Pa Pa Pa Pa

[Carba1984]

Hello, I'm still busy with carburizing and I have a doubt, when the exhaust explodes like popcorn is it for a poor mixture or a rich mixture? I think both, It usually explodes when I release the accelerator

Edited August 3 by Carba1984

[Pete Lewis]

both can give a poor exhaust note but any back fire noises can be unburnt fuel   so maybe on the rich side 

have you got or found the air piston lifting pins just under the main piston casting ????

these did get deleted when tamper proof emissions started to be introduced 

Carburettor lifting pins
At the side of each carburettor is a lifting pin, these pins enable you to check the movement of the piston.
Once the carburettors have been synchronised, the lifting pins can be used to check the mixture adjustment. Raise the lifting pin on the front carburettor to lift the piston by approximately  1/32 in (0.8mm).

• If the engine speed increases, the mixture strength of the carburettor is too rich.

• If the engine speed immediately decreases, the mixture strength of the carburettor is too weak.

• If the engine speed momentarily increases very slightly then returns to idle, then mixture strength at the carburettor is correct.

Repeat this operation for the other carburettor, and after adjustment re-check the first carburettor, since both are interdependent to some degree.
If the exhaust note is irregular with a slight of misfire and colourless exhaust, the mixture is too weak. If there is a regular misfire in the exhaust beat, together with a blackish exhaust, then the mixture is too rich.

 

[johny]

There can be several causes including as Pete says mixture, worn or incorrectly timed valves, too low exhaust back pressure (sports exhaust) or it now appears theres an additional possibility. The thinking is that the ethanol in fuels now burns more slowly than regular gasoline so that its combustion isnt finished by the time the exhaust valve starts to open and a pop is produced. The solution is to advance the igntion timing more than the manual recommended setting and my experience, along with others, is that this does help.

If you decide this is the cause theres no set value so its best to advance your timing in small steps of a few degrees each time and then listen for pinking (a rattling sound from the engine under load) and of course see if the back firing is improved....  

[Carba1984]

I have sports exhaust, I think the mixture is correct with the lifting pin, I have 17 degrees BTDC advance

Edited August 3 by Carba1984

[johny]

Ah Ive also put one of these in my exhaust pipe more for noise but it also increases back pressure...

[Carba1984]

I've never seen that before, con you explain to me a little about its function? But I don’t have problem with de noise, I just want the engine to go well

Edited August 3 by Carba1984

[johny]

Theyre really for motorcycles but if you get the right size it fits perfectly in the silencer tail pipe. I drilled a small hole in the bottom of the pipe so that you can lock it in with the small allen screw. The screw at the other end allows you to adjust an internal plug that changes the number of holes the gasses can pass through so altering the back pressure.

However another thing Carba is what are your cylinder compression readings like wet and dry?

[Carba1984]

I have not measured the compression of the cylinders, it has been 1400 kms since my engine has been rebuilt, I would like to know if the advance of the degrees of the distributor could influence having an unstable idle, now I have 17 degrees BTDC, I've followed the advice of a person from the forum, I think the car is going well, but I'm still having an unstable idle, Sometimes it even turns off when I stop 

Edited August 3 by Carba1984

[Carba1984]

I also have the spark plugs of the same color, they indicate a good mixture

[johny]

I think all you can do is keep experimenting, try weakening the mixture a little, less timing advance etc and see what happens.... Perhaps try a higher octane fuel if available?

[Carba1984]

El ralentí está estabilizado y de repente sube de vueltas, a lo mejor entra aire, otras veces se cae hasta apagarse, puedo experimentar pero creo que debería revisar juntas de carburadores primero 

[johny]

I assumed the carbs were all overhauled? If not yes air leaks is a good possibility....

[Carba1984]

Right now I'm going crazy, oil keeps coming out from the rocker cover due to the splashes inside and it also comes out a little through the hoses that go to the carburetor, I cleaned them two days ago, this has happened to me since I changed the rocker cover and I thought it was because of the oil hose but I don't wear it anymore

[Carba1984]

I hope I don't have excessive oil pressure, it wouldn't make sense with all the new parts

[johny]

Oil pressure is limited by the pressure relief valve and this very easy to inspect. You unscrew it and inside is a spring and plunger so that as pressure increases the plunger is pushed open against the spring to return excess oil to the sump. Obviously the plunger must be free and the spring the correct type and length (its correct measurement is given in the manual)👍

[Carba1984]

I will inspect it, the spring and the plunger are new, I don't think there's a way to assemble it wrong, the truth is that I'm worried about this, thank you Johnny for your help

Edited August 4 by Carba1984

[Iain T]

1 hour ago, Carba1984 said:

Right now I'm going crazy, oil keeps coming out from the rocker cover due to the splashes inside and it also comes out a little through the hoses that go to the carburetor, I cleaned them two days ago, this has happened to me since I changed the rocker cover and I thought it was because of the oil hose but I don't wear it anymore

Have you taken off the external oil feed?

