happy hour iv
Cadet
- Joined
- Aug 1, 2019
- Messages
- 8
Hope this is not too long. I have twin 454 gen iv vdrive mercs. Cam lobe wiped on the older engine. Top end tear down in the boat. Found wiped lobe, #3 exhaust valve sticking a little. surface rust around OEM manifold riser joint. some loose
valve guides. Replaced one valve, hand lapped the rest (they looked good) replaced valve guides. Everything else looked great. I have had the water reversion and the leaking riser gaskets in the past with both engines. Decided to upgrade a few issues as long as I was replacing cam with block still in boat.
I replaced with a Compcam with a 2 degree larger lobe sep angle to limit the reversion. I replaced OEM manifolds with 496 dry joint aluminum. Yes I know about the aluminum and salt water but I replumbed for full coolant into manifolds. I had full fresh water before so I know my exchanger is large enough.
Old distributor had a little bearing wear so I replaced with a DUI HEI distributor as I previously did on other engine.
Old mech fuel pump was getting old so I replaced with electric as per other engine (yes I have the oil pressure tied in)
I installed Crane Cam camsaver lifters (apparently stock except for a flat side to provide more oil to cam lobe).
used the assembly lube, preoiled and started with Shell Rotella 10-40 plus zinc additive.
Engine fire up, raced to 3k plus but as throttled down anything below 2k engine would stop. It also ran with an obvious
miss. sounded like valves not closing with occasional backfire. Break in on cam requires 2500 rpm for 30 min so we struggled along.
engine will start and race up to 3k+ but can only throttle down to 2.1k, below which it stalls. will not start for about 5 minutes then the same again.
I have swapped carbs, distributor with other engine with no change. I have installed new Petronix HEI wires with no change. I have added fuel pressure regulator to drop pressure down to 4 psi.
Other than what I changed/fixed everything else looked good.
This is a reverse rotation engine with camshaft gear to gear drive. I have triple checked my firing order for reverse.
I used the old cam gear as it looked almost new. Press fit with keyway. I marked the timing marks with white paint
so I would not goof
I measured lift on the valves and it looks good although not extremely accurate since I could barely see the degree wheel.
I checked the valve timing, but again not extremely accurately although it seemed in the ballpark.
I checked the sequence of valves for the reverse rotation and it was correct.
Because of the replumbing for coolant and my oil/transmission coolers are on top anything related to intake and valve covers is time consuming.
I suspected a lifter issue but I backed off lash to the point that the valves clattered. Since I can only run at 2k it is a mess
with valve covers off. I originally suspected the lifters as out of the box the travel on the plunger was dramatic. Comp cam lifters would not move ( I did not try a press). Both brands advised not not to presoak as per old school.
As of now I suspect a lifter issue since Crane lifters and COMP lifters seem so different yet backing them off to clatter should preclude this issue.
The other issue might be that I missed the timing marks on the cam. Removing the cam/lifters is real pain in the ass with vdrives in the boat.
Am I missing anything obvious ?
valve guides. Replaced one valve, hand lapped the rest (they looked good) replaced valve guides. Everything else looked great. I have had the water reversion and the leaking riser gaskets in the past with both engines. Decided to upgrade a few issues as long as I was replacing cam with block still in boat.
I replaced with a Compcam with a 2 degree larger lobe sep angle to limit the reversion. I replaced OEM manifolds with 496 dry joint aluminum. Yes I know about the aluminum and salt water but I replumbed for full coolant into manifolds. I had full fresh water before so I know my exchanger is large enough.
Old distributor had a little bearing wear so I replaced with a DUI HEI distributor as I previously did on other engine.
Old mech fuel pump was getting old so I replaced with electric as per other engine (yes I have the oil pressure tied in)
I installed Crane Cam camsaver lifters (apparently stock except for a flat side to provide more oil to cam lobe).
used the assembly lube, preoiled and started with Shell Rotella 10-40 plus zinc additive.
Engine fire up, raced to 3k plus but as throttled down anything below 2k engine would stop. It also ran with an obvious
miss. sounded like valves not closing with occasional backfire. Break in on cam requires 2500 rpm for 30 min so we struggled along.
engine will start and race up to 3k+ but can only throttle down to 2.1k, below which it stalls. will not start for about 5 minutes then the same again.
I have swapped carbs, distributor with other engine with no change. I have installed new Petronix HEI wires with no change. I have added fuel pressure regulator to drop pressure down to 4 psi.
Other than what I changed/fixed everything else looked good.
This is a reverse rotation engine with camshaft gear to gear drive. I have triple checked my firing order for reverse.
I used the old cam gear as it looked almost new. Press fit with keyway. I marked the timing marks with white paint
so I would not goof
I measured lift on the valves and it looks good although not extremely accurate since I could barely see the degree wheel.
I checked the valve timing, but again not extremely accurately although it seemed in the ballpark.
I checked the sequence of valves for the reverse rotation and it was correct.
Because of the replumbing for coolant and my oil/transmission coolers are on top anything related to intake and valve covers is time consuming.
I suspected a lifter issue but I backed off lash to the point that the valves clattered. Since I can only run at 2k it is a mess
with valve covers off. I originally suspected the lifters as out of the box the travel on the plunger was dramatic. Comp cam lifters would not move ( I did not try a press). Both brands advised not not to presoak as per old school.
As of now I suspect a lifter issue since Crane lifters and COMP lifters seem so different yet backing them off to clatter should preclude this issue.
The other issue might be that I missed the timing marks on the cam. Removing the cam/lifters is real pain in the ass with vdrives in the boat.
Am I missing anything obvious ?
