Slant Six Forum
https://www.slantsix.org/forum/

fresh rebuilt Engine overheating.
https://www.slantsix.org/forum/viewtopic.php?t=62601		 Page 2 of 3
Author:  emsvitil [ Thu Jul 19, 2018 1:56 pm ]
Post subject:  Re: fresh rebuilt Engine overheating.
Use IR gun on radiator to see temp distribution (you'll need to get close)
Author:  Rick Covalt [ Thu Jul 19, 2018 6:54 pm ]
Post subject:  Re: fresh rebuilt Engine overheating.
Sorry I didn't look back to see, but do you have an electric fan?
Author:  wjajr [ Fri Jul 20, 2018 4:30 am ]
Post subject:  Re: fresh rebuilt Engine overheating.
Stock factory four blade fan with fresh paint.
Author:  Rick Covalt [ Sun Jul 22, 2018 3:00 pm ]
Post subject:  Re: fresh rebuilt Engine overheating.
Quote:
Stock factory four blade fan with fresh paint.
Change that out and the problem will probably go away too. That fan doesn't move that much air especially setting still. The last engine I built for Andrew Shank's truck would get hot setting still too. We changed the 4 blade and went to a 5 blade fan with more pitch and the problem went away completely. Easy fix! :D :D
Author:  wjajr [ Fri Jul 27, 2018 5:55 am ]
Post subject:  Re: fresh rebuilt Engine overheating.
Over a week has passed since last post. Engine now has 303 miles on it now, has cooled down, and idles above normal temperature without over heating.

However in the last few days when cold engine starts a big cloud of blue smoke blows out, and engine chuggs on five for a minute until it clears whatever causes a misfire. I'm suspecting carburetor is in need of a rebuild, (it's been ten years since last rebuild) after all the sneezing back through carb during initial start-up and retiming of cam. After the first few miles, carb (Holley 390) started to leak aroung accelerator pump, turned out to be slack bowl bolts, and a slight tightening cured that.

Now I have a flat spot under acceleration before secondaries open, and engine back spin at shutdown even with 700 rpm in gear shutdown. These two problems have been developing slowly over the last 300 miles. Smell of fuel is stronger than usual with car parked in basement, and oil dipstick is not smelling gassy.

Timing is still at +12* where I set it when started brake-in and engine would just stop when shut down then. Lash still at cold setting of .014", +.002" over cam card .012".

I think there is some internal fuel leakage into intake (power valve perhaps), and or incorrect float level problem soaking one or more cylinders over night. Its been ten years since last rebuild. Fuel consumption seems to be quite high, but I haven't calculated mileage yet, deemed to be too soon after rebuild to bother with.

Later today after first start of day, I'll take temperature readings of each exhaust tube to figure out which cylinder is misfiring and go from there.

After writing the above, I decided to pull all six plugs; 1-3 soaking wet with fuel, 4-6 damp with fuel, and big stink of fuel once plugs were removed. Guess that points to a carb problem.

Next on list is float level, and power valve inspection.

Ideas?
Author:  Dart270 [ Fri Jul 27, 2018 6:56 am ]
Post subject:  Re: fresh rebuilt Engine overheating.
Valve lash is way too tight. I have run that cam around 0.024" intake and 0.028" exhaust after empirical testing on two engines. Do you have an AFR gauge? If not, get one on there for any tuning. AEM has the best ones. AFR tuning will be different with your new engine specs.

Lou
Author:  wjajr [ Fri Jul 27, 2018 9:24 am ]
Post subject:  Re: fresh rebuilt Engine overheating.
Lou,

I do have AFR gauge reading from a cheep three wire o2 sensor never can remember which is which; narrow or wide. I haven't gotten to playing with other than setting idle mix. Now that engine will idle without getting red hot in two seconds; I'll get after it soon.

Driving along under 3000 rpm Sunpro A/F gauge reads in first red rich zone. Under WOT acceleration it drops into "Ideal" yellow zone. Idle shows rich.

This morning I pulled carb float bowl, reset float level, replaced cork bushing at idle mixture screws, checked power valve for leak none found and replaced with 5.0, new gaskets. Presently running 53 jets on primary, and stock secondary metering plate, acc pump #25 nozzle- orange cam in #1 hole.

Test drive showed flat spot almost gone, idle 900 rpm in P, 700 in gear, trans kicks down quicker than before carb adjustment without any throttle position cable adjustment. Now very little spin back three big clunks at shut-down at 900 rpm and in gear at 700 rpm a half harted one clunk; progress but not right yet.


