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  1. #1
    Join Date
    Jan 2008
    Location
    Groveland, MA, USA
    Posts
    139

    Default "I have twin Gen. IV 454 carbu

    "I have twin Gen. IV 454 carburated Crusaders in a 1984 33 Egg Harbor convertable. The starboard engine won't turn up past 3200 RPMS; the port motor spins up past 4000 while dragging the starboard side along. Both props are 3-blade 19x20 in good condition. Problem has persisted since I took ownership 3 years ago. Compression check revealed cylinders 1 & 3 sharing compression (bad head gasket). Did head gasket job with Felpro marine gaskets; thought she was fixed but still won't turn up to rated RPM.

    Noticed an occasional backfire through carb. around 2500 rpms. Found a bad lobe on camshaft; replaced camshaft with marine grind cam, lifters, and pushrods. No backfire now, thought she was good but still won't spin up. Replaced 20 year old distributor and coil with integrated unit from Davis Unified Ignition (DUI). Changed all plugs and wires. Set timing at 12 deg. BTDC and verified advance with timing light, all looked good but alas, no joy. This was last year so I think maybe I will check to make sure the advance is stil working (had a problem with the advance not working on a new DUI on port motor-sent it back to factory for repair-is good now but makes me wonder if the starboard side advance is hung up).

    Floscan reports that the affected engine burns 25-40% more fuel than good engine, even when the good engine is turning faster! Fuel tank gauges confirm flowscan measurement. Fuel is fresh and stabilized and Fuel/Water filters were changed though they show no water and almost no particulates after a long run in heavy seas. Filter on engine changed and carb. filter cleaned. No change.

    Compression was 124-127-119-122 for cylinders 1-3-5-7. This was after the head gasket job. Sorry no numbers for the outboard side (hard to reach).

    Engine starts very hard compared to good port motor. Once strated, runs smooth and quiet at low speeds with no noticable misses, etc. Fuel flow at carb looks good (as expected from the flowscan values). Don't think its a fuel-related problem because it uses more than the other side. Carbs were sent out for cleaning/overhaul with no change.

    Again, engine runs smooth and quiet at low rpms but won't turn up based on analog tachs and digital synchro.

    Things I can think of checking are ignition advance (again), repeat compression check (all around this time), stuck choke (wired it open last year, no change), stuck valve? Could have internal engine damage, but head job revealed good looking cylinder walls.

    She's giving me the finger and I'm about to write a check for a new one...."

  2. #2
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    6,767

    Default "how many hours on the starboa

    "how many hours on the starboard engine?

    did you get the heads checked when they were off for the gasket replacement? condition of valve train is of interest

    Having compression numbers for all 8 cylinders is beneficial.

    Who did the cam replacement? Should be RH rotation which uses gear on cam - no chain - cam and crank indexing could be off

    Can you provide more detail on "Fuel flow at carb looks good"?

    Have you had a vacuum gauge connected? record any values? quick indicator of condition of top end of engine.

    Yes, improper timing advance (lack of) may cause your symptoms. Do you check it with the balancer or do you use the marks on the flywheel? Never seen a DUI - what approach do they use to advance things?"

  3. #3
    Join Date
    Jan 2008
    Location
    Groveland, MA, USA
    Posts
    139

    Default "Hi makomark: Thanks for

    "Hi makomark:

    Thanks for your comments. I've been following your posts--they are quite helpful.

    There are 1310 hours on the starboard engine, 1312 on port. At the time I removed the heads I didn't know enough to have them checked for flatness, etc. I hired a marine mechanic to help me, he said they looked pristine. The engine had been rebuilt just prior to my purchase, which is probably why they looked so good. However the wrong (auto) gaskets were used during the rebuild, which failed rather quickly, leading to the shared compression between #1 and #3.

    Will check compression all around--I'm betting it will show a problem somewhere.

    I replaced the cam. The Borg-Warner gear on this boat(1.91:1) reverses the rotation, hence the starboard engine is actually standard LH rotation and uses a timing chain, contrarly to how things are done these days. Again, no change after cam replacement.

    Can't meausure the fuel flow or pressure because I don't have a gauge. Could buy one but its doubtful it is lack of fuel, it consumes 24 gph at 3200 while the port burns 16 at the same speed. To me this is an indication that it the combustion effiency is way down (bad valve, low compression, etc.).

