425 engine techs please.

[TJ Hopland]

Just had another thought,  did you look close at the carb to manifold gasket?  Seems like I remember one of the gaskets in the kits having a couple of slots around the primaries that would leak on the 425 intake.  Memory sort of blurs but I do remember there were some gaskets that did not work on some intakes.   

[Otto Skorzeny]

I live in Atlanta and we had 58 days straight of above 90F weather and high humidity that pushed the heat index to over 100 most of those days. I've basicly stayed in the house all summer.

The last couple days it's been in the high 80s.

[R Schroeder]

TJ - OTTO- I have friends that live in both of your states and they are not happy with the heat.
Two friends in Mechanicsburg , PA. One friend in Alanta, GA. All have invited my wife and I to visit this year, but the heat is no fun to travel in, so we didn't make the trip this year.
One friend from PA, did come here, but had to cut his trip short.
This has been the worst summer that I can remember in a long time. We may get 2 weeks in Aug that are hot and muggy.This year it has been all summer.
I live about 35 miles west of Milwaukee , Wi.  Milwaukee is all over You-tube this year. They have had 6 to 8 inch rain storms all summer. Flood videos all on You tube........ha

Anyway, back to the carb.  I think I remember the slots in the base gasket of the carb. But , I did spray little spurts of carb clean at the base to check for leaks while it was running. There were no leaks there.

Worked on a lot of cars in the last 50 years, but this one has me stumped. But , I will find it..............ha
Roy

[TJ Hopland]

If I am remembering the correct intake manifold I think the 425 has raised sections around the bores and screw holes but is otherwise open underneath so if you used that gasket with the slots it could be open to one of those gaps underneath.

[Otto Skorzeny]

That wouldn't be a bad idea but I think your advance isn't working right. Perhaps the engine is already timed too far advanced? Driving with the advance disconnected should normally have resulted in a decrease in performance at WOT.

[R Schroeder]

Well, I didnt do a WOT. I just went through the sub-division. Took off about 10 times and it was nice and smooth.
I'll play around with the timing tomorrow I guess. The decal under the hood says 22 degrees before TDC @ 1400 rpms. The repair manuals say 18 degrees . Going down to the 70's and very low humidity.

[The Tassie Devil(le)]

I'll play around with the timing tomorrow I guess. The decal under the hood says 22 degrees before TDC @ 1400 rpms. The repair manuals say 18 degrees . Going down to the 70's and very low humidity.  

Ah ha, I see the problem.   Timing at 70 Degrees is way too far advanced.   And too much humidity inside the engine bay will really hurt performance.

Bruce.

PS.   Sorry, couldn't resist.

PPS.   It is the time the website uses.   But, it is 9.02 AM tomorrow down here.

[TJ Hopland]

You say you have the 78 supplement manual?   Page 6D-6 has the specs for both mechanical and vac advances.   Most of the aftermarket vacuum cans have way too much movement in them, sort of a one size fits all.   Some of the 'performance' versions come with or you can get a little plate to limit the travel.   On stock ones I have used a washer under one of the mounting screws to limit how far it can return to.  This then does change your base setting but that is easily corrected.

Mechanical is only 9.5* and all in at 1450 for most models.
Vac is 14.5* at 20" or 29* at 20" depending on which dizzy you have assuming non ca non altitude non efi.
Some are as low as 5.5*
That 29 is a lot.  I dont think I have ever seen one that has that much but that is a non ca, non altitude, non efi, "C" car.   If the carb was not matched to that dizzy I could see issues.   It may be worth looking at the carb numbers and dizzy numbers in the manual and making sure you have the right combo.


And to Bruce, thats 70* F, perhaps it would work better at what about 20*C?    Does C stand for crank or cam?

[The Tassie Devil(le)]

And to Bruce, thats 70* F, perhaps it would work better at what about 20*C?    Does C stand for crank or cam? 

Yes, that has to be it.

But, seriously, all timing settings should be done with the Vacuum off and plugged.

Bruce.

[R Schroeder]

TJ - I'll have to read all the info tomorrow. I must admit , I'm a little lost with your posting. But ,it will sink in one day.
Yes I have the 78 book as well as the 77 book, plus all the body and parts books. Full house.
Carb is correct one for the engine. Non Ca , non efi, non altitude. I'll have to check the dist, but it is the one that came with the car.

BRUCE - what can I say. 70 is to much...............ha

[TJ Hopland]

Just look at page 6D-6 and it will make more sense.  There are charts that tell you what the advance should be at given rpms and inches of vacuum based on the distributor model.  You can then confirm that it is working as it should be. 

