Marine BBC has squeek in valve terain and minor backfire
03-01-2012, 05:54 PM
#11
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There are different techniques for adjusting hydraulic lifters. Here are couple threads with tips.
http://www.offshoreonly.com/forums/g...djustment.html
http://www.offshoreonly.com/forums/g...clearence.html
Good suggestion by BillK - http://www.offshoreonly.com/forums/2001315-post4.html
http://www.offshoreonly.com/forums/g...djustment.html
http://www.offshoreonly.com/forums/g...clearence.html
Good suggestion by BillK - http://www.offshoreonly.com/forums/2001315-post4.html
03-01-2012, 06:24 PM
#12
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I made the leap and spent $42 on a compression tester. I went and tested the compression and all cylinders read too little to register the gauge. I assume they were nowhere they should have been. I literally just noted it as a few psi. The number one cylinder has no compression at all. Cylinder 7 reads about 107 psi.
I imagine I need to re-adjust all the valves because it appears they are not adjusted correctly. We had pulled the heads and had to set the valve lash and we followed a set of instructions I found online. Guess it isn't quite right. Odd how I can still get it to run though.
I wondered why I couldn't get it to start and I thought it was a ignigion problem because I could get it to run on occasion it was just really hard to start. Just thought the ignition was weak. Well I got the new ignition and it must really work well because it is lots easier to start this low compression beast than what it was before I replaced it.
I guess I need to set the valves correctly so I can tell what if any cylinder it is or if the valves being set incorrectly is causing my problem. What is the best and proven method to set my valves properly? What compression range am I looking to achieve for a mildly modified BBC?
I imagine I need to re-adjust all the valves because it appears they are not adjusted correctly. We had pulled the heads and had to set the valve lash and we followed a set of instructions I found online. Guess it isn't quite right. Odd how I can still get it to run though.
I wondered why I couldn't get it to start and I thought it was a ignigion problem because I could get it to run on occasion it was just really hard to start. Just thought the ignition was weak. Well I got the new ignition and it must really work well because it is lots easier to start this low compression beast than what it was before I replaced it.
I guess I need to set the valves correctly so I can tell what if any cylinder it is or if the valves being set incorrectly is causing my problem. What is the best and proven method to set my valves properly? What compression range am I looking to achieve for a mildly modified BBC?
03-01-2012, 11:33 PM
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I'm seeing a bunch of different methods. I found a method in Comp Cams PDF instructions. I searched the cam part number through the site and found installation directions that also told how to set the valves. I really liked the idea of setting certain valves at TDC and the others at 180 degrees but I don't see how reliable that is when each cylinder fires at a different time from one another. I'm going to set the valves individually.
It states that:
"First turn the engine in the normal direction of rotation. Start with cylinder number one. When the exhaust valve begins to move, adjust the intake valve to zero lash plus an additional 1/2 turn more. Rotate the engine over again until the intake valve reaches maximum lift and is almost all the way back down. Then set the exhaust valve to zero lash plus 1/2 turn. Adjust the valves on each cylinder in this manner until all valves are adjusted."
When I'm in there I'll check the push rods and see if I can look at the lifters also. Before I crank it to start I'll go back through and perform another compression test to check my handy work.
Thanks again, I'll keep my progress posted. I'll hit up the valve adjustment in the morning.
It states that:
"First turn the engine in the normal direction of rotation. Start with cylinder number one. When the exhaust valve begins to move, adjust the intake valve to zero lash plus an additional 1/2 turn more. Rotate the engine over again until the intake valve reaches maximum lift and is almost all the way back down. Then set the exhaust valve to zero lash plus 1/2 turn. Adjust the valves on each cylinder in this manner until all valves are adjusted."
When I'm in there I'll check the push rods and see if I can look at the lifters also. Before I crank it to start I'll go back through and perform another compression test to check my handy work.
Thanks again, I'll keep my progress posted. I'll hit up the valve adjustment in the morning.
03-02-2012, 01:22 AM
#14
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Here's another way that's pretty quick and simple. Remove all spark plugs. Write down your firing order which should be 1-8-4-3-6-5-7-2. Now turn the engine over till #1 cyl. is at TDC on it's firing cycle. Timing pointer will be on "0" and both valves will be closed. Adjust both valves on #1. Now turn the engine in it's normal running direction 1/4 (90*) of a turn and adjust both valves of the next cyl. in the firing order,#8. Turn another 1/4 turn and adjust both valves of the next cyl. in firing order, #4. Repeat this process until all are done. You will only have to turn the crank 1 and 3/4 turns total to do them all. Turn engine over with a breaker bar and socket on the balancer, not the starter.
