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Re: My Corvair Porche 914 Project
Posted by: ROD ()
Date: September 22, 2017 11:29AM

the end result for future mufflers was meant to be 2 cherry bombs welded on top of each other hanging from the stock rear muffler hanger. one dump out of each side .

hope the pics help.

Rod Tetrault
El Cajon , CA
65 Corsa Yenko Clone / 65 Corsa EO Creampuff Vert
66 Corsa "JIMISH" Mid engine Turbo LS1 currently 2nd fastest Corvair in the USA
Class 5 Corvair powered Baja
61 Vintage Rampy
Corvair powered Buggy x 3
Enough hidden parts to build a space ship

Re: My Corvair Porche 914 Project
Posted by: ROD ()
Date: September 22, 2017 11:33AM

JimBrandberg Wrote:
-------------------------------------------------------
> Where did you get the slant tubes? I haven't seen
> any that swoop out to the side like that.
> Jim Brandberg
> Isanti, MN
> CorvairRepair.com


I made them

Rod Tetrault
El Cajon , CA
65 Corsa Yenko Clone / 65 Corsa EO Creampuff Vert
66 Corsa "JIMISH" Mid engine Turbo LS1 currently 2nd fastest Corvair in the USA
Class 5 Corvair powered Baja
61 Vintage Rampy
Corvair powered Buggy x 3
Enough hidden parts to build a space ship

Re: My Corvair Porche 914 Project
Posted by: ROD ()
Date: September 22, 2017 11:54AM

AHH Jim , I see now your question was for the original poster. we were posting at the same time ggg

here this pic is an airplane style header that may work best with his style of angled exhaust.

Rod Tetrault
El Cajon , CA
65 Corsa Yenko Clone / 65 Corsa EO Creampuff Vert
66 Corsa "JIMISH" Mid engine Turbo LS1 currently 2nd fastest Corvair in the USA
Class 5 Corvair powered Baja
61 Vintage Rampy
Corvair powered Buggy x 3
Enough hidden parts to build a space ship

Attachments:
Re: My Corvair Porche 914 Project
Posted by: Seth Emerson ()
Date: September 22, 2017 01:44PM

Doug Hargrove used this style of exit tube back in the 70s. He bought tight 180 degree U-bends and sliced them in two. Then trimmed the straight part to slide up into the head. The side-facing parts had 2-bolt flanges welded on, as did the fabbed headers. I had a set on my race car. I called them "Headers by Doug"!

Seth Emerson

Check my new Performance Corvair Web site [www.perfvair.com]

Re: My Corvair Porsche 914 Project
Posted by: JimBrandberg ()
Date: September 23, 2017 05:50AM

When you wax the Porsche guys with a Corvair engine it will frost their jaws.
Our old Ice Racing driver Hank Godfredson was a dyed in the wool Porsche guy but would piss everybody off at the Porsche club autocross by posting FTD with a Datsun 510.
You're doing nice work there, thanks for posting.
I like Rod's headers too.
Jim Brandberg
Isanti, MN
CorvairRepair.com

Re: My Corvair Porsche 914 Project
Posted by: kholm ()
Date: September 23, 2017 06:04AM

Howdy DaveO,
I found this web site while researching my own header project. "coneeng.com", the thing that got my attention is weld it yourself merge collector kits. Well fabbed kit, went together well, can't find my pic's. Worth the cash. I used 1.5" ID primery tubes into 2.5" exit collector, there's lots of info. I do remember 30" primery tube length. Hope this helps.

Ken

Re: My Corvair Porsche 914 Project
Posted by: BobV66Vair ()
Date: September 23, 2017 08:57AM

Nice how that aircraft header exits under the head instead of outside it. Allows for more access and easier to trim the shrouds so it can be attached. Where does one buy that header? It's a great start.

Bob Vinnacombe
Sandy, Oregon
1965 Corsa 140 stock
1966 Monza Soon to be race car
1968 Monza Parts for now

Re: My Corvair Porsche 914 Project
Posted by: DaveO90s4 ()
Date: September 24, 2017 03:21PM

Hi all, thanks for your comments and advice.

The curved exhaust outlets came with the engine, along with high rise exhaust and muffler, not suitable for my application.

The coneeng stuff looks interesting. Thanks.

And also all the shots of exhaust options - very useful and thanks.

I think I have three basic things to marry together:
1. Exhaust outlet area - single pipes connecting into a 3:1 further back or joining almost immediately, a bit like stock and like the very nice aircraft style image posted. I'm inclined towards the latter - takes up less room under the car / engine, clearly works OK (OEM and aircraft application) and probably more simple to construct. That is the red arrangement in my picture below. (The green is the alternative multi-pipe set up.
2. Mufflers. The car originally had this mounted across the car at the rear, along with heat shields. I am inclined to do the same with this set up, as also shown in the image attached.
3. Crossover. From my limited knowledge, it seems this will be more important to reduce resonance as distinct from adding power. I don't want to go above the gearbox with this - will put heat into trunk. Nor under gearbox - will reduce ground clearance. So in the image below you'll see I'm thinking of putting this just before each muffler.

