Thread: First Post BBC Build for Jet Boat Project..long

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I am new here but I have been lurking here for a while. I have found this to be a great forum of interest. I mostly lurk on the BBC section cause I just got finished building a 454 for my Nordic Jet Boat project. I got the block from a person who had the motor in a Jet boat and it dropped a valve(possible water reversion).I got the motor in all apart condition. The block was in great shape. It had factory forged rods and pistons (Hi comp). The heads had battle scars from the valve flying around. They are Rect ports. I sold the parts I did not use on E-bay for a surprisingly good amount. I kept the block, factory forged crank and heads. Before I brought it to the machine shop I de-burred everything inside and outside.
I had it bored and torque plate honed for .030 over SPR pistons with the piston set at “0” in the bore. I also had it line bored/honed for ARP studs on the mains. The heads were redone utilizing Manley Severe duty larger valves and new hardened seats. I used a comp cams marine cam for Jet Boats to keep water reversion at a minimum. I also used matching comp. cams valve train throughout with roller rockers and 3/8 push rods. I also studded the heads as well (more on that later).
I assembled the complete motor after all machine work was done. This motor assembly fought me all the way. I used a cloyes chain with the Torrington bearing. I wanted to use a cam button. I had to machine the cam button to get .007 clearance. While doing this the retainer clip kept getting stretched out so I had to get new ones. Thanks to having a lathe in my garage. I also got an alum timing chain cover which I had to mill out the inside for chain clearance and re-drill the holes for the dowel pins. It is great having a Bridgeport Mill in the garage as well. I guess this is what you get when you get a timing chain cover on E-bay that was probably made in China. I then attempt to mock the Jet Boat headers and the flanges hit the lower head studs which required the flanges to be notched to clear. Setting a set of Jet Boat headers on the mill was a little scary to say the least but they came out good. After all assembled it is now time to test run and break in the cam on my home made engine run in stand. Here are some pics of the build and the run in stand. I should be ready to fire it in the next couple of days or so. Stay tuned for a video of it running. I have run small blocks on this stand and winged them up and the stand did not even move, however I am going to strap the stand down for the Big Block.

http://www.tjsperformance.com/images/bbcbuild09.jpg

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Sounds like a cool build. What was the reason you think you had the valve problem? I built a small block for a prop driven boat and have had this happen twice now. I suspect my problem was valve float at too high RPMs when the prop becomes unhooked when I get a boat that was never meant for this power out of the water. I'm having the heads redone now and will be installing a rev limiter. ---JR

Welcome aboard. We like hot rods whether they are on the land or water. I work at a Marina, so I have a soft spot for boats, anyways.

When we lived in Southern California in the late '70's, flat bottom ski boats were all the rage. We saw every configuration, even some with 426 Hemi's with blowers on top. Very fast way to cover the water. Funny part was on Lake Perris there was a 35 MPH speed limit, and some of these boats were doing 100, or better. Drove the cops nuts.

I also like your engine breakin stand. I started to build one a few years ago, but Hurricane Charlie hit the shop we were in at the time, so I scrapped it when I moved out. Yours is nice and compact.

I think JerseyRodder hit the reason these things swallow valves. Race boats have a throttle man who backs off when the boat is airborne to keep this from happening. It's a timing thing, and you have to hit it just right.

Again, welcome aboard.

Don

Originally Posted by JerseyRodder

Sounds like a cool build. What was the reason you think you had the valve problem? I built a small block for a prop driven boat and have had this happen twice now. I suspect my problem was valve float at too high RPMs when the prop becomes unhooked when I get a boat that was never meant for this power out of the water. I'm having the heads redone now and will be installing a rev limiter. ---JR

I do not know how it happened. I bought the engine from someone who it happened to. Water ingestion is easy on a jet pump engine if you do not know how to set up the water system and do not have the correct restrictors in place. Also the T valve has a lot to do with it. I am doing away with all that and getting an electric valve for this called a banderlog valve.
Thanks.
T.J.
www.tjsperformance.com

HI TJS,I don't have a boat my self but have a freind that owns one and I have turned a few wrenches on it,After scattering valves/bending push rods (ETC) we put MSD ignition with REV-limiter on it seem to help out when boat gets to much air and engine free revs befor you get off throttle.are you going to tube be hind it I like to put the jet down and blast riders off the tube when thay have been on it to long.

on the chain cover you can add gaskets for more end play the cover will not know were it is i do this alot and buy my timming cover gaskets in bulk and for the mill you can not do to much race engine work with out one .i have one and do not know what i would with out it and my lathe and tig

Originally Posted by FIDO

HI TJS,I don't have a boat my self but have a freind that owns one and I have turned a few wrenches on it,After scattering valves/bending push rods (ETC) we put MSD ignition with REV-limiter on it seem to help out when boat gets to much air and engine free revs befor you get off throttle.are you going to tube be hind it I like to put the jet down and blast riders off the tube when thay have been on it to long.

I will be running an MSD 7al-2, MSD pro billet dist and blaster coil. I know what you mean about getting airborne. It happened a lot to my friends Cheyene and glad he had the same set up. I keep asking my friends if they are ready to tube behind it after I show them the vid of the engine. They are like no way man.
T.J.

T.J. tell them I said no guts no glory!!!