Question for Raceman

[gaineso]

The saga of my I-6 continues. Original post is after this:

Took the idle stabilizer off. Went to the ICW and backed in. Started easily and idled smoothly. Made sure all the tie downs on the trailer were tight and put it in gear. Timing showed about –3* at 750 idle in gear in the water. Reved it to 2000 which is past full advance in gear tied down. All 6 showed about 17*. Went to 3700, all I could get out of it, and #1 and #4 were 17*. Boat, trailer and truck were shaking bad and other boats were heading in to the ramp so I didn’t check the rest.

Checked advance with plugs out in the garage and all 6 at WOT are within about 3* and all close to 18*.

Did compression, cold WOT, and got 132 to 136 on all 6. Leakdown, using Balzy's tester, was 96 to 97 on all 6. On easing down from Top Center, just before exhaust ports, there was a small area where it would drop to about 70% and then back to 95% and then exhaust. This was on all six at the same place. No way to check it coming up from intake. It was all I could do to hold it going down. No way to pull against it coming up.

Going to go back to ramp and try full compression test again, but can't do it until Monday or Tuesday. For one thing, you can't get close to ramps on the weekend.

Sho305 sent me copies of the timing procedure out of his Clymer. My book is ordered but not in. Set the idle and timing per the procedure in that book. Will run it again Monday or Tuesday.

My question is, based on these numbers and leakdown and compression and all, am I really stupid to gas up with premium (93), 32:1 oil and run it. It has to go another year.

ORIGINAL PROBLEM DESCRIPTION

Please HHEELLPP (Oh S**t)
1986 Mariner Inline 6 115.

Runnin' over near Palatka today. Cruisin' along nicely at about 5200K and 50MPH and saw a place I wanted to stop and fish. Backed down and as I gave it a little gas to get past the following wave, it sounded like it had a bad miss. Didn't think too much, 'cause I figured it would clear when I took off again.

It didn't. Missing on takeoff, but seemed to run okay once on plane. Idled smoothly and started easily. Had to run back to the ramp, because I was about 10 miles away.

Loaded up with no problems and brought it home. Pulled the plugs. Number 4 is fouled, looks like aluminum. Shined a flashlight in the hole and it looks like there is a clean spot right on the top of the ridge on the piston. Also a couple of very smal silver spots on other parts of the piston.

Couldn't get a picture inside the cylinder, and no head to pull off on an I-6. Broke out Balzy's Leakdown tester and it was less than 3%. Checked the other 5 and they were the same. Compression test showed 132 to 135 on all 6. Stuck an old plug in and fired on hose. Seemed to run good.

Plan to fill tank with 93 Premium and 40+:1 oil in the morning and try again. I think I have about a half tank of 6 week old gas with Quicksilver stabilizer in it. 89 mid-grade.

Questions:
Is it possible for 1 cylinder to somehow advance timing to the point of detonation???

Is it possible or probable for one cylinder, of the 2 fed by the center carb to lean out to this point?

[gaineso]

ttt

[Raceman]

Sorry Gains, I've been outta computer range and didn't see this until now. First of all, I don't have any experience with inlines with ADI ignition, all mine are distributor type. Somebody said he'd had reasonable success running one with a weak piston. It's against what I'd do, but he's certainly got tons of inline experience, so I wouldn't contradict it. If you're gonna do it, I think the lower timing & better gas is good insurance.

I'm just wondering how the engine's gonna perform with the timing that low. I think it needs the cushion since the piston's already started to fry a little, but I've never run anything below 21º, so I don't know if it's gonna be lazy. I'd sure watch that cyl close and check that plug frequently.

[Bill Gohr]

the actual prob I missed it, plug fouling, or detonating #4, or #1. If you're seeing a timing fluctuation, disconnect the white with black tracer between the switchboxes and see if it goes away, if so you have a bad bias circuit in one of the switchboxes and that will cause inconsistent timing and a detonation problem.

Raceman the timing on the later in-lines is 17 or 19 degrees, I know we would never run them that low.

[gaineso]

Raceman thanks. The timing spec on this motor is 18*. I know that with the idle stabilizer it was varying a bit. I reset the timing per the Clymer pages that sho305 sent me and fired it on the hose this afternoon. Just idling to 1500 Rs seemed to run OK and checked idle timing at 1000RPM and it was dead on 0*.

Plan to back it in at Vilano ramp Wednesday and check the timing and performance under load. Will check all 6 at full advance.

Bill, thanks for jumping in. I had detonation on #4 and I guess I was lucky 'cause it fouled the plug and so didn't do any more damage. You saw the things I've done and I will try it again Wednesday. If there is variation, I'll replace both switchboxes. Not sure what sort of offbreeds they are anyway. Last year I was afraid to do any more than a water pump, but I found out we don't have any mechanics in this area. Just parts replacers. Keep replacing things until it runs right. Problem was a leaking float in the center carb. After he'd replaced the entire ignition system.

Further question. Should I go one size larger on jets and should I add an electric fuel pump before the water separator to be sure it's not leaning out?

Thanks a bunch. You guys, everyone on this board, are great and I and a bunch of others appreciate all you give so freely.