7.4GL engine

[Rushan]

Hi I have the 7.4GL engine , the attached video for the sound of the engine on idle, disregard if the engine idle is low, can anyone advise if the knocking and cranking sound is normal or the valves or something needs to be inspected or tunes? Or it's normal sound for a big v8 block ?

 

[Don S]

Re: 7.4GL engine

Where is the sound coming from? Follow the sound. By speed it sounds like a rocker arm. Pull the valve cover on the noisy side and have a look.
Also do a compression test.

 

[Howard Sterndrive]

Re: 7.4GL engine

sounds like it's running on 4 or 5 cylinders.

 

[HorizonblueDK]

Re: 7.4GL engine

That is not a normal sound for nor a bigblock, neither a smallblock, they should purr like a kitten. My guess would be a valve lifter.

By the way, I can see that you have water in your bilge. Pump it out, every single drop. And if the original pump leaves 1-2 inch of water, install another pump, which has a hose on the intake side, that can be routed to the lowest point. Water splashing around in the bilge, will lead to a rotten transom and corrosion on the innerside of the sterndrive transomplate, which eventually will leak.

 

[Rushan]

Re: 7.4GL engine

That is not a normal sound for nor a bigblock, neither a smallblock, they should purr like a kitten. My guess would be a valve lifter.

By the way, I can see that you have water in your bilge. Pump it out, every single drop. And if the original pump leaves 1-2 inch of water, install another pump, which has a hose on the intake side, that can be routed to the lowest point. Water splashing around in the bilge, will lead to a rotten transom and corrosion on the innerside of the sterndrive transomplate, which eventually will leak.

Thank you for your note, yes I installed 2nd smaller bilge that fits in the lowest point and it take all the water, usually I have it dry but I had washed the hull so I got this water.

I will inspect the valves this week and update what I find.

 

[Rushan]

Re: 7.4GL engine

When I warm the engine it doing like 4000 - 4200 rmp, it's regal Ventura 6.8 and it's doing 70/kmh, if it's working on 4 or 5 cylinders is that possible?

Then if it's 4 - 5 cylinders if I fix it it can do better performance?

 

[Rushan]

Re: 7.4GL engine

Where is the sound coming from? Follow the sound. By speed it sounds like a rocker arm. Pull the valve cover on the noisy side and have a look.
Also do a compression test.

I feel like the sound coming from the middle of the block, I'm not sure I will get to the boat in the next 2 days and use the old school wooden or metal bar to listen and try to point where it's coming from.

I will compression test and post what I get

 

[Howard Sterndrive]

Re: 7.4GL engine

When I warm the engine it doing like 4000 - 4200 rmp, it's regal Ventura 6.8 and it's doing 70/kmh, if it's working on 4 or 5 cylinders is that possible?

Then if it's 4 - 5 cylinders if I fix it it can do better performance?

I haven't heard the engine when you're doing 70 km/h.
It definitely isn't firing all 8 every 720 degrees like a V8 should (in the video!)

Marine 454's usually have such a smooth cam they idle smooooth like butter.

 

[Rushan]

Re: 7.4GL engine

Hi again,

I opened the engine head cover and inspected the valve arms and lifters and found one broken spring!

I will replace that spring, my question now would that broken spring cause any internal damage inside the piston and cylinder or it won't have effect to damage such things?

If it has not effect then I will replace the spring and go ahead, if it may cause internal problem inside then I need to open the whole engine to inspect.

 

[Don S]

Re: 7.4GL engine

Hard to say if anything else is damaged. You could bring that piston up on TDC on it's compression stroke, and do a leak down test on that cylinder to see if it holds. Just pull up on the valve to get it to seal if it will. If it won't seal, time to pull the head and look.

 

[Rushan]

Re: 7.4GL engine

Hard to say if anything else is damaged. You could bring that piston up on TDC on it's compression stroke, and do a leak down test on that cylinder to see if it holds. Just pull up on the valve to get it to seal if it will. If it won't seal, time to pull the head and look.

