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Hey Joe, Sorry to be so long getting back to you but wanted to thank you so much for your help and advice. Will give it a go and let you know how it works out. Dumb question for you. If this works and a new HEI replaces MISAR a new temp sensor will replace the existing MISAR temp sensor but is there any problem or issue with removing the crank sensor as well. Is it simply a matter of unbolting it and gathering up the wiring and bundling it up somewhere out of the way or will a cover plate of some sort be required?
Picked up my reman/rebuilt carb today from the local carb re-builder and it looks pretty good. I was especially pleased about the fact that the casting has the same number as my existing carb and the new unit is not only really clean (except for one small part) they even go the trouble of replacing shaft bushings and resurfacing to ensure everything fits tightly. Even the needles have been set for a decent starting point based on their experience with this engine/carb combo.
So here are some pictures of my new carb
When I got the unit home and had a closer look at it something struck as rather interesting. As you can see from the 1st photo above there is a plate indicated with a yellow arrow between the primary and secondary.
So I went a checked the photo of my existing carb posted earlier in this thread and lo and behold that plate is missing and I never even noticed it before.
Here is a picture i took of the carb in the car about a week ago and as you can see no plate.
To determine whether this should be there I found a photo posted by Jaunty of his carb from another thread and sure enough he has the plate as well. Here is the pic of his
Now here is the dumb question. Could this missing plate in any way contribute to the problems I have been having? I have no idea why it would so maybe someone could explain its significance and what its absence might do.
Last edited by ByronF; May 15th, 2019 at 07:09 PM.
When I got the unit home and had a closer look at it something struck as rather interesting. As you can see from the 1st photo above there is a plate indicated with a yellow arrow between the primary and secondary.
So I went a checked the photo of my existing carb posted earlier in this thread and lo and behold that plate is missing and I never even noticed it before.
To determine whether this should be there I found a photo posted by Jaunty of his carb from another thread and sure enough he has the plate as well.
Now here is the dumb question. Could this missing plate in any way contribute to the problems I have been having? I have no idea why it would so maybe someone could explain its significance and what its absence might do.
Yes, my carb does have that plate. Here's a better photo of it. I took this photo after the rebuild. I don't know what that plate does. In the Rochester carburetor book I have, that part is called an "air baffle."
If you might want to one day resurrect your old carb, these are available for purchase separately. This site calls it an "air horn baffle."
Don.. based on the Quadrajet manual that I was bale to track down your suggestion is exactly why the plate is there. For any one interested I am going to try and upload a copy of the manual that I found. The reference to the air horn baffle is on page 8.
I have tried to upload the pdf file of the manual but for some reason it is not going thru. Any ideas on how to get it to upload?
Last edited by ByronF; May 20th, 2019 at 05:27 PM.
Just thought I would provide an update on my Toronado. Got it back last Friday evening after a very interesting week. As you know had the choke stove replaced as there was a hole in the old unit. Found a real GM new unit not far from here. The old guy in the parts department almost fell over when we asked for it. He hadn't sold one in years and was on many occasions tempted to throw it out.
Also as you saw from the pictures got a shiny reman/rebuilt carb with exactly the same casting number as my old carb.
The final piece was the shop who is also a local NAPA dealer was able to locate a Delco reman/rebuilt distributor for 77 Olds 88/98 with the 403 motor.
The distributor was installed following Joe's advice and the Temp sensor was replaced with a single wire unit hooked into the dash light.
I really like this new shop I am dealing with. They have a fellow who enjoys working on these old cars and even better they have no problem with me poking around under the hood with him. Heck they even think its great and have no problem with me bringing in the parts. The joys of a small town.
So we thought we were all set to go and headed off for a test drive. The car ran better but was still a little off and there was a miss. So back into the shop for a bit more tweaking on the carb and timing. After a few attempts we determined that 12 degrees was the magic number and not the 20 degrees specified in the manual. No idea why this is the case and maybe it just has something to do with the change in distributor with both mechanical and vacuum advance.
We also heard a clacking sound which I was initially concerned might be a lifter but we eventually tracked it down to the EGR valve just banging away. So we pulled the vacuum line and plugged the hose and the sound disappeared. Maybe that is why I discovered it was plugged last fall and then proceeded to clear the plug and hook it up.
Off we went on another test drive and all these little tweaks seemed to do the trick and the car ran fine. So I am now back in operation and even went on a few little test drives over the weekend with no problem.
So now I have the MISAR distributor and the temp sender out of the car and in a box and am trying to see if I can remove and salvage the crank sensor, none of which I need any longer.
In looking more closely at the distributor i noticed some wiring where the plastic casing had worn away and also it appeared that somewhere along the way someone had spliced the wires. Wonder if that had any bearing on the problems I have been having lately.