    Don't have a vaccum gauge and do not see anywhere to attach one. Advice would be aprreciated. I like diagnotic tests that confirm or identify problems...

    I'm pretty confident of the timing--this is one of the things I had to learn while replacing both distributors, etc. I used the balancer marks. The DUI has an integrated 50,000 V coil and mechanical advance. Could have hung up but it worked when I first put it in last year."

  4. #4
    Join Date
    Nov 2002
    Location
    Mullica Hill, New Jersey, United States
    Posts
    1,810

    Default "Tom, A couple more questio

    "Tom,

    A couple more questions, although Mark's are all right on, as are your thoughts. Where did the new cam come from and are you sure it is the right one?

    What is the timing at full advance and how does that compare to the other engine?

    Finally, since you are not the original owner, has the transmission ever been changed and can you confirm the ratio?"

  5. #5
    Join Date
    Jan 2008
    Location
    Groveland, MA, USA
    Posts
    139

    Default "Hi Rick, The cam was order

    "Hi Rick,

    The cam was ordered by a very knowlegeable NAPA owner/proprietier who knew all about the proper marine grind on the cam shaft. He was considering ordering from Mercruiser but found a truck cam with the same grind. So I am fairly confident that the lobes have the proper lift and duration necessary for producing the higher torque the marine application calls for. Of couse, I have no way of verifying this, I only know I ordered a marine cam equivalent, i.e. possibly a truck cam that has the same grind as the marine cam. That is what we set out to do.

    I can't say what the total degrees of advance is because my timing light is very basic. It looks to be about +20 from a base of +10-12 by eye. I will compare it to the other side and report back.

    The transmission looks old, original, and very similar to the one on the other side. Again, I'll verify this information and post back along with a full set of compression values done by the book."

  6. #6
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    6,767

    Default "Tom: Based on my experienc

    "Tom:

    Based on my experience, the merc cam is the speed pro cam, physically as well as spec-wise.

    If you have access to the tool, a leakdown test would probably be of value as well. Some of the racing guys like them much more than compression tests as they help get max output from an engine.Either way seeing all 8 values beats having 4 and guessing 4.

    You can measure the cam via the rocker arms, with a dial gauge for the lift. You can measure the duration, if you are careful, and well versed in math, using a degree wheel on the balancer.

    You need about 30 degrees total advance to get the engine making power at 3000-3200rpm. You may want to pull the plug and check the timing at the flywheel as the balancer may have shifted.

    There should be a pipe plug on the intake manifold to attach a vacuum gauge. You can also tap off the choke pull-off hose on the carb.

    My engines are 86 vintage. I believe they came with mallory distributors. Lets just say I wan't impressed with the longevity of the mechanical advance mechanism and swapped them out for the merc TB IV electronic stuff - worked for a dealer then - and haven't had any issues w/ advance since.

    regarding using the VAC gauge as a dianostic tool, the really old chilton's auto books have the best rundown I've seen. I'm sure you can find many equivalent descriptions on the www."

  7. #7
    Join Date
    Aug 2008
    Location
    Fairport, NY
    Posts
    1,625

    Default "vacuum test, leakdown test,

    "vacuum test, leakdown test, and compression testing all have merit, but; It may be easier for you to kill each cylinder spark, one by one; note which does not lower engine power. These big v8's tend to run pretty smooth on 7 cyl. but then show reduced rpm above 3300 or so. High fuel flow with reduced power is consistent with a cylinder out."

  8. #8
    Join Date
    Sep 2003
    Location
    New Tripoli, PA, USA!
    Posts
    15,200

    Default "Dave is right on--do the plug

    "Dave is right on--do the plug wire pull test. I had a motor that ran on 7 cylinders for some time--a bit slow, but it "sounded" about right and idled fine.

    Jeff


    PS: Forget about taking vacuum readings--there's virtually none at cruising speeds, where your problem is happening.
    "

  9. #9
    Join Date
    Sep 2007
    Location
    Egg Harbor, New Jersey, USA
    Posts
    1,574

    Default "I hate to admit this BUT...Af

    "I hate to admit this BUT...After re-assembly, my starboard engine exhibited the exact same operating characteristics. Minimal carb pops, 25% more fuel consumption, could not get her over 3000 rpm. Despite extremely diligent EVERYTHING, it turned out to be a timing advance issue. Some dummy forgot to return the timing plug on the distributor back to the RUN position."

