GM 454 barefoot nautique engine tappets

Hi,

A friend is looking at a barefoot nautique overhere in the uk and the seller claims the tappets are noisey.
As far as I know they are hydraulic and can't be adjusted so I guess they are worn.
Any advice from you yankee petrol heads?

Than ks in advance

I thought they were hydraulic too ? And I believe you can adjust them to a certain extent but not like a solid lifter of course. It may be possible that they are not getting the proper oil flow to them ? wait a day or two and someone that knows more will likely reply.

Big blocks are notorious for valve train issues (i.e. eating cams and lifters) due to poor oiling. The lifters are hydraulic in the stock engine...check for a spun cam bearing.

How many hours? How old?

An old mechanics trick is get a big screwdriver (like 2' long big). Start the motor and put the tip of the screwdriver on the motor in various places while you have your ear on the handle. This should allow you to identify where the noise is coming from. Depending on age, hours, maintenance and useage it could be a couple things.

My first guess would be collapsed hydraulic lifter especially if it has been sitting for a while. Sometimes they come back to life after some use.

Open the oil filler and see what the rockers look like. They should have a nice gold coat of oil, if they are black and crusty that a definate sign of lack of maintenance or overheating.

It's a great motor, engine of choice for most racers.

Zedz is right. If the engine has high hours and has not seen regular oil changes, then I would look at the cam/lifters.

There is a slight, and I mean slight adjustment available on the roker arm nut. There are several theories on how to set them. All work.
I use a stock valve cover that I have cut the center out of, and install it on the cylinder bank that I am working on. This keeps some of the oil from getting everywhere during the adjustment process.
Fire up the enigne, and SLOWLY back off the rocker arm locknut until you hear the rocker start to clatter, then run it down far enough to quiet it down completely, then back off just slightly, keeping the noise in check. If you can't get it to quiet down, or must really crank the locknut down to do so, either the cam has worn a lobe down, or the lifter is bleeding off hydraulic (oil) pressure, or both.

Run a static compression test, if the numbers are close to even all around, and
if the engine has reasonable oil pressure, which, in my mind is 10 PSI per thousand RPM,and good idle oil pressure when hot (15+) then I would do a cam/lifter swap, and take a good look at the cam bearings while I was at it.

A cam and lifter swap is doable for the average backyard mechanic. If he buys the boat and plans to keep it for a few years, I'd do the timing chain/gears, cam and lifters. Over here that stuff would set you back about $400.00 for parts through one of the large mail order house operations like Summit.

Good luck with it...

We had some similiar problems with our 454gm Barefoot... At the end the problem was a broken hydraulic lifter (eur7,- the piece). We replaced all of them, togetter with new oil seals for the valves and some gaskets. I think the whole price togetter was about eur150,-. And pretty doable within 2 evenings of work.

Some mechanics give us this advice when adjusting the rockers (they have to come of when replacing the hydraulic lifters); But the valve when adjusting in rest (rockterarm in high possition). Then, turn the rockerarms as tide until the lifter pens don't turn anymore by hand. Then turn the rockterarm for 0.5-0.75 turn tighter.
We did this 4 years ago, and the 454 stills runs like a champ (450 hours later). And never need 1 drop of oil exept when changing oil.
It's possible you hear the tappets when the rocket arms are not tight enough (anymore) or to tight. When looking for this it's always good to replace the rocketarm nuts (they are self fastening and are special nuts, some people replace them with standard nuts and the tappets gets noisy after a while, because the rocketarm gets lose).

Bottom line; the valves are hydraulic, but can still be adjusted at the rocketarms!!!!

Cheers for the info guys.
Hopefully its not too terminal then.