SoCal Jet Boats

Tech Talk => Engine Mechanical / Electrical => Topic started by: Zep654 on June 10, 2019, 04:59:52 PM

Title: Might have a serious problem. Please help!
Post by: Zep654 on June 10, 2019, 04:59:52 PM
I have a BBC 468.  I don't think it has been run for over two years.  The heads and valvetrain were new about three years ago.  I went to spin the engine over by hand, and I noticed some of the exhaust rockers were loose and not even touching the valves.  The valves I believe are either bent or seized/stuck.  The dual springs aren't even able to bring the valve back to the closed position.  You can see in the pictures, the valves that are working fine and closed, are about 1 7/8" high.  The bad valves (without the rocker touching them) are only 1 1/4" high just for reference on how they aren't closing.  There are five valves like this...and they are all exhaust valves.  The boat is new to me and I have yet to run it as I needed to check it over and fix a few other things.  I was thinking I was on the home stretch and might be able to have it on the water soon, but now I feel I have the biggest setback of them all.  Do you guys have any recommendations on what to do here?  I am somewhat at a loss, except for the option of taking the scoop, carbs, blower, manifold, exhaust, and heads off and dealing with it that way.   I'd really appreciate any help or advice on what to do.  Thank you

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Title: Re: Might have a serious problem. Please help!
Post by: Grimpala on June 11, 2019, 07:04:11 AM
I can't see the pics, but can you tap on the valves with a hammer and see if they might just be stuck in the guides? 

Or, pick up a cheap borescope from amazon and take a look from the spark plug hole.

They very well may be bent, but it's worth a check. 
Title: Re: Might have a serious problem. Please help!
Post by: jim brock on June 11, 2019, 04:46:03 PM
are the lifters hyd. or solid
Title: Re: Might have a serious problem. Please help!
Post by: mash on it on June 12, 2019, 08:58:24 AM
Possible rust on the valve stems, not letting the valve close?

Spring fatigue?

My luck? Bent valves.

Dan'l
Title: Re: Might have a serious problem. Please help!
Post by: Zep654 on June 14, 2019, 10:04:27 PM
I don't know why you can't see the pictures, however, I freed up all the valves.   None appear bent.  The lifters are hydraulic.  There is rust for sure from the exhaust being open to the atmosphere.  I am going to hone the guides and massage the valves to make them work.  Now, the main problem is ignition timing after I set up the valves 
Title: Re: Might have a serious problem. Please help!
Post by: BlackSheep on June 14, 2019, 10:35:30 PM
If it were mine I would take both heads to a competent machine shop and have the valves and guides checked. I have been building/racing since the 60's and have never stuck a valve in Bronze Maganize guides, which is what I run. The only shops who work on my machines depending on their back log are. "Katech" Parts only "Lingenfelter" (206) 727-2552 IN.  My LS7 heads were done by "West Coast Racing Heads" CA (818)705 5454. Whoever did the heads may have not honed the guides enough. I have seen others who stuck a valve because of not enough clearance. However, that occurred when the engine was hot. The previous owner obviously rolled the engine over five if not more complete cycles to have five stuck valves.  As you stated you rolled her over therefore depending on the valve relief in the pistons; the valves may have very likely come into contact with the pistons. Personally, I would rebuild both heads replacing the valves and guides for safety. Break or stick a valve @ 5k or better and you will likely be replacing the entire engine.
As far as timing, one could always take a felt pen and mark where the distributor was "Or" if you didn't; when you feel the valve issue has been addressed to your satisfaction. With the valve cover off and plugs out install a socket to the crankshaft bolt. Roll the engine over in the correct rotation until the intake valve on the #1 cylinder opens and closes. Look for TDC on the crankshaft dampener and if it is at or near TDC that will be TDC on #1 cylinder. Install the distributor and wire in the firing order, following the correct rotation. (if it previously ran and if you didn't change anything on the distributor cap it should be correct) It has always been close enough to fire, I always have my timing light and the open end/distributor wrench ready for the bolt holding the distributor. 
Title: Re: Might have a serious problem. Please help!
Post by: jim brock on June 15, 2019, 11:40:39 AM
replace the hyd lifters maybe they are stuck frm being compressed for 3 years.