345 Burning up valves???

[bwolcott]

First, I would like to warn that I am very inexperienced when it comes to engine work.

I am looking for some help with a 345 which is mounted in an 1982 International School bus. We keep burning up the top two valves (opposite the trans) I have been told that is has something to do with the engine being mounted at an angle slanted towards the rear of the bus. Right now it have the stock 2barrel intake and carb. I don't believe that the vacuum timing system works. I was wondering is someone could explain how, if possible, I can use an electronic distributor not points?

Would that help my problem? I need help.

[Jim Grammer]

Originally posted by bwolcott
We keep burning up the top two valves (opposite the trans)

What valves are we talking about? Intake? Exhaust? Not sure what you mean by 'opposite the trans'. The cylinder #'s are cast into the top of the intake manifold, 1-3-5-7 on the driver's side, 2-4-6-8 on the passenger's side. Which cylinders are affected?

I have been told that is has something to do with the engine being mounted at an angle slanted towards the rear of the bus.

Poppycock. The engine is designed to be mounted at an angle, just like nearly any front engine/rear drive vehicle. Look at the carb mounting area on the intake manifold, it will be pretty level. Even if it's a few degrees off, no big deal. Trucks manage to climb hills without breaking motors, don't they?

[quote] Right now it have the stock 2barrel intake and carb. I don't believe that the vacuum timing system works. [quote]

Not sure how this relates to your problem...has anyone tested the vacuum advance? Timing light and a hand vacuum pump are all it takes.

I was wondering is someone could explain how, if possible, I can use an electronic distributor not points?

In an '82 you should already have an electronic ignition unless your distributor and/or engine have been replaced with an earlier(much) model. Stock it would have had a Prestolite distributor with the ignition module inside. There is a Pertronix Ignitor available for these at about 1/2 the price of a replacement factory style module. If you do in fact have points, there should be an Ignitor available but you need to identify which distributor you have: Delco(very early), Holley, or Prestolite(w/points). Alternatively you can use a points distributor to trigger a standalone electronic ignition like an MSD or Crane.

Would that help my problem? I need help.

Don't think we know what your problem is yet , a lot more detail, symptoms, etc. would help a bunch. Who's working on this for you, and what else have they told you?

I have never seen a 345 mounted with any tilt to it. Sounds odd.

It is common for the cylinders that are farther away from the carb (1,2,7,8) to get a little leaner mixture than the cylinders closer to the carb. BTW, the cylinders are number from the front (where the distributor is) to the back with the cylinders on the left side being 1,3,5,7 and the ones on the right side are 2,4,6,8. So if I understand correctly, you are talking about 7 and 8.

A lean mixture going to those cylinders may be the cause of the burned valves. Lean mixtures can be caused by vacuum (air) leaks. In other words, additional air may be getting into areas where it is not supposed to, in this case the runners in the intake manifold or head ports for 7 and 8, causing the mixture of air-to-fuel to have too much air in it.

If the intake has been removed (and I assume it has if you have replaced or re-ground the valves) then there could be air leaking at the rear of the intake. Sometimes an intake will warp just a little over time and it can be difficult to get it to seal properly with just stock gaskets or no additional sealing material.

Some folks have used a high temp (gold) RTV sealant in the new steel shim type gaskets. Others have opted to use the thicker composite gaskets made by Detroit Gasket (Corteco). There is a guy on the older BB (http://broken-link/cgi-bin/webbbs/techtalk.cgi?noframes) that works at a place where they stock the Detroit Gaskets. His name is Will Marsh. Do a search on his name. One of his posts should have the phone number of the store.

A company called Pertronix (http://www.pertronix.com/) makes a product called the Ignitor that can be installed in many of the distributors used in IH SV engines including the 345. It replaces the points (or even the electronics in a Prestolite) and mounting plate inside the dizzy. Takes less than an hour to install and you have electronic ignition. Many of us have installed Ignitors. They sell through distributers like many of the vendors that run banner ads (see the top of the page) on the IH BB's. Give Super Scout Specialists a call. Here is their web link: http://members.aol.com/suprscout/. Their phone number is on the web site.

[bwolcott]

Thank you for your quick responses. I should have researched my situation a bit further before I posted my question.

I asked the guy who has worked on the engine, who is not very familiar with international engines and now have a few more details.

