140 HP HEADS FOR A TURBO APPLICATION ???

[Melb-Mike]

Since all these engines are basically air pumps, ease of air flow determines how much power can be developed. I had another brainstorm......What if we used the bigger valve heads for a turbo ?

Has anyone tried this ?

Does the bigger valves help or hinder power and efficiency ? I'm sure the carb jets would need mods.

[4carbcorvair]

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Definitely has been talked about. :)

[spyderman64]

Tom Keosababian did this in the late '60s. His car, which was otherwise surprisingly stock, ran with musclecars of the day. But water injection was a must to prevent detonation.

[66vairguy]

It's been done.

This topic could be argued from a lot of different perspectives.

In a naturally aspirated engine you ALWAYS have pumping losses. Pumping losses can be reduced using bigger valves, bigger intake passages, more and longer valve duration, BUT you can't have it all. The better you make an engine breath at higher RPM, the less efficient the airflow/burn process at low RPM and small throttle openings. Depending on your approach turbo charging can give good low RPM, partial throttle drive-ability, but overcomes pumping losses at higher RPM. Kind of a best of both worlds thing.

Folks have written books on airflow management. So to get to the point ----- A turbo motor with 140 heads and exhaust headers will definitely produce greater maximum power, important when racing or at the drag strip. The down side is it will take longer to get boost (exhaust headers loose a lot of heat and heat = pressure) and the transition from small to large throttle openings will leave something to be desired (there's a reason GM used four small carburetors instead of one big one on the 140). Another issue to consider is the larger valves, seats, less head material around the seats make the 140 heads more prone to heat damage at sustained maximum power.

Finally - a well built small valve, stock exhaust manifold (cast iron holds heat in) turbo motor with fuel injection, wastegate, electronic controlled timing can generate 200 - 220 HP and torque at the upper limit of the transaxle rating. You'll also have good throttle response and reasonable fuel mileage (if you keep your foot out of it - LOL).

So it comes down to what you want to do. Go Racing or street driving - either way you are going to spend a lot of $$$$$ for a really good turbo setup. That said the old stock turbo system is simple, reliable, and in the higher gears goes nicely. At least that's my opinion for what it's worth.

[bbodie52]

An alternative approach, if a daily driver or tractable, economical, reliable street machine is desired, might be to go with 110 hp or 140 hp heads with dual exhaust, coupled with modern 21st century Electronic Fuel Injection (EFI — better-breathing, computer controlled, less restrictive throttle bodies coupled with sensor and computer-controlled DIS — Distributorless Ignition System). This would likely produce a reliable, strong street machine that would run on Regular fuel without detonation and would get decent mileage.

The Corvair engine design is solid-enough that it is attractive to the private aviation world as a reliable, strong, lightweight powerplant. Of course, those who use it in aircraft give it a careful overhaul and tune it for aviation use with carburetion and ignition systems that are optimized and tuned for use in aircraft. My recommendation for a daily driver that is consistently used on the street would be a moderately-tuned but solid base engine that abandons the 1960's turbocharger, carburetor and distributor-based technologies and replaces them with modern 21st century GM-based EFI/DIS. This would build upon a solid engine design while upgrading the fuel and ignition systems with technologies that simply weren't available fifty years ago. This concept optimizes the Corvair engine for the aircraft world, and a similar approach can optimize the same powerplant for use on 21st century streets, while taking into consideration the modern fuels that are now offered at the pump. The basic appeal of the Corvair remains, but is updated to take advantage of the ignition and fuel systems that have developed over the decades.



http://www.corvair-efi.com/

http://www.corvair.com/user-cgi/pages.c ... ry=fuelinj

It is important to keep in-mind the target use for the car. Too many people decide to hot rod the Corvair using modifications that would be more appropriate for the drag strip, autocross, or the race track. A great deal of time, money, and often frustration is frequently the result — especially if the true use of the car will be on the street. The high performance, maximum RPM tuning appropriate for the track may make the car almost undriveable if everything is tuned for high RPM breathing — leaving little for average street driving. Turbocharged engines can also be difficult and temperamental, with demands for expensive high-octane fuel and lots of it. That might be OK for fun weekend romps on the mountain roads, but less appealing for daily drives, commutes, and family vacations in the old 'vair.

