cdaniel525

iTrader: (1)

I picked up this BBC Mark IV - 489 Stroker from another member on here.... Got it tested on the dyno prior to purchase to make sure everything was good and made some decent power... (534hp/579tq)
When it was on the dyno, it was extremely noisy in there.... so when I got it installed in the boat, and started it up, I heard a valvetrain ticking, probably a rocker that needed to be adjusted or a collapsed lifter. Took it for a short 20min ride to see if it pumped back up, but never did. FWIW, the boat ran great! Brought it back, Took valve cover off, and found the lifter for #3 was collapsed. No big deal in grand sceme of things

Ordered a new lifter and went to break into the motor to replace the lifter today, and I found some water in the oil... milkshake like spots here and there...

Pulled the exhaust manifolds completely off found water in exhaust manifold #s 6 & 8.... On the other side I think it was in the manifolds #3 & 5.

My buddy suggested hooking the hose to the crossover inlet after re-installing the intake manifold... and with that tested the head gasket after taking out the spark plugs... Let water run for few mins, and then turned starter of for a few, while he watched and found no water coming out.
Also pressure tested the exhaust manifolds with the same method... and applying heat to them, no leaks.
2 of the mechanics at the marina said they doubt its the oil/PS cooler because (1) there was no water in the PS fluid as well? and (2) the oil pressure was always higher (60psi even at idle) than the water pressure, so itd be more like the oil would push its way into the water.... not water into the oil??

Is it possible that I was getting water in the oil from that bad lifter? Im not sure, but I would think so BC how would I get raw water in the opposite side exhaust manifolds?

Or is it more likely that I am getting reversion issues since its in both cylinders?? I am running EMI Thunder manifolds with the HP Stainless risers that dump the water at the end of the riser.... Never had an issue with the previous motor and reversion.... I attached the cam specs.... [ATTACH=CONFIG]541558[/ATTACH]
Thing is the previous cam was almost identical specs with exception of lift.... it was allegedly custom cut to work with Gil/EMI style manifolds. The only other major difference has been the new cam is hyd. roller while the old was hyd flat tappet.... and the new motor is a 489 stroker 9.0:1 compression while the prev was 454 (330hp short block) with below cam specs and Edelbrock aluminum heads

Prev Cam specs:
Intake Duration at 050 inch Lift:236 (same as new cam)
Exhaust Duration at 050 inch Lift:246 (just a touch larger)
Intake Valve Lift with Factory Rocker Arm Ratio:0.553 in. (.588 on new)
Exhaust Valve Lift with Factory Rocker Arm Ratio:0.571 in. (.595 on new)
Lobe Separation (degrees):114 (same on new cam)


So do you guys think this was an issue from the collapsed lifter, OR the more likely reversion issue? If so, why is this cam causing the issue when the prev cam wasn't that far off?
And of course, suggested solutions other than changing the cam? I think id rather go to dry tails than change the cam..... dont know if I want to drop anymore money on headers...

Thanks a lot in advance guys!!

Drew555

Ask why lifter collapsed ? Is it a roller? If lifter is collapsed even on the exhaust port the valve would stay closed anyway. So it would not be reversion for that reason. Looks like you need to pressurize

cdaniel525

iTrader: (1)

Thanks for the reply Drew... It is a hyd roller lifter... Not 100% sure I am following though... I understand, that the exhaust valve being closed would prevent water from entering, but what about any overlap?

What are you suggesting I pressurize? Are you thinking I have a leak somewhere in the motor or ??

Thanks again for the quick reply!

Budman II

iTrader: (1)

I think I may have replied to a PM from you, because I had a thread over on the Technical board with a very similar issue on my 489. Basically, you cannot really rely on comparing a flat tappet cam to a roller based on listed specs at .050 lift. A roller gets the valve up off the seat much more quickly, resulting in more "area under the curve", and thus potentially more exhaust overlap. You probably need to call the manufacturer and see if they can give you the valve events at .006 instead of .050. Also, if the cam was not degreed and was installed incorrectly, this can affect the tendency towards reversion. Good luck with your issue.

Budman II

iTrader: (1)

Also, the longer stroke of the 489 is going to accelerate that piston down the bore faster than the 454, which means the back impulse will be stronger. Ergo, a cam that was reversion free in a 454 may not be so in a 489/496.

cdaniel525

iTrader: (1)

Budman II... thanks for the reply! That wasnt me in the PM, but your explanation made a lot of sense!
The duration at .006 was 288/300, do ya need to know the valve timing and what not?

Does thus definitely sound like a reversion issue? Does this cam appear to be too big that it would cause reversion?

Thanks a lot..

liquidlounge

iTrader: (1)

technically, whenever there is overlap of the valve timing event, there is reversion.. Someone here can probably can probably spit out quickly how many degrees of overlap you have, but it is considerable amount. A different exhaust or riser setup will definitely help. IMO, the EMI's are better suited to a smaller cam than what you have. Most of the risers I have seen on those are very low. Look how a CMI is built sometime with the dam built into the dry part of the tail.

SB

iTrader: (1)

At .006" (don't compare to a cam measured at .004" ((Crane/Merc and a few others))for seat) :

66° overlap
36° BTDC / 30° ATDC
otherwords, IVO is 36° BTDC / EVC is 30° ATDC

at .050"
12° overlap
10° BTDC / 2° ATDC
otherwords IVO is 10° BTDC / EVC is 2° ATDC

SB

iTrader: (1)

Ah, forgot years back I got .006 " seat info for Crane's + Merc Blue Camshafts

So to compare:

Crane's 741 has 68º overlap at .006"
IVO 37º (BTDC) / EVC 31º (ATDC)

and 14º overlap when measured at .050"
IVO 5º (BTDC) / EVC 9º (ATDC)
=================================

Merc 500 EFI:
at .006" has 59º overlap at .006" seat
IVO 33º (BTDC) / EVC 26º (ATDC)

and at .050" has 5º overlap
IVO 6º (BTDC) / EVC -1º (ATDC)