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[65 Bad Nightvair]

Hello,
New to the page and looking for advice and opinions. Like belly buttons everybody's got one. I have a 65 Corsa turbo that pulled out of a field 3 years ago in LA (Low Alabama), that sat over 30 years. Amazingly still turned over and after putting a new gas tank, fuel lines, master cylinder, brake lines, wheel cylinders and new rebuilt carb and turbo. I started and ran and drove it around. Through past couple of year during winter I would do a light tear down and deflash the heads, electric fuel pump and other things here and there. NOW it's time for a thorough rebuild. I know these items have probably been on past post sorry to bring them up again.

What are your thoughts on the following parts, if worth the changing over stock. I’m going for a good weekend driver w/ability to SCCA race.

Clarks Full Fin Cylinders - STD or any over?
Clarks Forged Pistons, Sealed Power, TRW? Long or short skirt
Pauter, Corvair Specialties or Mikes Corvair forged rods.
Remote oil filter with thermostat control to an oil cooler
Adapter and Weber DCOE 40 carb
Safeguard knock retard
Different Cam TB10 or TB20 (260 or 270)


Thank you for any advice you can give.

Pic of engine last year before in went back in the car.

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[66vairguy]

Hello,
What are your thoughts on the following parts, if worth the changing over stock. I’m going for a good weekend driver w/ability to SCCA race.

Clarks Full Fin Cylinders - STD or any over?
Clarks Forged Pistons, Sealed Power, TRW? Long or short skirt
Pauter, Corvair Specialties or Mikes Corvair forged rods.
Remote oil filter with thermostat control to an oil cooler
Adapter and Weber DCOE 40 carb
Safeguard knock retard
Different Cam TB10 or TB20 (260 or 270)


Thank you for any advice you can give.

Pic of engine last year before in went back in the car.


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qthcyn5e.png

I'm surprised nobody has chimed in! Just my opinion and its free so that is what it is worth.
You could keep the turbo engine as is during rebuild as it worked and was reliable, but suffered from turbo lag.
You could upgrade it for more power and better response with modern computer and fuel injection control. There are halfway measures. If you increase power a lot, then the transaxle will need a good rebuild and the 4 spider differential modification should be done.

The difference in money spent can be significant depending on what you want! Before proceeding, do your research and decide what you want.

Clarks Full Fin Cylinders - STD or any over? > I've never used them, but I've heard no complaints. The more you boost, the thicker the cylinder wall you want!

Clarks Forged Pistons, Sealed Power, TRW? Long or short skirt > I haven't kept up. At one time cast pistons were considered inferior and only forged was used. In the OLD day TRW forged was good, now folks have reported quality has slipped! Pistons should be balanced. I've used a few sets of the OLD TRW pistons and they were so close in weight that the DID NOT need to be balanced.

Pauter, Corvair Specialties or Mikes Corvair forged rods. > I've never seen an issue with the stock rods (64 and newer), BUT rebuilding them and installing ARP rod bolts/nuts is highly recommended. They must be torqued with the ARP lube to the APR torque specification!!!!!!!!!!!!!! Most rod failures happen with the caps come loose!! DO NOT get crazy balancing the rods as too much material can be removed that weakens the rod -- I usually go through a lot of rods to "cherry pick" the ones that are nearly the same weight. No the numbers do not have to be in order in the block.

Remote oil filter with thermostat control to an oil cooler > It is documented by GM engineer Benzinger the turbo engine has inadequate cooling, but this was not an issue unless throttle was held open for more than a minute (you can hit maximum vehicle speed in less than half that time). Some have used the "NASH" fan (he posts here) to increase cooling. For normal and occasional wide open throttle the standard oil cooler is adequate. If you are going racing - forget the turbo and build an multi-carburetor engine.

Adapter and Weber DCOE 40 carb > There are newer and better solutions IF YOU WANT to stay with a carburetor. Keep in mind the original carburetor was sized to prevent overboost!!! Bigger carburetor and you'll need a wastegate, or computer to retard timing to control boost.

