Re: The 2010 FrankenMerc Project
You're correct, cutting the heads does not change the squish band physically but it does cause the rise in cylinder pressure that will hold the squish fuel back closer to the edge of the piston while at the same time compensating by reducing the overall cylinder volume.
In fact, it works very well, I just put the heads back on it and changed the jets dropping it from .060 mains to .058's and increasing the idle air's from .054 to .060.
Compression is now 140 and idle head temp is 150 on the hose with 2lbs of water pressure at the pump.I have low water volume and pressure at the house.
If the engine holds true to form, that should be about 135 degrees in gear idle and 4-6 lbs in the water with a WOT temp of about 145-150 @ 15lbs.
The idle air screws are now functional on the carbs and the timing is setting at around 4 ATDC @ 900 RPM's in the tank. This should be telling me that the mains and the idles are sized correctly but I will keep a keen eye on the temps and plugs tomorrow when I take it out for a spin.
At this point someone is probably scratching their head asking why did he have to lean it down? It's simple really. Remember all the work I did opening up the rod slots (I actually did a lot more than you saw) and then there was the stuffing of the crankcase, cutting the front half down, adding in the spacer and then there are the finger ports (didn't show you that either). All these things equate to one thing.. They get the fuel into the cylinders way more efficiently.
The exahust chest is also cut between a drag cut and a sport cut. I showed you a gentle easing that I knew would improve things but not change the ability to idle in gear properly. I have another motor cut like that. When I sell this boat it will be on it.
O.K., O.K., so now your saying why didn't he show us this other stuff... That's simple too.. It's controversial and not going to work out well for most of you that still want to fish with your motors. The stuff in this post will get you a good sport motor.
So now you know why I can hit the speeds and RPM's I'm hitting with this motor on my boat. Hopefully I'll make the 8,000 RPM mark tomorrow. If not... I've got another one on the stand waiting for a break in.
