All You CHT Gauge Drivers Report Here

[Bleyseng]

Isn't someone making new 8mm rocker arms?

[Amskeptic]

Isn't someone making new 8mm rocker arms?

Research it and get back to us . . .

[Jivermo]

How about 38mm crank shims for type 4? Scott at German Supply has been out of stock for quite awhile. Are there any around at all?

[airkooledchris]

I have stashed away a set of 1700 rocker arms for a future build of a solid lifter type4 (my garage find Gex is getting the green bus around town no problem, but that bearing sound isn't going to go away on it's own.)

[Boxcar]

ah, seven pages ago this was a cylinder head temp gauge thread..?
75 Westy 1.8/auto with 8.5:1
The Aircraft Spruce CHT gauge people (1?)should remain mute?
Yes its analog, temps trend higher on 3/4. I added air scoops on the inlets, and my WOT duty cycles no longer threaten hi 300s only mid.
I have only idle to watch, as extended idle 10 minutes can put 3/4 300° as in f. My idle is around 1025, and theres a few RPM to cull there from my idle circuit. Which would help the Idle heat buildup.

[Boxcar]

oh ps on my 1.8 engine. not running a thermostat, although I just saw a link for some on the samba.

[SlowLane]

The "solution" from 1971 on was pretty much let the damn things hammer.

That's why the Porsche swivel foot adjusters are the "cats meow" and a worthy upgrade to any type4 engine.

Yes, but we please need Porsche swivelfoots with the new big screw diameters so we don't have to poach all the 1700s . . .
Colin

Continuing the thread digression: there is some question as to the advisabiity of using swivel-foot adjusters in hydraulic lifter valvetrains. John at Aircooled.net gives us this warning on the subject.

[Amskeptic]

there is some question as to the advisabiity of using swivel-foot adjusters in hydraulic lifter valvetrains.
John at Aircooled.net gives us warning:

No question about it. Do not use swivelfoot adjusters on hydraulic lifter engines.
Because there is no valve lash in the hydraulic valve train, there is no opportunity for the swivel balls/sockets to get oil. Fatal galling is the result.
Colin

(prior thread edit:
That's why the Porsche swivel foot adjusters are the "cats meow" and a worthy upgrade to any* type 4 engine.

* (01/25/14 SlowLane edit: any solid lifter only Type 4 engine)

[Amskeptic]

ah, seven pages ago this was a cylinder head temp gauge thread..?
75 Westy 1.8/auto with 8.5:1
The Aircraft Spruce CHT gauge people (1?)should remain mute?
Yes its analog, temps trend higher on 3/4. I added air scoops on the inlets, and my WOT duty cycles no longer threaten hi 300s only mid.
I have only idle to watch, as extended idle 10 minutes can put 3/4 300°f.
My idle is around 1025 rpm, and there's a few RPM to cull there from my idle circuit.
Which would help the Idle heat buildup.

Don't overthink this . . . I got's that tee shirt.

07/04/2011

I re-confirmed yesterday on I-15 that holding in 4th dropped my CHTs, when I down-shifted, they stayed at the lower reading. This is all very interesting to me.
I am discovering that I have been "over-thinking" the hell out of all of this, and the engine deals with load and ambient temperatures according to its own dictates. No driving technique makes a whit of difference. The conclusion I am rapidly arriving at is:
Just Drive

[asiab3]

Wanted to Report Here with All my CHT Driver-ing…

1600dp, German 009, German 34/3.

My past "dipstick grabbing tests" have always told me my engine prefers 28* of timing to 30* or 32*. Last month I changed my plugs and they looked slightly lean. Not wanting to change more than one thing at once (for science!) I installed the new plugs and didn't change anything at that point. All these readings were on the same route, 250 miles round trip each time I made a change. Ambients were between 60f and 75f. Filled up at the same Shell stations each time.

28*btdc, 127.5 main/75air, points measured 46*:
Temps sat at 370-380 cruising, one big hill saw 420* CHT. 24mpg.

