A few annoyances - need tips: temp gauge, tapping under load, and a potential vapor l

[greywurm]

Have a 72 SBC 350 in my 71, pretty stock.
Hugger headers, HEI, aftermarket intake, edelbrock 1406 carb.
Mileage unknown, but the guy I got it from said it had roughly 8000 since last rebuild as it was in a show quality 53 3100.

Temp gauge:
If running it in park, stock gauge works fine. Needle raises normal, drops when the efan kicks in. But when I'm moving, it will drop all the way down and not raise until I'm at a stand still long enough. I thought maybe I should reinstall the sender since I didn't put it in all the way - used thread tape and was concerned about cracking the manifold. Reinstalled it without tape and some anti seize so it can come be removed down the road without issues. Problem persists.

Tapping:
I've pretty determined its around the passenger head. Only really noticeable when the engine is under load. Pretty quiet at idle. I removed the valve covers this morning and adjusted the valve lash, but the tapping noise continues... Read somewhere it could be loose headers or bad gasket?

Vapor lock:
New mech fuel pump, have an inline clear filter between pump and regulator. Get a consistent 4-5 lbs fuel pressure between regulator and carb while running. After I shut it off, I can watch that gauge slowly drop to 0.
Hot starting or even cold starting in the morning, she'll fire right over and stall out after a second. 3-5 seconds of turning the key, it will fire right up (usually I pump the gas once or twice). Makes me think of vapor lock, but the rubber fuel hoses I think are far enough away from the exhaust header.

What do you all think? Need some ideas...

[greywurm]

Pics of fuel line and temp sender.
The filter is under the radiator hose a few inches from the pump.

[mechanicalman]

Originally Posted by greywurm

Pics of fuel line and temp sender.
The filter is under the radiator hose a few inches from the pump.

Temp gauge:
I don't think you have a temp gauge problem, just a problem with abnormal engine temp. So, it warms up (slowly?) and cools with the efan on and warms with the efan off, I assume? But, cools off when moving and won't warm back up until you are at a standstill.

Only difference moving is that you get radiator airflow without the fan on. Your thermostat is either missing or stuck open.

Tapping:
I've never seen valve train noise that was only under heavy load. Need to know how/if this tapping is related to engine temp (does it do it when the engine is not warmed up or right off the bat?) Usually tapping under load indicates pre-ignition due to timing or carbon build-up.

Vapor lock:
I don't think your problem is related to vapor-lock, it sounds more like your fuel is leaking down. That could be caused by weak needle/seat, weak fuel pump, or air leakage in the plumbing.

I'm wondering why you have the fuel regulator and in-line filter. Since 1983 I've only used the filter in the carb inlet and ran a solid steel line from the pump to the carb, and never had any problems. I know you have an Edelbrock carb so you would have to make a 3/8" double flare steel line with a bubble on the carb end from the pump to the carb with the shortest possible rubber section to connect to the carb using double hose clamps. You can go to Napa and get a 5' section of 3/8 line with the male double flare end that screws into the fuel pump then band and cut to length, use a double flare tool to make a bubble on the carb end.

I don't like all the hose connections you have right above the headers/spark plugs, too many possible disaster-inducing scenarios.

[leftybass209]

The tapping you hear can easily be confused for an exhaust leak, which would not be surprising because you're running headers.

The 1406 is a stupid simple carb to figure out if
A) You know it's clean
B) You know your engine is timed properly

I'd strongly suggest removing all of that rubber fuel line and replacing it with the factory intended and vastly safer steel fuel line. If you are certain you aren't pushing more than 6psi of fuel pressure, then you can add a 1/2 to 1 inch (or more if that's your thing) phenolic carb spacer.

99% of all complaints concerning Edelbrock carbs are because of improper fuel pressure and carb boil/vapor lock.

Also, it's debatable but pressure regulators significantly reduce the life of your fuel pump. You are essentially creating a bottleneck between the pump and the regulator, which is causing undo stress on those rubber fuel lines and the rubber diaphragm.

[greywurm]

Hey mechanicalman, you've helped me out in the past hooking up a serpentine belt system from the junk yard. You were a huge help!
I'm going to split my responses to each issue into separate posts.. both of you guys make great points...

