Rebuilding Mercruiser 165 - GM 250 I6

Status
Not open for further replies.

ethan169

Petty Officer 2nd Class
Joined
Oct 21, 2012
Messages
137
Mark,

Thanks for the info!

It looks fairly simple to drill and tap this area so I will look into that. However Im unclear as to where the tube goes to on the bottom. Is it just open to the air? It doesnt look like this tube brings exhaust gases up but just passes through a port and get heated as you mentioned. But is the bottom of that tube basically just open and the warm air travels up the tube into the choke assembly via convection?

Good to know about the fuel pump. I saw that brass barb at the bottom of the fuel pump "bow" and wasn't sure what it was for. There was an old hardened plastic fuel line that was attached to it. You can see the barb in the first and second picture with greenish sludge around it. It looked like that tube hadnt really been used and it just degraded. I was puzzled as to what it was feeding. Your explanation makes sense though.

What did you end up doing for ignition on your motors? Did you keep the points or do some electronic conversion?
 

johnkom

Petty Officer 2nd Class
Joined
Jul 26, 2004
Messages
163
"But is the bottom of that tube basically just open and the warm air travels up the tube into the choke assembly via convection?"

Yes. The tube carries air entering below the manifold up into the choke chamber. It is an interference fit. The tube just passes through the manifold and does not pick up any exhaust gases. When I rebuilt mine I was able to tap out the old and use a brake line to fabric a new one. Good luck.

JK
 

Mark72233

Ensign
Joined
Jul 11, 2014
Messages
926
Johnkom answered your question on the tube. I was a little off on where the line goes from the the bottom of the fuel pump. The hose is attached to the carb near the top not base. I will take a pic tomorrow and post it.
 

ethan169

Petty Officer 2nd Class
Joined
Oct 21, 2012
Messages
137
Thanks for the explanations guys. I got the head mounted up and torqued down last night and some painting done. I finally broke down and fired up the furnace in the garage since its -10 degrees here today.

I'll post some pictures of the progress later on.
 

Mark72233

Ensign
Joined
Jul 11, 2014
Messages
926
Ethan, here is that line on one of my engines. Ignore the dirt the engines got dusty sitting in the garage for months.
 

ethan169

Petty Officer 2nd Class
Joined
Oct 21, 2012
Messages
137
Thanks for posting the pics of your setup Mark. It will help with the plumbing of fuel lines.

I still haven't gotten around to getting updated pics. I'll try to post some tonight.

As for tonight's task it is to install the lifters and pushrods and set the lash. Maybe even install the valve/rocker cover.

I am also thinking about putting the main crank pulley on or balancer really. My crank doesn't have a tapped hole in the snout. The only other way I know how to install it is heat the hub of the pulley and tap it on wuth a hammer and 2x4. I think even the manual says to do it this way. I don't want to damage anything so any recommendations? Or alternate methods?

Ethan
 

Fishermark

Vice Admiral
Joined
Oct 19, 2003
Messages
5,617
When you do plumb your fuel line, go ahead and use a clear line for the overflow. It is not supposed to have fuel in it, and a clear line will help verify if you have a problem or not.

DSCF5703.jpg
 

Mark72233

Ensign
Joined
Jul 11, 2014
Messages
926
Fishermark, good idea on the clear line. I think I will switch mine out and make them clear.
 

ethan169

Petty Officer 2nd Class
Joined
Oct 21, 2012
Messages
137
Good call on the clear line. I think the line I took off was clear and I thought it was a little odd. Makes perfect sense now. I'll be sure to put it back with fresh clear line.

So tonight I got the lifters and pushrods installed. I also adjusted the lash. The manual says to tighten the rocker arm nut 3/472/322 turn down from zero lash. It describes zero lash as the pushrod not being able to turn at all. I tried this and its pretty tight. So tight that when I go to turn the engine over I get to a point where the lifter and valve are bottomed out. I cant turn it any further by hand. I redid the procedure but this time considered zero lash basically when there was no more up and down play in the pushrod. Then I turned it down 3/4 of a turn. This seemed much better and follows the method I had used on other engines.

