blown engine

i'm involved with a grand prix hydroplane this weekend we blew a motor it was running rich
468 bbc 9.5 compression 8-71 at 20% over 18psi hilborn bug catcher on alcohol.
seized on 1-2 journals rods broke and sheered the 3 cam bolts and dowel pin, jesel rocker mount torn from the head no other head damage other than a slightly bent exhaust valve what would cause this could it have hydraulic-ed, the motor faces backward on a 7* angle
any ideas on the cause thank you
we are new to blown alky motors turned in the second fastest time for the week-end

 

I came this forum because we are newbies to blown alcohol motors and the GP class, i realize that inboard hydroplanes don't have wheels, in the past you have help me tune a fed with the info i read here. the competitors seem to know less than we do which isn't very helpful.it's the sheering of the cam bolts and dowel pin that really puzzles me the eight stage dry sump pump runs off the crank and the mag turns normally.

 

What did the #1 and #2 pistons, and plugs look like ? Was there any pieces of the rod bearings left and if so what color were they ??

 

jeff/21,
Sorry man. It sounds like the cam stopped first and then caused the rest of the mess.

 

First I'd figure out why those rod brgs went bad. I'm thinking they siezed, broke the rods, the rods hit the cam and sheared your cam drive bolts(I had this happen last summer except the rod just had too many runs on it and we wrecked 12 valves) Its typical that the front 2 cyls get beat on harder than the rest of the cylinders especially with normal intake manifolds.

Are you running port nozzles?

Did the rod break in the beam or rip off the cap?

What else is broke, is the cam bent (was it hard to remove from block), is the crank cracked between the #2 rod and #2 main?

What do the other brgs look like?

 

What kind of lifters were you using? Had a new Comp tiebar break on startup, lifter turned, stopped cam and then done some more damage when it kept rotating with the valves open. Did you have the locating pin in the cam? I have seen the three bolts break when that item was "misplaced". JW

 

1&2 are black the other journals good, rod bearings all twisted in the pan, both rods twisted 45*broken in the middle of beam(steel I beam) wrist pins still in pistons. the cam just slide out #1 exhaust lobe a little messed up lifters ok came out easily, just the lower part of piston broke from being hit . we use Brad Penn 50

 

injection system bug catcher with 8 nozzles in the hat (as per rules), Enderle pump.

 

I'm not sure about steel rods and 18 psi boost, I'm not saying it won't work I've just never attempted myself.

Does the blower have a pie shaped outlet?

How long of a blower snout is it, like 3-4" long?

 

pie shaped out-let short snout the prop-shaft is also driven off the front the motor is mounted backwards in the boat at a 7-8* angle, the intake floor has a raised floor that is even with the bottom runners in the front half and a 1/4" lower in the rear 1/2 causing the frt cylinders to run richer. I was thinking of raising it to the same level, would it help to even it out?

 

I'd say your front cylinders are too lean because they are getting more air from the blower from the location of the blower outlet (this is real typical) and since you can't run port nozzles you can't feed them more fuel to compensate. If it were mine I would move the blower back, 11-12" total worked pretty good for me.

Read and study spark plug 101.

I'm curious what the rule about no port nozzles was supposed to do, sounds like another rule intended to save money and will end up costing more...

 

thank you guys. yes the rules were changed 3 yrs ago to curb the cost the class all but disappeared it was down to 3 boats now they have a full field every race, like any restricted class they don't always make the most sense. off to the races

 

back to the jessel stand

If the rocker stand was an exhaust rocker
that could be where it started. Just my 2 cents

 

yes it was #1 exhaust i was thinking on going to nitro 70 until we get this thing dialed in burn't 38 gals of alky in 8 laps

 

rod

Hi, what kind of rod?

 

I beam callies

 

Is 75 psi of oil pressure is enough for an rpm higher than 8000????,

 

my feeling is NO, even based on good old Smokeys formula of 10psi/ 1000rpm its not enough. Depending on the oil and clearances it may not be enough to stop some form of contact between rods and bearings. Having said that we only run marginally more with 50 weight oil and have never had a problem in a BB Chevy running upto 8,000.