Pontiac GTO Forum banner

1 - 13 of 13 Posts

·
Registered
Joined
·
52 Posts
Discussion Starter #1
Hey - made a significant timing change to my car last weekend. It is now sitting at 35 degrees total (15 initial). This morning, I took it to work, wanting the 20 mile drive to really listen to the engine at various speeds...listening for any knocks or pings.

One other thing - on Sunday, I finally hooked up the electric choke, which had been disconnected. No problem at all during the hot weather. This morning, however, it was about 45 degrees (northern VA). I forgot to check before starting, but I'm betting the choke was not closed - I need to check that.

Anyway, looking for some experienced ears here - can you take a good listen and tell me if you hear anything in the engine that doesn't sound quite right?

Note that there is an exhaust leak at the #5 port header gasket.

I tried to get a good sound from inside, from teh engine compartment, and at the exhaust.

What do you think??

Listen here:

Thanks for any input!
 

·
Registered
Joined
·
3,788 Posts
Hey - made a significant timing change to my car last weekend. It is now sitting at 35 degrees total (15 initial). This morning, I took it to work, wanting the 20 mile drive to really listen to the engine at various speeds...listening for any knocks or pings.

One other thing - on Sunday, I finally hooked up the electric choke, which had been disconnected. No problem at all during the hot weather. This morning, however, it was about 45 degrees (northern VA). I forgot to check before starting, but I'm betting the choke was not closed - I need to check that.

Anyway, looking for some experienced ears here - can you take a good listen and tell me if you hear anything in the engine that doesn't sound quite right?

Note that there is an exhaust leak at the #5 port header gasket.

I tried to get a good sound from inside, from teh engine compartment, and at the exhaust.

What do you think??

Listen here: https://youtu.be/YuZFt9xij6M

Thanks for any input!
Is there anything specific we are supposed to be listening to? To me, all I heard was an engine idling too low. Assume it is a 4-speed at that low of an idle.

From the 1968 Service Manual - you want your engine up to temperature to set your idle speeds.

Fast idle/cold - 2500 RPM - set with choke open and fast idle lever on top step of fast idle cam, and adjust fast idle speed screw for proper speed setting (RPM).

4-speed - with electric idle solenoid active - 850RPM with electric idle solenoid inactive - 650RPM

AT (set with trans in Drive) - with electric idle solenoid active - 650 RPM with solenoid inactive- 500 RPM

This is for a factory setting of 9 degrees initial - vacuum advance disconnected & plugged, and electric idle solenoid inactive/disconnected. You are running 15 degrees initial which should raise your idle just by advancing the initial as you have, but it appears that you have it set to the factory idle RPM's. Don't know if you have a bigger than factory cam or not. If you do have a 4-speed ( and bet you don't have the electric idle solenoid as these usually get ditched or pulled off) I would set my idle near 750 - 850 RPM's and see if it runs a little smoother. Not sure how high to take it for an AT transmission, but adjust the idle until it is in the 500-650 RPM or where you don't have to really hit the brake much to keep the car from rolling. You don't want the engine to be overpowering the brakes.

Assume you have your idle mixture screws adjusted correctly as well?

That's about the only advice I can give unless you are having a specific problem. :thumbsup:
 

·
Registered
Joined
·
52 Posts
Discussion Starter #3
Well, I had been trying to listen for anything to indicate my timing was out of whack. Knocks are easy to hear, but once an engine is running, hearing a little ping or tap that shouldn't be there is not so easy to hear...especially when there is the exhaust leak causing a little sound - a little tt, tt, tt, tt, in rhythm with the engine...hard to describe.

So from your notes, none of knocks or pings from bad timing seemed to jump out at you (me neither). But with the trip to and from work - about 40 miles round trip - I noticed a few things...

First, you're right... this morning it was hard to start and it was idle related. It stalled out three times before I could keep it running. That's unusual and had never happened before. Then, I noticed that the car smelled different today. I can usually smell the exhaust (the leak) but today it smelled MUCH richer - a gassy smell. I checked the area under the carb and didn't see any actual gas - just the stains.