I would recommend 3/4 turn extra from zero lash.
I would recommend 3/4 turn extra from zero lash.
Last edited by picklenjim; 03-02-2012 at 01:25 AM.
03-02-2012, 02:05 AM
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Just back all your adjusting nuts off and start over. From what I recall (I don't do it very often), I just followed one of the cam manufacturers guide and used some of the tips found on here (using the search button).
Billk's tip is especially helpful if you have a lifter that doesn't like to stay pumped up. It's really easy to over-tighten an adjuster nut and not realize you are pushing in the lifter plunger if you aren't paying attention and using the spinning method.
Billk's tip is especially helpful if you have a lifter that doesn't like to stay pumped up. It's really easy to over-tighten an adjuster nut and not realize you are pushing in the lifter plunger if you aren't paying attention and using the spinning method.
03-02-2012, 02:15 PM
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I went down to the shop and adjusted the valves according to a a tech article online through Centry Performance:
http://www.centuryperformance.com/ad...h-spg-149.html
I went behind and checked the compression again and see noticeable results already. There are a few cylinders I want to tweak to try and get a higher compression out of though.
Comparision results are as follows:
Cylinder Before After
1 0 124
2 a few psi 130
3 a few psi 117
4 a few psi 100
5 a few psi 125
6 107 120
7 a few psi 110
8 a few psi 135
* I noted most cylinders as a few psi because it wasn't even enough to really register on the gauge.
I wish there was a more scientific or exact of doing it to get the compression more consistant between cylinders but at least I know what to focus on tweaking.
Is there a way to determine what compression should be or is this a tweaking process to try and adjust the valves to get the compression value as high and as consistant as it will go?
http://www.centuryperformance.com/ad...h-spg-149.html
I went behind and checked the compression again and see noticeable results already. There are a few cylinders I want to tweak to try and get a higher compression out of though.
Comparision results are as follows:
Cylinder Before After
1 0 124
2 a few psi 130
3 a few psi 117
4 a few psi 100
5 a few psi 125
6 107 120
7 a few psi 110
8 a few psi 135
* I noted most cylinders as a few psi because it wasn't even enough to really register on the gauge.
I wish there was a more scientific or exact of doing it to get the compression more consistant between cylinders but at least I know what to focus on tweaking.
Is there a way to determine what compression should be or is this a tweaking process to try and adjust the valves to get the compression value as high and as consistant as it will go?
03-02-2012, 05:20 PM
#18
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a variation of 30 psi from high to low is out of spec, but not horrible. i am surprised it came back this much. the heads need to come off and be redone-probably. if you run it as-is, i don't think it will do any harm to the pistons. only hurt the valves worse. are these heads anything special? if plain old oval ports with 2.06 valves, they are relatively cheap and easy to find. rectangle ports you should not take the risk of burning out valve seats for the price of a couple of head gaskets. you have a couple of months. pull the heads.
03-02-2012, 05:33 PM
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Now that the valves are set correctly it is running a lot better than before. It's actually running smoothly and firing on all eight cylinders. The squeak from the valve terain is gone on the right side. The backfire is not there anymore, that I can tell of.
I remember that I had paid a pretty penny for those heads. They are rectangular port aluminum heads. I don't know for sure but I'm thinking the valves are stainless? I rather do it right and have it run correctly. I wish I didn't have to pull the heads again and have to reseal and reset all the valves again but the second time around shouldn't be such a pain in the @$$.
What needs to be done to the heads to fix/improve the compression?
I remember that I had paid a pretty penny for those heads. They are rectangular port aluminum heads. I don't know for sure but I'm thinking the valves are stainless? I rather do it right and have it run correctly. I wish I didn't have to pull the heads again and have to reseal and reset all the valves again but the second time around shouldn't be such a pain in the @$$.
What needs to be done to the heads to fix/improve the compression?
03-02-2012, 06:10 PM
#20
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pull heads. quicky leak test. turn chamber side up and pour gasoline into chambers. see which valves let gas run out and how much. get a valve spring compressor. pull valve springs, one cyl at a time, or lay everything out carefully so nothing gets mixed up. check valve seats and seat areas on valves for pits. check guides for looseness. unlikely as this usually takes 150,000 miles to happen. check guides for sticking. quite possible cuz this is what happens when motors and water meet. if sticky, just use valve stem as a reamer and work back and forth till it frees up. get valve grinding compound and a joystick. manually lap the valves, being careful to keep compound out of valve guides. see what the seats look like. if any pits remain, seats will need recut. once you have a nice wide matte finish that is same all way around, valves should hold gas with no springs. reassemble. i don't think you will need new valve seals.