First the engine is mounted at an angle but as mention in one the responses the intake carb surface is level. This should not have any effect, correct?

The valve that is burned is exhaust valve for cyclinder number 5. (passenger side second one in from the from the front of the bus)

I just had the heads professionally rebuilt they said that their opinion it was a mixture problem that burned the valve.

The vacuum advance is hooked up to the intake manifold, so that it is in "full manifold advance" if that makes any sense to you

And last, the bus does have an electronic ignition but I am not sure the type.

[Supremebeholder]

Sounds like it was running too lean.

Ahummm,

Cylinder # 5 is the thrid one back from the front on the left (driver's) side. The 2nd one back on the right (passenger's) side is #4.

Rarely do intake valves get burned as they get cooled by the incoming mixture every 4th stroke. And most often burned valves are the result of a lean condition in that cylinder.

What plugs are you using?

What does the plug from that cylinder look like after it has been run for a while? If it is white then that cylinder is running lean or the heat range of the plug is too hot or both. Ideally, the plug will be a light gray or light tan color. This indicates the correct mixture is getting to that cylinder and the heat range of the plug is correct. If a plug is black and sooty then that cylinder is running rich or the plug is not a hot enough plug or both. Learn to read the plugs. There are some web sites that show different conditions and what the causes are. Here is a link to one: http://www.buckeye-illinois.com/sparkplugs.htm

If the burned valve really is # 5 then check the routing of the # 5 and #7 plug wires. These two cylinders fire consecutively and cross fires are very possible causing a cylinder to fire at the wrong time and even twice. IH came out with a service bulletin recommending that the # 7 wire be routed down the right side of the carb then behind it to the spark plug (last one from the front on the left or driver's side) to prevent cross fires. Don't let the plug wire lay on the intake either. If the wire insolation is not in good shape it will short out the spark to the intake plus the intake is too hot and will cause the resistance of the wire to increase a lot and weaken the spark.

[Robert Bishop]

We have a large fleet of buses and run many Internationals. Back when they were all gasoline, we had problems with exhaust valves burning and breaking. We probably lost a dozen 345's and 392's over the years. #8 exhuast valve would often break and drop into the engine at 3600 rpm or so, doing extensive damage to the engine. Check and make sure that the engine governor (rev limiter) is hooked up and functioning. 3600 rpm is about what it should be set at. Over revs on a long trip are what killed most of our engines. When the engine is running full bore, the exhaust valves get red hot and the stem can erode from hot exhaust gases. When the stem gets too thin it is succeptible to breakage. When any of you gentleman buy a used SV engine that has been run in medium duty IH trucks, it is recommended that the heads be pulled and the exhaust valves be given a thorough examination.

[Baradium]

Originally posted by Robert Bishop
We have a large fleet of buses and run many Internationals. Back when they were all gasoline, we had problems with exhaust valves burning and breaking. We probably lost a dozen 345's and 392's over the years. #8 exhuast valve would often break and drop into the engine at 3600 rpm or so, doing extensive damage to the engine. Check and make sure that the engine governor (rev limiter) is hooked up and functioning. 3600 rpm is about what it should be set at. Over revs on a long trip are what killed most of our engines. When the engine is running full bore, the exhaust valves get red hot and the stem can erode from hot exhaust gases. When the stem gets too thin it is succeptible to breakage. When any of you gentleman buy a used SV engine that has been run in medium duty IH trucks, it is recommended that the heads be pulled and the exhaust valves be given a thorough examination.

Thanks for the info. Going to have to make sure about that. About how many miles would you get out of the engines before that would happen?

[bwolcott]

Thank you for your responses. I have a feeling us cruising at 65mph for hours probably killed our engine. I will definitely put a tac on this time around and the rev limiter.

Does anyone have a suggestion on what carb to use? I just bought a used squarebore 4 barrel intake. I have been told to use an Edelbrock 1406, sound right?

Also, any ideas on a transmission and/or rear end that would allow the bus to cruise on the highway? Right now it has a four speed manual with a creeper gear which is pretty much useless.

[Baradium]

How about getting an aux tranny? This would let you keep your current one and get an overdrive. Would give you more gears you could use in all situations too if you wanted to (probobly would come in handy if you get a class V or VI reciever hitch to go on the back to tow stuff).

You could also find an IH 5 spd with the overdrive (T-34?).