Lashing to .024" & .028" is going to improve idle vacuum, and perhaps low end torque, right? Will it help lessen spin back?
Quote:
I have run that cam around 0.024" intake and 0.028" exhaust after empirical testing on two engines.
What data have you on this lashing? Did it come from dyno or race times?

Heading out to relash to your recommended settings.

Bill
Author:  wjajr [ Fri Jul 27, 2018 12:05 pm ]
Post subject:  Re: fresh rebuilt Engine overheating.
Lou,

Reset lash to your specs. Big difference in idle vacuum up from 8 Hg to 14 Hg at 900 rpm in park; adjusted idle mixture by highest vacuum gauge reading. Exhaust has different sound, rocker clatter is a bit louder, and with engine turning a steady ~3000 rpm, vacuum goes to 19Hg.

Because of these improvements, power valve needs to be changed to 6.5 which is not on hand needing to be ordered. Accelerator pump lever needs to be adjusted, there is a little lag before it comes on line which I think is my slight flat spot.

A/F gauge reads a steady second red light (rich) while under way with steady throttle, and at idle, so probably jetting down two sizes to 51 may help lean out mixture while driving. Fiddling with idle air mixture screws doesn't move mixture reading, but changes idle speed. Screws are out about 1 1/2 turns

Good news, back spin at shut down seems to be gone.

Bill
Author:  Dart270 [ Sun Jul 29, 2018 4:17 am ]
Post subject:  Re: fresh rebuilt Engine overheating.
Amen. Nice work. I just drive the car until fully warmed up and see if the idle gets worse hot as compared to middle-cold. Then, I loosen the lash 0.004" and try again. I might tighten up a little after I find the point where it the idle does not change and see if it is the same idle quality.

I have never seen a performance Slant 6 cam that idled worth a crap ("up to its potential") with less than 0.015"/0.020". Idle, low end, starting, and sometimes midrange get better when you do this. Several of the old Mopar cams (big ones) had lash specs up to 0.028/0.032" and I've not seen anything that behaved better when looser than those lash specs.

Lou
Author:  wjajr [ Sun Jul 29, 2018 6:31 am ]
Post subject:  Re: fresh rebuilt Engine overheating.
Lou,

Saturday I was too occupied with car show, other things and then a bad case of sloth after supp'ah to report on how engine responded. Car is garaged in mty basement with a constant ambient temperature around 65*; so any cold starts are always at same temperature. Saturday morning took three restarts to get it out of garage, chalked up to stalls due to three big lean sneeze up through carburetor. Choke was set. But, I had not adjusted the slop out of accelerator pump linkage; that adjustment was made this morning.

This morning cold start went well, was able to drop in gear after a few seconds of steady idle, back out of garage with no lean sneeze, and then went for a 1/2 mile test drive. Once on road anything less than a slow slight throttle opening would bring on a very lean condition, flat spot, and a sneeze. Letting off, and with slow progressive opening produced easy sneeze free acceleration with shifting up through all three gears. She still had a cold intake once back in yard (Clifford with homemade hydronic hot spot under carb), and lean condition under moderate throttle openings. Inspection of accelerator pump delivery looks a bit anemic, now pump is suspect as cause of leaning out. Once engine was up on main jet flat spot all but disappeared making me think this is an idle/transition/ accelorator pump problem.

A/F gauge is reading front three just about two inches down stream from collector at head of exhaust pipe; a distance of about 27 inches from head. Carb bowls are orientated N & S. Reading plugs; front three are showing dark tan, back three very light tan to white. I wonder if there is too much idle air entering secondary half of carb causing leaner condition on back three? Do you think reducing secondary idle air would enrich back three, and allow screwing in primary's idle mixture screws to balance A/F mixture to all six cylinders? (currently idle mix screws out 1-1/2 turns set to highest vacuum reading)

Engine idle is smooth in park, now set at 900 rpm, and drops to a smooth 700 rpm in gear (base timing at +12*). Should I increase idle rpm with idle screw which probably would cause transition circuit to be activated over riding idle circuit, or try to increase idle with timing change keeping idle on just idle circuit and out of transition?

One more thing, I thought the back spin was a thing of the past, but no, it is back ever so slightly at times, and not at every shutdown. Shutdown in park usually generates spin back, and shutdown in gear occasionally makes a half harted partial spin back perhaps just driving piston to BDC.

