KAAMA

bt, sorry bro, you kinda scared me too in Post #23 in this thread. Listen, don't forget to do the exhaust side too. It's not as crittical as the intake size because of the intake's larger valve size. On my cousin's 454's he had some bowl/pocket porting work done to the heads and a bore notch job. With 8.6 comp ratio and everything remaining the same he picked up an additional 106hp. The heads he had were some old large oval port semi open chamber heads that weren't really known for it's hp potential. But JimV went in there and added larger stainless steel 2.19" intake valves and some 1.84" exhaust valves and did a little unshrouding of the valves within the combustion chambers, some pocket/bowl porting which includes short side radius work. He had the engines dyno tested about 4 years before and they made something like 355hp with a flat tappet hydraulic cam that was only about 4 degrees smaller. With all the new work his engines (actually 461") made 461hp @5100rpm and 510 torque which was very flat from about 3400rpm to about 5000rpm. This 106hp increase is mostly attributed to the head work and the bore notch done to the cylinder bores. My cousin will be removing his stock Merc trash cast iron exhaust manifolds and is adding a pair of GIL exhaust manifolds with DRY pipes. His boat is a 1988 32' Baja that he has replaced all the stringers in and beefed it all up. He has yet to install the engines in his boat. That should happen this spring. 106hp from head work and bore notching is nothing to sneeze at.

Waterfoul

KAAMA hit on something that we all forgot to mention....do NOT go too deep with the notch. If you go down as far as the top ring, you are toast....you'll be boring that one cylinder out and adding an oversized piston to fix it. Not what you want to do. Make sure you can see where the top ring comes to in the bore.....same as the top, don't come closer than 1/16" or you will create trouble for youself.

blue thunder

I am trying to stay about .100" away from the fire ring in the gasket and the top of the compression ring travel. This will give me some margin for blending (and error).

I really like your cousins numbers Kaama. I am going with the edelbrock alum rect port (CNC) head that I have. Probably not the best, but they are the best I have. Talked to JimV about wedges, but need to see how the finances are in a few weeks. Cash poor at the moment.

BT

blue thunder

Two hours later, engine one is done. Not a bad job once I got over the gitters and figure out a good system. About half the 2 hrs was spent duct taping thoroughly. I did the exhaust side as well, which was easier yet because there was less material to remove. Did end up going to about .060" of the gasket and ring wear mark. .100 away was not enough material removed. Thanks alot for the neat trick guys. Can't wait to try it. Gotta go, I think my crank gear in the toaster oven is done. Had to get up early and pop it in before the wife gets up. Now haow am I gonna get this burnt oil spell out... oh well. Here a pick of one bank.

BT

Waterfoul

The notches look good. But what's with all the nick marks on the top of the #6 piston???

blue thunder

Thanks Waterfoul. That is just reflection off the light oil I sprayed on just before the picture. Had to clean all the oil off so duct tape would stick. The rest is carbon flaking off. Was running very rich last 1/2 of last year. Should be better this year. I chose not to disturb it to make the piston prettier, so as to minimize contamination.

BT

KAAMA

At least from what I can see in the picture you did a good job. Prep work and all, how long did it take you to bore notch all the cylinders on one block?

blue thunder

Thanks Kaama. I'd expect my next engine to take 1.5hrs. This one took about 2 hrs. Took me till the second bank to figure out how to duct tape quickly. I got that licked and it really worked well.

Just got done checking piston clearance with some clay. Seeing the position the valve comes into the cylinder (impressed in clay) illustrated to me why this should help flow. Well, I am off to finish torqueing head bolts... thanks again fellers.

BT

Tinkerer

Sorry guys -- I have been busy. The first thing is to put the head gasket against the head and see how much material is between the valve pocket and the gasket. It wont help to notch the block out farther than the head is cut out. If their is 1/8 th inch of material between the valve pocket and the gasket than that is how far you valve notch the cylinder ( what you want to do is make the cylinder match the shape of the head.) Y ou need to follow the shape of the head gasket as close as possible. I did both of my engines still in the boat with the top half off. What I did was find a plastic lid that fit the bore size and yes I duct taped it in place. DON'T DO THIS WITH OUT SEALING OFF THE BORE AND ALL OTHER OPENINGS ON AN ASSEMBLED BLOCK. Follow the shape of the head gasket on both the intake and exhaust reliefs and even a 502 will have improvement. As far as loss of compression -- Increased air flow will overcome the loss. Just DON"T get TOO agressive with the grinder. Stay 1/16 inch away from the top ring mark. Remember if you are rebuilding the engine use the new piston ring location not the old one. This is an easy way to gain some HP and it can be done with a DREMEL hand grinder. ( What boater doesn't own a DREMEL)

blue thunder

Tinker... since you did this in the boat, I figure you didn't do much other than this at the time. How much of a difference did you feel when running the boat? Was it noticable? Anything gained on the top end, rpm or mph?

BT