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New Radiator - Heat Shielding - or ?
https://slantsix.org/forum/viewtopic.php?t=18485		 Page 2 of 2
Author:  SlantSixDan [ Mon Jul 24, 2006 9:06 am ]
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* I checked the heat riser and it was closed (standing in the front of the car looking at the motor the heat rise counterweight was turned clockwise as far as it would go - thats closed right ?).
Should it not be anti clockwise, standing in front of the car?
Yes. If it is the pre-1970 type of heat riser with the rectangular counterweight, it should be fully anticlockwise (counterclockwise) when warmed up. If it is the '70-up type with the round counterweight, it may remain lightly spring-loaded to the clockwise position when warm, but should very easily move to counterclockwise with just very light (GLOVED!) finger pressure. Any other status (stuck or heavily spring-loaded clockwise) means the heat riser is sticking in the "heat on" position, which can certainly cause lousy hot running.

Ricki, a few other pointers:

1) Quit using Bosch plugs, they are even worse junk now than they have been in the past. Can cause random and vexing driveability faults. Use NGK ZFR5N, gapped to 0.035" with points or 0.040" with electronic, without the ring gaskets that come pre-threaded onto the plug (only '60-'62 slant-6s use the ring gaskets). You'll need a 5/8" spark plug socket to install the ZFR5Ns.

2) Sam's idea to space up the carburetor is a good one, but you have to be careful to avoid spacing it up too high, which will screw up the rod-type throttle linkage geometry, as well as the kickdown linkage geometry if you have an automatic transmission. The thick carb gasket specced for '70-'72 slant-6s is about 3/8" thick and is a good one to pick.

3) What is your fuel line configuration? Have you done Fuel line mod yet?

4) What is the provenance of these two 1920 carbs you're running? Both new? Both used? Both "remanufactured"?
Author:  skraecken [ Tue Jul 25, 2006 11:20 am ]
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One more thing, if you run Dutra dual front exhaust, then you have only half the exhaust pressure (3 cylinders) to open the "flap".
Do you have to compensate for that?
Author:  ricki [ Tue Jul 25, 2006 1:23 pm ]
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Hi All
Sorry for the silence. I am now tied up with work for a couple of weeks and not all my parts arrived before the weekend, but did try some things since last last post ...
* larger and smaller main jets
* rechecked tappit clearances
* swapped around the vacuum tube from the distributor between both carbs
* made the mixtures richer and leaner again
* putt the accelerator pump arms in all 3 locations on both carbs
* advanced and retarded the timing
* removed the tube from the valve cover breather to the front air cleaner (thought hot air from the motor might be effecting things)

All made no difference to the problem at hand, but my motor and surrounding parts are getting cleaner every time I work on it!

To answer some questions and maybe the solution ???
* both carbs were "new reconditioned" - now I did notice in the weekend some seepage (really minimal - not dripping or anything) from the butterfly shaft on the rear of the back carb
* The new spark plugs are not bosch - but I do have the washers on them - I will take the washers off them and reinstall them. I think they are NGK - but dont remember what model - platinum some-thing-er-rathers (the ones in the picture are now the spare set)
* the heat riser counterweight is the later model round one - is this the clincher ???? (Now I do know that I put the metal gasket inbetween the rear exhaust manifold and the inlet manifold the right way up as I've already read about that trap!)

Unfortunately it will now be 2 weekends before I get back to the car. I will then take a close look at the heat riser, do the plugs, the new dizzy, coil, ballast resister. I will try and do them one at a time so I know what the problem is. If it turns out the be the heat riser - well I will be super happy its fixed - but damn annoyed at all I did to fix a simple problem :roll:

Stay tuned !
Author:  SlantSixDan [ Tue Jul 25, 2006 2:03 pm ]
Post subject:  Modifying late heat riser
Quote:
One more thing, if you run Dutra dual front exhaust, then you have only half the exhaust pressure (3 cylinders) to open the "flap".
Do you have to compensate for that?
That's a very sharp question. The round counterweight heat riser system was designed to remain in "heat on" position up to a vehicle speed of approximately 30 mph (50 km/h). This was done for emission control reasons (hotter intake manifold = more thorough vapourisation of fuel). But, if we take away half the exhaust gas hitting the flap, then we greatly increase the vehicle speed below which the flap will be putting exhaust against the floor of the intake manifold...maybe to 60mph (100 km/h) or higher!