A similar consideration should be given to tire selection. The 13" tires selected by GM for the Corvair economy car in the 1960's might have made sense fifty years ago, but fifty years of tire technology that could not have been dreamed of in 1965 should not be lost to the street Corvair of today. If a completely stock, beautifully restored original is desired for concourse-level car shows, then the original tires would be appropriate. The improved braking, handling, wet weather performance and safety available as a bolt-on with modern tires on 14", 15", or larger rims, and often without any modification to the suspension or body required, can really produce a fun Corvair for the road.

[Melb-Mike]

My thoughts were for street use, not track or the drag strip.

I just got a set of 1964 turbo heads and couldn't help but notice how small the valves looked. It almost looked like the valves off a Briggs & Stratton engine. So I thought, gee whiz, what if the valves were bigger, wouldn't the turbo find easier to stuff some air and fuel into the cylinder. However, the low rpm aspect of bigger valves would or could be a problem, as most of you have stated.

Brad, I agree with you that the best design would be to incorporate the benefits of EFI and DIS on the Corvair engine. That involves a considerable amount of modifications, not necessarily bad, but still significant. However, if one would go in this direction, the use of a programmable ECU would be ideal like the one I use on my Lotus Super 7 (Pectel 2 ECU). That way, with the lap top, and the use of an AFR gauge, you could dial in the right fuel level at all rpm/load situations, and control the ignition to prevent detonation if a know sensor is also used. What comes to mind is the Safeguard system, possibly in combination with the EDIS but it appears the Safeguard is still dependent on the distributor for a signal.

I have a 65 Corsa 140 HP and a 66 Corsa Turbo, and what comes to mind is to possibly run the 66 as bone stock as possible and then maybe convert the 65 into a modern EFI type car. Where would the two be afterwards in terms of net performance ? I also just bought a 64 Spyder turbo which I really don't know where I'm going to go with this one.............bone stock........slightly modified..........highly modified.

Hence my question on the use of 140 heads on a turbo engine. Since this forum is comprised of so many very well informed contributors who have walked the walk, so to speak, I value the input greatly. I admit I'm a greenhorn on this and now like a sponge abosrbing the data thrown at me. I noticed an EDIS-6 system on Ebay that can be used on the Corvair so I bought it. It was cheap enough at $120 + shipping. I can get the Megasquirt from Autosport for $214 so for less than $400 I can go electronic ignition. Clark sells the EFI system complete for around $1750 for the 140 engine, not a bad price. I've looked into the use of the TWM ITB's for the Corvair which would allow great flexibility on the AFR adjustments for a NA engine but would create a real challenge on machining the intake manifold conversions. I considred using a turbo type feed tube and then mounting one dual ITB on a center manifold adapter but wondered about air flow to the heads. So many different ways to do it............are any better than the bone stock system the GM engineers designed 50 years ago ?

Thanks to all for the input, it is greatly appreciated. Continue with any ideas you may have, I enjoy learning from you.

[notched]

You need to set a reasonable goal of what you want to do with the car. The Corvair engine is not a Porsche or VW engine in that the after market is much smaller. You will not have access to as many easily available parts. The cranks can be the weak point to a degree. Ray Sedman did have billet cranks made, but you are talking $2k+ for one.
As such, within the stock confines you will only be able to support so much horse power. The Corvair crank only has 4 mains compared to 7 on Porsche. Stock turbo set up's are very restrictive. The tubing diameter on the exhaust is too small. Gains can be made with larger exhaust tubes on the heads and larger manifolds. Heads always help. Tri porting removal of the intake manifold opens it up. Slant tubes on the exhaust with custom headers as well. But if you want to go further you need to make more boost as well as move more cfm. The old Rajay/TRW style turbos are really small in compressor size even in the largest E Flow. Modern turbos make a big difference but to do so would require blow through carb or EFI.
To go that route would require a lot of fabrication and money and time as well as the services of some Corvair specialists when it comes to the cylinder heads and some of the more specific machine work. Probably the most state of the art Corvair out there is Frank Parkers, which is EFI via FAST XFI, water to air intercooled, done up heads, ball bearing turbo, roller cammed, etc. He has been building it for a long time and probably has well over $20k into the set up. He is also a GM engineer which also helps :)
https://groups.yahoo.com/neo/groups/fas ... /151270308" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

