engine and drivetrain Setting Timing With 292 Cam And 38/38 Webber

[1971Ginger]

Hello,

What is the desired rpm to run at idle when using a 292 cam and a 38/38 weber?

Should I still set via the ball on flywheel or use a rpm guage?

Thanks in advance

[Preyupy]

It makes more difference what distributor you are using. Vacuum advance? If you are running flat top pistons you will want somewhere around 36 deg BTDC advance total (with vacuum if you have it)Run it up to 3500 or so and check with an adjustable timing light. Timing to the ball can be hazardous if you don't know EXACTLY what distributor you have and that it is working correctly. The ball is 25 deg BTDC and using it depends on knowing where you are in the advance curve of the distributor at an exact RPM. If for instance your distributor springs are shot and it is fully advanced at 1500 RPM and you set it at the ball at 1800 RPM you will be about 10 deg retarded. If however the distributor is sticking and not fully advanced until 3000 RPM and at 1500 it has only advanced 5 deg then you could easily be 8-10 deg OVER ADVANCED at 3500 and could have detonation problems and possible damage. I ALWAYS check for maximum advance just to be safe. If you are running 9.3:1 Tii/Ti pistons you MAY need 2-3 deg less.

[1971Ginger]

Thanks for your reply

I am currently running an 008 mechanical advance distributor. Where should I am to put the degrees at?

Thank you in advance,

Bottom end is stock stock stock, it's the top end that was just rebuilt with the new cam and carb (292 and 38/38)

[Preyupy]

What head are you using? With flat top pistons That could be as high as 8.3:1 compression ratio or as low as 8.0:1. You may be able to use more advance but I would start with 36 deg of TOTAL advance (the distributor should be all in by 3500 rpm) I would set it with an adjustable timing light. IF your distributor is working correctly you should see the "BALL", which is 25 deg BTDC, at about 2000-2100 rpm.

[1971Ginger]

Thanks for our help, I need all this info so I really appreciate it.

I have a 121t head, with stock Febi rockers (new) and the shrick copy Ireland engineering cam.

I've got hot spark ignition which is a Petronius knock off.

Thanks in advance,

[Preyupy]

The 121ti head will give you the highest compression ratio with flat top pistons. Depending on how much has been shaved off of it over the years I'm going to guess you are at 8.3-8.4:1. I would say 35-36 deg BTDC at full advance would be a good starting point. If you hear any pinging back it off a couple of deg at a time until it goes away. Also make sure you are rich enough, make a full throttle run up through 3rd gear and do a plug cut, make sure there is some color to the plug insulators. LEAN + to much advance = DANGER

[EdgarP]

Hello everyone I have a similar question as the topic. I bought an unfinished 1974 2002 project for my kids. Previous owner installed an edis 4 crank fired ignition. 292 cam. My question is do I fire it up using the flywheel TDC mark?  I’m just learning as I go, not auto savy.   
Any information is greatly appreciated. Thanks for your time. 

[jireland2002]

You need to set the timing at 3000+ rpm so you have full advance.  Full advance timing is the only thing you can control.  The rest is up to the curve in the distributor.  You can always check or plot the curve after setting the full advance.

 

I suggest 32-34 at full advance.

[EdgarP]

Thank you for the information. I am turning the engine by hand via crankshaft. Please correct me if I am wrong. 1. I lined up the flywheel to the TDC mark I am told that the valves on cylinder 1 have to be closed for compression but they are not despite the flywheel being TDC. Is it because the cam is after market and the flywheel markings are no longer applicable? I just want to find TDC on compression. will that suffice? I can use the megajolt software to set my advance after I get it to start. 

[jimk]

The M10 is a 4 cycle motor, it takes 720 degrees of the crankshaft.  The flywheel mark comes around twice per 720 degrees. You are probably at 360 degrees, not 0 or 720.  What do the valves on cyl 4 look like?

Edited May 1, 2020 by jimk

[EdgarP]

With the 292 cam and flywheel on the TDC mark. Cylinder 1 intake valve closed - exhaust valve open. Cylinder 4 intake open - exhaust closed. As you can see when I opened the cover all kinds of markings previously made. 

[Preyupy]

You need to check your TDC mark.  At TDC cyl #1 compression stroke both valves on cyl#1 will be closed and BOTH valves on cyl#4 wlll be partially open.  At TDC cyl #4 compression stroke it will be EXACTLY the opposite #4 closed and #1 open.  If you are setting the crankshaft at TDC and this is not the case then you either have TDC mismarked OR the cam is not timed correctly.  THOSE ARE THE ONLY OPTIONS!   

 

Are you using the mark on the front crank pulley and the timing cover?  Or are you using the OT mark on the flywheel through the sight hole in the transmission bell housing?  

[jimk]

There looks to be more going on with the cam position or the flywheel is not installed correct.  The flywheel has a keyed dowel on one bolt.  Maybe that is not installed and the wheel is not indexed for TDC. 

[Son of Marty]

Also the tdc mark on the flywheel is not the ball. 

[EdgarP]

Thanks for your knowledge guys the previous owner stated his last mod was the cam. New IE springs and such. I’m guessing the cam was installed wrong. I’m not an expert by any means but I knew both valves had to be open for compression on cyl #one. If the cam was installed incorrectly is there a way I can reset it without having to take it to a head shop? The cam is tell has a marking on the sprocket and it seemed like it didn’t line up