Compression a little low , should i yank the motor??

« **on:** August 15, 2009, 06:08:49 AM »

I did a compression test on my bbf and all the cylinders except one came back at 139 -142 psi .The one came back at 119 . I dropped a teaspoon of oil down the cylinder and it rechecked and it came back 150 . There motor isnt smoking and it runs good . Do you gys think it will get me through the season ? The motor was built by harman marine , would that be a good place to have her freshened up ? Thanks

« **Reply #1 on:** August 15, 2009, 07:38:34 AM »

What does the plug look like? If the engine doesn't show signs of distress I'd run it the rest of the summer.
IMO

« **Reply #2 on:** August 15, 2009, 11:08:13 AM »

Run some Marvel Mystery Oil in the oil and run it. Recheck the compression after the next trip.

« **Reply #3 on:** August 15, 2009, 01:02:18 PM »

the plugs are perfect chocolate brown , but now i have a knock in the top end , at idle .So looks like i might have to pull it anyway.

« **Reply #4 on:** August 15, 2009, 01:12:16 PM »

Is the knock on the same side as the low cylinder? Maybe time for a valve job new seals n what not...I would pull the valve cover and have a look see

« **Reply #5 on:** August 15, 2009, 01:20:28 PM »

Quote from: crewchief22 on August 15, 2009, 11:08:13 AM

Run some Marvel Mystery Oil in the oil and run it

The magic elixir for old V-8's

« **Reply #6 on:** August 15, 2009, 02:39:25 PM »

If it knocks I take it apart..... no questions asked.
Good luck which ever way you go.

« **Reply #7 on:** August 15, 2009, 03:15:04 PM »

Quote from: electrowoman on August 15, 2009, 02:39:25 PM

If it knocks I take it apart..... no questions asked.
Good luck which ever way you go.

if you need ANY machine work, i highly suggest Dave @ A&D (aka enginedoctor)

« **Reply #8 on:** August 15, 2009, 08:48:06 PM »

Just out of curiosity I advace my time from 6 degrees btdc to what harman marine recommended 10 degrees btdc last week . I run premium fuel , but i have heard the more you advance the time the more cylinder pressure you create , and i am wondering if thats where the knock i hear is coming from? Is that possible or am i just taking shots in the dark

« **Reply #9 on:** August 15, 2009, 09:30:48 PM »

Quote from: 79charger on August 15, 2009, 06:08:49 AM

I did a compression test on my bbf and all the cylinders except one came back at 139 -142 psi .The one came back at 119 . I dropped a teaspoon of oil down the cylinder and it rechecked and it came back 150 . There motor isnt smoking and it runs good . Do you gys think it will get me through the season ? The motor was built by harman marine , would that be a good place to have her freshened up ? Thanks

Your compression sounds fine, if it's consistent. I wouldn't stress about that.

« **Reply #10 on:** August 16, 2009, 08:55:14 AM »

Have you ever set the timing on this engine before?

Maybe the timing was set so low because the balancer is slipping and is way advanced when set at spec.

« **Reply #11 on:** August 16, 2009, 08:18:04 PM »

No , i put in a new distributor so thats the only reason i checked the timing . It sure ran good when i set it to 10degrees but i backed off to 6 for now untill i see a engine builder .

« **Reply #12 on:** August 16, 2009, 09:17:15 PM »

Quote from: 79charger on August 16, 2009, 08:18:04 PM

No , i put in a new distributor so thats the only reason i checked the timing . It sure ran good when i set it to 10degrees but i backed off to 6 for now untill i see a engine builder .

Give Dave a call (714) 879-9671 He will help ya

« **Reply #13 on:** August 17, 2009, 08:55:06 AM »

Quote from: 79charger on August 15, 2009, 06:08:49 AM

I did a compression test on my bbf and all the cylinders except one came back at 139 -142 psi .The one came back at 119 . I dropped a teaspoon of oil down the cylinder and it rechecked and it came back 150 . There motor isnt smoking and it runs good . Do you gys think it will get me through the season ? The motor was built by harman marine , would that be a good place to have her freshened up ? Thanks

Your range of cylinder pressure (119-142 psi) is considered acceptable by most standards, even if only 1 cylinder is on the low side and the other 7 are within 3 psi on the high side.

I would get that "knock" professionaly diagnosed before taking your engine apart mid-season. It could be just a loose rocker arm....or a con rod, or anything in between. In other words, could be fixable without an engine overhaul. If you find that you need an engine we could build you up a longblock lickety-split, pickup in San Fernando valley.

LO

« **Reply #14 on:** August 18, 2009, 07:36:17 AM »

Well i took it to the engine builder up here in the high desert the only one ....lol . The owners wife i assume wanted me to leave it there and fill out a service form lmao just to hear my motor . She wanted money ....so I told her hey Lady If i leave now and my motor does need work I promise you I wont be bringing it back to you . Her Husband overheard and came out and gave her a nasty look and came out and heard my boat . He said it didnt sound bad , and to try running a heavier oil . I was running 10/30 . So i put In 20 /50 and some marvels oil lastnight and it sounded quieter. Funny my motor only takes 5 quarts of oil

Must be the stock pan . Thanks for your help everyone . I guess I will run it until stops .

« **Reply #15 on:** August 18, 2009, 07:06:31 PM »

unless its a small block i would be suprised...did you check it after you ran it...about another quart is in the oil filter!

« **Reply #16 on:** August 19, 2009, 09:11:58 AM »

yes i checked it I actually overfilled it a little . Maybe all the oil didnt drain out initially . I let it drain for 2 hours

? Unless the dipstick is wrong it shows on the full side and oil pressure is good.

79charger

Compression a little low , should i yank the motor??

electrowoman

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crewchief22

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79charger

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Nordie

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Luckie Stiff

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electrowoman

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Brad @ SCJB

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79charger

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SLCKREG

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crewchief22

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79charger

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76NORDIC

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LakesOnly

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79charger

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Nordie

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79charger

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