Hissing sound on left side of motor

Have you done a leak-down or compression check on the engine?

If the spark plug is loose you'll have found it.

Thank you guys for those suggestions. I’ll check if the spark plugs are not loose.

When you retorqued the bottom studs how much movement did you find?  Have you checked the exhaust port to header nuts?

Another possibility is a loose intake manifold or bad gasket there.

@Lane Anderson posted:

Another possibility is a loose intake manifold or bad gasket there.

“I have done the following: replaced the intake manifold gasket“

i did an intake manifold gasket too. My sound was a chirp, chirp type sound. No loss in performance though.

My first choice would be a loose spark plug, too, but;

@Impala wrote: I have done the following:

Replaced the intake manifold gasket
(I'm assuming the manifold-to-head gasket, but just one or both?)

Took out and cleaned all jets.  That's always a good start, especially because it's so easy on Dells

I also changed the emulsion tubes because I found out it had .1 instead of .2 which is what VWs are supposed to have.  ???  That's news to me.  Besides, you engine probably isn't the same as a stock VW.  If it had been running well before with the old emulsion tubes, I would put them back in to eliminate another variable.  How long has this hissing been going on?

I would remove the carburetors and replace the carb-base-to-manifold gaskets.  A leak there could produce a rhythmic sound, depending on where the leak is.  Could be a hiss, could be a whistle but it will pulse with piston/valve action.  You're trying to find a leak that is probably one cylinder related, but'cha nevah know.   There is limited access around the carbs when installed, so wrapping a heavy rag around their bases to isolate the leak noise before you remove them, while possible, might be tough (but worth a try, for sure).  Another thing to try would be to get it idling when warm and stable, then pull one plug wire at a time from the distributor to see the result.  If one cylinder stumbles more than the others, that might point you toward where the leak is (but not guaranteed).

Carbs are Dellorto DRLA 40’s. I retorqued the bottom head studs and checked valve adjustment as well.  Also a good start but not my first choice.  What torque setting on the head nuts, just out of curiosity?  

I could be persuaded that this is a leaking exhaust gasket, so get under there and see if there is any carbon shadow blown outward from the exhaust flanges showing any leaks.  An exhaust leak is usually louder than an intake leak, on average.  If you can get it up on a lift while it is running it's easier to find an exhaust leak but that might be a big deal so look for carbon traces first.

**************************

Here's what I'm running on my 40mm Dells, set up by Dave Hoagland when he was still at Blackline Racing, for a  2,110cc,  MOFOCO big valve heads, port-matched heads and intake manifolds, Engle 120 cam, 1-5/8" header tubes (Berg headers).

The jet sizes are:

.45 idles

1.30 mains

160 air correctors  

.35 Accelerator pump jets

32mm Venturis  (These work GREAT on my 2,110 with 40mm Dells)

To show us a video, first, upload that video to Youtube, get it playing then click on the "Share" button and copy the link to it.  Then bring up a post reply on the SOC, click on the little movie icon in the menu bar at the top of the post and paste the link into the source window, then post the reply.  We should be able to see it after that.  You can delete it from Youtube after you get it fixed.

Buena Suerte....

@ALB posted:

When you retorqued the bottom studs how much movement did you find?  Have you checked the exhaust port to header nuts?

I did find some movement but not a lot. Exhaust ports look kosher with no signs of exhaust leaks.

@David Stroud IM Roadster D posted:

i did an intake manifold gasket too. My sound was a chirp, chirp type sound. No loss in performance though.

If your carbs are Dellortos the chirp is totally normal.

@Gordon Nichols posted:

My first choice would be a loose spark plug, too, but;

@Impala wrote: I have done the following:

Replaced the intake manifold gasket
(I'm assuming the manifold-to-head gasket, but just one or both?)

Took out and cleaned all jets.  That's always a good start, especially because it's so easy on Dells

I also changed the emulsion tubes because I found out it had .1 instead of .2 which is what VWs are supposed to have.  ???  That's news to me.  Besides, you engine probably isn't the same as a stock VW.  If it had been running well before with the old emulsion tubes, I would put them back in to eliminate another variable.  How long has this hissing been going on?

I would remove the carburetors and replace the carb-base-to-manifold gaskets.  A leak there could produce a rhythmic sound, depending on where the leak is.  Could be a hiss, could be a whistle but it will pulse with piston/valve action.  You're trying to find a leak that is probably one cylinder related, but'cha nevah know.   There is limited access around the carbs when installed, so wrapping a heavy rag around their bases to isolate the leak noise before you remove them, while possible, might be tough (but worth a try, for sure).  Another thing to try would be to get it idling when warm and stable, then pull one plug wire at a time from the distributor to see the result.  If one cylinder stumbles more than the others, that might point you toward where the leak is (but not guaranteed).

Carbs are Dellorto DRLA 40’s. I retorqued the bottom head studs and checked valve adjustment as well.  Also a good start but not my first choice.  What torque setting on the head nuts, just out of curiosity?  

