1969 70 hp Idle question...

[huskerdaninva]

OK, after a minor issue with my newly rebuilt fuel pump (mud dobber mess in inlet elbow) I got my '69 70 hp fired up after a prolonged hibernation for major maintenance. (Cleaning/painting, new head gasket,water jacket gasket, rebuilt carbs and fuel pump, re-plumb all fuel lines, clean/set points, new custom wires, plugs, re-sealed LU, etc.)

I set the timing to 36 degrees at WOT and did the whole link/sync for the carbs, set air/fuel screws to 1 1/8 to about 1/1/4 out, etc. via my Glenn's manual and some guidance from here. She fires right up w/o choke at the bump of the key. Fires on all three cylinders, pumps water, doesn't get hot. I'm happy as a clam. My questions is about an occasional surge at idle. Now I realize that this engine isn't going to purr like your basic V8, but she'll idle up considerably (don't know the rpm's as my tach is not working.) some times and then slow back down. I was able to briefly put her in gear (Fwd) in my test tank at low rpm's and she idled OK and didn't die out. I thought perhaps the idle surge might be caused by low fuel level causing inconsistent fuel pressure as I had not put but about a gallon or so in the tank and she idled for a good 30 mins. She did eventually cut off from running out of fuel, so I added another 1.5 gallons mixed and she fired right back up but with the same occassional surge. I haven't had her in the water yet, but need to do a shake down cruise and want to try and cover my ample arse on everything prior to heading out.

Any thoughts? I can't really complain for a 42 year old motor, maybe that's just the way she idles??

 

[jerryjerry05]

Re: 1969 70 hp Idle question...

Re-adjust the carbs in the water.Turn in till it buck/coughs/sneezes/slows down.Then out 1/2 turn.Idle about 750 in gear in the water.J
When you re-did the carbs the mainjet has small holes in the side were the jets for idle.They must be clean.Surging might be water.J

 

[huskerdaninva]

Re: 1969 70 hp Idle question...

Thanks for the input Jerry. The carbs are clean, I don't think it's carb related per se, but I started thinking last night that I need to perhaps check the nuts on the carb mount studs since I've ran the motor. I re-torqued the head bolts so I ought to check the carb mounts make sure they are tightened to specs, and then do a little spray test with fuel mix around the carb base gaskets.

I do need to get her in the water to make final adjustments. As I said though, overall I'm pretty stoked about how well she seems to run, especially as old as she is.

 

[Frank Acampora]

Re: 1969 70 hp Idle question...

Please reset the timing to 32 or 30 degrees advanced at WOT. The 36 degree line is only for determining top dead center. It should be set 4 lines to the left of the large scribed line on the block pointer. If you only have one line, you should have a decal on the flywheel. If no decal, then you need to set the 36 degree line on the flywheel about one tooth and one gap to the left. (if you count the teeth on the flywheel ring gear and divide into 360 you will find out how many degrees each tooth represents. 97 tereth into 360 equals about 3.62 or 3.6 degrees. Thus the distance from one tooth to the next is 3.6 degrees.)

Timing at 36 degrees is on the edge and MAY cause damage at full throttle.

 

[huskerdaninva]

Re: 1969 70 hp Idle question...

Please reset the timing to 32 or 30 degrees advanced at WOT. The 36 degree line is only for determining top dead center. It should be set 4 lines to the left of the large scribed line on the block pointer. If you only have one line, you should have a decal on the flywheel. If no decal, then you need to set the 36 degree line on the flywheel about one tooth and one gap to the left. (if you count the teeth on the flywheel ring gear and divide into 360 you will find out how many degrees each tooth represents. 97 tereth into 360 equals about 3.62 or 3.6 degrees. Thus the distance from one tooth to the next is 3.6 degrees.)

Timing at 36 degrees is on the edge and MAY cause damage at full throttle.

Frank as usual you are dead on! I mispoke in my first post. I actually set the 36 degree mark on my flywheel to the -6 mark on my timing index plate as per my Glenn's repair manual. (The manual shows this specifically for 1968-1969 models.) So technically I guess she is set to 30 degrees timing at WOT. I know at idle the "0" on the flywheel lines up with the "I" on the timing index plate perfectly as verified by timing light.