Doc and I have been kicking around ideas for altering the round counterweight to restore early-type operation (heat riser goes to heat-off as engine heats up, regardless of vehicle speed). We'll see how these ideas pan out, stay tuned.
Author:  SlantSixDan [ Tue Jul 25, 2006 2:07 pm ]
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Quote:
removed the tube from the valve cover breather to the front air cleaner
Put it back. It's not mission-critical, but removing it won't have helped anything and will make your engine bay get dirtier, faster.
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both carbs were "new reconditioned"
"Remanufactured", bought at a parts store?
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I did notice in the weekend some seepage (really minimal - not dripping or anything) from the butterfly shaft on the rear of the back carb
Loose/sloppy throttle shaft bushings. Typical of "remanufactured" carburetors. You won't get actual dripping unless you work at it (repeatedly operate the throttle lever with the engine hot and not running, or heat it up hot enough to boil the gas in the bowl, then shut it off and let it sit).
Quote:
The new spark plugs are not bosch - but I do have the washers on them - I will take the washers off them and reinstall them. I think they are NGK - but dont remember what model - platinum some-thing-er-rathers
Try to get ZFR5N next time. They are better and less costly than Platinums.
Quote:
the heat riser counterweight is the later model round one - is this the clincher?
Try unhooking the spiral spring that's sandwiched between the counterweight and the manifold casting. This can be difficult, just pry/push it off its post with a screwdriver or two. Manually rotate the counterweight fully counterclockwise as viewed from the front of the engine bay, and see how the engine reacts.
Author:  ricki [ Sun Aug 13, 2006 8:10 pm ]
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An update (this is turning into a blog!). Tried a few things, but still the same symtoms. Every change does make a small difference to the car overall but has not fixed the problem. Things done over the past week:

I removed the counterweight spring from the pin that holds it on. When I rev the car the counterweight now turns fully counterclockwise (closes).

Installed a new coil (flame thrower 2).

Removed the washers from the sparkplugs.

Swore and cursed (this didnt make the car run any better, but I felt pretty damn good!).

On saturday morning I drove the car to a swapmeet that was about 25 miles away. Drove there in the morning - car was perfect. 4 hours later drove car back about 20 miles then stopped to shop for an air compressor - car was perfect. 20 mins later got back in the car and there was my problem rough idle and running rough in the lower revs, especially off the line and keeping an even throttle. Heavy accelerating is fine. I can basically replicate the problem by driving the car 5 mins +, stopping for 10-20 mins then starting it again. (This is in cooler weather, it hotter weather - 90+ - It will do it without stopping). It does appear to be a heat sink thing. The carbs are very hot to touch. My water temp still seems ok (I have a new 180 deg thermostat in the car).

Next on the list is the new distributor (might as well stick it in rather than leave it on the shelf), then spacers inbetween the carbs and inlet manifold to try and isolate them from the manifold heat. Stay tuned...

cheers
ricki
Author:  64'4$peed [ Thu Sep 14, 2006 6:42 pm ]
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Any luck Ricki? I am planning on running the same intake and exhaust only with the carter 1bbls. Keep us posted.
Author:  ricki [ Sat Jan 13, 2007 12:44 pm ]
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I know its been a while but heres an update.
I put some heat shields under the carbs (made from 3/4" thick delryn or phenolic (sp?) stuff). They keep the carbs a lot cooler but dont leave enough clearance for the front aircleaner, so I will get some 1/4" thick stuff and make them again.

I changed the fuel line to braided stainless fuel line.

I put on a brand new distributor and cap. Checked the gap on the pertronix plate.

New coil (msd blaster II from memory).

Put some heat shielding underneath the front intake, right above the dutra dual. The dual runs really close to the bottom of the intake so I was trying to keep the intake cooler in that area.

Problem still the same. Just before I put it under a cover for winter I found that when the problem occurs if I rev up the rear carb a little, the motor revs up. If I rev up only the front carb a little it stutters. This lead me to think its the front carb (of course its a reman'd carb!) ?

Last week I finally pulled apart the front carb and the metering block is warped. I replaced it with a true one from a spare carb. Now its too cold, wet, icy, snowy to take the car out to see if that fixed it or not. But there it is, an update to the most infrequently updated thread on the site !

Other things for the car are to finally get around to install some new speakers using the plate that Jerry ( 74 sport) made for me and put on a nos superior 500 wood rim steering wheel. Lets see how long it takes me to get those done!
Author:  ricki [ Sun Apr 22, 2007 10:02 pm ]
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Update!
Well I might have finally sorted this out!

The metering block replacement made a big difference. Yesterday I warmed the car up, adjusted the front fuel mixture, took it out for a drive that would have reproduced the hesitation problems and didnt suffer them. I drove the car about 20 miles, parked it while I bought some tools, got back in, drove home - all was good except the timing just seemed a little retarded. Advanced the timing today, took it for another drive and all was good. Dare I say it GREAT !

Bottom line, the front carbs metering block was the main culprit and heat was a factor (may still be as its by no means "hot" here yet). The front carb is the second "remanufactured" carb that I had on there and confirms other posts about remaned carbs. Its one of those things though, sure it would have been great if the first carb was spot on, but I have learnt alot doing this and the car wasnt harmed (I dont think).

Everything helped in small doses (new dizzy, coil, condensor, plugs, hoses etc taking off the spring for the heat riser, heat barriers, fuel line mod, also little things like noticing the throttle return spring was rusty and having it snap when I went to remove it! you know small maybe life saving items :oops: )

I now want to address heating/cooling under the hood, redo the fuel line mod I have in place and undo some of the heat barrier bits I fabbed and installed along my great journey of discovery! Oh and when thats all sorted out I have the erson cam kit, just to keep me on my toes :roll:

thats all for this thread, I'll be out driving and not in typing...

cheers
ricki
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