setting timing with overlap

[darky82]

Hey new to v8s i own a vs 5.0L and having trouble getting dizzing timing right because of my cam overlap had a look a holdenpeidia at timing and it explains the overlap will cause back firing through the manifold but im getting is flash flames from my headers every now and than mostly nothing all marks are in line all leads in right position tried going back a tooth on the dizzy same thing. Also may have stud mount roller rockers too tight but rods still spin with some resistance.

[db_notso]

5.0L not starting after rebuild

trying to sort a similar problem here

[immortality]

what are the cam specs?

have you put the ecu into diagnostic mode to lock out any timing advance?

[Blown V6 Hatch]

Is the cam timing right? 9 links between the dots, not dot to dot?

[darky82]

08052011086.jpg08052011086.jpgI used a gear drive its set right my machinest done it. Cam specs

[Blown V6 Hatch]

It doesn't matter what cam it has in it, the ignition timing is still set exactly the same way. Number 1 cylinder, TDC on compression stroke, drop the dizzy in pointing at number lead, start engine.

[darky82]

could my roller rockers be set to tight, whats the best way to set stud mounts

[Blown V6 Hatch]

Well, assuming the cam is hydraulic and not solid, you wind the adjuster screw down until you can just turn the pushrod with your fingers (this is whats called the zero freeplay point) then give the adjuster 1/2 a turn and lock up the locknut.

If it's a solid cam, it needs to have clearance between the valve tip and the rocker.

Edit: Just looked at the cam card, it's hydraulic so dis regard the second part of my post.

[ari666]

then give the adjuster 1/2 a turn and lock up the locknut.

you are totally right BV6, but the only thing is different rollers adjust at different rates. my YT's say 1/8th of a turn. i think the crane stud mounts are 1/2.


but yeah OP, if an inlet valve is too tight, itll backfire through the manifold cos the valve is still open. but thats pretty extreme. what type of rockers are they?

[Blown V6 Hatch]

I've always adjusted adjustable rockers (rollers or pressed steel) with the half a turn method regardless of the brand. Never had a problem. I guess if they are adjusted wrong, it will hold the valve open, but like you say it'd have to pretty extreme.

OP, when it's cranking over, does it sound like it has compression? I.e does it sound different to when you cranked it over without the plugs in it?

I'm still tipping 180 out on the timing though, go back to basics and start again with the timing.

[ari666]

I'm still tipping 180 out on the timing though

id have to agree

[darky82]

Yeh man only did my rockers 1/4 of a turn after they nipped up they are the gold pro comp ones lol yeh i know they are crap but budget retricted me, yeh sounds like it has comp, hard as to turn over with plugs in it busted my arse

[darky82]

Ok thanks to all for your help, i solved the problem, when i got my engine back from the machinest after we dialed the cam in the engine was left were it was on TDC, we forgot to turn the engine one more rotation to its comp stroke before putting the dizzy in, she fires up and needs a remap bad lumpy as about 1500 wont idle below about 1200, cant wait sounds wicked of the headers, Cheers happy hellies..