[Melb-Mike]

You are right, one needs to set the goals. What do we want ? A full race car or a mildly modified street car ? Do we want an easy to drive but slightly higher performance Corvair, or do we want a smoother driving Corvair, or do we want a more efficient Corvair ??

Since I already have some very high powered cars, making the Corvair into another high horsepower car is not appealing to me. I would like to retain the basic concept/design of the Corvair;

1) Simple 6 cylinder air cooled car with few bells & whistles
2) Good performance as current design allows
3) improve the reliability with some electronic aids but nothing drastic
4) maximize the performance with what is available to the Corvair, stock or slightly modified (i.e. TBI EFI max)

I was wondering initially if the use of the 140 heads on a turbo engine had any merrit............would it help or hurt. Apparently, the downside is the low end, and since we're talking street use, that would a detriment. I would value low end torque just to make easier to launch the car. Who wants to rev the car to 3000 rpm just to start off a red light ? If I can help the mid range and upper rpm range, I'm interested. If I can make the Corvair a little bit better without bastardizing the original design, I'll be happy. I never thought the Crown conversions were worthwhile as it drastically changed the car's balance and character.

The other consideration is the running gear. If we develop a great deal more HP, will the tranny and differential be able to handle it ? Even worse is the thought of 50+ year old running gear which may well have seen some abuse during its many years. I don't want to tear it up.

[bbodie52]

The engineering complexity and experimentation, as well as cost, to build a good modern turbocharged engine is amazing. The outcome can be exciting, but the cost and experimentation necessary to "get it right" in an air-cooled engine coupled with a turbocharger can be a real challenge. Add the cost of modern anti-detonation subsystems and hardware and the outcome can be a real challenge to obtain good performance while keeping that pin in the grenade.

The Corvair 140 hp heads have already developed a reputation for dropping valve seats as they age. Although I have never experienced this, the Corvair I currently own does have a record of dropping one valve seat before I purchased the car. Deep valve seats in reworked heads are a somewhat expensive cure, and I would be concerned about using 140 heads in a turbocharged configuration, since the added heat may aggravate the situation — increasing the chances of dropping valve seats in heads that have not been modified with deep valve seats.

The EFI/DIS system offered by Clark's and developed by Ted Brown has had a lot of development and refinement time already invested by Ted Brown. The system utilizes existing GM components, and seems to be a well-developed upgrade, although it is not cheap. It is not intended to be a racing upgrade, but targets an audience that might enjoy better ignition and fuel system control and efficiency, and the potential for high reliability with reduced maintenance that modern automobiles enjoy. I suspect that the Corvair might enter this efficiency, performance and reliability world enjoyed by 21st century automobiles with an upgrade of the fuel and ignition systems. The rest of the engine is relatively bulletproof, and the transaxle would not be over-stressed with such an engine configuration. Most reliability problems seem to be rooted in the mechanical fuel pump, carburetors, and distributor components of the aging Corvair engine. I suspect that the EFI/DIS upgrade would produce decent gas mileage, good reliability with low maintenance while retaining the unique qualities and characteristics of the Corvair. The new sensor-based computer-controlled Corvair engine would likely tolerate modern fuels better, and detonation would be less likely to occur when traveling in a heavily-loaded Corvair on long trips, summer vacations, etc. The increased reliability would increase the enjoyment of driving these cars on on such lengthy journeys.

