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Re: Increase max RPM
Posted by: American Mel ()
Date: May 15, 2019 03:29PM

Corvair brakes, though drums, are GREAT.
They are oversized for the weight of our cars.
Remember, the Corvair brakes are cross-overs from the FULL-SIZED Chevelles and Malibus.

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WA. state, 1 mile south of the Canadian border,
I am not at the end of the world, but you can see it from here.
'66 Monza Coupe - 4spd, 140 Daily driver beater
'67 Monza Vert. - PG, 140 Daily driver beater
'67 A/C Moredoor Monza - 140 4-spd. driver

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Re: Increase max RPM
Posted by: LeadFootLogan ()
Date: May 15, 2019 03:42PM

My parents(I’m 17) demanded that I have disc brakes and I wasn’t opposed to it. As I said before, my Corvair will be used on the street as well. I’m willing to sacrifice some performance for safety so my parents can have peace of mind when I eventually drive my Vair

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Re: Increase max RPM
Posted by: American Mel ()
Date: May 15, 2019 05:02PM

If you were driving a 5-ton Luxo-barge, I would agree.
Most of us drive our Corvairs on the street, (some of us even drive above posted freeway speeds eye rolling smiley) and still safely use the factory drum brakes.
They are MORE than adequate! ie. COMPLETELY safe!
If your parents don't understand that, and demand an unnecessary modernizing of your ride, then that is fine, always respect and do what the parent figures want, life will be easier.
After all, they are just looking out for you.

.
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
WA. state, 1 mile south of the Canadian border,
I am not at the end of the world, but you can see it from here.
'66 Monza Coupe - 4spd, 140 Daily driver beater
'67 Monza Vert. - PG, 140 Daily driver beater
'67 A/C Moredoor Monza - 140 4-spd. driver

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Re: Increase max RPM
Posted by: MattNall ()
Date: May 15, 2019 05:08PM

Discs are "safer" for new drivers... and old! ggg


They do eliminate the occasional "darting" to either side..


The do "self dry" after running thru deep water! Drums don't

MODERATOR
Sea Mountain, between Charleston Harbor and Coos Bay! SW Oregon Coast
Click HERE for My Website...Click HERE for My TechPages!
..............................110-PG.................................................Webered-Turbo

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Re: Increase max RPM
Posted by: LeadFootLogan ()
Date: May 15, 2019 07:00PM

I live in the DFW area and I’m always on the highway, so discs would be great to have. Which is one of the reasons why I got them, especially with the unexpected Texas weather recently with 60 and raining to 85 and hot. Now going back to the original question, I suppose lighter and stronger pistons and connecting rods would increase the maximum RPMs. And is there a formula where I can calculate the max rpms?

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Re: Increase max RPM
Posted by: MattNall ()
Date: May 15, 2019 07:13PM

Not that we know of.. That's where experience comes in..

here's a 380 hp Vair engine at 9100 rpm......case stiffeners, etc..

MODERATOR
Sea Mountain, between Charleston Harbor and Coos Bay! SW Oregon Coast
Click HERE for My Website...Click HERE for My TechPages!
..............................110-PG.................................................Webered-Turbo

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Re: Increase max RPM
Posted by: wv-geo ()
Date: May 16, 2019 06:57AM

Increasing the max RPMs of the Corvair engine would be similar to other engines by doing the following:

-Roller cam that allows the engine to make power at higher RPMs, and roller rockers.
-Firmer valve springs and lighter components (keepers, retainers, valves)
-Better fuel delivery using individual throttle bodies (Weber 40IDA or EFI)
-Better exhaust flow using slant tubes, extractors, and silencers.

Of course, you'll have to modify additional engine components (crank, pistons, rods, oil cooling, air cooling) to handle the extra stress of higher RPMs.