All this to say...specific problems are there and they seem to be carburetor related - there is some kind of little leak. The fast idle is out of whack because it was idling way slow this morning on a cold start. And lastly, I think once warm it is running way rich.

I have no idea the history of this Holley, but I was thinking maybe it's time just to replace it. I'll play with it Saturday and see what I can do with fast idle, mixture screws and idle. I watched this video about adjusting mixture...do you think this guy gets it right? Watch especially between 2 and 6 minutes -

Sorry the post deviated so, but I think my timing is fine, the engine I think sounds okay. But my carb needs serious tuning.... damn hijacked my own post... :)
 

·
Registered
Joined
·
3,788 Posts
Video is for a Q-jet and I am not familiar with a Holley as I have never used one. However, the idle mixture adjustments would be the same principals between the Holley or any other carb, so the video looks OK and you can follow the procedure.

Hard to start and stalling out are usually because the engine is cold and the choke is not doing its job. Too low of an idle will contribute to this. It also depends on what thermostat you are running. The hotter 195 T-stat will warm your engine faster that a 160 T-stat which may not really warm your engine enough in the 40 mile drive. So in cooler/cold weather, your carb needs heat to operate at its best.

Advancing the initial timing may indeed give you that "burn your eyes" sort of rich gas smell. Found this which better explains the situation - "There is a distinct smell that most will call rich when you have the initial timing advanced especially if it idles relatively low. The combustion chamber starts to cool significantly and therefore the Exhaust Gas Temperatures (EGT's) drop causing a very different environment for any unburned fuel."

To aid in better emissions, cars of the 1970's had their timing retarded so as to build more heat in the cylinders and raise EGT's, so the engines ran hotter. My 1973 Fury with its 360 is a good example. The initial timing is set at 0 degrees and the engine does run warm. It is a little sluggish at times, so I bumped up the timing a little. Runs better at idle and is just a tad bit peppier on take-off. It might be why the factory owners manual states that if the car shows signs of running hot at idle in stop and go traffic to put the car in neutral and raise the engine speed to cool down the engine. Higher engine speeds not only spins the fan faster, it also changes the timing and advances it to aid in cooling the cylinders. I have used this technique in stop/go traffic in the hot summer weather when in line at a couple car events and it has worked.

So your call on the initial timing setting, lower idle, or carb rebuild. A big cam with a lot of overlap will also give you that "burning my eyes" experience. Again, "pinging" of the engine under load/wide open throttle is bad and what you don't want. You may not experience this as the weather is cooler, but come 95 degree summer temperatures, you may find that you have engine "pinging" at the timing settings you now have. Just be aware of it and don't let detonation destroy your engine because it can take out pistons.
 

·
Registered
Joined
·
52 Posts
Discussion Starter #5
Thank you again for then insight. I made more progress yesterday...

First, I got under the hood and really listened for anything that sounded like pings or knocks and could hear nothing. It actually sounds pretty dang good through the RPM ranges.

But when I was under the hood, I started seeing something that I didn't like - gas. I had seen the stains on the carb and on top of the manifold, but I had thought it was a very slight, slow build up. What I saw was gas - enough to drip in front of me about 2-3 drips a minute.

See attached pictures - the gas is coming out right from where my finger is - you can see wet gas on top of the manifold. The carb hold down bolt, spacer - it's all wet...not sure if you can see that from the pic.

So...here's what I think: I think I have a crapped up carb. :) Perhaps a stuck open float? That would make it really rich and could (I was thinking) back up the gas going in.

Oh and get this: The plastic ring, that sits on top of the carb, that the air cleaner sits on top of.... That plastic ring was so tight it was preventing the choke from moving - it was completely stuck open.

Instead of rebuilding it, I am going to replace it.