That is the theory I am subscribing to anyway, and I am planning such an upgrade on my Corsa. My wife and I are hoping to use that car on a cross-country vacation to the west coast and back — exploring parts of New England, Canada, and the northern-tier states as we head west, and then following Route 66 as much as possible on the return journey. In our younger days while serving in the Air Force we traveled in a Corsa several times as we journeyed across the nation, and we want to do it again before we get too old to make the attempt. Ted Brown's adaptation of a EFI/DIS system to the Corvair appears to be the right approach for us.

[Melb-Mike]

The EFI/DIS system offered by Clark's and developed by Ted Brown has had a lot of development and refinement time already invested by Ted Brown. The system utilizes existing GM components, and seems to be a well-developed upgrade, although it is not cheap. It is not intended to be a racing upgrade, but targets an audience that might enjoy better ignition and fuel system control and efficiency, and the potential for high reliability with reduced maintenance that modern automobiles enjoy. I suspect that the Corvair might enter this efficiency, performance and reliability world enjoyed by 21st century automobiles with an upgrade of the fuel and ignition systems. The rest of the engine is relatively bulletproof, and the transaxle would not be over-stressed with such an engine configuration. Most reliability problems seem to be rooted in the mechanical fuel pump, carburetors, and distributor components of the aging Corvair engine. I suspect that the EFI/DIS upgrade would produce decent gas mileage, good reliability with low maintenance while retaining the unique qualities and characteristics of the Corvair. The new sensor-based computer-controlled Corvair engine would likely tolerate modern fuels better, and detonation would be less likely to occur when traveling in a heavily-loaded Corvair on long trips, summer vacations, etc. The increased reliability would increase the enjoyment of driving these cars on on such lengthy journeys.

That is the theory I am subscribing to anyway, and I am planning such an upgrade on my Corsa. My wife and I are hoping to use that car on a cross-country vacation to the west coast and back — exploring parts of New England, Canada, and the northern-tier states as we head west, and then following Route 66 as much as possible on the return journey. In our younger days while serving in the Air Force we traveled in a Corsa several times as we journeyed across the nation, and we want to do it again before we get too old to make the attempt. Ted Brown's adaptation of a EFI/DIS system to the Corvair appears to be the right approach for us.

Well stated. You have a way of making sense out of any situation. Actually, the Clark EFI system really isn't expensive when you consider you get both the EFI and EDIS combined in one package and all of the necessary attachments to go with it. $1750 isn't a whole lot of money when you consider all you get. I spent almost $600 on four rebuilt carbs which I ended up re-building myself after I got them. Keep in mind I'm coming from a mindset of my prior 87 Porsche 930 Turbo where anything needed was over $500. The fan and pulley had to be replaced due to a prior poor installation, $850. The K33 racing turbo had to be rebuilt, $1,450. New Carbotech pads for the Brembo racing brakes, $675. The day I cut that car loose at the Mecum Auction was one happy day.

Your trip around the country and traveling on the legendary Route 66 sounds fantastic. We did a small part of route 66 in Arizona and the feeling I had was hard to describe, almost like seeing the Grand Canyon. Thanks for making sense out of my ramblings. I only wish I had but 10% of your knowledge base.

[66vairguy]

Notched made a good point or as I like to sum it up "Sometimes it's cheaper to buy a Porsche" if you want maximum performance. I appreciate your interest in doing more with the parts you have, but sometimes it's best to leave the stock stuff as is, or at least don't get too carried away.

About the idea of "bigger valves" in a Turbo. The LIMITING factor on the stock Corvair turbo motor is the CARBURETOR, NOT the valve size or exhaust system!!. Without a waste gate GM (wisely) chose to limit boost via a small carburetor. Many install larger carburetors or throttle bodies to boost horsepower to the limits of reliability using the stock turbo heads. FORGET USING THE 140 HEADS on a turbo motor. Spend the money on a new turbo with a computer controlled wastegate, EFI and computer controlled ignition. With proper computer controls you can use a higher compression ratio like modern turbo engines. A set of 110 heads with quality valves and seats would be a good choice. Of course all this requires a lot of $$$$ and knowledge to build a reliable computer map to run things.