Safeguard knock retard > For the stock engine it is a very effective control to prevent damaging detonation. Many installed and no complaints. Others use computerized fuel injection, boost control, and ignition control to avoid detonation.

Different Cam TB10 or TB20 (260 or 270) > These "OTTO" cams are an issue based on forum posts. Based on other's posts, the original vendor sold out to Clark's who found a manufacturer and folks have noted problems with the grind not being correct. Just what I've read. Isky cams have a good reputation, but I cannot recommend one for a turbo. KEEP IN MIND the turbo overcomes "pumping losses" so you DO NOT need an aggressive cam for most driving. Once the boost is on the power increases substantially. With a mild cam you get good torque until the boost comes on. If you really want a powerhouse that is all at upper RPM then an aggressive cam works.

Well just my and others are free to add or disagree.

[joelsplace]

There is a rear cover mod that feeds the turbo cooled oil instead of hot oil. Do that.

[65 Bad Nightvair]

Thanks 66vairguy..
I do have a 66 4speed with posi and a 69 4speed reg transaxle. I going to replace the 65 trans/diff with. Don't know which one yet. I do have a RB block and 140 heads as a back up build. I've had no real trouble with the YH carb and i have the hopped up hot/cold on the turbo. I might just do the cylinders and piston just to see if there is any improvement as the old cylinders and pistons probably had bad compression and burning oil after sitting 30 years. I have another set of 180 heads ready to go on and the crank has been turned new cam gear.

[thewolfe]

A word of advice on using a DCOE...yes they look really cool and can make good power but they are difficult to tune. There are a lot of variables and parts that you change to dial it in. Problem is you have to buy a large selection of jets, tubes, air bleeds etc to try. Plus you likely won't be able to get much better than 12-13 mpg without driveability suffering. I know, I had one with the progressive secondary mod for a while. There are better carbs out there. I run a quadrajet now and it will make gobs of power, easy to tune, and I can get 22-23 mpg. Others here have used Mikuni carbs with great success.

I'm running a TB-20 cam now that I bought from Clark's a couple years ago with big valve modified 95hp heads, 140 exhaust tubes and manifolds, big crossover pipe, E/F turbo. Before this engine was built, everything was the same except for I had a stock cam. I like the TB-20. The car feels strong and peppy on and off boost and the upper RPM range is significantly better than with the stock cam. You will want to upgrade your valve springs if you choose this cam, if you haven't already. As for pistons - there really isn't a good forged piston option these days unless you get custom pistons made by a company like Wiseco or JE. The problem is that all the current offerings by Clark's have slotted oil returns which is where they always fail, regardless if its forged or cast. Obviously forged is stronger but they still fail if pushed. Clark's used to offer a forged piston with drilled oil returns and I have an old set of keith black hypereutectic pistons with drilled returns in my car. Those pistons have taken a serious beating over the years and I reused them in this engine build because they were perfectly fine.

The safeguard works well but I'd advise to go fully programmable in addition to that. The CB black box is cheap and very effective. You'll also want a waste gate, boost controller, and some sort of water/methanol injection if you decide to ditch the YH.

[KenHenry]

If you’re at all considering EFI, here’s ’a Mikuni EFI throttle body I plan to use in a turbo build, from a Suzuki TL1000R. It has a 2” bore and I’ve swapped in 870cc injectors… I had adapters cnc’d for the “top” and “bottom” and plan to do a more detailed post when I get to assembly.
I believe Ted Brown now has an EFI system for the turbo now. Good luck! Ken

[jimbrandberg]

It would be difficult to keep a Corvair turbo engine cool on long straightaways when road racing. Cylinder head temperature just keeps going up with long periods of boost.

If spending a lot of money and designing a turbo engine from scratch I would wonder about using the LM open chamber heads vs. something with a squish. The open chamber heads may be more likely to ping.