[greywurm]

Temp gauge:
Correct. It shows correct temp when the truck is not moving. Goes up as the engine warms, goes down when the fan kicks in. Back up when it stops.

I initially thought the thermostat was bad, so I already replaced it. Maybe the new one is also bad?
The thing is, I pull over when the needle is dead cold, and can grab the upper radiator hose, and its hot like it should be... I know the temp sender is in the intake manifold, but I would think with warm coolant going in, it should at least register a temp. It flat out drops to 0 like the truck was never run within a minute of pulling out of the driveway...

Could it be a bad connection? Maybe the original thermostat was in upside down and since I installed the new one the same way, its still upside down? idk... I'll do some looking for correct placement of it and double check.

[greywurm]

Vapor lock:

I bought the rubber hoses because they said they were for a carb and didnt have the tools or experience working with fabbing up metal lines. I dont mind getting the tools and figuring it out. You do make an excellent point as far as failure and disaster scenarios.

I added the regulator because I was having an issue that it would hesitate and almost stall when i hit the gas from stop. Read a lot of info that edelbrock carbs are cranky when fuel is above 5 psi, and the line was running 5+, sometimes upwards of 7. The regulator didn't help, eventually it was a combination of the accel pump and that I was using ported vacuum that didn't give the motor enough initial advance. More on the vacuum later.

If I go metal lines, do I just bypass both the filter and regulator and go for the carb? Even if it still turns out to be too much fuel and have to add the regulator back? If I use the regulator, where is the best place to mount it? Everything said it needed to be level or higher than the carb...

The fuel pump is brand new. It was my first suspicion with a lot of the issues I was having initially.

I do have a carb spacer, but I think its aluminum. Has a chrome looking finish, so I don't mind looking into a phenolic based spacer. Looks like they are 30 bucks. Worth it if the fuel line doesn't make a difference. I think I saw 1/8" gasket looking shields that protect against heat. I was also thinking of that route.

[mechanicalman]

Originally Posted by greywurm

Temp gauge:
Correct. It shows correct temp when the truck is not moving. Goes up as the engine warms, goes down when the fan kicks in. Back up when it stops.

I initially thought the thermostat was bad, so I already replaced it. Maybe the new one is also bad?
The thing is, I pull over when the needle is dead cold, and can grab the upper radiator hose, and its hot like it should be... I know the temp sender is in the intake manifold, but I would think with warm coolant going in, it should at least register a temp. It flat out drops to 0 like the truck was never run within a minute of pulling out of the driveway...

Could it be a bad connection? Maybe the original thermostat was in upside down and since I installed the new one the same way, its still upside down? idk... I'll do some looking for correct placement of it and double check.

OK, now I'm stumped. Here's a picture of right side up. Maybe your coolant is low? Do you have an overflow tank? Somehow it sounds like the sensor is losing it's signal while you are driving like maybe the coolant is somehow not getting to it.

You might have to put the sensor in the driver's side cylinder head. You may need to re-route the sensor wire to the driver's side of the engine then bring it either over the top or under the manifolds through a holder on a water pump stud over to the side of the cyl head between # 1 and 2 spark plugs.

What kind of heads are you running?

[greywurm]

Tapping:

I will have to go out and double check later, but I dont think I noticed any taping intially after starting. I usually warm the truck up a bit before leaving, and I hear the tapping under acceleration. Its especially annoying at 70-80 mph on the freeway.

I do need to do some more work on the exhaust headers... when I initially installed them, the header bolts I had didnt have clearance to make it to past the outer header tubes to the inside bolt hole on both headers/outer tubes. So I am running sans 2 bolts per. I did pick up a different style set of bolts that have smaller headers and an allen type drive with a driver that allows for angles. I think those will get a better clearance.

Timing wise, I have checked since I switched over to manifold vacuum last week. I had it timed to 14 deg with everything plugged up, and used the ported vacuum port on the edel carb because thats what the previous owner used... After some trial and error, and a suggestion from someone on board, switched to the manifold vacuum port, and bam... idle smoothed out nicely and the hesitation/near stall under initial throttle was gone.