It's not going to be race car - just an occasional weekend driver - so getting the last ounce of power is not critical.

I hope my image that I'm about to attach is legible.

What do you reckon?

Attachments:
Re: My Corvair Porsche 914 Project
Posted by: moomba32 ()
Date: September 24, 2017 05:10PM

To me the red looks like more what you're after also looks like it will make the car easier to maintain.

Don Marlowe
66 Monza 2Dr 140/pg
64 Spyder convertible now, 110/pg
Eutawville SC

Re: My Corvair Porsche 914 Project
Posted by: DaveO90s4 ()
Date: September 25, 2017 12:26AM

Okay dokay. If I go with the red option, which I'm favouring, the obvious question is can I use OEM 140 hp exhaust logs with each turned to face the opposite direction.

Does anyone have a set of heads and logs that they could see if they work the other way around? If so then I should probably just buy a pair, plus an engine set of OEM log to head pipes.

Sorry for all the questions on this - there simply are no Corvair's in Australia for me to check out this stuff myself.

Do I need a fact finding to the good ole U S of A?

You betcha!!

Dave O



Edited 1 time(s). Last edit at 09/25/2017 12:29AM by DaveO90s4.

Re: My Corvair Porsche 914 Project
Posted by: MattNall ()
Date: September 25, 2017 08:01AM

Stock logs will NOT work....forget them Your heads have been modified





MODERATOR
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Re: My Corvair Porsche 914 Project
Posted by: BobV66Vair ()
Date: September 25, 2017 08:28AM

Logs can be installed either direction. If you had your exhaust tube modified either in size or angle, they won't work. You would then need to custom all of it.

Bob Vinnacombe
Sandy, Oregon
1965 Corsa 140 stock
1966 Monza Soon to be race car
1968 Monza Parts for now

Re: My Corvair Porsche 914 Project
Posted by: eidolon ()
Date: September 25, 2017 10:40AM

Dave O,

Rhys (rhysaccess) is in Australia, as are others. Send him a PM!



Edited 1 time(s). Last edit at 09/25/2017 10:41AM by eidolon.

Re: My Corvair Porsche 914 Project
Posted by: j3m ()
Date: September 26, 2017 06:22AM

Dave, you have a cool project underway.
Ground Clearance and "packaging" should be considered because you do want to have something that is Porsche factory like and not something that Jethro Bodine conjured up to be minimally functional.
Your thinking and engineering prep thus far has shown to be top tier so why not continue in that direction even if it takes longer or requires revision or more time thinking about how to..
I would seriously give thought to replacing the Zeniths with EFI.
A 140hp Corvair engine is realistically more like 115 to 118hp so the gain over a stock 1974 2.0 liter 4cyl Bosch injected 914 is minimal if any, and you lose driveability and mpg with Carbies.
The Corvair engine in factory form is far less reliable than the stock 1974 fuel injected VW-Porsche Type 4 engine.
The Corvair engine can be more reliable than the TYPE 4 but you must rid the Corvair engine of its DIZZY, CARBIES, and factory Mechanical Fuel Pump.
IF YOU DO GO to Distributorless Ignition and Computer Controlled Electronic Fuel Injection on the CORVAIR engine, it, the Corvair engine will prove to be as RELIABLE as the Best Ever aircooled engines to come from WOLFSBURG or STUTTGART.
Going Carby on a 914 with the factory engine is a step in the WRONG direction versus keeping oem injection or an improved more modern efi substitute.
VW engines (type IV included) do Okay with Carbies, because there is a much better and evolved head design than what the CORVAIR is frozen in time with.
Everybody that is building nice VW and type IV (porsche 914) cars is building them with modern efi and such. NOBODY is doing the ancient way of WEBER IDF and Dellortos that was how it was done 30+ years ago. Check out Aussieveedubbers site if you don't agree.
IT IS JUST STUPID TO GO BACKWARDS, IF RELATIVELY SIMPLE AND COST EFFECTIVE WITH TODAYS TECHNOLOGY AND METHODS.
The Corvair engine has proven to be excellent when computer controlled electronic fuel injection and distributorless ignition is used instead of the old factory carbies and dizzy.
You have painstakingly designed your 914 thus far so one would think that EFI for the Chevy flat six should be on your radar too.
Porsche folks would respect an improved EFI vair engine, but if your just gonna be running a sputtering/pinking carbied, dizzied Corvair, even with the ancient 911 Zenith carbies, you'll likely be viewed properly perhaps as having a POS Corvair engine, slightly upgraded with 50+ year old ZENITHs from an ancient junkyard 911.....if you can call such ancient Zeniths an upgrade to the Corvair in the first place. Old carbs, don't match what EFI can do. A computer does wonders for the CORVAIR.
Think smart. Don't go backwards!
The Corvair engine in the 914 is a good move if you incorporate EFI and DIS.
Why not maximize driveability and reliability?
Backwards with Carbies and distributor is worse than going to carbs on the original factory type IV engine.
Corvair = great with EFI and distributorless ignition
Corvair = near POS in best situation if it retains original factory components