I'm not saying it can't be done but those would be my first considerations. Not everyone agrees that open chamber heads are bad, some think they are better at chamber filling. I'd be interested in discussion.

My own turbo aspirations lean towards EFI and better spark control but I'm not working on it at this time.

Jim Brandberg
Isanti, MN
CorvairRepair.com

[66vairguy]

It would be difficult to keep a Corvair turbo engine cool on long straightaways when road racing. Cylinder head temperature just keeps going up with long periods of boost.

If spending a lot of money and designing a turbo engine from scratch I would wonder about using the LM open chamber heads vs. something with a squish. The open chamber heads may be more likely to ping.

I'm not saying it can't be done but those would be my first considerations. Not everyone agrees that open chamber heads are bad, some think they are better at chamber filling. I'd be interested in discussion.

My own turbo aspirations lean towards EFI and better spark control but I'm not working on it at this time.

Jim Brandberg
Isanti, MN
CorvairRepair.com

There is a lot of pros and cons written on open chamber heads. Most assume they cause detonation (emmisions control heads), but they can be designed to work well. That said I have no idea if the LM open chamber turbo heads are a problem or not. I suspect GM did it to lower compression as was the norm back then on turbo engines. Today higher static compression turbo engines are the norm, BUT it requires a lot of serious computer control of fuel, ignition, wastegate, etc.

[66vairguy]

Thanks 66vairguy..
I do have a 66 4speed with posi and a 69 4speed reg transaxle. I going to replace the 65 trans/diff with. Don't know which one yet. I do have a RB block and 140 heads as a back up build. I've had no real trouble with the YH carb and i have the hopped up hot/cold on the turbo. I might just do the cylinders and piston just to see if there is any improvement as the old cylinders and pistons probably had bad compression and burning oil after sitting 30 years. I have another set of 180 heads ready to go on and the crank has been turned new cam gear.

I prefer the 65 box for smoothness, but the 66-69 box is sturdier and preferred for a turbo engine. Oddly is is easier to get parts for the 65 and earlier transmission than the 66-69 transmissions. The 66-69 uses the notorious "wavy washer" used to eliminate some of the tedious shimming done in the earlier transmissions. The "wavy washer" can fail anytime from 40 to 100K depending on abuse and lubricant changes. One it goes, then bad things happen. Hard to find correct Corvair washer (different vs. big car units). If you need it post and I'll ask around.

Someone has commented on pistons. The original cast pistons will fail in short order if you have detonation during boost. The Safeguard a good option to install.

Steve Goodman at Rear Engine Specialists in Golden Colorado has a good reputation for fixing turbo cars. The stock carburetor was revised often. Mixing up parts is an issue. Set up properly they work. Folks have posted that Steve fixed their turbo carburetors.

The differential pinion shaft has internal splines the transmission output shaft fits into. These DO WEAR OUT. Clark's had reproductions, but I've heard they are all gone (and there was an issue with the splines - fixable). Now most use a good used shaft (you can press pinion gear on and off). WARNING -- installing a 1965 pinion shaft in a 66-69 differential will cause a failure!!! See.

[joelsplace]

Excellent document. Thanks!

[BZanella56]

Cylinders: I like Clark's full fin, but there is little difference in power increase between std & .060. But great for budget!
Forged pistons can't be beat. They hold up great but require slightly more skirt clearance due to more
expansion/contraction. The PTFE coated are even better. Short skirts: racing only not good as a daily driver. Hypereutectic
are a great choice also, you can keep the tolerances tight like standard cast pistons and still turn a good RPM with
reliability.
Forged Rods: you can't go wrong. But also consider RPM's and engine purpose/use if you really need them!
Cams: The 260/270 works well with a turbo, just depends what RPM range you intent to run at1

[jimbrandberg]

"They" seem to be selling pre-bored cylinders and forged pistons with cast piston clearances.
Jim Brandberg

[joelsplace]

Newer forged pistons use tighter clearances.