  10. #10
    Join Date
    Sep 2003
    Location
    New Tripoli, PA, USA!
    Posts
    15,200

    Default "That guy wasn't you, I ho

    "That guy wasn't you, I hope!

    Jeff"

  11. #11
    Join Date
    Sep 2007
    Location
    Egg Harbor, New Jersey, USA
    Posts
    1,574

    Default "I make sure only 1 dummy work

    "I make sure only 1 dummy works on those engines...Yup, ME!"

  12. #12
    Join Date
    Oct 2007
    Location
    orlando, fl, usa
    Posts
    91

    Default "THis engine should have been

    "THis engine should have been a reverse rotation motor, Wonder if someone converted it at some point. The rebuild that was described could not have been very comprehensive since the cam was warn that bad. Suspect it was a pull the head and have it machined and calling it a rebuild. I understand that timing being retarded will make the engine quieter so I also vote for harmonic balancer. Good idea checking timing at the fly.

    I also have a similar issue as described in my prior thread. My reverse rotation engine running 250 rpms lower than starboard and at cruise speed it is using about 20% more than the other. Been through the whole thing and can find no problems. Only thing not checked is the balancer. However I did try to advance it beyoind 12 and it made no difference. My compression is however way better 160 to 165 on all 16. My next thing is to pull timing cover and make sure cam is alligned properly. Possibly pull the cam and have all lobes checked. However I did replace all lifters and none had unusual wear so suspect cam is ok.

    On thought for you however, Pull the props and have them prop scaned. verify they are the same. Also wonder if your transmissions are actualy the same gear ratio.

    Do compressing test on both engines and compare timing and advance on both. Try swapping components. Also make sure you have full voltage to your coil while it is under load.

    By the way i found an excellent deal on a good timing light with advance feature on Amazon.com. I signed up for their credit card and go 50 off of the purchase and got free shipping. Light has timing, advance and tach. Excellent tool."

  13. #13
    Join Date
    Aug 2008
    Location
    Fairport, NY
    Posts
    1,625

    Default "Yeah, once you determine all

    "Yeah, once you determine all cylinders are producing power equally, it makes sense to then look at things like cam timing and exhaust blockage.

    Can someone answer a question on the DUI distributors? Do they use a standard HEI distributor cap or a custom?"

  14. #14
    Join Date
    Jan 2008
    Location
    Groveland, MA, USA
    Posts
    139

    Default "Makomark and Diver Dave: I

    "Makomark and Diver Dave:

    I agree the whole thing could be explained by a dead cylinder, cause unknown. I was thinking of verifying the timing advance and then going around to each cylinder head after a cold start and see which ones are getting hot. Seems like a dead cylinder would be cold for a while...

    I'm not adverse to pulling a few plug wires and noting any changes (or lack thereof) but I think I'll try to narrow things down a bit first.

    Stephen P. --normally the starboard engine would be reverse rotation except that this particular Borg-Warner gear reverses the rotation. Trust me, the cam is chain driven, not gear driven, and the belts and pullys go roundy-roundy clockwise as viewed from the front.

    As far as the rebuild, there were new oversize pistons in place (0.010 over?). Cylinder walls appeared very smooth. Heads looked "new" and there was virtually no carbon on valves, etc. These observations led the mechanic I hired to forego additional tesing or the heads, etc. and proceed with the gasket work. To his credit it was sharing compression exactly as he had predicted, something I never would have guessed on my own. However, I wish I had known more at the time because I would have sent them out.

    I will obtain a full set of compression values this Saturday after warming up the engine, removing all plugs, and opening the throttle.

    Thanks for the suggestion on the use of vacuum gages, leak down test, etc. I have a racing buddy at the marina who swears by the leakdown test. Maybe he can help me.

    The DUI distributors can been seen at http://www.performancedistributors.com/.

    50,000 volt coil on top of distributor. Mechanical advance. Probably a custom cap.

    Best wished to all and thanks for the help. I will report back on Monday with new compression data and other discoveries."