Thank you for your reply,

My friend told me he got a microscope camera that I can look with it into the cylinder from the spark hole,

Will do it tomorrow and inspect inside, in general the video was taken during the broken spring and the engine was running although it was rough idling but no backfire or misfiring , the valve didn't fall in so I hope the cylinder won't be damaged. I hope!!!

 

[Rushan]

Re: 7.4GL engine

Thank you for your reply,

My friend told me he got a microscope camera that I can look with it into the cylinder from the spark hole,

Will do it tomorrow and inspect inside, in general the video was taken during the broken spring and the engine was running although it was rough idling but no backfire or misfiring , the valve didn't fall in so I hope the cylinder won't be damaged. I hope!!!

Hi again,

I had chance to check the piston and cylinder wall by the camera and to make sure I pulled out the head and inspected, thankfully I don't have any scratch or damage inside, the good thing that when the spring broken from middle the 2 parts spinned into each other almost one turn so the sprint didn't come apart.

I changed the spring and replaced another spring that I felt its not 100%,

I will assemble things tomorrow and run the engine to check the sound and tone.

I will post my updates when done

 

[Rushan]

Re: 7.4GL engine

Hi all,

Just a quick question,

When the engine warm and idle when you open the oil cap on the head I can see its oily inside in general, my question is that normal or it should be like in the new cars when you open the cap it will splash the oil from the oil cap opening?

In my pajero car and BMW when I open the cap while engine running I can see oil splash around and it even spill out few drops but in the boat big block I can see its oily with wet oil and oil vapor inside but not splashing around! Is that normal? My oil pressure is normal on almost 40 in the guage and no alarms

 

[Maclin]

Re: 7.4GL engine

I bet the cars you are thinking of have overhead cams, so the cam and valvetrain are all right there, lots of oiling activity inside the valve cover. With a cam-in-block pushrod engine there is not that much oiling activity inside the valve cover.

 

[Rushan]

Re: 7.4GL engine

I bet the cars you are thinking of have overhead cams, so the cam and valvetrain are all right there, lots of oiling activity inside the valve cover. With a cam-in-block pushrod engine there is not that much oiling activity inside the valve cover.

Hi,

Yes you are right the BMW and pajero it twin cam engines , so my v8 Volvo 545 block is normal and the oil is how it should be.

Thanks for the explanation.

 

[Rushan]

Re: 7.4GL engine

Hi again,

Here is the video of the engine after replacing the broken valve spring,

I hope now the sound of the engine is normal?

Any suggestion or hence if everything is ok?

 

[Rushan]

Re: 7.4GL engine

Thank you for your reply,

My friend told me he got a microscope camera that I can look with it into the cylinder from the spark hole,

Will do it tomorrow and inspect inside, in general the video was taken during the broken spring and the engine was running although it was rough idling but no backfire or misfiring , the valve didn't fall in so I hope the cylinder won't be damaged. I hope!!!

I had replaced the valve spring and tried to tune the engine,

Here is the video of the engine, is it normal running sound? Any suggestions or issues?

http://www.youtube.com/watch?v=o8TTCvOoNT0&feature=youtube_gdata_player

 

[Don S]

Re: 7.4GL engine

Sounds like you still have a lifter noise. What is your idle rpm? 400? Idle it at around 650-700 and listen.

 

[Rushan]

Re: 7.4GL engine

Sounds like you still have a lifter noise. What is your idle rpm? 400? Idle it at around 650-700 and listen.

I'm not sure if my rpm reading is accurate but the the now with that video show 900 - 1000,

From the sound do you think it's like 900 - 1000 rpm? Or my rpm idle reading wrong?

 

[Don S]

Re: 7.4GL engine

I'm not sure if my rpm reading is accurate but the the now with that video show 900 - 1000,

From the sound do you think it's like 900 - 1000 rpm? Or my rpm idle reading wrong?

No it's not 900 to 1000, it sounds like 400 to 500 rpm.