Atomic 4 Rebuild (Inprogress)

[Night Watch]

I've tried posting the Q at Moyer Marine Forum, but I don't seem to have the correct privileges over there.

I've started a rebuild (spare engine) using a 1977 "freshwater cooled" engine I purchased last year.
Currently at a work stoppage awaiting parts. The reassembly is going as planned, but I have a question for those that know the answer. The question concerns my initial cylinder head pressures. The engine spec range is 95-110psi, mine are spot on (all 4 cylinders) at 75psi. I'm getting these pressures using the starter to turn over the engine. The engine is freshly rebuilt; cylinder's honed to .010 overbore. The cylinders are lightly lubed and not under full oil pressure yet. I'm guessing I will see higher pressures after the oil pump kicks in at 40psi at "first startup", but this is my first engine to rebuild so I'm not familiar with what to expect.

Condition of parts/block: The engine has new valve guides, valves, valve job by a reputable machine shop in Tacoma, the block was high frequency cleaned, crank and flywheel were balanced, and the block deck was milled, new pistons, rings and bearings, new head and two gaskets. Valves were adjusted and checked twice for proper adjustment. The engine went together with no binding, turns freely. The new head is torqued to OEM spec and the head bolts are holding the torque as I've retorqued and checked several times.

Before I tore the original engine down the cylinder head pressures varied between 70-90psi, the block water jacket passed a 20psi pressure test for 20 minutes, so the block was a "good" candidate for a rebuild.

What am I missing, or am I just paranoid?

 

[kloudie1]

Stuff probably needs to be broken in a bit.. Remove one plug and put in a teaspoon (not more) of engine oil then open the throttle fully and recheck compression in that cylinder.. You'll probably see a significant increase which would indicate that the rings /cylinder interface needs some running.. I am assuming that the rings are installed right-side-up and the ring end gap was checked and corrected if necessary.
Note that if a good bit of the gooey assembly lube was used, the compression oil check won't show an increase and will indicate a different problem that will require some head scratching (Cam timing maybe?) .. I wouldn't think a cracked block or head since that woould most likely affect one or two cylinders and not be uniform as you've indicated.
Good Luck

 

[Night Watch]

Stuff probably needs to be broken in a bit.. Remove one plug and put in a teaspoon (not more) of engine oil then open the throttle fully and recheck compression in that cylinder.. You'll probably see a significant increase which would indicate that the rings /cylinder interface needs some running.. I am assuming that the rings are installed right-side-up and the ring end gap was checked and corrected if necessary.
Note that if a good bit of the gooey assembly lube was used, the compression oil check won't show an increase and will indicate a different problem that will require some head scratching (Cam timing maybe?) .. I wouldn't think a cracked block or head since that woould most likely affect one or two cylinders and not be uniform as you've indicated.
Good Luck

Yes, I did install the rings "right-side" up and used assembly lube to reassemble. So, thanks for your input.

 

[Night Watch]

Will be down in your neck of the woods to see the grandkids next week.

 

[fox9988]

As mentioned, do the compression test at wide open throttle. Please post the results.

 

[Night Watch]

As mentioned, do the compression test at wide open throttle. Please post the results.

You can't see it in the photo, but there's no carburetor or manifold on the block yet. So, can't comply with your request.

 

[fox9988]

Understood. Worst case, run it. It'll go for years.

 

[kloudie1]

That .looks like wide open throttle,

 

[Night Watch]

Finally, almost ready to go back in the boat. Will run for an hour or so to work out seeps/leaks before moving down to the marina.

 

[Indysailor]

Did you get the the issue with posting questions on the A4 site sorted out? I think that will help, though some the folks there may be on SBO as well. It's not a high compression engine and I'd guess seeing consistent and not drastically low psi is ok.

 

[Night Watch]

Did you get the the issue with posting questions on the A4 site sorted out? I think that will help, though some the folks there may be on SBO as well. It's not a high compression engine and I'd guess seeing consistent and not drastically low psi is ok.

Yes, I finally got the correct permissions to post over there. Just before cranking this engine up for the first time, I rechecked the compression and it's still at 75psi per cylinder but will be expecting an increase after the rings wear in a bit. Currently waiting on a new carburetor as the one I salvaged from the old engine turned out to not be salvageable.

 

[Indysailor]

I have gotten a lot of good "calm down, it'll be ok" advice on that site.

 

[Night Watch]

Did you get the the issue with posting questions on the A4 site sorted out? I think that will help, though some the folks there may be on SBO as well. It's not a high compression engine and I'd guess seeing consistent and not drastically low psi is ok.

Yes I did

 

[Night Watch]

update on the engine rebuild. My photos are too large to post, but this morning my brother-in-law and I moved the rebuilt engine from the garage to the boat, no hitches, no oh-shits, smooth as silk, from the pier to the engine compartment took 1 hour, three chain falls and a dash of brute force.

 

[Stu Jackson]

update on the engine rebuild. My photos are too large to post, but this morning my brother-in-law and I moved the rebuilt engine from the garage to the boat, no hitches, no oh-shits, smooth as silk, from the pier to the engine compartment took 1 hour, three chain falls and a dash of brute force.

That's good to hear, about the engine.
Resizing photos to post on the internet should have been covered in your Kindergarten 101 class, did you cut skool that day?

 

[Night Watch]

 

[jssailem]

Oh my... Looking great. What a rush of accomplishment. Well Done. Will probably live in the boat longer than you own the boat. That is a bonus.

 

[Project_Mayhem]

Looks great so far! We're eager to hear how it's running

 

[Night Watch]

Looks great so far! We're eager to hear how it's running

I'm taking my time hooking everything up. What I can say so far is the transmission shifting is much better than my old engine. This week I had to order a new fuel pump as the one in the picture failed to properly function. Waiting on it's arrival. Heat exchanger arrives next week. That's the last component to install. Still have to wire the alternator and finish plumbing the heat exchanger. So far, no surprises other than the failed fuel pump.

 

[Indysailor]

Lovely looking engine, ready for another 40 years.