  15. #15
    Join Date
    Sep 2003
    Location
    New Tripoli, PA, USA!
    Posts
    15,200

    Default "..." I was thinking of ve

    "..." I was thinking of verifying the timing advance and then going around to each cylinder head after a cold start and see which ones are getting hot... "

    Waste of time, and it won't show you a thing--and even if you use a temp gun. (There's a lot of metal being heated up there.)

    Take insulated pliers and heavy gloves, and pull each wire off individually. THe motor should slow, then speed back up as the wire goes back in.

    Trust me; this is the way to go!

    Jeff"

  16. #16
    Join Date
    Oct 2007
    Location
    orlando, fl, usa
    Posts
    91

    Default "If your engines are original

    "If your engines are original then one would have been reverse rotation. I was wondering if someone changed the reverse rotation engine to regular rotation.

    I believe compression is on the low side esp for an engine that was reported to be a total rebuild. Make sure you put some lube on the compression tester o rings, better seal."

  17. #17
    Join Date
    Jan 2008
    Location
    Groveland, MA, USA
    Posts
    139

    Default "Thanks, Steve. Yes, the port

    "Thanks, Steve. Yes, the port engine is reverse rotation. I though the compression values I posted were a little low myself but they weren't taken quite right. Now I know how to perform the test and am determined to generate a full set of reliable numbers. Hopefully they will be high and even. Just bought another compression gauge in case I can't find the one on the boat. I will coat it with some o-ring sealent as you suggested. Thanks again."

  18. #18
    Join Date
    Oct 2007
    Location
    orlando, fl, usa
    Posts
    91

    Default "We are chasing similar proble

    "We are chasing similar problems so I am interested in what you find. I have been through fuel and ignition systme, props. everything. Found a bunch of problems along the way and as you found they made no difference. Going to the boat this weekend to do some glass work so may mess with engines some if I have time. Never thought to ck the timing at the Fly and compare with Harmonic Balancer but will give it a try.

    I said on another forum, 454's are masters at masking problems. Damn things run fine with stuff that would disable a small block.

    Again Run volt test on your coil with it running to make sure nothing breaking down there."

  19. #19
    Join Date
    Jan 2008
    Location
    Groveland, MA, USA
    Posts
    139

    Default "I've followed your posts

    "I've followed your posts on this forum and it does appear we are fighting similar gremlins. When we found the head gasket problem I was sure it ws fixed... Then the cam... Then the distributor replacement...No luck. However I have a feeling I'm going to find out more this weekend, and I will post my findings.

    I'm going to verify base timing and advance, check for even heat at all 8 cylinders, make sure the choke is working, check throttle, disconnect each plug wire sequentially, fully warm up engine, and measure compression all around.

    Based on the above results further tests may be indicated.

    Best regards,"

  20. #20
    Join Date
    Aug 2008
    Location
    Fairport, NY
    Posts
    1,625

    Default ""check for even heat at a

    ""check for even heat at all 8 cylinders, "
    too bad you don't have a 8 point EGT gauge. In all seriousness, the bottom of the exh. manifold is the only part not water jacketed. You MIGHT be able to use your fingers to detect gross cylinder on/off after maybe 5 - 10 seconds of operation. Beyond that time, better not use your fingers!! And if you let the off engine settle too long, the thick cast iron will conduct off any heat delta in a pretty short time. Let us know how that all works out!"

  21. #21
    Join Date
    Jan 2008
    Location
    Groveland, MA, USA
    Posts
    139

    Default "Point well taken, Diver. I h

    "Point well taken, Diver. I hope you tried not to laugh too loud while you were typing.

    O.K., checking by hand out. But I may be smarter than the average bear. Then again, bears are probably not too swift.

    Back to the 5-10 seconds of operation. A cold engine sits in the bilge at 65 degrees. It is started up and run for 10-15 seconds. The temperture of combustion is, well, damn hot, well in excess of 500 degrees F. After shut down each plug is removed. A mis-firing or dead cylinder should yield a much colder plug, as well as other differences in appearence."

