I'll check the numbers on the battery using this test and see what it shows. The in gear idle is fine until it gets to 180 and then the problems set in. I'll check the position of the rods after its get warm in gear too. It will be Saturday now before I can get to it but I will keep you all posted with what I find.

i'm really interested to hear the outcome
my loot is on the alt giving you the trouble
i just sort of went thru this problem
with a little different set of circumstances.

when the car was started in the morning below 30 degrees it would run like crap with a real bad idle until it warmed up, the lights were also dimming.
once warm, it would run great for the rest of the day.(100 plus miles a day)
after some head scratching and thinking of many reasons like
computer,grounds,coil,bad wiring harness, ect..
for some reason i had a extra alt on the shelf and my gut said what the hay to change it out..
and guess what?
it hasn't happened since..

I stopped at Costco for a battery and they didn't have any group 27s which is what I am finding is the correct battery for the car. Could a 24 be used in place of the 27 without issue?

i believe it will work,but it might not last as long..

If I remember correctly the 24 is simply shorter than a 27 so you will have extra room on the long side of the battery box, post are in the correct position. Typically back in the day a 24 was a Chevy battery, 24 F was a Ford (swapped post position) and 27 was for Chryslers if memory serves.

Ford used the 27F and the 24F, Mopar the 27 and 24.
Top post GM batteries were 22F, 24 and 24T(tall 24), AKA Delco Y55, R59, R69.
The 27 isn't hard to find, it's the 27F that's not as common.

I've been using a 27F as a replacement for the 31 that came in my tractor. Last week, the Walmart 27F that I had in it died, so I went to get another. Neither Waldoworld or Sams Club had a 27F, only 27's. My cables are just long enough I could get by with a 27 so I bought a Duracell 27 from Sams. Cost was $101+tax.
If I couldn't have been able to make the 27 work, I was going to use the Duracell 24F. The reason I was going to try the smaller 24 is the Duracell 24 has a CCA rating higher than many 27's of other brands.

Go with a good group 24 and forget the heavier 27, it will start a 451, especially if you have a modern starter.

If you think all Walmart or other box store batteries are inferior, I've used Walmarts batteries for 25 years. Most last 50% longer than the warranty period. The best one I had was in my '68 V200. Bought it in 2001, it died last summer, 15 year life span.

I picked up a 27 tonight @ O'Reilly's. Its slightly larger but not much and has another 170 cranking amps over a 24. I had the old one tested and it was bad, no surprise there. Going to tackle it tomorrow and do the test for the alternator and swap the boxes and see what happens. I'll send out the updates.

all the wallyworld battery's i have bought over the years were made by johnson control. they have lasted way past the warantee as was stated. a couple things worth mentioning though, in my opinion. get the biggest CCA and reserve cranking amps you can in the size you need regardless of what brand and place you purchase from, and go through the rack and pick out the newest manufacture date that is stamped [usually on a separate sticker, but not always] on the battery you choose.

OK, so I put the new battery in, the diode test shows the alternator is fine. I tried both a chrome box and orange box, same idle conditions using both boxes. I got the best idle highest vacuum with the mixture screws out 2 turns. The idle is better but not great still. I didn't have a helper today but I opened the rod covers and for the most part the rods stay down and don't bounce while in Park but when the idle takes a dip and idles down they bounce a little. I can rev it a little and they instantly come up as you would expect. I stretched the springs a little to make them longer and it did help some by doing that but I feel the idle could be more consistent. What do you all think now?

I would blast the idle mixture ports with starting fluid & retry it then I would block the metering rods up with something under the springs & retry it.

I gave it a blast of carb cleaner. So you are saying block the rods from coming up, thus keeping them in the down position with no chance for upward movement?

No, block them up so it is on the power circuit. EDIT When working in that area I take off the AP rod to keep from kicking raw shots of fuel into the intake while I am manipulating the throttle, not a dealbreaker just my OCD talking. its gonna be interesting to see what it ends up being.

OK, I see.

You sprayed into both of the idle mixture ports with the thin red straw?

Yes. I'm not sure I follow you on what taking it off the idle circuit by raising the rods is going to tell us. My other thought is to bump the timing by 2 deg and see what that does. If it doesn't detonate I don't see what it will hurt. I guess its a chicken or egg situation. Is it idling down because the rods are bouncing or are the rods bouncing because the idle drops?

I was thinking that it might be lean cuz of a partial blockage and or vac leak & being on the power circuit might temporarily straighten it out if that be the case.. bumping the timing wouldn't hurt either & I would go more than 2 deg.

The rods are fairly consistent with little to no movement when in Park or neutral or but will bounce when in Drive with no chance of staying put at all. I have not bumped the timing yet so that will be next. I raised the rods and held them up with no change in he idle quality. I am going with the assumption that in no way is it lean at idle. Just got back from a 45 mile drive and the car runs absolutely great other than the idle. No flat spots or laying down in any gear at all past 6500.

Unless I missed a prior post from you - no mention of timing fluctuations when in gear, and no mention of vacuum fluctuations when in gear. Hold the rods down when hot and idling in gear and see if things smooth out. ( take the springs out for this test ). Rods up = more fuel ( you don't want that at idle) - you state it runs down the road great with no surging or misfire that means you should be close on your mixture while driving - at idling the surge could be the rods popping up and or the timing fluctuations from the change in engine speed. Putting more timing in it may help too as long as you don't get detonation.

what is your initial? you might bump it up to 18 or so & see how it does.(I run 18 on a dead stock 85 318). I would blast out the carb idle ports. we're getting closer to a fix.