Mark72/233 and Fishermark how did you adjust your valves?

Here are a few pics of the head installed.



I am trying to figure out a good way of taping the labels off on the valve cover so I can paint it without painting over them. They are in good shape and have the engine specs (like dwell and hp etc.) as well as engine serial number on them. This is the reason Id like to keep them looking nice.

That all I've got for tonight.
 

ihc1470

Seaman
Joined
Jun 21, 2015
Messages
65
You might check out Rock Auto or Summit Racing for that vent line. Carter 88874 is the number that I used. The line is not clear it has a light yellow tint to it but you can see in it. It is a material that is suppose to stand up to fuel where you clear tubing may not. It also comes with a couple of fittings which I did not use.

As I understand zero lash it is the point where the play is just taken up between the lifter and the push tube. Your 3/4 turn then basically centers the plunger in the center of its travel in the tappet. So your second time around should have you pretty close.
 

Fishermark

Vice Admiral
Joined
Oct 19, 2003
Messages
5,617
YAs I understand zero lash it is the point where the play is just taken up between the lifter and the push tube. Your 3/4 turn then basically centers the plunger in the center of its travel in the tappet. So your second time around should have you pretty close.

That's exactly right. Finding the point where all the slack is removed takes practice. It is easy to go too far. I like to move the push rod up and down while turning the adjustment. Go slow when approaching the end and then stop. I go back a forth with the adjustment a couple of times at that point to see where the slack is actually removed, then make the final 3/4 turn.
 

Mark72233

Ensign
Joined
Jul 11, 2014
Messages
926
Ethan when I did my engines I rotated the crank until I was at or just shy of top dead center in #1 where your rotor on your distributor is at #1 position. Than adjust the intake valves on 1,2 & 4, exhaust valves on 1,3 & 5. Back off the rocker arm nut until you feel lash or looseness and you can freely spin the pushrod. Then slowly tighten until lash is gone from rocker arm or no longer loose feeling and you can't turn the pushrod with your fingers. Then tighten it 3/4 to 1 full turn. Then rotate crank one full turn until rotor cap points at #6 position. Now do the same thing with intake valves on #3,5&6 and exhaust valves on #2,4 & 6 using same method. You can google adjusting valves on a Chev 250 also. Once engine was running I went back and tweaked them. I did screw up on both of my engines when I put the distributors in. I had them out 180* degrees so when I tried to start them it was quickly evident because they won't start and they will backfire. I knew right away so I had to pullthe distributors out and spin them 180* and than I had to go back and readjust all my valves. Luckily I didn't break or bend anything.
 

ethan169

Petty Officer 2nd Class
Joined
Oct 21, 2012
Messages
137
Thanks for all of the replies about adjusting the valves.

This weekends project was to paint some parts and to rebuild the carb.

I have a question on the float adjustment and the float bowl gasket. In the kit that I have ordered for the rebuilt I have two gaskets to choose from for the float bowl. I have one that looks like the one I took off and a slightly different one. The one I took of has clearance where the float sits in the up position (float is "up" towards the carb cover when oriented how it would be sitting on the engine. The alternate gasket has gasket material in this area so the float would make contact with the gasket before it was bottomed out. Take a look at the picture below to see both gaskets.


The installed gasket it the one that covers the recess area where the float could potentially go. The gasket that I am holding is the type of gasket that I pulled off of the carb and allows the float to float higher into the cover. (above)


Here you can see the float is installed and is resting on the gasket surface. (above)


Here is a picture of how the carb was setup when I took it apart. I see that the float looks basically level here too. Perhaps I should try the thicker oring/gasket for the needle seat that is supplied with the rebuild kit. The instructions said to start with the thinner one and adjust as necessary.