Now, I have read a number of different opinions on timing, most online stating small blocks love higher time, 14-16 deg. My repair manual says 4. I went higher because at 4, the headers would glow. But that was on ported vacuum, so perhaps on manifold 4 might be better... idk. Just thinking out loud.

[greywurm]

Originally Posted by mechanicalman

OK, now I'm stumped. Here's a picture of right side up. Maybe your coolant is low? Do you have an overflow tank? Somehow it sounds like the sensor is losing it's signal while you are driving like maybe the coolant is somehow not getting to it.

You might have to put the sensor in the driver's side cylinder head. You may need to re-route the sensor wire to the driver's side of the engine then bring it either over the top or under the manifolds through a holder on a water pump stud over to the side of the cyl head between # 1 and 2 spark plugs.

What kind of heads are you running?

I am 95% sure stock heads. I looked up the casting number a while ago and if I remember correctly, they matched the year range that the guy I got the motor from said it was.... 72. If you want I can go try to locate the casting number again to look it up again... I started this all months ago and took almost 3 months off to recover from a broken ankle right before thanksgiving.

Anyways, I have been suspect of wiring. I can't get a solid crimp on the butt connector to the wire, and the connector is too close to fit on the temp sender tipple, so I had to open it up. I have been considering tracing the wire back and replacing it with a slightly larger gauge wire. I have had wiring issues in the past due to pretty bad hack jobs done by the PO, so who knows what I will find.

[greywurm]

Ok, thought I saved the casting number somewhere... Stock heads for a '72. Some info here... Casting #3998993

[mechanicalman]

Originally Posted by greywurm

Vapor lock:

I bought the rubber hoses because they said they were for a carb and didnt have the tools or experience working with fabbing up metal lines. I dont mind getting the tools and figuring it out. You do make an excellent point as far as failure and disaster scenarios.

I added the regulator because I was having an issue that it would hesitate and almost stall when i hit the gas from stop. Read a lot of info that edelbrock carbs are cranky when fuel is above 5 psi, and the line was running 5+, sometimes upwards of 7. The regulator didn't help, eventually it was a combination of the accel pump and that I was using ported vacuum that didn't give the motor enough initial advance. More on the vacuum later.

If I go metal lines, do I just bypass both the filter and regulator and go for the carb? Even if it still turns out to be too much fuel and have to add the regulator back? If I use the regulator, where is the best place to mount it? Everything said it needed to be level or higher than the carb...

The fuel pump is brand new. It was my first suspicion with a lot of the issues I was having initially.

I do have a carb spacer, but I think its aluminum. Has a chrome looking finish, so I don't mind looking into a phenolic based spacer. Looks like they are 30 bucks. Worth it if the fuel line doesn't make a difference. I think I saw 1/8" gasket looking shields that protect against heat. I was also thinking of that route.

I'm sorry, a mis-communication. I run the carb filter on a quadrajet, the Edelbrock does not have one so you need the filter.

Still don't know if your "vapor lock" problems is only when you first start the engine? Vapor lock only occurs when warm enough to vaporize the fuel in the line or carb. As for the pressure regulator, I like this one:
http://www.4wheelparts.com/Performan...FcVgfgodJWwAZw

Your present regulator appears to have a blocked off port, maybe for a return line. I wonder if this affects the performance of it.

You will always need a section of rubber hose between the frame rail and the engine to account for engine movement.

[mechanicalman]

Originally Posted by greywurm

Tapping:

I will have to go out and double check later, but I dont think I noticed any taping intially after starting. I usually warm the truck up a bit before leaving, and I hear the tapping under acceleration. Its especially annoying at 70-80 mph on the freeway.

I do need to do some more work on the exhaust headers... when I initially installed them, the header bolts I had didnt have clearance to make it to past the outer header tubes to the inside bolt hole on both headers/outer tubes. So I am running sans 2 bolts per. I did pick up a different style set of bolts that have smaller headers and an allen type drive with a driver that allows for angles. I think those will get a better clearance.

Timing wise, I have checked since I switched over to manifold vacuum last week. I had it timed to 14 deg with everything plugged up, and used the ported vacuum port on the edel carb because thats what the previous owner used... After some trial and error, and a suggestion from someone on board, switched to the manifold vacuum port, and bam... idle smoothed out nicely and the hesitation/near stall under initial throttle was gone.