Re: My Corvair Porsche 914 Project
Posted by: jmaechtlen ()
Date: September 26, 2017 08:54PM

Eh - airflow makes horsepower. That motor is certainly more than a 140 by far, just looking at the head inlets and exhausts.
Look at the dyno results on Hot Rod Magazine - FI doesn't necessarily get you more HP - though a good EFI can gain you driveability.
The driveability gains are especially big over wide temp swings or big altitude changes. Oz isn't known for huge mountains, afik.
A car is personal, and part of the fun is making your own combo work.
Since when is a distributor that big a deal?
Ok, yeah - we are spoiled. Points can be a nuisance.
I think this well be a plenty healthy package.

Re: My Corvair Porsche 914 Project
Posted by: DaveO90s4 ()
Date: September 27, 2017 12:04AM

Dear J3m,

Please send me all the parts I need, along with tuning software, WBO2 sensor, etc etc and please pay for the tuning time and I will willingly adopt all of your suggestions.

Otherwise I'll just have to carry on my way, given my budget, my time constraints and my expertise or lack thereof.

I reckon it'll be ok on the day.

Regards
Dave O

Re: My Corvair Porsche 914 Project
Posted by: DaveO90s4 ()
Date: September 27, 2017 12:37AM

And - to soften my reply above that could sound a bit harsh, there are I understand plenty of Corvair's still running with carbs and points and so on. Quite a lot of money has been invested in these Zeniths, including having the throats enlarged for the increased air flow of the 2.8 L corvair (2.7 L + 60 thou' oversize) v the original 2.0 L 911T they probably originally came from. The ignition system is I am pretty sure some pointless system. Haven't bothered taking the cap off the aftermarket distributor to look!

Without at least trying it as is I believe I'd be foolish to turn my back on what has already been done.

You may be right, it may be a POS. but then again it may be just fine. I'll find out if I do have a problem before I spend time fixing a problem I may not have.

I truely believe my considered approach to leave well alone if it works to be a sound approach.

I hope this better explains the method to my madness.

Regards
Dave O

Re: My Corvair Porsche 914 Project
Posted by: JimBrandberg ()
Date: September 27, 2017 04:50AM

I think what you're doing is good. Carburetors are good. Everything doesn't have to use modern technology. We like old cars. Keep up the good work.
Jim Brandberg
Isanti, MN
CorvairRepair.com

Re: My Corvair Porsche 914 Project
Posted by: isucorvair ()
Date: September 27, 2017 11:04AM

I'm with Jim - keep up the good work. Don't let J3M get you down...I mean, who, on a CORVAIR FORUM says:

"Corvair = near POS in best situation if it retains original factory components"...


Eric P.
DeWitt IA

Re: My Corvair Porsche 914 Project
Posted by: DaveO90s4 ()
Date: September 27, 2017 10:05PM

I found this maths on the internet on an engine building page

"An engine requires about 2.2 CFM per horsepower, and exhaust gas flows about 115 CFM per square inch.

"Assuming 1,400 hp / 2 (since there are two exhaust pipes) means we have 700 hp per exhaust pipe. Multiply that by 2.2 cfm / horsepower and we see we need 1,440 cfm. Divide that by 115 cfm / square inch, and we need 12.5 square inches of pipe area. The area of a 4-inch round pipe is equal to (pi r (squared) = 3.14 x 2 (squared) = 12.6 square inches. So a 4-inch exhaust is just barely big enough to support 1,400 hp.

"As an aside, 1,400 hp means each primary tube in the header needs to support 1400 / 8 hp = 175 hp. Doing the same calculation 175 x 2.2 / 115 = 3.3 square inches. The area of a 2-inch tube is 3.1 square inches, so the headers might be the limiting factor in ultimate horsepower in Unfair."

(Note that 700 * 2.2 is 1,540 not 1,440).

So I made an excel model to replicate this on a V8 to verify my maths, then did the same with a 140 hp 6 cylinder

posts to follow.

Dave

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