[ST4]The Canary Flies Again!

I finished the engine upgrade for my '75 ST4 this past weekend. The new engine is a custom 1915cc VW type 1 engine. I've not pushed it too hard while breaking in, but I have to agree with Lyndon's comment on bigger VW engines - I won't be needing 1st or 2nd gear any longer!

Other things I did were a complete 12v conversion and rewiring as this was a 24V former military unit. Also added a new VDO oil temp gauge and sender (mounted in the front oil relief plug), modified a header exhaust and built exhaust pipes to route the muffler to the rear of the vehicle.

Cylinder head temperature is a concern since mine is a large bore engine and I retained the old-style fan shroud and oil cooler.One of the most critical additions I made is a Dakota Digital cylinder head temp gauge. Dakota's gauge is the only affordable CHT gauge/sender I could find that gives an accurate reading that's corrected for ambient temperature. Tested it in boiling water and it is spot on. I placed the thermocouple ring under the spark plug for the #3 cylinder because that's the jug that the oil cooler dumps most of the hot air on. Despite low operating oil temps (~175' F max), the #3 head can get awful hot when going up a grade in 4th gear, but the gauge tells you when you need to back off the throttle a bit or downshift.

Cheers - Paul

Sounds like a very nice engine upgrade.

Do you have any pics of the engine compartment to share?

I like your idea for the cylinder head temp guage.

Nice write up and a nice looking machine.

Here's a shot of the engine compartment. Note the weber progressive carb. You can see the heat risers. They are the brass lookin' tubes behind the fresh air ducts that draw hot exhaust from the headers into the intake manifold just below the carb throat. There is a tendency for the intake manifold and carb throat to suffer icing because vaporizing fuel is a cooling process, and because the fuel/air mixture has a long way to travel from the single, center-mounted carb to the heads, not to mention that we run these things when it's frickin' cold out! Therefore, the heat riser tubes are essential.

Next is a shot of the Dakota Digital cht gauge. I was told that cylinder head temperature is largely independent of outside air temperature and I am amazed to find that to be true so far. So far I've run the engine from a low of -14' up to +17' F and haven't noticed any real difference in head temperature. Engine oil temperature is a different story, it seems to be very much affected by air temp.

mtmogs said:

we run these things when it's frickin' cold out! Therefore, the heat riser tubes are essential.

I was told that cylinder head temperature is largely independent of outside air temperature and I am amazed to find that to be true so far. Engine oil temperature is a different story, it seems to be very much affected by air temp.

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Correct on all counts! Number 3 is always the problem child whether it's on rail buggies, Beetles, (or ST's apparently), due to the doghouse oil cooler and the way the air flows within the shroud. It will be affected by warmer climates but probably won't get run hard in those conditions so you won't really notice it. On my buggies I always ran a remote cooler instead of the doghouse to reduce the tendency to overheat it. There is also an aftermarket shroud that addresses the problem but I honestly don't remember if they come in a version that uses the stock oil cooler. The oil cooler is subjected to direct cooling using ambient temp. air and therefore air temp will cause marked differences in oil temperature.

You'll like the driveability that the Weber gives you, but you'll also find that your fuel use may greatly increase. (I think in my case it was from the tendency to plant my foot all the time because of the increased power ) I have put those little two barrels on all of my rails that I've built and love them. I've used them on everything from 1500's as well as warmed up 2.0 liter bus motors and they perform great. Their only weak spot is that the float tends to creep up and flood the engine when you are running it hard and there is a lot of boucing or vibration getting through the suspension to the carb, or under a steep climb with heavy throttle. I know we used to have a pretty simple fix that helped this problem out, but can't remember it off the top of my head. Next time I see my buddy whose specialty is high-perf V-dub engines I'll ask him what it was and get it posted up.

Cool Snow-Trac by the way. You'll need to post a new vid on youtube with your new motor-WITH sound please

That looks like a very nice job on the engine! WHich Dakota Digital gauge did you use?

Round Cylinder Head Temperature</SPAN> HLY-3111

Odyssey Series II, Cylinder Head Temperature</SPAN> ODYR-11-1


Solarix, Cylinder Head Temperature</SPAN> SLX-11-1

http://www.dakotadigital.com/index.cfm

willie said:

Their only weak spot is that the float tends to creep up and flood the engine when you are running it hard and there is a lot of boucing or vibration getting through the suspension to the carb, or under a steep climb with heavy throttle

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Thanks for your comments willie. I'll have to watch out for the float issue. It seems like the conditions you describe sound like typical Snow Trac operating conditions. I guess the other rub on the progressive carb is that, although they run fine out of the box, I've heard it can take 8 hrs. of tuning to get the most out of them.

I'll get a new video posted one of these days. Right now I've got to fab a few new cleats, and a pair of snow deflectors.

Cheers - Paul

couchloafer said:

That looks like a very nice job on the engine! WHich Dakota Digital gauge did you use?