Now, I have read a number of different opinions on timing, most online stating small blocks love higher time, 14-16 deg. My repair manual says 4. I went higher because at 4, the headers would glow. But that was on ported vacuum, so perhaps on manifold 4 might be better... idk. Just thinking out loud.

Header leaks usually start out when the engine is cold and either get better or go away as the engine gets hotter with the metal expanding and compressing against the gasket harder.

Pre-ignition usually gets worse as the engine gets warmer. However, fix the headers first regardless so you don't chase your tail on something that might not exist. Either the smaller heads or shorter bolts are sometimes necessary. I've NEVER been able to put a full set of the long bolts on a set of headers, you most always have to mix/match with longs and shorts.

4 degrees timing is not enough, and probably a source of the cracked manifolds these trucks develop. GM took creative license with timing specs I think to get around emissions laws.

If you still have the tapping after the headers are verified as not leaking, then let me know and I'll give you some homework, LOL.

[mechanicalman]

Originally Posted by greywurm

Ok, thought I saved the casting number somewhere... Stock heads for a '72. Some info here... Casting #3998993

Like you say they are stock and they are large combustion chamber. Hopefully when he rebuilt it he put some flat top pistons in it to get it up from the 7.8:1 to around 8.6-8.7:1.

[mechanicalman]

Originally Posted by greywurm

Ok, thought I saved the casting number somewhere... Stock heads for a '72. Some info here... Casting #3998993

Scratch that regulator I like, I think it's for a holley dual inlet. Doh! I just liked where it mounted. You could maybe use a plate like that to mount your regulator if you confirm you really need it.

Funny though, I think they left a 1 off on the price, as in $100.00 dollars (I think it should have been $132.99 not $32.99, so that would not be a bad price on it for the plate, you could sell the regulator on craigslist. Just cut off the throttle bracket part if you don't need it.

[mechanicalman]

If you can live without the fuel pressure regulator....

I like this fuel line, has the adaptor for the fuel pump and it can be shortened easily.
http://www.jegs.com/i/Edelbrock/350/...FYhgfgodL3kAJw

And I like this fuel inlet/filter.
http://www.jegs.com/i/Edelbrock/350/8131/10002/-1

[mechanicalman]

Originally Posted by greywurm

Pics of fuel line and temp sender.
The filter is under the radiator hose a few inches from the pump.

Move your coolant sensor to the driver side cylinder head.

This is the connector that slides on sideways similar to the one that came on your truck from the factory.
http://www.summitracing.com/parts/pco-5665pt/overview/

Use metal only butt connectors and use heat shrink to cover them. Use 14 gauge wire from where you cut it on the harness to the pigtail connector.
http://www.ebay.com/itm/50-14-16-GAU...cbf379&vxp=mtr

http://www.ebay.com/itm/1-4-Black-Ad...03698717&rt=nc

You might get this stuff at a local parts store.

This is a picture of a typical crimping tool. Notice there are 2 different places to crimp connectors, one on each side of the pivot. The one on the end is for shielded connectors.

The one I want you to use for the bare metal connector is on the handle side of the pivot next to the wire strippers. Don't forget to slide the MARINE heat shrink on before you crimp the connectors. Do it right and it will never pull apart, absorb moisture, or have conductivity issues.

[greywurm]

Thanks for all the info mechanicalman. A lot as usual... Love it. Need some time to process it all.

The regulator I have is a holley 4-9 psi if I remember correctly. The second port that's capped off is if I was running a second carb. It came with the cap for single carb set ups. Let me see if I can dig up a link.

Like I said, its in there because I was getting higher pressure than edelbrocks like, but the issue I was working on might not have been related.

Vapor lock issue may not be vapor lock. It is only starting, hot or cold. Not while driving. I do not notice any boiling, just loss of pressure at the gauge when sitting. I'm really thinking its more of an issue with the fuel line not being air tight, perhaps around that plastic gauge. I think O'Reilly/auto zone carries those flexible hoses so I'll check them out.

I'm not excited about moving the temp sender... I think I'll start with the connection and line first. There looks to be a port already for it but its plugged... I don't know if its been sealed with JB weld or not.