Butler suggested this: https://butlerperformance.com/i-24769953-jet-pontiac-quadrajet-carburetor-stage-1-800-cfm-jet-32101.html?ref=category:1234876

I found the same model at Summit for less: https://www.summitracing.com/parts/jet-32101

So this leaves me with a bunch of new unanswered questions:

1) I need to find the right fuel line from filter to carb - I assume the fitting is different on the Q Jet? On the current setup, the fuel filter sits about a foot from the front of the carb, actually sitting on top of the intake. But the only fuel pump to carb line I could find doesn't show an inline filter at all - where does the fuel filter go on a Q Jet?

2) The intake is an Edlebrock Performer. Will a Q Jet even go on it? I've heard adapter plates for spread bore don't work so well, and may cause problems?

3) What air cleaner will fit on this carb? I thought the 14" air cleaners were pretty much all the same, but the one that's on there now is definitely not the right one (earlier note about it pressing against the choke arm preventing it from moving).

4) I've hear a couple guys mention - be careful where you buy the Q Jet from because some re-man's are jacked up. Where should I get it?

5) The Holley has a spacer under it - should I be looking for one for the Q Jet too?

Man.... one thing after another. Why really sucks is that I can't drive it until I deal with this. I hate gas fires in engines. :)
 

Attachments

·
Registered
Joined
·
3,788 Posts
Bredfan: "First, I got under the hood and really listened for anything that sounded like pings or knocks and could hear nothing. It actually sounds pretty dang good through the RPM ranges."

PJ: You will not hear any "knocks" or "pinging" when the engine is not under load, ie driving. If you hear any knocking running your engine in the garage, then you have a problem. "Pinging" will show up when driving the car and the engine is pulling it. It will show up when you put the pedal to the floor to accelerate. Fuel Octane & compression are the main reasons for "pinging". Adjusting the timing is the typical way to reduce pinging by retarding the timing at the sacrifice of horsepower. With your car at running temperature, the best way to test this is to find a good hill and accelerate hard up the hill. Pinging usually shows up between 35-55 MPH with the engine under load. It generally does not show up just cruising along under light throttle conditions unless your timing is too far advanced. It may also show up on a down shift when you are passing or accelerating Loud pipes/exhaust can hide the pinging sound, but typically you will hear it. Again, pinging is detonation and can destroy an engine if it is not fixed.

Bredfan: "See attached pictures - the gas is coming out right from where my finger is - you can see wet gas on top of the manifold. The carb hold down bolt, spacer - it's all wet...not sure if you can see that from the pic."

PJ: Looks like the plug may be leaking? The carb probably needs a good going through with a rebuild kit and float adjustment. But if that fuel plug is leaking, then I think that is something a carb shop might have to service. Again, not a Holley guy nor a fan of them.

Bredfan;"I found the same model at Summit for less: https://www.summitracing.com/parts/jet-32101"

PJ: Looks to be the same carb to me as well at a cheaper price. Summit also offers free shipping when your order is over $100 and one of the reasons I use them.

Bredfan: " I need to find the right fuel line from filter to carb - I assume the fitting is different on the Q Jet? On the current setup, the fuel filter sits about a foot from the front of the carb, actually sitting on top of the intake. But the only fuel pump to carb line I could find doesn't show an inline filter at all - where does the fuel filter go on a Q Jet?"

PJ: I would order a pre-bent fuel line. It will go from the fuel pump to the carb and that will take care of the fuel line. They come in steel (factory type & cheaper) and stainless steel. You want the 3/8" line for 1968 and up cars. Get the correct line for the year of your car. 1968 is different from 1969 and I believe it is due to the fuel pump outlet line location. However, someone could have easily changed your out with some other year fuel pump as they all bolt on and will work, just depends on the fuel line port locations and if you have the 1/4" fitting for a return line going to the gas tank. Fuel filter is located right in the Q-jet itself behind the large nut that you attach your 3/8" fuel line to. So you will not use the current fuel filter that you have in front of the Holley carb.

Bredfan: "The intake is an Edlebrock Performer. Will a Q Jet even go on it? I've heard adapter plates for spread bore don't work so well, and may cause problems?"

PJ: "The Edelbrock Performer is made for the Quadrajet, so it bolts right on - no adpaters needed. Intake Manifolds - Pontiac - Performer Series - Edelbrock, LLC. There is a NOTE on their website saying to use their Part #8015 Throttle Bracket, so you may need to purchase this.