Do all of the above and you'll have an engine that revs a lot higher than stock, and will hopefully stay together.
But then you'll have to run a lower rear axle ratio (3.89 or 4.11) since low end torque will be non-existent, and install a transmission with overdrive so you
can drive down the Interstate at a reasonable speed/RPM. Or, instead of an OD transmission, wear a pair of earmuffs to handle the engine noise.

The engine that MattNall references can rev to 9100 RPM, but the usable torque and peak horsepower have been moved WAAAAAAAAAAAAY up the RPM scale.

NASCAR teams run a V8 that will turn over 9500 RPM and make 850+ HP, but it only has to stay together for less than 1000 miles.
Honda made a 4 cylinder engine for the S2000 that redlines at 9700 RPM and makes 240 HP from 2 liters, but their engineers had to come up with special
engine components so it would stay together for 100,000 + miles.

Modifying an engine for a particular goal whether that's increasing torque, RPM, HP, durability, or drivability can affect low end torque, redline, peak HP, durability, and drivability.
You have to decide what you want and what your willing to give up to achieve your particular goal.

Dan Stark
Hurricane, WV

1961 Lakewood 500, 80HP, PG
1964 Corvair 500 Coupe, 140HP, 4spd (Christine)
1965 Mustang Coupe, 6cyl, 3spd

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Re: Increase max RPM
Posted by: Chet Jr ()
Date: May 17, 2019 03:02AM

I’d strongly suggest you consider changing the gearing (tire size, diff, and trans ratio) before highly modifying the engine.

If you look at a gearing chart you might be surprised at the difference it can make in both performance and driving enjoyment.

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Re: Increase max RPM
Posted by: DaveO90s4 ()
Date: May 17, 2019 03:49AM

Lead foot Logan,

If others around you are not driving very well that does not mean you need bigger brakes. It means that you simply need to leave a greater stopping gap. And less of a heavy right foot.

Next time you drive, before heading off, say to yourself that you’re going to try to not use the brakes. Then drive accordingly. You may be surprised how a reasonably small change in driving style has such a significant reduction in the need to brake. And hence no need to spend money on an unnecessary ‘upgrade’ to your car.

Cheers

DaveO

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Re: Increase max RPM
Posted by: LeadFootLogan ()
Date: May 17, 2019 07:34AM

I completely understand the performance and I thank y’all for the advice, but I already have the brakes installed. I have a limited slip 3.55 differential that may get the 4 spider conversion on it and I’m going to rebuild my 4 speed. Also this was a demand from my mom and dad. I’m also putting in a roll bar in request of my mom as well.

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Re: Increase max RPM
Posted by: solo2r ()
Date: May 17, 2019 09:09AM

Another major thing to consider is the class you want to run in. Rules dictate what you can and cant do to the car! Also, by seat time, I was not talking about driving on the street!
Hope you know how to set up that posi for auto-x!

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Re: Increase max RPM
Posted by: LeadFootLogan ()
Date: May 17, 2019 12:13PM

Solo2r I understood what you meant by seat time, and I was making a joke that I said I had 2 years. My Corvair hasn’t left my driveway since October of 2016.

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Re: Increase max RPM
Posted by: Wallygator ()
Date: May 17, 2019 01:14PM

Another approach is to get to red line quicker. By reducing the rotating mass you can accelerate quicker. Often this is more cost effective. I'm not sure how this works for autocross or the covair but in dirt oval it is huge

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Re: Increase max RPM
Posted by: MonzaDave ()
Date: May 17, 2019 01:36PM

Here's what I did to build an engine for a 6,500 rpm red line:

Engine Build

Dave Keillor
Rochester, MN

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Re: Increase max RPM
Posted by: LeadFootLogan ()
Date: May 17, 2019 02:03PM

Thanks Dave! This will help. Also I have taken in account for rotating mass. I’m going to run 15in ultralite wheels. They’re about 13 pounds. I can’t run stock 13s because my disc brakes are on 13in rotors so I have compensated by the wheels I chose

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Re: Increase max RPM
Posted by: LeadFootLogan ()
Date: May 17, 2019 04:40PM

Dave, who built your engine?

