454 Valve Lash Adjustment

D

dcogaming

New Member
Oct 20, 2010
15
Lower Niagara River - Lake Ontario
Boat Info
340 Sundancer 1987
Engines
454 Mercruisers
Hi everyone,

I have a 1987 340 SDA. It has the twin 454s (340 MIE). I had to do the head gaskets on the starboard engine and was hoping for some advice on adjusting the valve lash. I would normally do this warmed and running on my street motor but with the exhaust set-up on the Mercruiser this is far from easy to do. So I was hoping someone could lend some advice on the cold engine off procedure. :smt100
 
DCO
Take a look at this thread. I just went through the same issue. and found that it is possible to remove the covers (I do not have exhaust risers, only elbows).
http://clubsearay.com/showthread.php/50132-Valve-Cover-Removal-on-454-7-4L

This is the procedure for cold and hot (running) straight out of the Merc Manual for my 7.4MIE Gen IV with hydraulic lifters. Either way (hot or cold) works perfectly but don't make the mistake I did and forget to adjust one!

100_3266.jpg


100_3267.jpg
 
Much better off doing each cylinder, rotate motor untill the intake valve for that cylinder opens and then closes, now your on compression both valves closed. tighten nut untill all slack is gone, ( cant spin rod with fingers), then go 3/4 more.
valve sequence E,I,I,E,E,I,I,E
http://boatinfo.no/lib/library.html
 
Last edited:
Awesome Ron ty for your help


rondds said:
DCO
Take a look at this thread. I just went through the same issue. and found that it is possible to remove the covers (I do not have exhaust risers, only elbows).
http://clubsearay.com/showthread.php/50132-Valve-Cover-Removal-on-454-7-4L

This is the procedure for cold and hot (running) straight out of the Merc Manual for my 7.4MIE Gen IV with hydraulic lifters. Either way (hot or cold) works perfectly but don't make the mistake I did and forget to adjust one!

100_3266.jpg


100_3267.jpg
Click to expand...
 
DCO, it's straight from "The Bible." I've done it now three times and if you do it right, you'll be ok. Sounds like you are no stranger to this type of thing so you won't make the stupid rookie mistake I did.
 
I did mine hot. I replaced the two studs/nuts near the riser on the valve cover with allen socket bolts. They are now very easy to remove with
a ball type allen wrench. Just like a car there is very little oil splash when running at idle.
 
Three's a fair amount of debate about how many turns to go on a big block after lash is removed. I've heard 1/2, 3/4, and full (Merc Manual). I did a full turn using the cold method.

When we went back in to do the hot, we checked all 8 valves by backing off til lash noise and then retightening according to the manual (with the engine running). When backing off on each nut, rattling started right at one turn. Sort of proves that a cold adjust is just as reliable as a running adjust.
 
Looking for some help. I'm down on power on Port did compresson test found 160 across except 2 at 130. I want to pull heads and send them out.

all my manual says on gen V is to set rockers at 45lbs torque. is that true no vavle lash adjustment???
 
I believe that Gen V that is correct. My post (above yours) from 2012 describes the Gen IV process. Gen V is simpler.
 
wow I kept reading the manual thinking im missing something so put it all together and just torque the rockers down and done??? wow
 
I have a Gen 6 and the rockers are bolted down. If yours have studs with nuts you need to adjust them. 0 lash then 1 turn. cold engine. If my memory is correct, flat tappet cam is adjustable and roller cam is not? You can go on You Tube, lots of vids on how to do it. You do not have to run the engine. It will start right up and have no noise or mess! You will impress your buddies too!
 
Gen 5 is a torque spec. Follow what your manual says.
 
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