Wanted to say thank you to everyone for all thoughts, ideas and suggestions in helping me work through this latest problem. Hopefully now that is behind me and I can get on to working on the good stuff like restoring the body side moulding, pinstriping, fixing the exhaust with new tips and new mufflers, updating to a factory radio with bluetooth and getting the power antenna working again.
Byron,
20* of base timing? That figure is likely additive...10-12 base with 8-10* vac advance included. I can't imagine the timing tab on the crank has more than 12* marked on it.
Try 12* Base. (sounds like your there already). See how many degrees the vac advance can adds. Then rev it up to see how much more the centrifugal advance adds. At say 2600 RPM you should see a total of 36-38* of total timing. Give it as much total timing as it will tolerate before it knocks(preignition). I keep my distributor loose enough that I can tweak it either way when road testing. Then record that setting for reference.
Adjustable(travel, don't buy an adj rate can) vac cans are available and will allow you to custom tune the timing at idle. You'll need an adjustable backset timing light to see the total. It should be all in between 2500-2600RPM. The smog era distributors centi advance needs to be tweaked for performance. I can't remember if the springs n weights are too light or too tight on a 78. Likely too tight. Weight, spring and stop kits are available. You can use two different rate springs to achieve the end goal, keeping similar weight sets of course for balance.
A faulty or leaking EGR will show as a rough idle and/or off idle hesitation on throttle tip-in. It should not be fluttering. It should transition open/close smoothly as the throttle is opened and closed. Check its vac source for obstructions, collapsed, cracked hoses etc...
You may still have a vacuum leak. If the air/fuel screws need to be backed out more than 2, 2.5 turns to achieve the highest vacuum reading this indicates a vac leak somewhere.
Don't rule out a bad or wrong PCV valve. Disconnect and plug off each vac circuit until the roughness goes away. That will locate the leak.
Is there a thermal flap in the exhaust manifold(s)? If yes check it to see if it's stuck.
Steve
Drolds, thank you for the information and advice. In terms of the timing I think we have what you suggested which is 12 degrees base with 8-10 vac on top of that. My service manual stated 20 degrees at 1100 but then that was for the MISAR system. But that is where we started and soon realized it wasn't right with the change in distributor so we dropped it. The timing tab on the crank on the Toronado is actually calibrated up to 24 degrees. Again I suspect that this was MISAR related where the distributor was simply an on/off switch for the analog computer which provided all the timing based on fixed starting point. At least that is my understanding of it.
All the vacuum hoses for the EGR were replaced and even the check valve was tested and everything was ok. Previously someone had blocked the vac line to the EGR with a screw and even installed a second check valve that was completely blocked. These 2 items were cleared and then the EGR started banging like crazy. So for the time being I have unplugged it and plugged the line with a golf tee and everything is quiet. Wondering if the EGR itself is broken.
The PCV valve has been checked a couple of times and seems to pass the thumb test. Virtually all of the vacuum lines have been replaced. The only ones that were not changed were the vac lines running to the MISAR controller but now that we have disabled it by going to a regular distributor it probably would be a good idea to find where they hook in and cap those connections.
I don't know if there is a thermal flap in the exhaust manifold. will have to check that out as see.
Thanks again for your input. You have given me some more things to look into.
Your welcome,
Keep in mind a "will fit" PCV may have a different spring and orifice rate than what is recommended for your application.
Another note for rough idle: Today's gas doesn't play well with carburetors. It can boil at a lower temp verses 1978 gas. A solution is to set the carb float slightly lower in the bowl. This prevents burble over. You can see this by looking down the carb at hot idle. If you see gas spitting out of the orifices above the venturi tubes the float should be dropped 1/32" or more. Also, steer clear of ethanol laced gas. Ethanol-free is all I run in all carbed machines.
I am with you on fuel. I only run premium fuel from one of two sources, (either Shell or Ultramar) - which do not contain ethanol. I am very leery of ethanol because my car sits in storage for 5 months of the year due to winter. So before it goes into storage I try to run the tank as close to empty as I can before topping it up and adding fuel stabilizer. Good tips to know about PCV valve spring rates and float adjustment, Thank you again.
Fortunately the car is running great right now with a very smooth idle. If anything needs a little tweaking it may be the high speed idle with the choke on. Seems a bit high to me. But on the plus side the choke is working well, it closes by depressing the pedal about 1/4 way on the first shot and it fires right up very nicely.
What I am now trying to find the answer to is can I remove the crank sensor from the old MISAR system. Is it just a bolt on arrangement or will I need some sort of cover plate. From what I can see from under the car it looks like it is just bolted on, kind of like an alternator or compressor are just bolted on. Any thoughts or advice on this?
May 15th, 2019, 04:57 PM