28*btdc, 127.5 main/60air (one size richer), points measured 46*:
Temps sat at 370-380 cruising, same big hill saw 420* CHT. 20mpg.

30*btdc, 127.5 main/60air, points measured 46*:
Temps sat around 400, big hill hit 440 when I got scared and backed off. 20mpg.

Next week I'm going to keep the timing at 30*btdc but go back to the leaner air correction jet. I predict similar or higher temps. If it's too high, I'll make a drastic timing retard, like 5* and take more readings. I personally feel like having the gauge installed makes my right foot more reserved. I think I'm seeing similar readings because my brain is telling me not to push my bus harder. Someone want to come take a ride with me and keep my CHT gauge to yourself? I also think winds could be a factor. I also have not pulled the plugs to see any change in color from the new jetting combo.

I see why people on VW forums make such a big deal out of timing!

[Amskeptic]

30*btdc, 127.5 main/60air, points measured 46*:
Temps sat around 400, big hill hit 440 when I got scared and backed off. 20mpg.

Next week I'm going to keep the timing at 30*btdc but go back to the leaner air correction jet. I predict similar or higher temps.

Don't even waste your time keeping the timing at 30*. There is a conventional wisdom, coming from people who do not drive where the engine seriously has to hold together, that says to get as much timing advance as possible for "better performance". What your engine is doing though, is wasting its own energy overcoming the compression stroke/combustion pressure wave. It presents to you as heat, low power, lousy gas mileage.

You would be happier with a vacuum advance distributor that allows you to back off the maximum centrifugal advance to less than 28*. A Type 1 engine is grateful for gentler connecting rod-to-crankshaft hits. You can hear the crankcase noise get thrashy with too much advance. Why not take it easy on the bearings and the heat generated? See how lean you can run it without bleached white spark plugs. A little tan/grey is good.

Looking forward to updated readings. These cars really should be able to run at almost constant full throttle without you worrying. My singleport 1600 in midsummer has had difficulty hitting 410* at 110* ambient. A couple of times, I screwed up my timing / mixture / left cooling flap, and was punished with 420*.
Colin

[asiab3]

30*btdc, 127.5 main/60air, points measured 46*:
Temps sat around 400, big hill hit 440 when I got scared and backed off. 20mpg.

Next week I'm going to keep the timing at 30*btdc but go back to the leaner air correction jet. I predict similar or higher temps.

Don't even waste your time keeping the timing at 30*. There is a conventional wisdom, coming from people who do not drive where the engine seriously has to hold together, that says to get as much timing advance as possible for "better performance". What your engine is doing though, is wasting its own energy overcoming the compression stroke/combustion pressure wave. It presents to you as heat, low power, lousy gas mileage.

Thank you. My engine Seriously has to hold together.

You would be happier with a vacuum advance distributor that allows you to back off the maximum centrifugal advance to less than 28*. A Type 1 engine is grateful for gentler connecting rod-to-crankshaft hits. You can hear the crankcase noise get thrashy with too much advance. Why not take it easy on the bearings and the heat generated? See how lean you can run it without bleached white spark plugs. A little tan/grey is good.

DVDA has troubled me for a while, and the NOS can is still lost in the mail. I ordered a new SVDA from AC.N and haven't installed it yet.

Looking forward to updated readings. These cars really should be able to run at almost constant full throttle without you worrying. My singleport 1600 in midsummer has had difficulty hitting 410* at 110* ambient. A couple of times, I screwed up my timing / mixture / left cooling flap, and was punished with 420*.
Colin

I've never floored my bus... I do keep pushing closer when I see head temps maintaining a safe level. I should be able to get updated readings this weekend.

Out of curiosity, do you or anyone else trustworthy have some 'splainin' about how vacuum only distributors work? I'm mostly confused how you can set your timing to 0* static but still have enough advance under low-vacuum conditinos like a near full-throttle run.

[Amskeptic]

I've never floored my bus... I do keep pushing closer when I see head temps maintaining a safe level. I should be able to get updated readings this weekend.

