Pulling through 4000RPM

[df14936]

My 65 turbo (stock build motor) does not like to run past 3500RPM. If I go through the 3500 – 4500 RPM at a low throttle opening it does fine say in 1st or 2nd gear. Once I get past 4500RPM it will pull OK but not great to 5000PRM. But If I try to go through that range in 3rd or 4th gear it wants to sputter and does not make any power. In second gear at full throttle it will pull though the range but roughly. I have replaced the fuel filter and that did not help.
Dave
df14936@hotmail.com

[flat6_musik]

Maybe something to do with the boost retard unit rotating the distributor breaker plate and changing the point gap/dwell or a bad ground on the plate?.......also (if you've still running points) maybe try a fresh set and definitely a new condensor. They can be touchy and go bad early sometimes. Your timing's correct, right?

[Motornoggin]

Hard to say without being there, but in addition to the above (I was thinking timing as well), maybe your fuel pump is weak/failing? Check a spark plug to see what color the insulator is. Should be dark brown/gray. If it's white it's starving for fuel. Does it ping under load?

[df14936]

Haven’t had the plugs out yet. I have the timing retarded to 22deg as it does want to ping. The centrifugal advance works perfect as well as the vacuum retard. I am still running points. They have maybe 1500 miles on them. I do have something going on with the dwell. I have the point gap set at only 0.010 vs book setting of 0.016 and this gives me a dwell angle of 28deg vs book setting of 31-34deg. (larger point gap gives lower dwell angle) I suspect that the distributor cam is worn. This has not changed since before I started having this problem. The car seems to run rich. The exhaust is quite black.

[Motornoggin]

22 deg retarded, or 22 deg advanced? Initial timing should be set at around 24 deg advanced, warm, at idle with the vacuum/boost line to the dist. pinched. Worn distributor cam or bushings maybe?

[df14936]

22deg advanced vs spec setting of 24deg advanced. Im guessing cam or bushings worn, but wanted to keep engine stock as opposed to going electronic ignition.

[Motornoggin]

Might be worth trying a new set of points. If it doesn't fix it, maybe then try a Pertronix set up. I have one and other than the second wire out of the dist. it looks stock.

[miniman82]

Distributor is crap, guaranteed. And it's not a vacuum can, it's a pressure retard.

To test it, pull the line from the can and plug it. Then retard the timing like 8* and see if it runs any better at higher RPM and load, if it does the retard can is shot. If that doesn't get rid of the ping, you have a fuel issue that needs to be corrected or a bum turbo. Personally, there are much better ways to control timing than that stone age distributor and I've never liked the YH carb either.

[df14936]

I agree with your sediments on the YH carb. I know that the retard can was working, but I will have to check it again. I like your idea of pulling the hose and then manualy retarding the timing.
Thank you,

[df14936]

Ok, so I’ve been looking at this some more. The pressure retard is definitely working on the distributor. I have tested it statically. And as I suspected, the car is running rich. I have an O2 sensor in the outlet of the turbo and it reads over 0.9 volts. Under 0.5V is lean. So I probably need to address this at some point. It has run rich since I put the motor together and I have not started messing with jetting the carb yet. I pulled the plugs and they all look OK and I pulled each spark plug wire off at idle and the RPM dropped about the same for all six cylinders.
The other thing that I have observed is that it pulls great before the engine gets too hot. I don’t have the head temp gauge, but do have a temp gauge in the oil pan. With oil temp under 180deg it runs great, starts getting iffy at 200 and by 220 the problem is back in earnest. I have never seen the oil temp get over 230 or 240 on a very hot day.

[mikevair]

Sounds like you have the same issue I did. I went thru all the checks. Plugs, Wires, Timing and even installed The SafeGuard System. My issue was I was running too rich at full throttle. I'm also running a YH. I had been playing around with different jet sizes and ended up with one that was a little to rich at full throttle. My set up not completely stock. I'm running 110 heads on my 180 turbo that Steve Goodman built many years ago. The dizzy was recently rebuilt by steve also. If I remember right he had a custom curve to handle the normal issues you have with a high compression turbo. The safeguard solved the pinging. I'm in Texas and the heat was killing me. And, the .104 jet solved the other issue. Hope that helps.