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Thanks couchloafer. I used the odyssey series gauge. The sender ring fits under the spark plug and takes the place of the copper crush ring. The I.D. of the sender ring is 1/2" but the spark plug thread O.D. is 14 mm (= 0.55"+) so you'll need to enlarge the I.D. of the sender ring a small amount. The ring is soft so be careful. I chucked a chainsaw file in a cordless drill and slowly filed away the needed amount.

I found it was impossible for the plug and the tail of the sender ring to fit into the spark plug recess together, even with the tail bent up parallel to the axis of the plug. Using a 3/8" bit, I drilled a pocket on the edge of the spark plug recess for the tail to sit in. This will also keep the sender ring from spinning and being ruined (I hope) when the spark plug is removed/installed. Anyway, senders are cheap, 9 or 10 bucks I recall, so get a couple. I got an extra ring and thought about installing the it on #2 and using a toggle switch to display the output from #2 and #3. Much cheaper than buying another gauge.

Thanks for the information mtmogs! I am placing my order tonight!

couchloafer said:

Thanks for the information mtmogs! I am placing my order tonight!

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Good Luck! Here's a link to a technical article on installing CHT senders that might be of some help:

http://www.germansupply.com/xcart/customer/home.php?gspage=customer/main/tech/cht/cht_install.tpl

Now that you'll have an accurate CHT...the $1MM question is "How hot is too hot?" I can't find a definite consensus from searching the web. Some say 400' F, some say if you reach 450' then the exhaust valve seats fall out of the head and you're done, some say they cruise all day (buses) at 425'. I read that the heads in the flat-4 Corvairs ran in excess of 500'. Maybe Lyndon or Willie can chime in here. For my purposes, I will keep it below 400' and try to maintain around 350' ish.

If I have a problem keeping a lid on that range, then I will switch to the external doghouse style cooler and shroud that removes the oil cooler from the fan shroud. The general operating condition I see on my new engine is that the oil temp is a bit on the cool side whereas #3 CHT is a bit high. The stock oil cooler is doing a great job of cooling the oil, it's just that it's dumping all the waste heat on the #3 head. Removing the oil cooler from the fan housing should at least help reduce the CHT on #3. Of course I'll have to modify the snow trac intake horn to accommodate the newer style cooler.

Another option would be to leave the old-style cooler/shroud in place to maintain proper airflow/pressure in the shroud and add a full-flow aftermarket cooler and fan (with a thermostat to raise oil temp) to take some of the waste heat off of #3. Anyway, it seems that the CHT is dropping a few degrees every time I run it (as the engine breaks in) so I'm guessing I won't have to make any modifications .

Cheers - Paul

I must admit that is one nice looking ST4. You did a fine job on her. I hope you get to spend many hours playing in the snow with her.

ALLEN PARSONS said:

You did a fine job on her.

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Thanks Allen. I think Bill Guthrie at Snotrans is probably responsible for the cosmetic refurbishing, including the custom cab.

How is the cab heated ? Like the old VW . Or like the old vans with a gas heater

It's just like the old bug heater, with the exception that it actually works! In the snow trac, the heat has only about a 2' journey up from the heater boxes to the dash vents and works very well. My heater boxes must be in very good condition because if the vents are open the heat will just about drive you out of the cab unless it's well below 0' F. Some in the forum may own a snow trac with the stock gas heater.

mtmogs said:

... Also added a new VDO oil temp gauge and sender (mounted in the front oil relief plug), ...

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Paul,

Looking good!

Can you please provide more info on how you setup the oil temp sender and gauge? I have mine hooked up off of the oil pressure sender tee and it does not seem to work real well. Is there an adapter or busing for the front oil relief plug to adapt the sender there? Some pics or part numbers of that would be most imformative.

Also, is that a brand new "009" mechanical advance distributor? I'm using a "010" mechanical advance distributor, but tune up parts are getting kind of hard to find for it.

Thanks, Fred

Thanks Teledawg!

Here's the temp sender I got for a VDO electric pressure gauge, it takes the place of the and oil relief plug (can be either the front or rear if you have a newer dual relief case).

http://www2.cip1.com/ProductDetails.asp?ProductCode=VDO-323-064

Anyway, as you look at the underside of the engine case, you'll see 1 or 2 large (quarter-sized) slot-head screws tapped into the bottom of the case. (See pic I copped from the Samba and labeled) The one in the front (for an ST4, rear for a bug) holds the oil pressure relief valve, the one toward the flywheel(if you have 2) is the pressure control valve. I removed the screw for the pressure relief valve and replaced it with the sender. A spring will force against the screw and will want to send it flying a bit so be careful when you take it out. A spring and a small cylindrical thing (valve) that rides on top of the spring should come out. You don't have to drain your oil beforehand, but prepare to lose half a cup or so through the hole. Just replace the slot-head plug with the sender, route a wire to it and you're good to go. Here's the gauge I got to go with it:

http://www2.cip1.com/ProductDetails.asp?ProductCode=VDO-310-709

Yep, it's a new 009 mechanical advance dizzy. Is the "010" the original? If so, I think the #3 lobe on the shaft is ground slightly different than the other 3 lobes to retard ignition timing on the #3 cylinder to cool it down a bit. I'd hang on to it if it still works. Replace the points/condenser with a Pertronix or other type electronic ignition. Set it and forget it! Carry along the old points/cond as a backup.