Bredfan:"What air cleaner will fit on this carb? I thought the 14" air cleaners were pretty much all the same"

PJ: Most are. You want to get an air cleaner that has the same diameter that fits the top of the carb - 5 1/8". Some inexpensive air cleaners do not fit correctly or are nor made to be used with some carbs - I have had this experience myself. You want to make sure the base fits and that it does not interfere or hit any of the linkages, top plate projections, or choke housing. Some bases lay too flat and will not fit on the Q-jet, so you want to test fit or make sure the air cleaner states for use for a Q-jet.
 

·
Registered
Joined
·
3,788 Posts
Great answers - Thank you!

Where do you come down on carb spacers? My Holley has one - you can see it in the pics. It looks like less than 1". For 4 bbl spread bore, there are not many, but I did find this: https://www.summitracing.com/parts/tay-450/overview/

Thoughts?

HUGE help - thanks, PJ!

Why do you want a spacer? What is your goal?

The one under you Holley is more of an adapter than spacer. You cannot put a square bore carb (Holley) on a spread bore intake (Performer). You need an adapter which acts as a spacer so you can bolt the mis-matched carb to the intake.
 

·
Registered
Joined
·
52 Posts
Discussion Starter #9
Gotcha - that makes sense about the one I have now being an adapter.

As far as goals - I just want to get the most performance out of the car I can. It'll never see the strip. I have the car to learn on, have fun in and cruise. I just enjoy everything about these cars...working on them, driving them, taking the kids out in them, going to meetups, talking shop and on and on. I know that's kind of subjective - maybe even wishy washy.

With experience I'll be able to translate what I mean by "the most performance out of the car." That can mean different things to different people. But I just don't (yet) have the knowledge to give you quantitative goals.

I think first, I'd like nice responsiveness. Getting that initial kick - put back into the seat feeling - it's what's so fun about these cars. But then that extends into getting the right response all the way through the rpms.

Actually, maybe you have some thoughts about how best to define goals?
 

·
Registered
Joined
·
3,788 Posts
Goals are what you want out of the car/engine. Stock, modified, performance, handling, braking, 500HP, etc..

Reading your post, it sounds like you want stock, but want to maximize the horsepower you have with the engine you have. This has been recently covered in another post, carb, ignition, & exhaust are the three areas to focus on to maximize the potential of the stock/factory engine. If you rebuild the engine at some point, then you can change some of the internal parts and raise the horsepower level.

Your timing you have done. If you change over to a Q-jet, it can be fine tuned, and the carb will be done. Next would be going to the Ram Air cast iron exhaust manifolds and a good set of pipes and free flowing mufflers. Other modifications, in my book, would be a shift kit for the automatic transmission IF is is not the factory original GTO TH-400. These were already calibrated for a good fast/hard shifts. I used to chirp tires on an all out blast 1st to 2nd shift on a '68 GTO I had with the TH-400. I have also installed shift kits in those transmissions that needed a snappier/harder shift - it is just how I like an automatic to shift versus a mushy/easy shift.

You can also get into higher stall torque converters and changing rear-end gearing to improve performance, BUT, gas mileage will suffer and so will driveability.

So just a few things can be done with the engine as it is to maximize the most out of it. The next step involves internal changes or a rebuild.
 

·
Registered
Joined
·
52 Posts
Discussion Starter #11
So, with my timing done, exhaust getting done (all parts arrived except my RAR manifolds) and the carb on its way, that brings me back to the spacer.

I've read a ton about them now and it seems like it would help make throttle response better...perhaps get a little more punch out of the car.

Worth getting and setting up when I install the new carb?
 

·
Registered
Joined
·
3,788 Posts
So, with my timing done, exhaust getting done (all parts arrived except my RAR manifolds) and the carb on its way, that brings me back to the spacer.

I've read a ton about them now and it seems like it would help make throttle response better...perhaps get a little more punch out of the car.