[miniman82]

I have an O2 sensor in the outlet of the turbo and it reads over 0.9 volts. Under 0.5V is lean.

Respectfully, trying to tune an engine with a narrow O2 sensor is like trying to shoot a target at 1 mile, blindfolded with no spotter.

Get yourself a wideband, only then will you know exactly where you are. Sure the one you have is reading 'rich', but .9 volts can be anything under 14 AFR (see response chart below). In reality, you could still be substantially lean and not know it. Narrow sensors are only accurate near 14.7, which is why they get used so often for tuning milage. They are useless for tuning WOT, don't even think about it.

I pulled the plugs and they all look OK and I pulled each spark plug wire off at idle and the RPM dropped about the same for all six cylinders.

If your plugs aren't black with richness, you likely need more fuel when wide open. Again, you won't know till you get a wideband.

The other thing that I have observed is that it pulls great before the engine gets too hot. I don’t have the head temp gauge, but do have a temp gauge in the oil pan. With oil temp under 180deg it runs great, starts getting iffy at 200 and by 220 the problem is back in earnest. I have never seen the oil temp get over 230 or 240 on a very hot day.

Not to sound like I'm bashing everything you say, but oil temp has almost nothing to do with the way air cooled engines react. Head temp, head temp, head temp. If you don't have an ACCURATE meter, get one. And I don't mean the silly thing in the dash of Corsas, either. Get a temperature compensated thermocouple based one, like the aircraft use. Don't push it over 400*F, that's seat dropping territory.

Once you know you're not lean and you know the heads aren't getting too hot from the bogus timing, then you can begin to attack this problem in earnest. Till then it's like I said, taking shots in the dark. Again, not bashing, just speaking from experience. You need to know what you're working with first, then you test the results of your tuning against the baseline.

[cvair4life]

While on the topic Nick... what is your favorite brand of wideband O2 and accompanying gauges?

[Eurobilly]

Just a thought. What is the health of your turbo? How much boost are you making in 3rd and 4th? Before I sent a spare turbo to Miniman82 for a rebuild and upgrade, I bolted it on my ’65 setup. I am running a Crane ignition with Safeguard - take advantage of the electronic ignition options! Otherwise it is a tight stock setup. Before rebuild the turbo would barely turn by finger (from the turbine end). But to my amazement when hot it did make boost ... a measly 2.8# in 3rd and 4th. The setup seemed to be significantly slower revving after 4000 RPM. After the rebuild, it makes a quick 11# thru the YH & I get decent boost in thru the RPM range. I am using a MAP style gauge with recall. The next step is a Weber and a wastegate over the winter.
BTW - A/F-wise - I use an Innovate Motorsports MXT-L widemand controller. My YH is lean-rich-leanish with upgraded turbo thru the RPM range. I have issues to address with the Weber!

[Trip]

Another thought, bad Coil possible. A weak coil starts producing weak spark when the load is heaviest... high RPM in high gear would be when the coil really has to work hard.

Probably if it was a bad coil you'd also notice hesitation at low RPM when you floor it.. but if you don't find the problem anywhere else it is something to consider. Any time I'm in doubt I swap in a known good coil. One great thing about having several Corvairs is being able to swap parts when troubleshooting!

[miniman82]

While on the topic Nick... what is your favorite brand of wideband O2 and accompanying gauges?

A long time ago when we still had an economy, I bought Techedge widebands because of the exchange rate (Australian company). I was able to buy the 2A0 DYI system with connectors, gauge and sensor for under $200. I put it together at work one day, and it's been with me ever since. Can't do that anymore because, well, you know why. Anywho, CB Performance sells a cheap wideband though I don't have any personal experience with it.

http://cbperformance.com/catalog.asp?ProductID=1673

People who have it tell me good things, and it's become cheaper than the Techedge stuff. I also built a JAW wideband a long time ago, but it's not made anymore. They came up with a newer version, called SLC DIY. Looking at the site, you should still be able to get a functioning wideband with sensor for around $200 if you don't mind building the cable.

http://14point7.com/SLC-DIY-2.php