Predetonation Q

[dlb]

hmmm, that's a bummer because i drove the car with the #1 port blocked last night and the ping was almost gone. it only occurred in 5th gear, at the start of and at at the crest of hills. oh well.

i remember a few threads on catch cans on the forum here so i will look them up and give it a shot. why would there be excessive oil mist or other liquid contaminates flowing through the PCV system though? is there an underlying issue causing this?

[4wdchico]

From your earlier post I think that your PCV system hoses might be mis-connected. Does the hose that attaches to the PCV valve connect to the air cleaner? Your description makes it sound like that is the case, and that would be wrong.

Also remember that night = lower air temps= less ping.

As far as excessive oil mist goes, any is too much, if your goal is to prevent ping and keep the insides of your engine & oil clean. Even a very tight motor will generate some blowby. Of course, one built with gapless rings will have the least. If you search the web for catch can issues you will see plenty of very new & lower mileage vehicles that have had the catch cans put on them & most of them are pulling a fair amount of gunk out of the system.

You can reduce the level of oil mist flowing thru your PCV system and improve your MPG by never running your oil level more than halfway up the operating range on the dipstick at any time. That gives you less margin for error in monitoring the oil level, your choice.

Your 4a was used right? So it might benefit from a 24 or more hour Seafoam soak to free up the ring pack. I did one to my 3ac when it had about 148k miles and the compression went up across the board and was more even as well.

[dlb]

chico, you're right. i just took a look and my weber has been hooked up incorrectly the whole time! shit. sometimes i wish i had done this work myself even though i wouldn't have known where to start at that time--if someone's gonna mess my stuff up it should at least be me. my car is at the muffler place right now so i'll have to look at routing the lines properly when i pick it up. i'm sure getting those lines sorted out will be a big help in the pinging department.

the 4A i have in car was used but i did a huge seafoam treatment on it already, through the carb. pretty sure i also poured it down the spark plug holes and let it sit for a few days. did you make your own PCV catch cans or did you buy them somewhere?

[4wdchico]

For the fresh air side i use one of these: http://www.uprproducts.com/mustang-bill ... ished.html

Told them I did not want the fittings or hose, just the can and the mount and they sold an unpolished one to me for $80. Nice unit & the only one that I found that will do just as good a job pulling out gunk regardless of which way the air is flowing thru it. Honestly, if you car no longer needs to be smog checked you could, for a whole lot less cash, just go with something like this: http://www.summitracing.com/parts/AID-775-480/

For the pcv valve to manifold vac side you can go on the cheap with a small air compressor oil trap/ filter. Mine is a Home Depot Husky brand with a 20 micron sintered bronze filter element. Sorry, but it is no longer available, and the one that they now sell I have no input on. Tons of info on this subject on the web for the gleaning...

[takza]

Check here....

https://tercel4wd.com/forums/viewtopic.php?f=7&t=3293

[dlb]

thanks takza, i have taken a look at that thread already. for purely aesthetic reasons i will probably buy a few catch cans rather than DIY it. first off i want to try just hooking up my PCV system correctly and see how that works though.

[takza]

I use a HarbourFreight air line filter on my wagon right now...works OK...but they don't sell the cheap one's anymore. I do take out the filter part cause I thought it might be too restrictive...but maybe not.

[Petros]

you know, it seems to me this device should not be necessary. If the system is operating normal there should be no significant amount of oil getting into the airfilter, even if the engine has a lot of blow-by. I would make sure everything is working properly before I added any extra devices. The operation of the PVC should interfere with engine operation, nor affect fuel economy, and it should work properly with the Weber presumably it is connected properly.

[dlb]

so i hooked up the fresh air intake of the PCV system to the port on the underside of the air filter but cannot find the port that others have hooked the PCV valve to.

if you look at this photo from the weber install thread, you can see the hose that runs from the PCV valve to a port at the base of the carb:



i don't have a port at the base of my weber though. the nearest i can see there is what appears to be a brass-coloured plug in approximately the same area. you can just see it here, below the brass arm:



is there some way to connect to this port that i'm unaware of? or should i remove the EGR (which is disconnected anyway) and make up something like splatterdog did to connect the PCV outlet hose to:



also of note is that i don't have that metal plate that sits underneath the carb (the big shiny silver piece seen in the first photo) installed. is that a heat shield to protect the carb from the heat of the exhaust manifold? should i put it on? i don't know why my bud didn't put it back on when he installed the weber.

thanks again guys.

[Petros]

I would definitely keep the heat shield. The other device where the hose plugs in is an insulator with the heater element on the primary, the heater is not required unless you live in an area where it gets really cold, it prevents ice build-up under the throttle plate. Without it you take your chances of getting icing under the carb before the exhaust manifold heats up the intake. Not a big problem, just a cold run nuisance. The car will have more power without the heater element since it restricts the size of the primary barrel.