  22. #22
    Join Date
    Aug 2008
    Location
    Fairport, NY
    Posts
    1,625

    Default "Between the probing the hotte

    "Between the probing the hottest area of the engine with digits and the "disconnect the spark plug on a running engine test", I'll predict ur in for an exciting week end!
    Consider a high speed stretch of water where you can disconnect each plug, one by one, on the off engine, then do a high power run. Also, I think your high energy ignition system will be happier with the open plug boot shorted to ground, rather than open. The 50kV will stress the cap/wiring/coil more than when it's driving a small spark gap or dead short."

  23. #23
    Join Date
    Sep 2007
    Location
    Egg Harbor, New Jersey, USA
    Posts
    1,574

    Default "Tom, Frankly, I was quite

    "Tom,

    Frankly, I was quite aprehensive about standing between those engines or elsewhere at 3500rpm. Between the movement of the vessel and/or the wake from another boat I was thinking....chopped meat

    Just keep that in mind and BE CAREFUL...Yes I know it goes without saying but better to think once and be clear of those spinning parts. I tried to keep the laser dot on the flywheel to measure RPM's, that was tough enough let alone grabbing sparkplug wires"

  24. #24
    Join Date
    Sep 2003
    Location
    New Tripoli, PA, USA!
    Posts
    15,200

    Default "Man, you guys sure like to do

    "Man, you guys sure like to do things the hard way! Pulling plug wires is a simple, easy to do test that pin points a bad cylinder every time.

    Jeff"

  25. #25
    Join Date
    Jan 2008
    Location
    Groveland, MA, USA
    Posts
    139

    Default "Al, I'm not planning on r

    "Al, I'm not planning on running the "power up and kill each cylinder one at a time test", at least not right now. (I'm a little afraid of all that whirring machinery, to tell you the truth). I'm going to make some observations and some careful measurements of compression and report back to the board. Frankly, I think I am going to find low compression on one cylinder or perhaps all around. I'm almost afraid of what a compression test will reveal but I'm resigned to it now.

    One thing I have learned is that you must be careful on a boat in order to avoid being injured all the time."

  26. #26
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    6,767

    Default "Tom: which one of those DU

    "Tom:

    which one of those DUI units did you get? I ask as I took a quick look thru the GM systems and didn't see anything about a marine rated item.

    I agree with Dave - too much thermal mass in the manifolds to see the temp difference from the outside.

    You might want to try hooking the timing light to each wire individually. a dead one won't generate any light when it should. You may also want to check the plug wires - I changed mine one season only to find out 5 of the 16 were 'open' itermittently. They spun up to rpm but boy did they burn some fuel. it ain't any fun when the fuel gauge is bouncing of E and the loran says 20 miles to go...

    You might want to go thru the cap, too. I've seen some of the 'hot' systems find all kinds of new paths to ground when the spark plug wasn't a viable one."

  27. #27
    Join Date
    Sep 2003
    Location
    New Tripoli, PA, USA!
    Posts
    15,200

    Default "The plug wire test is done at

    "The plug wire test is done at IDLE, not under power.

    Jeff"

  28. #28
    Join Date
    Nov 2002
    Location
    Mullica Hill, New Jersey, United States
    Posts
    1,810

    Default "I've actually found that

    "I've actually found that it works best at 1500 rpms, it makes the rpm change much more noticeable. In fact, when you perform a cylinder kill test using Diacom, they require you run the engine at 1500 when doing the test."

  29. #29
    Join Date
    Oct 2007
    Location
    Germantown, TN, USA
    Posts
    227

    Default "One additional method I have

    "One additional method I have used is to pull the spark plugs. The dead cylinder has a wet spark plug. If the cylinder is firing part of the time the plug may not be wet. The wet spark plug may not mean something is wrong with the cylinder, it may just be a bad wire or plug. I have pulled mine off while the engine is running. One time it cost me a distributor module because of arching at the distributor cap. Since then I have just grounded the removed wire. I find that if I take off one wire and while it is off take off another the drop in RPM is more noticeable.

    Chuck Hanson"

  30. #30
    Join Date
    Nov 2002
    Location
    Mullica Hill, New Jersey, United States
    Posts
    1,810

    Default "Actually, I didn't want t

    "Actually, I didn't want to say this on the air, but I do this in gear. I don't want to encourage people to do it this way for obvious reasons, but I do and it works very well, just make sure your dock lines are secure and your propwash is not going to do any damage. It puts a load on the engine similar to what you are doing by pulling one wire."

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