Out of curiosity, do you or anyone else trustworthy have some 'splainin' about how vacuum only distributors work? I'm mostly confused how you can set your timing to 0* static but still have enough advance under low-vacuum conditins like a near full-throttle run.

I floor Chloe all the time. I have to in a headwind while climbing some interminable grade. Feel free to do so. The engineering of a stock bus allows you to floor it all the time because the carburetion/compression ratio/timing/exhaust allows you to extract every ounce of the restricted power output that was determined to make the engine fail-safe.

Imagine that a 1600 VW engine in a bus could give you a decent 80 horsepower. Imagine that this 80 horsepower would overheat if you needed it for an extended period. If it were up to you, you would have to lift up on the accelerator to prevent overheating. VW preemptively "lifted up on the accelerator" by giving you a laughably tiny carburetor and that insanely small tailpipe, so you could floor it without having to think about it. They knew full well that the car magazine reviews would be cursing the low power, but at least the customers would enjoy an almost full service life.

I revel in the low power. I am not in a hurry. When Chloe is climbing the hill at 35 mph, I know that the combustion chambers are creating only as much heat as the cooling system can take away. I know that the engine is in a state of homeostasis just doing its thing in the 120* heat in Death Valley . . . slowly.

Vacuum-only distributors start the curve at 0*. When the engine is off, the timing is 0*. When the engine is idling, the timing is 0*. As it accelerates, the air flow past the vacuum nipple begins to affect the vacuum advance unit, you get advance. The brilliance of this set up is that as the throttle plate edge gets closer to the wall of the carburetor, the "local" (just at the vacuum advance nipple) air flow speeds up, increasing the vacuum. As the throttle plate edge moves away from the wall of the carburetor, the "local" air flow slows down and reduces the vacuum, just what you want under full throttle.
BUT
this system is also reading total air flow. That means that full throttle at slow engine speed is indeed almost vacuum-free, but at high speed-full throttle, there is the total air flow passing by the nipple and therefore a "base line" vacuum advance occurring.
A vacuum-only distributor is so fluid in the curve that it provides, that you cannot read the advance based solely on engine speed. The interplay between throttle plate position and air flow speed is constantly changing. Therefore, the only safe place to catch the timing is with the engine off. Questions?
Colin

[asiab3]

Thank you for the vacuum distributor explanation- I have not found any great resources on their operation. Much more info on the SV/DVDA/009s out there.

I floor Chloe all the time. I have to in a headwind while climbing some interminable grade. Feel free to do so. The engineering of a stock bus allows you to floor it all the time because the carburetion/compression ratio/timing/exhaust allows you to extract every ounce of the restricted power output that was determined to make the engine fail-safe.

I always see a huge rise in CHTs when I get the pedal past about 80%.

Tonight I got the Mallory SVDA installed, and got it approximately dialed in how I want. It came set with 20* vacuum advance and 30* mechanical . When I first started it, idle was 0* and max centrifugal was 30*, so I cut it back to 28* max, which took my idle down to 2*atdc. Then came test drives gradually lessening the vacuum advance until highway runs didn't spike the temps. I started with 15* vacuum advance available and by the time I reduced it to temps that were acceptable I was left with 4-5* vacuum advance. (That's about the range mentioned in Bentley for the DVDA witht he 34/3 carb I have.) Now when I hit the hills from Camp Pendleton to San Diego I watch the CHTs climb and just park themselves at 396, even with 80% throttle. I do notice downhills cool more than before, and low/midrange torque is better with the spring setup I have. I want to get the key set so I can reduce the total centrifugal advance and get my idle timing up a bit while keeping the max advance the same.

I also want to put my stock exhaust back on and try all this. I like to experiment, but I don't know if I could do that experiment in an evening after/before work.

[Amskeptic]

I also want to put my stock exhaust back on and try all this.
I like to experiment, but I don't know if I could do that experiment in an evening after/before work.

I like reading the results of experiments . . .