I suspect you can find any port into the intake manifold to install the vac line for the PVC.

[dlb]

hmmm. it doesn't get SUPER cold here but last winter i did find the weber took about 8-10 minutes to warm up. during that time it was prone to stalling during idle. i would like to decrease that warm up period but don't know if i want to sacrifice the power--probably not!

now what i'm wondering in regards to my missing heat shield: since the pinging problem is happening after the engine has warmed up, could it be that the heat from the exhaust manifold is rising up to the carb and heating both the gas and the air there, before both even enter the intake manifold? danzo's comment about a heated intake charge causing predetonation got me thinking about that, though i don't know if the heat would really make too much difference to the carb. it must though, if it's designed to operate with a heat shield there. my dad mentioned that he has heard of gas in carb floats boiling from similar circumstances but i'm not sure that this would create predetonation either.

my dad is making a copy of splatterdog's EGR to PCV conversion plate as we speak!...

[Petros]

On the exhaust manifold there is bi-metal strip controlled flap that directs exhaust heat to the intake manifold, to heat it during cold starts. Danzo had that flap stuck in the "open" position so it was always heating the intake manifold, you might have the same issue. WHen it was warm out (which is the case where he lives), over heating the intake manifold was causing the ping, once the flap was freed up, it ran normal again.

[dlb]

yes, i checked that out first but mine is working fine. i even wired it in the closed position just to see but it didn't help. do you think the heat shield could be playing a role in all of this? it seems to me that the air and fuel could be getting heated in the base of the carb similarly to how danzo's malfunctioning heater flap was heating it in the intake manifold, but i have no idea. i'm just trying to think of different possible causes.

[Petros]

I do not think the lack of heat shield would cause that except in very hot conditions, in heavy trafic or up steep slow grades. IT is possible that if you do not have that plastic base plate the carb will heat up through the manifold. Consider the intake manifold is bolted right to the exhaust manifold, and the carb bolted to the intake manifold right above it. It will heat up through conduction. Even fuel injectors in the modern engines have these plastic insulators on them.

There is a reason there is a plastic insulator plate under the carb. You might make one to fit the Weber out of suitable high temp plastic. Phenolic or perhaps some high density polyethylene, or acrylic perhaps; you need something that can take the heat of the engine. you could test it with a piece of plywood, but I would not leave that in place for long. You can reinstall the heat shield when you get the insulator installed.

[dlb]

it's been a while but i've made some progress in this department. i was having some pinging occur when under load ever since i had put the weber on my 3A. i had hoped that when i switched to the 4A that this problem would disappear. it did not, so it appeared likely the problem was not with the engine but somehow related to modifications made in relation to the weber. i had seafoam'd the combustion chambers, checked for vacuum leaks, retarded my timing back to stock 5* BTDC, tried cooler heat range spark plugs, got my PCV system set up properly, wired the heat control valve on the intake manifold to never warm the intake air, disconnected the vacuum advance, made the fuel mixture richer, and reinstalled the heat shield that normally sits beneath the spacer. none of this stopped the predetonation. i never bothered trying high octane gas because buying even MORE expensive gas is not an option and didn't seem like it would help me diagnose anything. when my friend helped me install the weber we never put the shield or spacer in because of concern over hood clearance so the spacer was the last thing i wanted to try but i finally did and i had interesting results.

the engine ran considerably cooler according to the gauge, and the predetonation was gone. first i drove with no air filter on the weber so that i could close the hood. i drove like this for maybe 40 km. this yielded the cooler/no pinging result, so i put the filter back on and had to leave the hood only partially latched and fastened with bungee cords in order to drive it around. i drove it like this for at least 150 km and this yielded the same result, which was great news but now i'm left with having to deal with the hood clearance issue. like tom, i replaced the engine mounts when i put in the 4A last year, and also like tom, i need at least 3/8" more clearance to close the hood, though 1/2" would be ideal. i don't like the idea of shortening the weber air filter (it's the 2" one already) because that lowers the lid for the filter towards the intake throat, making it more difficult for the air to squeeze in there. i know tom has reported no problems with this but i'm looking at alternatives anyway. i'm considering getting another hood and installing a hood scoop but i am also talking to K&N about either a low profile filter or low profile adapter so that the filter would sit in the space between the engine and the passenger side of the engine bay. sort of like what board member pearson has:



i'll be figuring out what i'm going to do about this over the next few weeks while ron gets his ass fixed at the body shop and i go over his front end. stay tuned for the conclusion of this gripping tale.