Re: harvs ek 327 wagon
Posted: Thu Feb 23, 2023 2:05 pm
Chasing a new issue on the wagon. Small block Chev, Holley carb, TH350. Has run for quite some time now, so probably not a "installed new parts and they are wrong" issue. Car is regularly abused at Eastern Creek, so breaking something is on the cards. Starts fine, though of late seems to take a little longer to warm up (maybe I'm imagining that bit). Idles fine.
Put it into gear (like when you are stopped at the traffic lights) and it struggles to idle... runs, but will stall after 30 seconds or so if left alone. Put it from Drive to Park/Neutral and the idle comes up and it is happy again. I'm getting tired of throwing back to Neutral in Sydney's stop/start traffic.
Car has become slightly hesitant off idle. At cruise (say 60km/h) it surges. No pinging. Accelerates from cruise with no issue all the way up to WOT. Sounds healthy all the way.
A drive or two before this started I gave the gearbox a workout. Inadvertently left it in 2nd, and did 10 minutes on the freeway. Gearbox got hot (I suspect) and warmed up the engine oil via the radiator. Coolant temperature increased, but did not boil. Oil pressure started getting low (~20psi), but not low enough to put on the idiot light. Got off the freeway, put it into drive, and drove for 20 minutes. Car cooled, oil pressure came back up to 50psi or so. No ill effect noticeable. Have changed the trans fluid since then, fluid looks fine (clear, not burnt at all), as did the pan (very slight amount of grey shadow in the pan, a very small number of ally particles, and just enough steel particles to cover the magnetic sump plug).
Don't think this is a trans issue. Have changed nothing else, but may have busted something in the months of driving this thing gets. Gut feel it is one of three things:
a) the timing is a little tardy. Put the timing light on it, and it is pulling 20.5 degrees at idle. That should be fine. Timing light was playing up so didn't get a chance to check it across the rev range. From memory this thing runs either 32 or 36 degrees all-in.
b) the main metering circuit is slightly lean. Idle circuit must be OK as it idles OK. Accel pump might be crook (hence the slight hesitation) but that does not explain the surging at cruise. Maybe partially blocked main metering jets. It has a fuel filter, which I pulled. No evidence of heavy gunk that might have got through the filter. It's not a filter/fuel supply issue as it behaves fine under heavy throttle (... and still surges with a new filter).
c) it has a vacuum leak. Sprayed Start Ya Bastard around the carb, inlet manifold and at the transmission vacuum connection and did not get a response. Hard to tell though as this thing does not "jump" much in idle even when you spray down the carb throat. Most of the trans line is steel pipe, there is no brake vacuum connection. No rubber caps have blown off the carb.
My plan of attack:
a) Swap timing lights and make sure it advances up the rev range. If it does, then timing is not the problem.
b) Fit a wideband oxygen meter to the exhaust and see what the values look like at cruise. Should be around 13-14.7 AFR at cruise, the lower the less likely to be lean. Results higher than 14.7 or so probably mean it is lean from either lack of fuel or a vacuum leak.
c) Repeat the vacuum test with something that has no oxygenates in it (more fuel heavy like WD40) so I can hear the rev change better.
d) If there are no vacuum leaks, pull the front float bowl, pull the main metering jets, blow them and the passages out with air.
Opinions welcome.
Cheers,
Harv
Put it into gear (like when you are stopped at the traffic lights) and it struggles to idle... runs, but will stall after 30 seconds or so if left alone. Put it from Drive to Park/Neutral and the idle comes up and it is happy again. I'm getting tired of throwing back to Neutral in Sydney's stop/start traffic.
Car has become slightly hesitant off idle. At cruise (say 60km/h) it surges. No pinging. Accelerates from cruise with no issue all the way up to WOT. Sounds healthy all the way.
A drive or two before this started I gave the gearbox a workout. Inadvertently left it in 2nd, and did 10 minutes on the freeway. Gearbox got hot (I suspect) and warmed up the engine oil via the radiator. Coolant temperature increased, but did not boil. Oil pressure started getting low (~20psi), but not low enough to put on the idiot light. Got off the freeway, put it into drive, and drove for 20 minutes. Car cooled, oil pressure came back up to 50psi or so. No ill effect noticeable. Have changed the trans fluid since then, fluid looks fine (clear, not burnt at all), as did the pan (very slight amount of grey shadow in the pan, a very small number of ally particles, and just enough steel particles to cover the magnetic sump plug).
Don't think this is a trans issue. Have changed nothing else, but may have busted something in the months of driving this thing gets. Gut feel it is one of three things:
a) the timing is a little tardy. Put the timing light on it, and it is pulling 20.5 degrees at idle. That should be fine. Timing light was playing up so didn't get a chance to check it across the rev range. From memory this thing runs either 32 or 36 degrees all-in.
b) the main metering circuit is slightly lean. Idle circuit must be OK as it idles OK. Accel pump might be crook (hence the slight hesitation) but that does not explain the surging at cruise. Maybe partially blocked main metering jets. It has a fuel filter, which I pulled. No evidence of heavy gunk that might have got through the filter. It's not a filter/fuel supply issue as it behaves fine under heavy throttle (... and still surges with a new filter).
c) it has a vacuum leak. Sprayed Start Ya Bastard around the carb, inlet manifold and at the transmission vacuum connection and did not get a response. Hard to tell though as this thing does not "jump" much in idle even when you spray down the carb throat. Most of the trans line is steel pipe, there is no brake vacuum connection. No rubber caps have blown off the carb.
My plan of attack:
a) Swap timing lights and make sure it advances up the rev range. If it does, then timing is not the problem.
b) Fit a wideband oxygen meter to the exhaust and see what the values look like at cruise. Should be around 13-14.7 AFR at cruise, the lower the less likely to be lean. Results higher than 14.7 or so probably mean it is lean from either lack of fuel or a vacuum leak.
c) Repeat the vacuum test with something that has no oxygenates in it (more fuel heavy like WD40) so I can hear the rev change better.
d) If there are no vacuum leaks, pull the front float bowl, pull the main metering jets, blow them and the passages out with air.
Opinions welcome.
Cheers,
Harv
I was going over Franks engine after I got back from the nationals and found one of the exhaust manifold bolts missing altogether, since I have found another couple have also backed off, I’ve tightened them I think twice now, hard to know how tight without over stressing them and not sure if there is an actual torque setting for them, think I’ll have to check the manual.
