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I have built Onan industrial engines that have 4.9:1 CR... They run a constant speed and do so for 20 years before they ever wear out...

Once we bumped one up to 6:1 and it ran much better, but kept breaking drives on input side of the water pump it was turning..

I ended up slapping it into a go kart frame and almost killed myself when I hit a 'Box hedge" at wide open throttle..... Its still laying out back.

MASSIVE TYPE IV wrote:I have built Onan industrial engines that have 4.9:1 CR... They run a constant speed and do so for 20 years before they ever wear out...

Once we bumped one up to 6:1 and it ran much better, but kept breaking drives on input side of the water pump it was turning..

I ended up slapping it into a go kart frame and almost killed myself when I hit a 'Box hedge" at wide open throttle..... Its still laying out back.

LMAO...i would love to work for you!!!!!LOL

Well....... I'd have to ask you that after the first week.....

Hi All -

For a look at a fresh Type I upright design and how we attempted to build a motor that would keep up with traffic, run cool, pass emissions, and last in my '71 Kombi, take a look at a full writeup and parts list at:
http://eeb8.biosci.arizona.edu/nick/

Based on my previous three attempts and Tim Jordan's 12 years of full time air cooled work, we decided that for this 78X90.5 motor that 6.8:1 teamed up with a Type IV cooler in a stock doghouse fan shroud would do the trick. Prior to dyno testing we estimate 90-95 wonderfully usable HP with scads of torque as it pulls well to 4,500 rpm in the first three gears.

After 600 miles, and based on readings from my trusty 22 yr. old vdo oil temp guage with sender in the blockoff plate on the rear of the sump (right where it's been for the previous motors and 165,000 miles) it looks like this design works. After touching 210F on the initial breakin run up the Tucson Mtns., it is now resting at 185-190F on the 25 mile run home from work in 60F weather at 65 mph. This with stock gearing and 195X75 rear tires on a 6" rim. Though this summer will tell the tale, I'm expecting freeway temps to stay below 220F.

So..... my take is that conservative CR motors for Type II's is the way to go - and it's just cost me $4,000 to illustrate the point.

Nick

How hot are the heads?


Steve

This motor is using a set of semi-hemi stock valve heads, cleaned up ports and Manley ss valves. Without a hd temp guage, my experience so far says that head temps will not be an issue at cruising speeds. I'm using Kadrons on stubby manifolds to get the gas in and home brewed heater boxes with 1 3/8 " J tubes and a Berg extractor exhaust.

Nick

6.8:1 is way too conservative for me... I run 9:1 on my 74 Bus and tow my beetle across mountains.. Its got my CIS injection upgrade and has only been together for 45,000 miles so far. In 2 years it has not seen a single adjustment other than the valves, and thats been just a couple.

The correct CR is much better than too conservative of CR.

MASSIVE TYPE IV wrote:............ Its still laying out back.

When I come see ya, can I DRIVE IT?


Don

Its dead... killed it 10 years ago.

MASSIVE TYPE IV wrote:Its dead... killed it 10 years ago.

But we can rebuild it!

We can make it
FASTER!
STRONGER!
WEAR FUNNY 70s Aviation glasses!


BUWAHAHAHAHAHAHAHA!!

Don

Nick, I'm with Jake on this one. I raised the CR on my engine (among other things) and saw a 20ºF drop in oil temps while cruising 10mph faster. Tight deck = lots of turbulence = resistance to pinging = cool running with more hp. I burn exclusively 87 octane (including Magna Sin).
Changing your main jet to get through smog was the wrong thing to do. Your AZ test is identical to the test I have to go through, and while you are on the dyno, the idle jet is the one feeding most of the fuel. Go back down to your original 130 (smaller in the mtns) and get better mileage. Your heads won't carbon up so bad, you won't foul plugs as easy, and it'll run cooler without all that carbon buildup.

Bump it up- Hear it thump!

Hi All -

Ah, good to get feedback. Also got an informative mail from Torben Alstrup (aka Farmer), noting that the stock Kadron venturis may easily be enlarged to 30 or 31 for 'More power and torque, better consumption and cooler running' and that a larger exhaust system might also be in order. I'm going to take off the bumper and single QP muffler for a run with a stinger this weekend.

As the previous (74X88) motor ran well at 6.3:1 CR for most of 10 years. ready for kerosine, at least this one is headed in the right direction, eh? We split the extra deck into (if memory serves) .090 shims at the bottom and .060 copper gaskets at the top, giving some leeway to adjust the CR at the next teardown. This might not be soon though, considering my delight with it so far.

Is there general agreement that a CHT gauge is a meaningful measuring tool - and that the 'best' mounting point for the sender is?

Thanks for your opinions -Nick

Under the spark plug...

That much deck height is definately killing your efficiency and that causes uncontrollable EGT in most instances.

Question on the CHT sender under the plug: Does the heat rating of the plug have any effect on the temp readings? The heat range is a rating of the plugs heat transfer from the electrode to the rest of the plug and consequently the head. This is controled by the amount of porcalin ( Why cant we have spell check?) So anyways I am wondering if this effects the heat at the sender.

Ron