Classic Australian Wooden Power Boat Association

High flow needles could be the solution on 2x carb set up. Rolls Royce 6.7 v8 use 2x carbs & turbo 6 cylinder use 1x su with great success.
Doc.

Bob Vic wrote:So did you fit two or three? Same manifold?

Just two larger ones on the same manifolds Bob.

Well Fridays run was a disappointment. 46mph now. The one thing this engine has been plagued with is reversion at full throttle when maxed out. This run it was particularly bad. The camshaft has a lot of exhaust duration, more than what would be expected of a serious high performance engine. Enough pontification. Engine out tomorrow, camshaft gets replaced.
The bigger carbs made a very noticeable improvement before the reversion hits.

Dialing in the new cam. Of course it's out by 10 degrees. On the hunt now for a camshaft gear offset woodruff key.

shim the gear?

Alan wrote:shim the gear?

I thought of that but I don't like the idea of using a shim and would rather go a thicker retaining plate. A shim wouldn't last in that application.
Offset woodruff key is my first option (I may have to make one out of a 1/8" key).
Second option will be making a new thicker retaining plate.

Or you could make an adjustable set up like this and have to opportunity to 'play' with the timing

OK, did some rechecking today.
To move the lifter a further .020" I'd need a spacer about 3/16" thick which would offset the gears too much. This is due to the slow ramp rate on the lobe at that point.
Something wasn't right so I started to check lobe centre angles and they weren't too bad. After some more deliberation and checking and changing the cam position I finally spotted the issue, and it wasn't anything I was doing. Anyone see the problem?

Well Craig I have looked at the info you posted and cant see the fault unless its the fact the rockers you made have a different ratio which will skew the numbers? or you could enlighten us of the real problem?

Will wrote:Well Craig I have looked at the info you posted and cant see the fault unless its the fact the rockers you made have a different ratio which will skew the numbers? or you could enlighten us of the real problem?

By the card, if the inlet valve is .050" off it's seat at 1.8 degrees BTDC (not much off TDC anyway), how is it going to be off it's seat .071" at TDC?

It took another 10 degrees after TDC to get that extra .021"
I rang Clive up and it seems he wrote the wrong lift figure down. I also found and old Wade listing I had and it specified .054" @ TDC for the inlet which is a couple of thou from what I was getting. I'm a bit happier now. Nothing like chasing a red herring.