I was just thinking it was odd that there was such a difference in the vacuum specs for 2 different distributors.  The mechanical is almost identical for the two models but for some reason one has a heck of a lot more advance in the vacuum.   They both show as pretty normal applications so I am not sure what the reason would be.  I could see something crazy for altitude or ca but its listed as a standard car 'C' body car so its not like one is the commercial chassis.

The reason I was asking about the carb is with that huge of a difference in the advance spec the carb would have to have quite a different tune to it and I could see a stumble if they were not a match.   On my 'normal' car the distributor vac went straight to the manifold.  I wonder if perhaps that distributor with the 29* spec went to a port on the carb like many other models and years did.   On page 6D-5 there is a note on that model that says 'denotes later models' so it may have been a mid year change, perhaps what they did in 79?  I dont have a 79 book. 

[TJ Hopland]

Ya its in the book for what appears to be the later 78 regular C car distributor.   

If you set the timing by the plaque at 20* at 1400 that means the mechanical 7.5-9.5 should all be in so that would in theory mean that you would be at 10.5 - 12.5 at idle.  It then says that at 20" of vacuum (which you had unhooked when setting the timing) that it will pull in another 14.5 or 29 depending on the model.  So that means at idle with everything hooked up you should expect to see around 25 or 40 depending on the model.  25 seems pretty normal to me, 40 seems like a lot. Seems like I have had some engines that idled in the low 30's but 40 seems like a lot.  I really have no idea why they wanted it set at 1400.  They had to come up with a new timing marker and everything to do that.  Gotta love the way they they were trying to meet emissions in those days.   

Now looking at the vacuum diagrams the normal cars the distributor connects direct to the intake, its got a nipple right there on the #2 cylinder intake runner IIRC and its the only thing connected there.   The rest of the cars CA and Altitude show the distributor running through a thermal switch and getting mixed up with other devices.  My guess is the switch is located sort of under the dizzy pointing forward sort of hidden by the ps bracket.   If yours is or was one of those cars there could be issues with that switch or other devices connected to it.  I would also imagine that the carb and distributor itself would have a different tune to match those devices.  If any of that stuff has been altered or is not working you no longer have a matched system.

[R Schroeder]

My vacuum runs directly to the manifold. No switches.
I guess I'll do what the book says on the timing , and get back to you on what I have.
If it isn't advanced far enough ,would this cause the flat spot ?
Decal says 22 degrees before TDC. I think when I last checked it , it was 20 degrees before TDC.

[TJ Hopland]

Just look at the charts in the book and confirm that both the mechanical and vacuum systems are doing what they should be doing.   You will need a hand vacuum gauge / pump to test the vacuum portion and either an advance timing light or more marks on the pulley to check it all.    Those hand pumps are really cheap now.  Harbor Freight has one with the brake bleeder option for something like $15.  My guess is you will find that either the mechanical or vacuum is not working in its proper range.

[R Schroeder]

OK, now I understand where you are getting the controlled vacuum from. I need the pump to do the set up.
I'll have too look into one of those.
Were getting up to speed now. I'll check with my local NAPA dealer tomorrow.

[TJ Hopland]

Looking at Napa Online

I find one similar to the harbor freight one but does not include the can for doing brakes for about $55 and its in stock at my local store so there is a good chance your store has one also.  Looks the same as the one I bought at sears years ago. 
Part number is BK7002335


But if I was going to spend that much (and had time to wait assuming its not in stock) I would spend a few more bucks and get this set because it has more uses.     
Part number is BK7003882   Price shows $70

[35-709]

   You'll have mulch more fun working on the car!   
Geoff N.

[TJ Hopland]

Better she wants wood chips vs. to put you in a wood chipper. 

Not sure if they still sell em or what name they are under now days but several years ago I bought a 4 stroke 'weed eater' that you could attach various ends to.  Mine was under the Ryobi name but I know I also saw them under the Sears name and seems like I have recently seen them at one of the large home stores under yet another name.  Anyway for that rig I got a sawzall on a stick attachment.   It will do up to about a 3" limb.

[R Schroeder]

Going out tomorrow again to look.
Looks like I wont get back to the car until Friday.

[Tim Groves]

Sounds like the APT (adjustable part throttle) metering rod is out of adjustment.  When the rebuild was done did the rebuilder reinstall that metering rod in the same position?  It is adjusted like idle screws, but is under the air horn, so the top has to be removed to adjust it.  They were factory adjusted, and it is a pain to adjust by trial and error.  The late 70s Quadrajets had these APT metering rods.  Tim