a thermoquad at the april swap meet, I'll order up a remanufactured Edelbrock Thunder AVS from summit racing.  I'm leaning towards 650CFM, but there is an 800CFM model.  However at that point the primary side starts to become quite large for this little engine, and the velocities will start to be rather low.  Since the AVS series carbs don't have annular discharge tubes in the secondaries It's something I have to keep in mind.  Oddly the theromquad DOES have annular discharge tubes in the secondaries!  I get a straight leg in the primary, and annular in the secondary, which is ideal for my application.

[SPARKY]

OK  I bought PipeMax---

-have sorta have my eng in it! and have it real close to matching my dyno sheet by addressing VE

Now to the altitude ?

Should I get the HP output down to what its going to be a B'ville to get a pipe size for what the eng is producing there or 

[hotrod]

It has been a very long time since I played with pipe max but I would suggest you contact Larry Meaux directly and ask him how you should proceed.

He is a regular participant on speedtalk forum ( http://speedtalk.com/forum/ )
and of course his own web page has contact info on it.

http://www.maxracesoftware.com/

[SPARKY]

Thanks HR

[wobblywalrus]

Sparky, tell us what Larry says.  That is a good question.

Poly, the idea of equal length intake tracts tuned to a harmonic that enter a plenum tuned to a resonant frequency is done with success by guys with little inline fours in jap cars and on in line twins and fours by all sorts of bike tuners.  The tuned engine share in common one trait.  The pistons are at BDC and TDC at the a same time.  This promotes harmonious resonance throughout the inlet tract and plenum.  Careful tuning can get contribute to substantial volumetric efficiency.  That is why I mention it.

It sounds like the pistons do not reach TDC and BDC at the same time on your engine.  This might lead to a discordant cacophony of reflected sound waves in the inlet tracts and plenum and be hard to tune.  Choosing a carb and manifold setup developed for your application might be the best bet.  It would be tricky to get the Helmholtz principles to work in a plenum.  Maybe someone can.  It would be to complicated for me.