3.7L 165hp Engine Knock

[ta400man87]

I have a 87, 3.7L, 165hp, 4cyl. 470, Ford cst iron head with Alu. Block, with issues. The engine ran fine when I put it away last year. I did an oil change and used the lucas oil additive. The first time out the motor ran fine, it had pleny of power. I was cruising for 10 minutes and then started to hear some weird noises. When I throttled back I started to hear a knock from the motor. Now I the engine bearly has enough power to get on plane, but sound fine at idle and knocks under load.

Now here is what I checked so far.
Dwell is right on the money, it has a new coil from last year.

Timing is advancing (through watching a timing light speed up)

Compression is 1-109, 2-120, 3-136, 4-90, which has not changed in the last 2 years. I also added some oil into the cylinderr chamber of #4 and then repeated the compression test, the compression remained the same, 90psi

Ran the boat on a remote tank thinking I had water in the tank, I also sprayed starting fluid down the carb when the engine was under load to see if the engine was lagging fuel.

When the engine was knocking I pulled each plug from the cap to see if the knocking went away, this is did nothing, the knock did not go away.

I thought maybe the fuel pump, but I would figure that i elimated the fuel pump because i think that is getting enough fuel, when I sprayed in the starting fluid with no response.

The knock does not happen at idle, and only sometimes at rpm without a load. Once the engine is unload and warmed up the knock is really bad.

I am thinking maybe cam, but I would think I would hear that all the time.

Any Ideas or Experiance.
Thanks In Advance

 

[Big Boat Bay Buster]

Re: 3.7L 165hp Engine Knock

The 470 has a reputation for a rod knock in #4, usually from water ingestion from a bad riser..Considering your lowest compression reading is in #4, that might be a clue.You need to identify the type of knock and where its coming from. How is your oil pressure? I see you checked the timing and dwell. I assume this is a mechanical knock and not pinging. It seems to me the engine has a few problems that are adding up to 'rebuild time'
Chris

 

[Bondo]

Re: 3.7L 165hp Engine Knock

Compression is 1-109, 2-120, 3-136, 4-90,

It seems to me the engine has a few problems that are adding up to 'rebuild time'

Ayuh,..... I Agree,.. It's a Wonder that it runs, At All......

 

[ta400man87]

Re: 3.7L 165hp Engine Knock

I do believe that it is a mechanical tick and not pinging. I am a little confused on why I am losing power with a rod knock. I was reading that the engine coupler can make a ticking noise, what kind of noise does it make and can you lose power because of it being bad.

The knock is bad enough to the point that I am planning on a complete engine rebuild. Figures the timing is great for a rebuild in the middle of the summer.