Cheers - Paul

Paul,
I noticed you have an original turn signal switch. Does it work?
If so what type of relay does it have for the blinkers?
Thanks,
Kevin

Kevin,

I just noticed that the switch was original the other day after looking at the pics posted here. I don't know if it works, I didn't work with the old 24v electrics, I think the flasher was toast. The flasher is the cylinder type about the size of a "D" battery. I can't remember off hand if it had 3 or 4 poles. The parts manuals show it as a 3 pole so I bet that's it. At your nearest NAPA, etc. you can pick up a Buss brand 3 pole flasher for about $2.99. I've got some of these around and will hook up next time I pull the dash.

Cheers - Paul

Paul,
I finally got around to installing the Cylinder Head Temp Gauge as I have no snow to operate in County wont issue groomed trail stickers to Snow Cats any more.....another story.......Can you give me an update on what your gauge has been running for temp since you installed the aux oil cooler?
Thanks,
Kevin

p.s. you got any snow to run around in?

mtmogs said:

Thanks couchloafer. I used the odyssey series gauge. The sender ring fits under the spark plug and takes the place of the copper crush ring. The I.D. of the sender ring is 1/2" but the spark plug thread O.D. is 14 mm (= 0.55"+) so you'll need to enlarge the I.D. of the sender ring a small amount. The ring is soft so be careful. I chucked a chainsaw file in a cordless drill and slowly filed away the needed amount.

I found it was impossible for the plug and the tail of the sender ring to fit into the spark plug recess together, even with the tail bent up parallel to the axis of the plug. Using a 3/8" bit, I drilled a pocket on the edge of the spark plug recess for the tail to sit in. This will also keep the sender ring from spinning and being ruined (I hope) when the spark plug is removed/installed. Anyway, senders are cheap, 9 or 10 bucks I recall, so get a couple. I got an extra ring and thought about installing the it on #2 and using a toggle switch to display the output from #2 and #3. Much cheaper than buying another gauge.

Click to expand...

i went to a local snowmachine shop and got my cht gauge about 100 bucks with a sender for a 14mm plug works great the product came from western power sports an after market parts supplyer

No, very little snow here. This winter has been dismal with record low snowpack and record high temps. I'm hoping we get dumped on in March or else the coming fire season could be nasty. We have less than 2' here at the house and maybe 3' or less at the cabin. No powder anywhere at lower elevations so we even took the 8x8 Argo with tracks up to the cabin the other day. The Argo is a fun little vehicle, but it is so slow compared to the snow-trac.

The CHT on #3 runs noticeably cooler than it did before I moved the oil cooler. I'd have to say in general that it runs 20º-30º F cooler than it did before. I can still knock it up above 400º if I'm going up a long steep grade in soft snow while pushing it in 3rd, so 30º means a big difference under these conditions. What sort of temps are you seeing? Just cruising around without trying to whip her to much I see an operating temp range of ~310º-340º. Oil temps never seem to get too much warmer than 190º or so, but that's thermostatically limited by the external cooler and fan.

Groomed trail sticker? What's that? My "trail sticker" is a big, fluorescent orange triangle ; ), but I don't ever go on groomed trails, just USFS roads.

couchloafer said:

Paul,
I finally got around to installing the Cylinder Head Temp Gauge as I have no snow to operate in County wont issue groomed trail stickers to Snow Cats any more.....another story.......Can you give me an update on what your gauge has been running for temp since you installed the aux oil cooler?
Thanks,
Kevin

p.s. you got any snow to run around in?

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Don, what brand of gauge are you using? One thing to keep in mind is that most of the cheaper gauges/senders like VDO are *not* compensated for ambient temperature so you get an inaccurate reading. As I recall, the VDO CHT gauges are calibrated for an engine compartment temp of around 70º F. The rub of it is that if your engine compartment warms to 120º, then your cht will be reading 50º too low. That's not a big deal if you're not running hot, but what about if you see 400º on your gauge? That will mean barbecue time for your exhaust valve seats if you keep it up for too long. Just something to keep in mind.

dds said:

i went to a local snowmachine shop and got my cht gauge about 100 bucks with a sender for a 14mm plug works great the product came from western power sports an after market parts supplyer

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the gauge is a thermo coupled gauge for a snowmachine it was cheaper but looks identacal to the ones used on aircraft engines i will poste some pics later i'm in the process of an engine re build to corect excessive endplay also found a missing wrist pin clip on #3 cylinder