Try fitting the cork head/rocker gasket as per my post in your other topic. It stops any oil leaks. 

Iain

[Carba1984]

Yes, I taken off the external oil feed. What post? I don’t see anything now, can you copy paste here? Sorry 

[Carba1984]

The loss of oil is due to the plug

[JohnD]

22 minutes ago, Carba1984 said:

Yes, I taken off the external oil feed. What post? I don’t see anything now, can you copy paste here? Sorry 

But you haven't!  Unless the pic above was taken before it came off.   And "The loss of oil is due to the plug"   Do you mean that the oil filler cap on the rocker cover doesn't fit?  It might be that it lacks a rubber sealing washer - I can't see one in your picture.

John

PS Carba, we appreciate you posting in English!  I suspect that few of us, me certainly, could  not do so in Spanish!  J.

[Iain T]

35 minutes ago, Carba1984 said:

What post? I don’t see anything now, can you copy paste here? Sorry 

It's in your 'a little problem' topic

I suggest you take the rocker cover off and start the engine then look to see how much oil comes out of the rocker assembly. At tick over it should be a slow drip from each of the rocker arms. The oil then drains down the head where the push rods are.

As John suggests check the rubber seal on the filler cap.

Note some aluminium rocker covers do not have a small splash plate on the inside of the air hose outlet. This can result in oil being splashed down the hose.

Iain

Edited August 4 by Iain T

[Carba1984]

42 minutes ago, JohnD said:

But you haven't!  Unless the pic above was taken before it came off.   And "The loss of oil is due to the plug"   Do you mean that the oil filler cap on the rocker cover doesn't fit?  It might be that it lacks a rubber sealing washer - I can't see one in your picture.

John

PS Carba, we appreciate you posting in English!  I suspect that few of us, me certainly, could  not do so in Spanish!  J.

Yes John, it’s and old picture, the cap this fit but I suspect not good, yes, the cap have rubber sealing washer, maybe it’s insufficient, sorry for my English, I’ll try 🤦🏻‍♂️

[Carba1984]

48 minutes ago, Iain T said:

It's in your 'a little problem' topic

I suggest you take the rocker cover off and start the engine then look to see how much oil comes out of the rocker assembly. At tick over it should be a slow drip from each of the rocker arms. The oil then drains down the head where the push rods are.

As John suggests check the rubber seal on the filler cap.

Note some aluminium rocker covers do not have a small splash plate on the inside of the air hose outlet. This can result in oil being splashed down the hose.

Iain

I’ll check with the rocker cover off and maybe yo fabricó una nueva junta de corcho porque parece que la de goma es insuficiente, I'm worried that oil will go through the pipes to the carburetors, some idea for small splash plate on the inside of the air hose outlet? When you open the rocker cover, is it normal for smoke to come out? I think so, it has always come out even with the engine rebuilt, the oil heats up...

[Carba1984]

12 minutes ago, Carba1984 said:

Yes John, it’s and old picture, the cap this fit but I suspect not good, yes, the cap have rubber sealing washer, maybe it’s insufficient, sorry for my English, I’ll try 🤦🏻‍♂️

this it’s the rubber sealing 

 

56 minutes ago, JohnD said:

But you haven't!  Unless the pic above was taken before it came off.   And "The loss of oil is due to the plug"   Do you mean that the oil filler cap on the rocker cover doesn't fit?  It might be that it lacks a rubber sealing washer - I can't see one in your picture.

John

PS Carba, we appreciate you posting in English!  I suspect that few of us, me certainly, could  not do so in Spanish!  J.

Yes John, it’s and old picture, the cap this fit but I suspect not good, yes, the cap have rubber sealing washer, maybe it’s insufficient, sorry for my English, I’ll try 🤦🏻‍♂️

[johny]

25 minutes ago, Carba1984 said:

 When you open the rocker cover, is it normal for smoke to come out? I think so, it has always come out even with the engine rebuilt, the oil heats up...

Fresh oil at normal operating temperature shouldnt produce smoke. It can only come from the combustion and a little always gets past the piston rings even when new and the rocker box system is there to remove it and send it to the carburettors. I still recommend a compression test just to confirm that your rings have bedded in correctly and the valves are sealing well...