BTW - buy a good turbo book and engine management book(s). The tubocharging process is complex and often counter intuitive to what one might expect - at least for me - LOL.

[Melb-Mike]

Notched made a good point or as I like to sum it up "Sometimes it's cheaper to buy a Porsche" if you want maximum performance. I appreciate your interest in doing more with the parts you have, but sometimes it's best to leave the stock stuff as is, or at least don't get too carried away.

About the idea of "bigger valves" in a Turbo. The LIMITING factor on the stock Corvair turbo motor is the CARBURETOR, NOT the valve size or exhaust system!!. Without a waste gate GM (wisely) chose to limit boost via a small carburetor. Many install larger carburetors or throttle bodies to boost horsepower to the limits of reliability using the stock turbo heads. FORGET USING THE 140 HEADS on a turbo motor. Spend the money on a new turbo with a computer controlled wastegate, EFI and computer controlled ignition. With proper computer controls you can use a higher compression ratio like modern turbo engines. A set of 110 heads with quality valves and seats would be a good choice. Of course all this requires a lot of $$$$ and knowledge to build a reliable computer map to run things.

BTW - buy a good turbo book and engine management book(s). The tubocharging process is complex and often counter intuitive to what one might expect - at least for me - LOL.

Ok, how many Porsche cars have you had? NO, IT WILL NEVER BE CHEAPER TO OWN A PORSCHE. You're talking to someone who spent a LOT of money on a Porsche. I have relatively deep pockets UNTIL we talk Porsche. You have no idea what it takes to campaign a high HP Porsche. My 87 turbo with a Porsche 962 race engine was a major financial drain. We're talking about a $125,000 car that runs on 114 octane fuel, consumes 26 quarts of Mobil 1 0-50W race oil per oil change and requires constant repair....every time I looked at it. Oh yes, 800+ HP is a thrill but at a cost that questions sanity. My cheap Corvair is petty cash expense and to tell you the truth, gives me as much pleasure. It's easier to work on, easier to fix, and easier to modify. But you are very correct in that the basic design limits the modifications and the gains are small. I'm ready for small gains, tweaking and tuning, and spending $3K to $5K to get there is pocket change compared to the Porsche. Having said that, I still very much enjoy my 2004 996TT but I don't work on it either, I take it to a shop that has all the computers to figure out its little problems.

Corvair is like a return to nature......pure simplicity.

[miniman82]

What I couldn't do with a machine shop, a Corvair and $125k....

[CorvairKid]

Here is my 65 turbo dfi using Accel Gen 7. Blow through turbo system using t3/t4 turbo and blowing through a 750cfm Accel throttle body. I'm also running Mazda intercooler with snow performance water/methanol injection. I ran this system through 140 heads for about two years major problem with 140 heads I found was air scavenging between the heads. How the crossovers are designed on 140 heads two cylinders are fed almost directly and one is starved. This threw off wide band sensor badly. Whenever I pulled exhaust manifolds off two exhaust tubes would be black and the last one would be orange due to running lean.

If you want to run turbo best thing would be to use turbo heads with one port on each or if you wanted bigger valves take 140 heads and have them tri ported like I had done. Made HUGE difference on bottom end going with tri port because each cylinder is fed the same amount of air and no scavenging issues. Motor runs a lot smoother with wide band not having that one one lean cylinder on each side.

As for performance I have not had it on dunk with this motor and tri port but possibly making 250 hp+ running 11-13 psi and getting about 22 mpg down interstate.

Currently tuning motor to run E-85 for racing

[bbodie52]

Now THAT is an impressive engine configuration! One that represents many hours of research and experimentation, and perhaps that is what is needed to get the most out of a turbocharged Corvair.

It seems like an experimental vehicle that you really don't expect to ever finish, but rather enjoy the development, trial and error, etc. that goes with the territory.

With the appearance of that intake manifold, your Corvair could be deemed to be a true late model Monza Spider (or Spyder, if you prefer). Maybe even call it a Monza Spider CPR, since you blow through the intake!

I hope you will continue to post updates as you refine and modify, to let others on the Forum learn from your efforts.