Yesterday after backing car out of garage, I left it idling while washed & dried it, a long enough time to bring engine up to temperature. I'd did not over heat, but did push gauge a bit east of straight up and down; seams it is wearing in and running a lot cooler. Current mileage is at 342.

As for lashing over 0.026", all my sets of feeler gauges don't go thicker. I SWAGED it to 0.028" by feeling no or very little drag with 0.026" gauge.

Bill
Author:  Dart270 [ Tue Jul 31, 2018 2:55 am ]
Post subject:  Re: fresh rebuilt Engine overheating.
Sounds like good progress, and lean mixture due to carb is main issue. Are you running premium gas? I do not think you need/want to raise the idle RPM. Lower idle will lead to less spinback. What plugs are you using?

Lou
Author:  wjajr [ Tue Jul 31, 2018 4:28 am ]
Post subject:  Re: fresh rebuilt Engine overheating.
NGK UR5
Quote:
Sounds like good progress, and lean mixture due to carb is main issue
I'm confused. A/F ratio gauge reads in rich zone during idle, and while motoring on down the road. Mixture due to carb is main issue... Are you suggesting changing main jet?

Yes, at the moment using 91 octane, only other choice nearby is 87 with 10% Jim Beam added.

Anyway I'm off on a ride down river to son's house for a little house-fix'en project this morning which will roll on another 100 miles.
Author:  THOR [ Tue Aug 07, 2018 10:28 am ]
Post subject:  Re: fresh rebuilt Engine overheating.
I've encountered spin back as a result of too little timing, and the idle speed on the carb turned up too high. Are you absolutely sure your balancer and timing mark are in the correct spots? With what you mentioned earlier about putting the timing at 8 degrees BTDC and it not wanting to run makes me suspicious. It should "run" more or less even down to zero degrees initial advance. If you find that it has indeed slipped, I think you may find that your timing still needs to be advanced.

Just my .02 :D

~THOR~
Author:  wjajr [ Wed Aug 29, 2018 7:16 am ]
Post subject:  Re: fresh rebuilt Engine overheating.
After a lot of other stuff going on in my life such as getting caught up on yard work, weeding shrub beds, dicing up last year's blow blow-downs and other distractions plus 11 days of the worst head cold/bronchitis spell ever uncounted, I got around to messing with the Dart's flat spot yesterday.

Oddly the back three plugs have been running lean showing white porcelain, and front three dark tan. Carb has been leaking down into/onto intake after shut down, just how much I can't tell; and seems that if car sits for a few days bowl dries out or becomes very low; oil has no heavy gas smell. When starting after sitting a few days it would fire off quickly, than stall out gauge showing excessive lean condition. After 5 - 10 seconds of cranking engine would light off, act very lean, and on occasion sneeze back up through carb and stall. I have Clifford headers and 4v intake hydronicly heated via heater loop, and once engine has run 30 seconds or so would settle down and idle with no throttle input.

I once again tightened the bowl bolts, and now there is no fuel smell from hot engine once parked.

Based on the back three being lean, I discovered secondary throttle plates were not fully seated on their stop and were able to flutter adding additional idle air to intake. Remedy was to bend secondary lockout rod such that it disallowed any throttle plate movement off their stop controlling the addition of unneeded air.

I also bumped up base timing from +12* to +14* which increased idle in park rpm around 100 rpm, which also increased in drive idle rpm to 650 rpm.

Flat spot has all but gone under all throttle openings, spin back also so far has gone as long as engine is shut down in gear. It just stops running with no drama.

After a round 20 mile trip into town, #2 still shows dark tan, and #5 now slightly darker than bright white.

Looks like I need to pull carb, double check secondary idle air/ throttle plate stop adjustment on the bench, and lean up primary idle mixture screws.

Getting closer.

Several weeks back I tightened the lash to 0.016" I and E. Valve clatter is much quieter, and engine seems to like this setting; cam card called for 0.012" on I & E. More lash re-adjustment to come.
Author:  THOR [ Wed Aug 29, 2018 9:42 am ]
Post subject:  Re: fresh rebuilt Engine overheating.
Are you running true duals? Where is the O2 sensor located?

~THOR~
Page 2 of 3 All times are UTC-08:00
Powered by phpBB® Forum Software © phpBB Limited
https://www.phpbb.com/