Engine timing issues

[Sprinkler-Man]

Rebuilt 350 bored 40 over
Dart aluminum heads, roller rockers, aluminum dual plane intake
Street demon carburetor
Radical cam
I am having problems getting the timing set correctly.  I have never delt with a cam this radical and it just doesn't seem to want to run properly.  If I advance the distributor to where it runs nice it won't start when hot and I have to retard the distributor to get the engine to turn over.  Is there any tricks to tuning a race engine?

[Irish_Alley]

where do you have the vacuum advance hooked up? is it working right?
if you hook it up to manifold vacuum you can have the timing retarded more then once it starts it should advance it and it should be running good. if its on a ported vacuum then you dont see no advance till the throttle is moved

[Sprinkler-Man]

I tried it on manifold vacuum but the truck started to rev but I didn't try to retard the timing first.  I did take it to a speed shop and they set the timing and left the vacuum advance off and told me with this type cam it would need to be all mechanical advance.  I only have 10 inches so I also have a brake stopping issue which I will address later.  Even with their help is doesn't seem to run right.
Maybe I will try and hook up the advance and go from there.

[Irish_Alley]

with the vacuum timing you can start it at 16° and the starter shouldnt have any problem with that then once its started it will advance to 36° or so. im not a speed shop so they "should" know more than me but i never heard only being able to run mechanical advance. someone like rich should be able to chime in

[rich weyand]

With that little vacuum at idle you need a special VA can so the advance is all in at idle, or the thing will hunt.

You probably ought to be running a VC1825 can.  It's all in at 6 to 8 degrees of vacuum.  18 crankshaft degrees of advance, which is a little high but not bad.  Probably don't want more than about 34 degrees of total timing with that (which would give you 52 degrees at cruise), so a normal 20* on mechanical would give a top base timing of 14.  Maybe best to run 12.

But you need a can like this that doesn't take a lot of vacuum to pull all the way in, or it will be on the edge, and the idle timing will hunt up and down and give you a crappy idle.

http://www.napaonline.com/Catalog/CatalogItemDetail.aspx/Vacuum-Advance-Control/_/R-ECHVC1825_0460863168

[Irish_Alley]

I slightly remember you talking before about the cam and it not producing enough vacuum at idle. What size is too big for vacuum?

[Sprinkler-Man]

Thanks for the advice on the vac can. I am not sure what the cam specs are. I bought the lower end from a guy who didn't know the specs on the motor. I think my vac can is adjustable. Maybe I will try playing with it.

[FlatBlack77]

are you setting the timing by ear? or using a light?

[rich weyand]

Thanks for the advice on the vac can. I am not sure what the cam specs are. I bought the lower end from a guy who didn't know the specs on the motor. I think my vac can is adjustable. Maybe I will try playing with it.

You need to set it real light, so it pulls in without much vacuum.  That will make sure it pulls in hard and doesn't hunt when idling.

[HAULIN IT]

Rich has you on the right path. A couple things I'll add are: You will need to be a bit careful with mid RPM if I'm correct in assuming you have this engine in the 4x4 you mention in your profile...there can be quite a difference between what the same engine can tolerate in say a 2900 lb car with a high stall converter & steep gears used mainly at idle or full throttle & that of a 4x4 that weighs 4600 lb with 35" tires or so with 3.08 gears you are planning to lug up a hill.

To add my thoughts...you will likely find your engine (assuming "radical cam" is a 230+ duration @ .050) will love 24-30 degrees of timing at idle, which is not a problem at all. It will make for a much crisper & cleaner running engine. If you can drive it in your daily travels with this amount in will depend on the compression, fuel & several other factors.

The vacuum can that Rich mentioned is a start. Using light springs & altering the weight cam plate to move A BUNCH right away can be done to allow what you need...cranking at a reasonable number & near instantly jumping to mid 20's as the engine fires. You will likely need to limit the travel of the weights & also the vacuum advance so you don't end up with too much total timing. There are companies that sell a little notched plate to limit the vacuum advance & a small screw can limit the weight travel. Start with the vacuum can Rich showed & go from there.

Unfortunately there is such a thing as: The "right" parts used in the "wrong" application...something like a 240 @ .050 cam in a daily driven, big clunky truck would be a fine example! My Two Cents, Lorne
   

[Sprinkler-Man]

Thanks for all the advice. This truck will not be a daily driver. Just a toy to drive in the summer. After I got it in the truck and started I quickly realized I had the wrong combination for a daily driver. I did put in a 2500 stall converter to help a bit.

[BIG RED 1983]

Have you had  any more luck with it?

[Sprinkler-Man]

Not yet, I have a problem with my transmission or transfer case so I haven't been able to drive it.   

[BIG RED 1983]

Sprinkler, have you any idea what kind of compression this engine has?

[Sprinkler-Man]

should be about 10-1 but I don't know for sure.