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Re: Increase max RPM
Posted by: vairmech ()
Date: May 17, 2019 07:15PM

Dave's engine is good but I can see a couple of changes and still be very streetable and even raceable. I don't recall if I caught what type of racing you want to do, there was a fair amount of talk of solo/autocross. It makes a little bit of a difference on how you would build the engine or rather cam choice and timing along with carb choice.

As far as what it takes to get a Corvair engine happier to to turn higher
RPM's? Cam is one, better valve springs, better breathing - port work, better than stock pistons and more air through the carbs.

ARP is just a little insurance but not really needed. I have run my road race engines on stock rod bolts turning to 6800 rpm. There seems to be a couple of magic numbers as far as rpm goes, stay under 7000 and the engine lives longer, go over and parts then really need to be first rate. One reason why I build for under 7000 rpm and the reason for my 6800 rpm rev limit.

This is just a brief summary and there is a science to putting an engine together for a purpose.

Ken Hand
Handy Car Care
248 613 8586

Vairmech@aol.com

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Re: Increase max RPM
Posted by: Jonathan Knapp ()
Date: May 17, 2019 08:50PM

Lead Foot Logan -

Contrary to many of the comments, I think that disk brakes are essential for high performance driving. I originally started out autocrossing with drum brakes and raced that way for several year. They had Velvetouch metallic linings, 15/16" bored out front wheel cylinders, and a dual master cylinder. They worked very well for drum brakes.

However, when I upgraded to fixed caliper Willwoods with vented, scalloped, and drilled disks the improvement was astounding! It took me nearly a full year of racing to catch my abilities as a driver up to the new potential of the car. It made a huge difference in my times as I could brake later and harder while being more precise at the same time.

In my mind, disk brakes are the third most important improvement for an autocross car. First is light-weight wheels and performance tires. Second is correct suspension geometry and improved Ackerman. All three are ahead of more power and higher rpms.

Once you do get around to thinking of more power, I would say that Keillor's engine is a good place to start if you are going to stick with normal aspiration, a flat-tappet cam, and carburetion. I built an engine very much like that: 10.1 CR; forged pistons; 280 Isky advanced 4 degrees; Holley 390 4-bbl.; headers. Dave doesn't mention how much port work he did. I did quite a lot, though I never had the heads on a flow bench. My engine rev limiter was set for 7,000 and I would reach it occasionally, depending on the course. It revved willingly up to that rpm.

The one thing that I did that I thought was worthwhile for autocross that I have never heard others talk about doing was my choice of lifters. I used Rhodes variable hydraulic lifters. They are kind of like a reverse V-tec Honda. Instead of higher lift and longer duration at high rpms, the Rhodes lifters give you lower lift and less duration at lower rpm (below about 3000). These were remarkably effective for me with the 280 Isky for keeping low-end punch. If I were building another flat-tappet engine, I would use them again.

Jonathan Knapp
Now in Martins Ferry, OH
'66 Corsa Autocrosser

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Re: Increase max RPM
Posted by: MonzaDave ()
Date: May 18, 2019 06:55AM

LeadFootLogan Wrote:
-------------------------------------------------------
> Dave, who built your engine?

Gary Funkhouser. I haven't had the car on a dyno, but it feels like the torque peak is around 5,500. It was built for autocross and track days, but it turned out to be used for neither due to a variety of reasons -- the biggest of which was the lack of suitable venues in my area. It's a bit overbuilt for a street car. I haven't had it past 93 (when the Wyoming highway patrol intervened), but it was very stable and still pulling hard. I suspect that the top end is near the redline (20 mph per 1,000 rpm) -- I was hoping for at least 120 mph, but was glad I didn't achieve it.

Dave Keillor
Rochester, MN

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