Worth getting and setting up when I install the new carb?
OK, lot of info on the web and I too do the research, so here is my opinion on it all. A spacer may or may not make some improvements. Two theories of thought, four hole spacers & open spacers. A taller four hole spacer like you submitted the pic of, maintains flow velocity, and can raise the carb up enough that the air/fuel mixture does not slam into the intake floor disturbing air flow - you get a smoother transition, some increase in HP.

An open hole spacer raises the carb up and rather than each side of the carb being "split" as two separate sections, left side & a right side, and half the engine drawing off one side and half of the engine drawing off the other side, the bottom of the carb is now open and what used to be a "split" carb becomes as one bigger carb with all cylinders drawing off the entire carb. So in effect, you are making a bigger carb out of the same carb, some increase in HP.

The height of the spacer is what seemingly makes a greater improvement. The Edelbrock Performer RPM manifold builds in a taller carb height without the use of a spacer. Take a look at the specs on it as compared to the Performer which I gave you the specs on. Intake Manifolds - Pontiac - Performer RPM Series - Edelbrock, LLC. The intake ports are the same as the stock Pontiac heads, BUT, note the height of the manifold is 1 1/4" taller than stock. The Performer actually has a smaller intake port height @1.92" but the same port width of 1.06". It has a stock height on the carb mounting.

Note the difference in the given RPM range for each manifold. The Performer is idle to 5500 RPM's, while the Performer RPM is 1500-6500 RPM's. The Performer has a smaller intake port and stock carb height, so it will develop a higher velocity at lower speeds but begin to reach a peak flow at a lower RPM, thus the idle to 5,500 RPM - so should be a good responsive intake. The Performer RPM provides more flow with the larger intake ports and the taller height of the carb mounting - which I am guessing is 1 1/4" higher and would be a height you could try as a spacer under your carb. The best performance for this intake now moves up the RPM scale at 1,500 RPM's and peaks out higher at 6,500RPM's - which a stock Pontiac 400 is not going to spin unless you just want to blow up your engine. With this intake, the engine may not be as responsive in the lower RPM's, but come alive in the lower mid-range and upper RPM's.

Note both intakes are of the 180 type - split manifold where the carb supplies air/fuel from each half of the engine. I suspect the Performer RPM raises the carb and smooths out the air/fuel flow as I mentioned earlier when using a spacer. Keep in mind hood clearance could become a problem with a spacer or raised manifold. Might need a thinner air cleaner element.

So you could experiment a bit. A factory stock manifold will give you the correct intake port size - bigger than the Performer, so that makes the stock intake a plus, short of the fact that it is heavier. Then you could experiment with spacers, both 4-hole and open either on top of your Performer or the factory intake. I would go at least 1" on the spacer. You might even consider using a phenolic spacer which would help to keep the carb cooler as it insulates it from the intake heat.

So if it were me, I'd work with what I had first. Use the Performer and play with a spacer. You don't have to go big bucks on these. If you find an improvement on either, then you could look into other more expensive brands for what it is worth. Here is a 4-hole 1" phenolic spacer with the longer studs: Mr Gasket 3406: Phenolic Carb Spacer Quadra-Jet Flange - 4-Hole | JEGS Here is an open 1" spacer: Trans Dapt 2109: 1" Quadrajet Carburetor Spacer Open Plenum | JEGS

Once you have a base height of 1", you can then build that up 1/4" with gaskets or 1/2" with an additional spacer. If you notice any loss in power, then you know the last height was the best for your engine combo.
 

·
Registered
Joined
·
3,788 Posts
PJ:"Reading your post, it sounds like you want stock, but want to maximize the horsepower you have with the engine you have. This has been recently covered in another post, carb, ignition, & exhaust are the three areas to focus on to maximize the potential of the stock/factory engine."

OK, found the post and did not realize it was your post. You could have continued your post versus making a new one as it is related. So I am including a link to go with this posting to bring it full circle. :thumbsup: http://www.gtoforum.com/f12/power-cant-really-simple-123290/
 
1 - 13 of 13 Posts
Top