Something wrong with the old trusty 202
#1
Posted 16 September 2019 - 07:05 PM
202 running a stage 3 yt head and some decent cam with a 350 Holley.
I got this engine with the car so it was a bit of unknown. It drove off the trailer, idled fine, blew no smoke etc so i took a punt on it. Fast forward 6 years later after the car has been put back together, it’s drives fine.....not setting any land speed records but it went ok, no pinging etc just a bit sluggish. Right of to the mechanic for a tune. Now this guy has been around for a long time and has been in the preformance game before I was born so I trust his judgment. But I’m confused with what happens next. Gives me a call and tells me that it appears the top dead center mark was out as well as it was advanced heaps so set it where he thinks it should be. Remember this engine drove ok and no pinging etc. After he sets the timing etc it starts ‘exhausting’ out the inlet manifold. So looks like compression test is in order. Down on 3 cylinders. Maybe it’s the valves??? Did a leak down test and the valves appear to be fine. Maybe it’s the cam timing? Looks like that’s ok so it’s got to be the rings? Then why isn’t there any signs of blow by? Can some one give any ideas on what’s missing here? Like I said I didn’t expect this to happen today as it was all good but now it won’t even hardly drive without a heap of throttle etc. I’m going to go through the basics myself to see if it’s all correct but I’ll take any ideas on what you guys think?
#2
Posted 16 September 2019 - 07:39 PM
#3
Posted 16 September 2019 - 08:05 PM
#4
Posted 16 September 2019 - 08:49 PM
Had a similar problem with 1/2 race LJ at a Hillclimb, a factory dizzy with a worn top bearing resulted in a foam filter fire ( tripple Webers) as it fired with inlets open.
Got talked into a Chinese Bosch copy electronic dizzy. At Challenge Bathurst, same thing, foam filter fire...this time it was found tbe little key in the shaft of the elecronic dizzy reluctor wheel had sheared off, changing the timing.
Moral - dizzy issue?
Moral for me - dont buy crap.
Hope that helps mate
p.s. Aussie "Scorcher," electronic dizzy fiited an no more dramas
Edited by RallyRed, 16 September 2019 - 08:54 PM.
#5
Posted 16 September 2019 - 08:59 PM
#6
Posted 16 September 2019 - 09:36 PM
#7
Posted 16 September 2019 - 11:31 PM
think it's obvious the mechanic is a goose . Put more advance back in it
If i remember right to check the balancer the keyway on the crank should be at 12 0'clock when the timing mark is at TDC ( to give a ruff idea )
#8
Posted 17 September 2019 - 06:39 AM
Attached Files
#9
Posted 17 September 2019 - 07:58 AM
I would start with 6 deg advance and go from there.
#10
Posted 17 September 2019 - 08:05 AM
#11
Posted 17 September 2019 - 08:21 AM
With the plug on #1 out use a rod that the piston will hit down the hole and rotate the engine (by hand) both ways so the piston hits the stick as it comes to TDC. Mark the balancer against the 0deg mark at both points where it hits. The balancer mark should be exactly in between the two marks. I still think the balancer ring may have moved.
As UCSLE says though just feed it some more advance and see if the problem goes away. Make sure the dizzy is free though and that the balancer ring isn’t going to come off on you.
#12
Posted 17 September 2019 - 09:35 AM
#13
Posted 17 September 2019 - 11:46 AM
Was the dizzy ever re set and regraphed for the new cam?
Think thats the words anyway. Damned painkillers fog the brain.
Have you dropped a bit of oil onto the felt for the bob weights under the rotor button?
Other good suggestions have been made above.
Cheers
Rob
#14
Posted 17 September 2019 - 11:57 AM
#15
Posted 17 September 2019 - 01:00 PM
Just to clarify 6 deg initial advance, if you have the mark on the balancer aligned with the 6 deg advanced mark on the timing cover, then the scribe mark on the rotor button is aligned with the mark on the edge of the distributor housing?
#16
Posted 17 September 2019 - 01:48 PM
#17
Posted 17 September 2019 - 02:30 PM
Check plugs are clean,
leads have same resistance reading, dizzy cap underside are clean (no white corrosion buildup),
and put in a set of new points with a matchbox cardboard thickness gap.
Also do a tappet adjustment (hydraulic cam and lifters only),
while engine idles (oil will run over motor a little, unless you cut the top out of an old cover),
with tappet cover off, turn anti-clockwise each of 12 tappet nuts,
one at a time, and hear loud tapping,
then clockwise turn nut until tapping stops and turn 1/8 of turn more and stop.
All 12 tappets are now set properly.
Now loosen dizzy retaining bolt a little,
and by hand rotate dizzy either way while motor running till it runs nice,
then tell us what the strobe light reading is.
Regards Dave I
P.s. Hydraulic Tappet adjustments works for any cam, head, or carbs used,
except for solid cam and lifters, you use feeler gauge tappet adjustments while engine off.
#18
Posted 17 September 2019 - 05:46 PM
#19
Posted 17 September 2019 - 06:07 PM
#20
Posted 17 September 2019 - 06:18 PM
by the way,
you will also notice the sound changes when doing the tappet check,
and know if the cylinder is working or not.
p.s. you never know what the mechanic did, so back to basics for us.
#21
Posted 17 September 2019 - 07:30 PM
Bosch HEI ignition you say. What gap have the spark plugs been set to? Do you have 12v at the coil with ignition in the ON position? Do you have the correct coil to suit the HEI?
With the initial timing set at around 6 deg advanced and backfiring in the inlet manifold could be a sign the cam is out a tooth or could be a very lean idle fuel mixture.
Edited by S pack, 17 September 2019 - 07:31 PM.
#22
Posted 17 September 2019 - 08:34 PM
#23
Posted 17 September 2019 - 09:13 PM
You should be able to get a good indication of the camshaft phasing just by checking when the crankshaft is at TDC.
Remove the plugs and the rocker cover. Turn the engine over by hand until the exhaust and inlet valves are on the rock on #1 cyl (dissy will be firing #6).
When the timing mark is at TDC the exhaust valve should be closing and the inlet valve starting to open.
Try richening up the idle mixtures. Lean mixtures burn slower. Perhaps that is why the engine needs lots of initial advance, so a lean mixture has time to burn completely before the inlet valve starts to open again.
#24
Posted 17 September 2019 - 10:07 PM
Might seem like silly questions but:
Auto or manual?
Where is the vacuum advance connected on the carb?
Are you using ported or full vacuum for the dizzy advance?
If you are using full vacuum are you disconnecting the vacuum advance to do the initial timing check?
Note that most carbied Holden engines use ported vacuum for manual and full vacuum for an auto for vacuum advance. This is why pre-canister cars (pre 1/75) have different carbs for manual and auto, but after 12/74 they are the same as all cars need ported vacuum for the canister purge.
#25
Posted 18 September 2019 - 05:42 AM
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