351c issues MAYBE

[Jayro]

Hey all,

To be honest not 100% sure I've got a problem but just wasn't right tonight. So engine is a relatively fresh build 351c. Nothing crazy.

Not having any issues. Took it out tonight and noticed when I went to merge onto the freeway and I opened right up and there was like a metal/rattle noise seemed to be coming from engine bay passenger side. Only at WOT. Done it a few times but then not again.

Then when we went to come home it wouldn't idle well. I generally idle at around 900-1100 rpm. Tonight coming home it was JUST not stalling at traffic lights and revs were about 600rpm. Can temp affect this as it is a bit chilly tonight around 10 deg C

2 issues could be totally unrelated maybe. Just seems odd I've had no issues then both these tonight.

Thanks in advance all

Cheers
Jase

 

[Steve McMahan]

The first thing sounds like detonation. What is your initial and all in timing? Also, what is your compression ratio? Since the engine is newer, you may need to do further carb refinements and tuning.

 

[giantpune]

Thats what I thought, too. Detonation during load/acceleration. My guess is too much timing at that RPM+vacuum+load combination.

 

[Don C]

Probably two issues. I would pull the spark plugs, see what they look like and make sure the gaps are correct.

After the engine is warmed up the colder temperature shouldn't have any affect, unless your choke was closing due to lack of heat to the thermostatic spring.

More likely need to check intake manifold bolt torque and carburetor gaskets. After the first few runs it's not uncommon for some things to loosen up and start leaking vacuum.

 

[basstrix]

Agree with the others that the rattle sounds like a classic case for detonation. The 2nd situation could be that one cylinder is mis-firing, aka missing. As Don suggests, I'd pull the plugs and inspect. You're looking for one plug that's fouled or damaged. The quick way to check for a misfire is to pull each plug wire with engine running and listen for change is RPM. I don't recommend unless you have the insulated tongs used for this purpose.

You'll also need to check and re-set your ignition timing. Where is the vacuum advance connected? If it's connected to timed/ported vacuum, it's probably getting too much advance at higher RPMs.

 

[Bill Kanode]

Agree with the others that the rattle sounds like a classic case for detonation. The 2nd situation could be that one cylinder is mis-firing, aka missing. As Don suggests, I'd pull the plugs and inspect. You're looking for one plug that's fouled or damaged. The quick way to check for a misfire is to pull each plug wire with engine running and listen for change is RPM. I don't recommend unless you have the insulated tongs used for this purpose.

You'll also need to check and re-set your ignition timing. Where is the vacuum advance connected? If it's connected to timed/ported vacuum, it's probably getting too much advance at higher RPMs.

Here is a trick that I learned as a diesel mechanic instructor in the Army. Back then I felt the exhaust manifold for the cold port but now I use an infrared thermometer. With a cold engine start it up and let it run for a few seconds then with the engine off quickly measure each port temperature for a cold (dead) cylinder. It is easier to find with your hand if headers are installed as the tube will stay cold longer.

 

[AcesArneson]

Hey all,

To be honest not 100% sure I've got a problem but just wasn't right tonight. So engine is a relatively fresh build 351c. Nothing crazy.

Not having any issues. Took it out tonight and noticed when I went to merge onto the freeway and I opened right up and there was like a metal/rattle noise seemed to be coming from engine bay passenger side. Only at WOT. Done it a few times but then not again.

Then when we went to come home it wouldn't idle well. I generally idle at around 900-1100 rpm. Tonight coming home it was JUST not stalling at traffic lights and revs were about 600rpm. Can temp affect this as it is a bit chilly tonight around 10 deg C

2 issues could be totally unrelated maybe. Just seems odd I've had no issues then both these tonight.

Thanks in advance all

Cheers
Jase

Did you replace your harmonic balancer during the rebuild? Sounds like maybe it is old and the rubber between rings has dried to the point it has slipped. You will never get your timing right again with that balancer if it's bad, it will need to be replaced if that is your issue. This is an issue that usually pops up right after a rebuild because the engine has likely sat for a long time during the process without being used.

 

[Jayro]

Did you replace your harmonic balancer during the rebuild? Sounds like maybe it is old and the rubber between rings has dried to the point it has slipped. You will never get your timing right again with that balancer if it's bad, it will need to be replaced if that is your issue. This is an issue that usually pops up right after a rebuild because the engine has likely sat for a long time during the process without being used.

Yeh new balancer when we had engine built. I took it out again next day. Ran great again. Idled around 900rpm at traffic lights etc.

So we don't run any thermostat (utilise a "restrictor" in its place. And don't have any choke system connected.

 

[Steve McMahan]

Did we ever find out base and all in timing?

 

[Cleveland Crush]

Jayro, do you have an in car engine temp gauge? Or at least measure the block temp with a temperature gun near the thermostat house. Excessive temperatures=knock and ping under load/WOT. Also please reconsider your decision to not run a thermostat! Good luck with it.

 

[Jayro]

Jayro, do you have an in car engine temp gauge? Or at least measure the block temp with a temperature gun near the thermostat house. Excessive temperatures=knock and ping under load/WOT. Also please reconsider your decision to not run a thermostat! Good luck with it.

Yeh I think my issue is that the boys that tune it and got the ICE ignition etc all sorted......they just basically do race engines and hence they don't like stat's or chokes but I'm not convinced that's best for my set-up which is primarily a cars n coffee type use.

I do have a temp gauge mate. Was only down at 160deg F while cruising.

 

[AcesArneson]

Jayro, do you have an in car engine temp gauge? Or at least measure the block temp with a temperature gun near the thermostat house. Excessive temperatures=knock and ping under load/WOT. Also please reconsider your decision to not run a thermostat! Good luck with it.

Second that motion! If you are driving your car with a restrictor plate instead of the designed thermostat it is a ticking time-bomb, in my opinion.
Just go to YouTube and search for 'The Correct 351C Thermostat' and watch a couple of videos. Without the thermostat these Clevelands DO NOT circulate coolant through the radiator. A restrictor plate will force flow through the rad but it is not controlled by engine heat. Hope this decision doesn't leave you stranded on the side of the road with a blown gasket and warped head.

 

[Jayro]

Second that motion! If you are driving your car with a restrictor plate instead of the designed thermostat it is a ticking time-bomb, in my opinion.
Just go to YouTube and search for 'The Correct 351C Thermostat' and watch a couple of videos. Without the thermostat these Clevelands DO NOT circulate coolant through the radiator. A restrictor plate will force flow through the rad but it is not controlled by engine heat. Hope this decision doesn't leave you stranded on the side of the road with a blown gasket and warped head.

Mate she runs cold not hot even in the peak of our summer the thermos cycle le nicely. High temps and head issues are not an issue at all. I do agree a statement will obviously give greater temp control but no high temp issues with my set-up.