Working on our 1969 Firebird Conv

[Goldfire]

We recently purchased a 1969 Firebird 400 Conv. Nice car and we have posted some oictures on the social section of the forum. The car is in really good shape, but we want to make some improvements over the winter. There are 3 nagging problems that need addressed. We have always had Ford's but decided to sell a 57 Fairlane Conv and go over to the bright side!!!

Anyway, issues:

1. The car is cold nature and the choke will not stay engaged. The thermostat is the one bolted to the manifold. Do these wear out and cause the choke to be erratic??
2. Once we get the car warmed up, there is a big difference between idle at park and idle in gear (about 800 RPM). I know this is vacuum, but can you help direct us where to look??? Are there usual suspects???
3. Maybe this is related to #2. When in park, shifting to reverse or drive, there is a huge clunk and violent jolt, actually squealing the tires. I have not been under the cat, but could the modulator valve be bad, leaking serious vacuum, creating the issue in #2????

Thank you so much for your patience. Since we are more familiar with Ford's you help is much appreciated. Lynn

[bri2203]

The choke and thermostat are not related. You might want make sure you have a choke on the carb first and make sure it is connected properly.

What kind of trans is it? Powerglide 2 speed or turbo 350 3 speed? It sounds like a Powerglide.

[ezcruisn71]

Issue #1 There is a vacuum operated Choke pull off that will open the choke once the car is started. This could be improperly adjusted causing it to open to much or the Thermostatic choke could be defective.

Issue #2 There should only be about a 250-300rpm drop when put into gear. It depends on how radical your camshaft is in that engine on how much the rpm will drop when you put it in gear. If the person that built the engine put a radical camshaft in the engine without going to a higher stall speed torque convertor then this could be the issue. It could also be your ignition timing is not set correctly or you may need to adjust your idle mixture screws on the carburetor.
Put a vacuum gauge on the engine and let us know what the vacuum is at idle in park and then when it is in drive.

Issue #3 If you get the idle speed issue resolved then it should take care of some of this problem.
If the vacuum modulator valve is bad then it should not effect going from park to drive. You will notice a bad modulator with
excessive smoke out the exhaust and when the transmission is shifting from 1st to 2nd gear. The shifting will be very harsh.
You can remove the line going to the vacuum modulator at the intake manifold and cap the fitting and try shifting the car from park to drive and see if it goes away, but I don't think it will.
As far as the clunking noise goes make sure you also check the U-Joints on the driveshaft for excessive play.

Here is a helpful web site for carburetor adjustments. Every car is different so please go by your service manual for the
actual adjustment specs.
http://arrc.epnet.com/autoapp/8977/8977CH05_ADJUSTMENTS.htm

[ezcruisn71]

I know I have a book on that carburetor for tuning it. I think the book has over 100 detailed pages in it. I will have to look around the house for it. That book is over 20 some years old, but I don't think I will need it any more.

[Goldfire]

Brian, thanks for the response. The trans is Turbo 350. I agree with making sure the choke is connected properly. I will take a look.

[Goldfire]

Rick, thank you for the detailed response. Lots to review. I will be in touch.

[ezcruisn71]

Well I went home and went though my manuals and here are the adjustment specs. for your Carburetor. Just match up your model number on your Carburetor to the number that I scanned from the 1969 Pontiac Carburetor. This is a PDF File. I don't know how to load it on here.
So I loaded it here. Click on this site then click on the download button at the bottom and you can see the adjustments for your 4 barrel Carb.
http://pdfcast.org/pdf/4-barrel-carb-specs

[Goldfire]

It has been a couple of weeks since this thread was posted and we have been able to implement many of your suggestions. THANKS AGAIN FOR ALL OF THE HELP!!!!

We were able to get the choke to operate properly. The timing was way off...it was so far retarded, I am surprised the car would start at all. The idle mixture scews and overall idle setting were also way off. With these items fixed, the car runs great!!! We were able to get the idle speed varience from park to drive to be withiin the 250-300 RPM parameter suggested. This allowed us to reduce overall idle speed (down to about 1000RPM). With this lower speed, the "clunk" when shiting into gear is greatly reduced to a managable amount...another small victory.

We noticed that in either park or drive there is still an RPM drift of +/- 200 RPM. This is causing us to keep the overall idle speed at 1000RPM. I think this is still too high and suspect a vacuum leak. We did the starter fluid spray test and noticed engine surges when spraying near the base of the carb. So we bought some new carb to manifold gaskets but have not had time to put them on yet. Hopefully this will help control the idle drift.

One other unsolved problem, it takes the car about 5 minutes to warm up before you can kick off the fast idle. If you kick it off before it is properly warmed...it will not stay running...once warm it is great!!! We noticed that the PCV and heat tube to the carb were not hooked up...so we purchased some parts and hooked these items up. I was hoping the extra heat from the tube would improve warm up time but so far not yet!!! We will keep working. In the meantime, when attaching the heat shield to the exhaust manifold, we notice that one headbolt had a stud for mounting. The other position did not have a stud. Looking on ebay there are several options to purchase head bolt kits with the proper studs included. However, they are expensive and we wondered if anyone had this type of head bolt laying around they would sell as a single unit...if so, we would love to hear from you. One last thing, and sorry for the long post, we question the wisdom of removing one head bolt and re-torguing a different one into the engine. In your opinions, is this a wise move or would all the other bolts hold the torque to make this change out???? Thanks for the help.

[ezcruisn71]

I am glad to see you are making progress on your car issues.
As far as the head bolt goes if you have a picture of the bolt with the stud we might be able to help you.
Removing one of the bolts and retorquing it should not be a problem however on some engines those bolts go into the cooling passage of the block. So when the bolt is removed you will loose coolant out of the bolt hole.
I am not familiar with this engine, but that is how the small block chevy's are.
If this is the case then you will need to drain the coolant first and then use a Thread sealant on the bolt thread before you install it.

[Boost Addict]

^^ What he said, you don't want coolant inside you engine from that, ask me how I know

[Goldfire]

Here is a picture. The bolts are like the ones on the left side bottom row. ThanksHead Bolts.jpg

[Goldfire]

Thanks for the tip. This problem is something I did not think about. You have suggestions on how to do it??? Please let me know.

[Goldfire]

We have finally got the car running good and looking better!!! However, I have met the end of my capabilities when it comes to the HVAC system. Heater works great but defroster and AC do not work at all. Will not engage with the dsh control. I would like to get some professional help. Can anyone recommend a good shop to take the car and have it looked at?? Appreciate the help.

[bri2203]

I will send you a PM

[ezcruisn71]

Have you checked the cables coming from control head? They might be binding up or disconnected? Most of these cars were cable operated for the different modes of operation and some of them were vacuum operated.
I had a car once that bent the control cable from behind the head unit and you could only see it by removing the control head unit!
If it is vacuum operated then it is pretty easy to check also.
You should be able to check for vacuum going to the control door acuator at the defroster by removing the vacuum line to the defroster control door acuator with the car running and see if it has vacuum when it is in the defrost mode.
If it does have vacuum then the problem is probably at the vacuum control door acuator.
If it doesn't have vacuum then the problem is probably behind the heater a/c control unit head.
You can also apply vacuum to the defroster vacuum control door acuator with a vacuum pump and then see if the the defrost works.