I could be persuaded that this is a leaking exhaust gasket, so get under there and see if there is any carbon shadow blown outward from the exhaust flanges showing any leaks.  An exhaust leak is usually louder than an intake leak, on average.  If you can get it up on a lift while it is running it's easier to find an exhaust leak but that might be a big deal so look for carbon traces first.

**************************

Here's what I'm running on my 40mm Dells, set up by Dave Hoagland when he was still at Blackline Racing, for a  2,110cc,  MOFOCO big valve heads, port-matched heads and intake manifolds, Engle 120 cam, 1-5/8" header tubes (Berg headers).

The jet sizes are:

.45 idles

1.30 mains

160 air correctors  

.35 Accelerator pump jets

32mm Venturis  (These work GREAT on my 2,110 with 40mm Dells)

To show us a video, first, upload that video to Youtube, get it playing then click on the "Share" button and copy the link to it.  Then bring up a post reply on the SOC, click on the little movie icon in the menu bar at the top of the post and paste the link into the source window, then post the reply.  We should be able to see it after that.  You can delete it from Youtube after you get it fixed.

Buena Suerte....

I did replace the gasket on the left side; which is where the hissing comes from. Actually both gaskets had been replaced not too long ago but I did this one again to eliminate that variable.

The hissing came before I switched the emulsion tubes. The 9164.2 tubes, from what I’ve read on VW forums, are considered the ones for street use while the 9164.1 tubes are more for racing use. The .1s probably came with the set up for an Alfa Romeo. I have the following: 140 main jets  9164.2 emulsion tubes, 1.80 air correction, .60 idle jets. I believe that was the stock setup that CB Performance used back in the day when they sold them as per the Dellorto book by Tomlinson. Haven’t checked the Venturi sizes but it wouldn’t surprise me they were the 34s they came set up with from CB as well.

I retorqued the heads to between 23 -25 ft/lbs. (my torque wrench is the old style with the needle and the dial).

I don’t see any leaks or loose nuts or studs in the carb body itself but that is another possible place. I did get a full rebuild set for both carbs along with the .2 emulsion tubes from Gabriel in Italy; he has a store on EBay but prefer to not break them up until a full refurb is warranted. Maybe I can make a new gasket by tracing the old one. I have gasket material.

So the two things I need to verify now is that gasket in the carburetor and the spark plugs.

That set up you have is pretty peppy; nice displacement and good stuff in it; should haul ass!

@Impala posted:

If your carbs are Dellortos the chirp is totally normal.

I have 48 webers.

@David Stroud IM Roadster D posted:

I have 48 webers.

I see; I would say if the car is working fine I wouldn’t worry about it.

@Impala posted:

I see; I would say if the car is working fine I wouldn’t worry about it.

We fixed it a couple of years ago. New gasket. No more chirp.

I finally managed to post a video of the sound:

https://youtube.com/shorts/EHV...?si=GPnFjGqtgrOQKWZ9

Sure sounds like either an intake leak or exhaust leak on one cylinder.

If it isn't intake or exhaust it is most likely a broken head stud. Or the aforementioned loose or stripped spark plug.

Do a compression check and/or a leakdown.

That is NOT a Dell "chirp".

I agree with you all; this is not the chirp. This thing has happened and has rectified itself not quite sure how a couple of times before and quite a few years ago. I will certainly check the spark plugs and do the compression tests as well. I first tried the obvious ones like the intake gasket. I hope it’s not a head stud; if it is it should be one of the top ones since I went over the bottom ones that are accessible and there were no signs of a broken one.

If this had happened before and "fixed itself" it is most likely a sticking valve. Or something in the valve train.

From the sound, I’m still thinking spark plug.

Keeping my fingers crossed; I haven’t had the chance to go to the garage to work on it. Apart from spark plugs the only other thing that comes to mind would be something in the carb itself; something loose or missing. The vacuum hose is hooked up and the rubber plugs over any other unused inlets/outlets were in place.

Nope, I don’t think it’s a carburetor noise - Too loud and pulsed from where your phone was and it certainly is NOT a vacuum hose noise.  

CHECK YOUR PLUGS!.  

Try this: Take off the coil wire so it won't start and have a buddy crank the engine over while you have a hose with one end in an ear.  Move the other end of the hose from pug to plug and see if you can localize the sound.

Been lurking on this one, and am anxious to see how it settles. Curiouser and curiouser. I've seen that all the usual suspects have been mentioned and pursued here, and so far the root cause eludes.  ??

Loose and worn fan belt?  Something with the fan?  Something rubbing but only at low rpm?

@Lane Anderson posted:

Try this: Take off the coil wire so it won't start and have a buddy crank the engine over while you have a hose with one end in an ear.  Move the other end of the hose from pug to plug and see if you can localize the sound.

"Take off, eh?"

I used to tune the SUs on my MG by sound using a hose.

@El Frazoo posted:

Loose and worn fan belt?  Something with the fan?  Something rubbing but only at low rpm?

Tried that too. Ran it without the belt and same noise.

"Move the other end of the hose from pug to plug and see if you can localize the sound."

Great advice, if you happen to own one.  And just where do you insert it?

One of my funnier typos.