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Lesson #6....The 160 lb compression rule

First, I will explain the reason for the rule. It was a simple solution to a problem. WE THOUGHT!
The problem.
If we went with the 2 motors in the class that we have complete UIM spec sheets for [the 49 OMC and the 70CES Yamaha] we would limit the number of boats. The last CBF rule in the class allowed both the 2000 model 56 OMC and the 59 cubic inch 60 hp Mercury. CBF had never posted any spec sheets for the motors and racers running 56 OMC motors raced mostly 1987 to 1992 fishing motors or SST 60 motors. The inspectors let them run because they had no spec sheets.
When we started working on getting T back, all of these motors were out there and people wanted to run what they had. They didn't want to invest more money in a class that may never get restarted. Totally makes sense.

The solution
We needed to find a LOW COST way to make all of these motors equal and keep class running at the 2009 UIM speeds. [63 to 70 mph] . We knew that if we were too fast, the class would not get approval in CBF with NO CELLS.
The 49 OMC and the 70CES were not a problem. The big problem was the 56 OMC. The fishing motor was too slow compared to the 49 model and the SST 60 was too fast.

The testing
We spend a year testing and racing different heads on the 56 models. The SST 60 needed to be reduced in performance and get the horsepower down from 90 to 100 hp to 75 to 80 hp, we had to increase the fishing model 56 up to 75 to 80 hp.
The cylinder head made a big difference on both. Put a 28.5 cc head on the fishing motor it was very close. Put a 32 cc head on the SST 60 and it was close. In the races no motor had a real advantage.

What happened in 2012.
The problem was the 56 fishing motor with the decompression hole. The porting on the 1986 to 90s fishing model is the same. The only difference is the hole. As you saw in another thread on this site. The readings on those motors were much lower with the same head. Some of these racers actually ended up with a head close to 21 cc. Much smaller that even the SST 60 head . Because of the rule, they did nothing wrong. Did the added compression help?

What will happen in 2013
This is TOTALLY at the racers option. We are not changing the rule. However, there will be 3 heads for the 56'r based on cc measurement.
one for the SST 60
one for the bridge port 56 fishing motor.
one for the non bridgeport 56 fishing motor.
These heads will be numbered and assigned to the racer that has them.

i don't believe the facts are correct, the 21cc head that was measured was on a non-decompression 56 and my understanding was that the compression readings were in the 160 area and not more even if the cc is less then the sst60 spec head, if this is incorrect perhaps they can speak up. I was the only one who raced a 56 with the decompression feature and I ran the same head from my 86 block as I ran on the 92 block, I have not measured the cc's of that head but compression was the 160 on the 86 block. If that head is 21cc then it's 21cc that gives me the 160lb. The compression reading on the 92 block was less as indicated on the other thread due to the decompression feature. If you think someone is going to go around the 160lb rule with the decompression feature then put a cc limit on that head and block combination, for all the other ones why alter the rules from where it is ...160lb compression.

Come to think of it Erik raced a decompression block at Dunnville when he put on the driving clinic but he did not run a cut head.

[quote="LittleCharger
If you think someone is going to go around the 160lb rule with the decompression feature then put a cc limit on that head and block combination, for all the other ones why alter the rules from where it is ...160lb compression.

LC read the post again you missed alot.
[1] we are not changing the 160 rule.
[2] we are going to let racers have a cc measured head that should provide the 160 .
If they want it. No one broke any rule.
The 28.5 cc head is a SST 60 head. On an SST 60 it is 180.
We tested that head on 3 1986 blocks and Steve in Thunder Cat is another, so that is 4 similar powerheads. We all got the same numbers. 157 to 162.
Why yours is different?

Like I said I have never cc'd my head so I don"t know what it is but do know what my compression gauge says. The 21cc head was not mine but someone elses, but I do believe they were within the 160lbs.

LC correct on both statements. It was not your head and it did read 160 on the powerhead which has the decompression hole. So totally legal by the rule.

Just to be clear when that 21 cc head read 160 lbs it was on a block without the decompression holes. I do not believe that head has ever been on a 56 block with the decompression holes and tested for compression (maybe it has for compression testing but never raced).

Sorry to get the school thread off track...I'll keep quiet now.

Cheers,

LC: "Sorry to get the school thread off track...I'll keep quiet now."
Pls define your understanding of 'now',....any chance your definition includes an extended period of the future??

Respectfully signed,
STFU

Lesson # 7 Motor Parts, what to use and what not to use

Cranks
All cranks are not created equal. They are mass produced and there can be minor differences in performance.
I good used crank in many ways is BETTER than a new one.
-cost new can be $700. to $1200.
-buying new does not mean it will perform better than a used one.
-if the crank is one in your current motor and it performs well. KEEP it.
-if there are marks and nicks on the bearing surfaces, use another crank
If it is a modular crank, pin or weld it.

Pistons
-some of the latest OEM stuff comes from China and is not a good.
-there are lots of options in makes of pistons
- Wisco pistons swell more especially in a 49 OMC. Watch their clearance.

Rod and rod bolts.
-rods are selective and they are not all exactly the same. Best to have a number to choose from
-if you do not know how many hours are on the motor and it could have 100’s of hours..use new rod bolts.

Bearings, gaskets , seals and O rings
-do not go cheap..use good quantity for all.

Assembly
-torque as per the manufacturers specs
-re-torque the head after running the first 2 hours.

Fuel mixture
-break-in motor with an oil based oil…you need to seat the rings
When you think mixture, think the amount of FUEL not the amount of OIL
-when breaking in a power head run more oil….say 18 to 1
REMEMBER that mixture is RICH in oil, but low on fuel….THE MIXTURE IS LEAN! Especially at high RPM.
In break in run larger jets. You want lots of oil on the rotating parts and you want lots of fuel .
Once you have time on the motor. Change your mixture and your jetting. Again 32 to 1 has more fuel than 18 to 1 so there is less chance of hurting the motor due to being too lean.
-never run 100 to 1 ratio. 50 to 1 will be highest and I would only try that on a Yamaha.
-I like 32 to 1..just my choice. I like it because I can go up to 25 to 1 on hot/humid days when you want to be leaner and I can go to 40 to 1 on colder days where I need to be richer. Remember think fuel in the mixture.

Lesson # 8 What is the maximum RPM my particular motor can turn?

The motors
Most if not all of the stock fishing motors can turn in the 7000 range.
Hard to believe that a motor designed to run 5500 can turn 7000.
It is true and the motor will last longer than it would on a family boat.
Reason: It doesn’t have to work nearly as hard.
Their performance really drops above 6500, so there may be little or no advantage
trying to run 7000. ET and prop selection will tell you what works best.
Also each model, even though it is the same can and WILL perform a little different.
Some better than others. Luck of the draw.
The fishing ones are:
56 OMC
Yamaha…70CES has to be here. It really is nothing special.
Chysler..put that one in for Paul. I heard his turns 8000 with no prop.

Sport
Stinger 49…in can run close to mid 7000s

Super Stock
SST 60…this one even with our rules will turn mid to high 7000’s and it has to been in that range to get performance.

BOTTOM LINE!!
You can win with any of them.
The Chysler has yet to prove itself.

Pfffffft....wait until you see my Elgin...


This is all good info Don. Thanks for rebuilding the original T thread....it's even better this time. I'll try to keep my "input" to a minimum....Go Team Elgin!!