Yamato 302 cooling

[bill boyes]

Try Digitron. They are in Washington. Combined unit Temp gauge and RPM. Be careful how you mount it to the dash. They sell a shock mount. Many 102/302 racers use this unit. They make many Go Cart stuff. Good people to work with.

[glen wesanko]

Hello Blueskyracer, I got my cyl head temp guage setup from a company called Aircraft Spruce.They are a great mail order company specializing in aircraft parts and supplies.Also a great resource for clevis pins (shear pins) and any other aircraft hardware.The guage is sold as a separate item as well as the wire harness (make sure you order one long enough)and the sender.Specify either 18mm or 14mm (spark plug size)The system is self powered working on the resistance of the sensor under the upper spark plug.The whole system is less than $100.00. I applied a red sticky "red line" on the face of the guage so I can tell at a glance when it's getting too hot.Hope this helps.

[ZUL8TR]

ring replacement

Team B&H, for those of us who are less experienced this is the kind of knowledge that is really appreciated . At the risk of hijacking the original thread I was wondering if you had any basic rules of thumb as to when to replace rings on a 302. I understand that ring replacement is relative to running time, motor condition and a list of other factors. That said is there a point based on run time where you would think about changing rings.

Thx,

Sam

---------------------------

Although out of scope here but why not keep it interesting.

I monitor ring replacement with a simple compression check. When I purchased new in 1973 my 25ssh I took compression readings, then broke in the engine and took another reading, then continued taking readings for comparison and when compression was about 10psi lower than the broke in value in both cylinderes I did the rings. Also monitored the compression difference between cylinderes. One time at a race during the Fla Grapefruit Circuit when I didn't have enough time to rering between weekend races I knew the rings were needed by compression reading and finally by the performance drop to swing the prop I normally ran-it ran like crap. So I had to rering before the next weekend or run last again. I broke in the engine during some very minor testing at the race and during the first heat. Kept getting faster as the race progressed thru the laps and the second heat and the finals, best brake in I ever experienced (back then there were usually 30+ boats in 25ssh so eliminations were the norm).

Important: get a decent compression gage and always use the same gage and rope the engine the same number of times (I use 3 and observe the readings at each pull) and do hot or warm as long as kept consistent as all things are relative so says A. Einstein.

Although I have never done this a revealing test would be to place a pressure/vacuum gage on the crank case and measure the +/- pressure as the engine is roped over.

During conversations with Marshall Eldridge at his shop in Yalaha Fla I asked how he monitors his engine aside from compression checks. He checks leakage past the rings and reeds by pressurizing the crank case with about 5 psi (recalling?) and observe the leakage. Similiar to a leak down test on cars.

[johnsonm50]

I guess I am a lazy racer but I have better things to do at a race than switch heights all the time. I always run 3/4 for both classes. But I must add I still have fun.

I left my 102 at 3/4 in 20SS too. Being a new driver having alot to learn about the finer points of getting a 1/2 mph out of several points around the hydro & a few from dieting LoLs. While stiil learning to drive I thought it better to go with the assumption that it would handle better.

[Team B&H]

I have used a Digitron gauge for cylinder head temp but currently just use an ordinary multi-meter that has a K temp function. I have more money in the plug adapter and wiring than the meter- probably $50-60 total and the meter is useful for many other projects. I found one that has 1 inch display so you can read it easily.

Ryan Burdick won the APBA Nationals at Moses Lake in CSR with a 302 that he hadn't hadn't had apart in 7 seasons. I wouldn't go that far myself but rings are probably changed more often than absolutely necessary.

[Trihedral_1]

.....the most significant thing with a 302 is that the exhaust cover and the engine block MUST be flat and seal well. Most 302 exhaust covers are far from flat on the gasket surfaces as they come out of the box. If not too bad, you can lap it flat with a piece of 80 wet or dry paper on a flat surface. If really bad, you might need a trip to the Bridgeport to mill it flat. Even a slight exhaust leak here will pressurize the water jacket area and cut off the cooling water when the pressure drops to a minimum when you get going fast. Don't forget to check the block surface when you have the exhaust cover off. This also applies to 102 and 80 motors but they generally don't have the issue here that 302s do. We've had probably 8 or 9 302 motors and I'd only say that 1 or 2 were OK in this area.

This is an excellent tip. Care to share how you assemble it?
When we re-assemble ours, we add a very, very thin layer of Permatex (orange) around the exhaust area. The spec for tightening is not much, 6-8lbs (we use an inch torque wrench). When it's apart, check for water marks and exhaust stains on the gasket surface, especially near the bottom. I've heard of some people putting stainless helicoils in so they can really tighten up the exhaust cover, although I've never tried that for fear of warping the cover.

We try and run 350 degrees taken at the top plug for everyday racing. Any higher and it will continue to rise until the race is over. I must compliment my driver (Guedo) for saving a whole lot of equipment in '09 by looking at the temp gauge.

Jimi O (305-R)

[seanp3]

But the most significant thing with a 302 is that the exhaust cover and the engine block MUST be flat and seal well. Most 302 exhaust covers are far from flat on the gasket surfaces as they come out of the box. If not too bad, you can lap it flat with a piece of 80 wet or dry paper on a flat surface. If really bad, you might need a trip to the Bridgeport to mill it flat. Even a slight exhaust leak here will pressurize the water jacket area and cut off the cooling water when the pressure drops to a minimum when you get going fast. Don't forget to check the block surface when you have the exhaust cover off. This also applies to 102 and 80 motors but they generally don't have the issue here that 302s do. We've had probably 8 or 9 302 motors and I'd only say that 1 or 2 were OK in this area.

I had an issue with one of the new 302's we purchased - could not get it to cool. After checking everything else I could think of, I took the exh manifold off another of our 302's and installed it with a new gasket and bingo - started to cool. So, I took the manifold back to Montoya for him to check it. Turns out it was warped. I had it resurfaced and put it back on. I still could not get it to cool with this manifold. I ended up buying another manifold and the problem went away. I'm still baffled over that manifold. I couldn't see anything wrong with it, but obviously there was.

Anyrate, I had someone tell my by resurfacing a manifold - if you take too much metal off it can actualy change the exhaust tuning. I don't know this for certain - just something I was told. Maybe someone who knows more about this can elaborate.....