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Post by lockie1994 on Dec 5, 2012 21:40:45 GMT 12
just got chevette going again was adjusting tappets and noticed inlet manifold gets VERRY hot i measured it with a laser thermometer it read 102 deg has anyone successfully blanked these off?,
I tried blanking if off but it seemd to mess up my fuel mixture?when i take off from 80kph it missed heaps now (without the heater ports blanked off )will put new plugs and leads on see if fixes the miss but would like to know if anyone has done this before,
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Post by gordo on Dec 5, 2012 23:04:16 GMT 12
I did for exactly that reason on the modified engine - what I did was to partially tap the ports in the head and grind some of the thread back on a bolt until it would screw in level with the top of the exhaust port, then it was cut off, a slot cut in it and screwed into the head firmly before starting the porting.
Even with a direct cold air feed from the front of the radiator mount bulkhead, it was fine even in very cold weather (icing on the windscreen, front of the car and lights) - however, part of that would have been down to numerous other mod's that had been made, including a richer needle. I think it may even have idled better when dead cold, without choke, as well!
Bear in mind that at it idle, it may be a little hotter as the incoming air is cooling it down less. It's primarily to ensure the fuel is properly mixed by heating any fuel droplets so they evaporate well for good low speed response and fuel economy.
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Post by lockie1994 on Dec 6, 2012 17:54:02 GMT 12
how do the std 1256 engines idol mine just will not idol smoothly iits got new points,condenser,coil,HT leads,spark plugs and all adjusted to spec but just wont idol smoothly not to shure why i have messed with carby made richer leaner ect it idols better when i lean it a bit but then wont drive without missing as its running to lean ? cant get my head around it haha
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Post by gordo on Dec 6, 2012 20:41:09 GMT 12
Wear in the distributor bushed and/or the vacuum advance/base plate can cause problems - why I recommend rebushing the housing it there's discernabvle play from side to side but the base plate can be a bit more of a problem, usually you can tweek it to take the play out, though, if you haven't spare parts for making up a good combination.
Easiest way to get an idea if this is an issue is using a timing light as a problem with irregular timing will show up as a mark that moves around.
I use a go-not go system for setting the points gap, BTW, carefully bringing it to the maximum opening and then using the size guage i want and the next size down - the smaller size should slip through without drag and the correct size should just have a very light drag.
As for the carbie, did you do any work on it, as I would first think the float level was incorrectly set, if it is correctly set, and the needle is in the correct position - O ring flush with the bottom of the piston - I'd gently screw it right in until resistance is felt then screw it out 2 turns as an initial setting. Then I may try adjusting it slowly one way or the other - in leans it out and gives a sharper misfire or rough running and screwing it out gives a more muffled misfire, rough running and sometimes a little puff of black smoke. if you have trouble turning the mixture adjuster, or if it's a later model carbie with the raised casting around the nut, you should still be able to buy the tool for the adjuster nut - I got mine from Repco quite some years ago.
Other carbie issues than can give problems are the diaphram if it has a pin hole somewhere and the hot idle adjustment - this is intended to introduce a little extra air when very hot, but sometimes people play with it and introduce problems (it's the bi-metallic stip under the white cover with a couple of retaining screws, IIRC) - if it has been touched, I think the default is to increase the tension so it doesn't operate.
You're unlikely to get it perfectly smooth, but a good steady idle is certainly possible.
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Post by lockie1994 on Dec 6, 2012 21:51:27 GMT 12
Timimg light flickers a small amount say 1_2mm and I completely stripped cleaned and re built carby fitted new leads and plugs today missfires gone and I.leaned it off a touch seems to idol better but not perfect yet it will be ok at a fast idol but roughat a normal idol speed
Havent thrashed it yet due to still running in
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Post by gordo on Dec 8, 2012 14:39:15 GMT 12
Should be right for a while, hopefully, then.
Did the carby still have the little guaze filter behind the needle valve seat - it would often clog up and most people seemed to just remove it and run an in-line filter.
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Post by lockie1994 on Dec 16, 2012 20:42:01 GMT 12
i thing i pulled gauze thngy out when i re built carb it has got an inline filter in her now also the engine now seems dull and not as peppy for some reason i wonder if fuel psi is getting low?
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Post by gordo on Dec 16, 2012 20:49:12 GMT 12
If you set the float height correctly, set the needle in the correct position and the idle mixtuure is set correctly, it should be fine.
The only other thing, that I can think of at the moment, is a pinhole leak in the diaphram - there are little tabs and recesses that are used to correctly align the parts as well, perhaps in one of those was also incorrect?
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