I'c inclined to say I should use the same gasket type that came off of the carb. However the mercruiser manual show the gasket that doesn't have the clearance for the float. And the rebuild instructions for the carb that came with the kit show the type of gasket that I pulled off (the one with the clearance). To add more confusion the video guide that I'm using shows the gasket that has no clearance for the float. I attached the link below. This video was made by the same place where I got the kit from. I'm inclined to say the gasket doesnt matter since the float shouldn't be touching that surface when it is at the correct level anyway. I think I need to try the thicker gasket for the seat which should raise the float up off the gasket a little. If not Ill need to adjust by bending the bracket I suppose.

Normally I would say well it came apart one way it should go back together the same way. But unfortunately I have no idea if this engine ever ran or ran correctly. It was clear that someone tried rebuilding it at one point and never really ran it. Water go int he block somehow. I found later it has a crack that was detected by the magnaflux test. This is a new (old) block with no cracks that Im using of course. So my point is the carb could have been rebuilt improperly last time. I don't know.

Any tips would be appreciated!
 

ihc1470

Seaman
Joined
Jun 21, 2015
Messages
65
I normally use the same gasket that came off. I rebuilt 2 of those carb within the last year and both used the closed gasket and I knew both engines and neither had been touch in that area before. I think you would be fine changing to the other gasket.
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
40,582
My suggestion is to use the one with the large opening, reasoning behind, if the gasket does any sagging it could hinder the float.
 

Mark72233

Ensign
Joined
Jul 11, 2014
Messages
926
ethan, I also just rebuilt my 2 carbs and both had the open gasket so that is what I used. I know that you will set your float level for up and down so as long as that other gasket doesn't interfere with that setting then I guess either will work that being said I would go with AllDodge's suggestions and go with the open gasket.
 

ethan169

Petty Officer 2nd Class
Joined
Oct 21, 2012
Messages
137
Progress update - I ended up using the open gasket as suggested. I adjusted the float level and drop and assembled everything. The carb rebuild really wasn't all that difficult. We will see how everything runs when its done. I still need to get a set of new idle mixture needles. One of mine was pretty bad. I have another 2gc carb that came off of the donor engine. I opened it up just to take a look and it was nastyyyyy. Heres a pic of the float bowl.


Now I needed to paint the block and head. Here is a pic of me mocking up the manifold and testing two different spray paints to see what I liked better.



And here are a few pics of the long block all painted and the manifold installed.



I was able to rig something up for the choke tube. I basically bored the ID of a piece of 3/8 OD tubing to 1/4" and then pressed it into the top hole. Then I used 1/4" OD tubing to press through the top sleeve I installed and then into the 1/4" Id hole in the bottom of the port. It seems to snug. If needed I can tack weld it in place or use some sort of high temp JB weld on the bottom. I don't think its going anywhere though. I then bent the 1/4 tube to meet up with the choke housing and put a compression nut on the end and then used a flaring tool to flare the end. Its weird the flare nut I had didn't really fit right but the compression nut did. Not a huge deal this line is only carrying heated convected air.

I still need to decide weather or not I want to paint the carb. Its not in bad shape paint wise but I can tell that its not mint new paint like the rest. Most other probably wont notice especially when the flame arrestor (sp?) is ontop. I'm just concerned about gunking something up with paint on the carb.

Tonight I plan on getting the distributor installed and the water pump as well as the t-stat housing.

I will also need to install the crank pulley / balancer. The manual basically says to pound it on. I know this was standard practice back in the day but is there a better way? Or should I just do it? I dont want to damage the new bearings thrust surface. The crank nose is not tapped either. How did everyone else get theirs back on?

Ethan
 

Alumarine

Captain
Joined
Feb 22, 2005
Messages
3,684
Motor looks nice.
If you can freeze the crank snout and warm up the harmonic balancer (not too hot) that will help to install it.
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
40,582
I would take a leather mallet or block of wood and hammer and install the balancer.

Don't remember if you have adjusted the valves yet.
 
Status
Not open for further replies.
Top