Anyone had this 454 problem?

[Pete Peterson]

We have owned a 1985 Midas with a 454 motor for several years.  The previous owner told us that there was a small problem, it would "pop back through the carb" under load.  I tried lots of things and finally found the culprit.  Manifold heat was so hot it would cause failure of the number 7 spark plug boot.  The splash shields on the right side of the motor have been removed I assume in an effort to let some of the engine heat escape.   I have finally found a way to keep the heat from attacking the boot.  I use the heavy duty boot, place it inside of the heat sock (used on race cars and such), and fill the heat sock with silicone designed for wood stoves.  It is a little unusual I guess, but it does work and has for a couple of years. I have asked a number of people and have been told that it is a motor home issue caused by the dog house engine cover and that the 454 was redesigned around that time to increase engine heat to increase millage.  My question remains, is it just my 454 or have other people had the same problem?  Any other thoughts?   As I say, I have been able to get past the problem just curious.  Thanks, Pete  (The Drive-by Tourists)

[George Murphy]

I had this problem on my 94 flair. The plug wires burn out from the heat. I was told to get a good set and replace evvery 25000 miles. I figured may I would cut holes in side panels to let the heat out. In aviation we always figured the heat outlet should be twice the inlet size. Good luck.  George

[Pete Peterson]

Thank you for the comments George.  I spoke with an ex-454 owner last night via telephone.  He told me that he had the problem with a car powered by 454 several years ago.  In that case it had been modified for performance and the headers created so much heat that they caused the problem.  He added some home built heat shields and that had cured the problem.  In my case, there are no splash panels on the right side of my engine compartment, (removed by a previous owner).  It's middle of winter here so I am a little reluctant to dig through the snow right now, however..as I recall, there are no heat shields above my headers or around the spark plugs.  So far, the insulated boot seems to work but I think I will ad heat shields if there aren't any (just in case).  I don't know if you are aware of this but there are two types of spark plug boots.  One is black in color (standard) the others are orange (heavy duty).  A couple summers ago when the ambient temperature was in the mid 90's and had melted a spark plug boot on the road.  I could not find the orange boots at the local auto parts and ended up with several black.  I could only make a few miles at a time before they failed.  I found the heavy duty (orange) boots and they lasted much longer.  An auto parts supplier should be able to supply just the boots if you ask.  Thanks again an I will sure post if I find a better way to fix the problem.

[George Murphy]

Hi   Pete

  When I first got my p-30 I was told I needed super plug wires and sheild for about $325.00. I went discount auto and got a $20.00 set of wires. That was 35000 miles ago. Mine had the sheild around plug. I was told that the heat brakes down the wires. Good luck.  George 

[Robert J Pollock]

I have a 1984 Itasca SunFlyer with the GM 454 engine that has heavy duty spark plug boots and wires. My problem with the hot engine has been vapor lock and hot starter problems. The vapor lock problem has taken a winter holiday. I appear to have fixed the hot-start problem by wrapping the starter with a reflective fabric, wrapping the exhaust header near the starter with heat blocking wrap, inserting a double layer cookie sheet between the exhaust header and the starter, and replacing the cable from the positive battery post to a junction to which the starter positive cable also attaches. This last change was probably the most important. Although I do not have backfiring, my motor home hesitates from a stop if I try to accelerate rapidly. It also starts sputtering to a stall when I am into a significant climb on the freeway. If I let up on the accelerator pedal and slow down to about 40 miles per hour, depending on the incline, then the engine recovers. This latter symptom seems worse after I have driven a while. My motor home has a fuel-efficiency gauge (vacuum meter) and the stalling starts when I enter the yellow to red zone (low vacuum, I guess) and disappears when it is back to the green zone.

[Pete Peterson]

It sounds as if it's the 454 curse to me.  Especially the stall you mention when you accelerate.  Take a good look at #7 spark plug boot (passenger side rear plug).  I believe you will find it directly over the starter motor (hot spot).  I noticed the failure of the spark plug boot (the first time) when I was checking the spark plugs.  They would actually soften to the point it was easier to fire through the boot to ground than fire the plug.  In my case the heat shield between the header and the spark plugs has been removed.  I had not taken notice until someone advised me he had the same problem with a car he built and had the same problem.  Come spring I plan to fabricate a heat shield as a back up (just in case).  As I posted earlier, I have cured the problem for a couple of years now but it gave me fits until I found it.  I took a "heat sock" (a silicone cover used on race cars), fit it over a good spark plug wire and a new heavy duty boot, squeezed in a good layer of sealer and let it cure a couple of days.  The sealer is used on the seams of wood stoves, comes in a tube like bathroom sealer but has an extremely high heat tolerance.  I still carry two spares I made up but have not had to use.  At any rate, pull the boot off that plug and take a good hard look.  I couldn't believe one that failed in only about five miles, had a pin hole as pretty as you please with a burn mark to highlight the spot.   Now that I read your post, I think I replaced the starter last year...  I have to check my records.  That was the only failure if it did go bad (for the starter I mean).  I had a problem with the exhaust and can't remember right now if it was just that or the starter at the same time.  At any rate, I hope this will help you (and maybe some other poor soul),  and I sure will check on the starter, an ounce of prevention sure makes for a better road trip.  Thanks for responding and good luck.  Pete  (Pete and Gigi Drive-by Tourists)

[George Murphy]

   I had starter problem on 74 chev van a few yearsback.Wouldn't startafter towing trailer. It burned out and discount auto had a high temp rebuilt.It was just a starter that had armature and selinoid turned down. Never had another problem. I even thought oftaking off mine electric fan to get goodflow to regular. What are your thought on this?  George 

[Pete Peterson]

I really don't know about the starter George.  I haven't had much problem with mine, but I am glad to hear they make a high temp (just in case).  When you think about it, I guess rotating the solenoid a little further from the heat and toward the cool would make a big difference. I thought of adding an exhaust fan to help exhaust the heat out of the "dog house" and may still just for a little extra cooling.  When I thought of it at first I decided to figure out why I was having the problems and once that was over I started to wonder if I was the only one that was having the problems with heat.  Turns out I had lots of company.  Thanks for the starter tip.  Pete

[Pete Peterson]

Hello Robert.  I checked my maintenance records a few minutes ago and ran into a couple of things I thought I would share with you (about 454 heat/spark problems).  When I looked again, I noticed that I replaced the exhaust flange seals at the connection of the headers to tail pipe and at the same time I replaced the starter.  You think recall would be a little better, but after I read my notes I remembered a little more information.  We had taken a few hundred mile road trip and I noticed I was picking up some exhaust noise.  We were fairly close to home at that point so I continued on home.  When I checked, the nuts had loosened on the right side exhaust (at the seal joint).  I remember now that I replaced the seals again and then after re-assembly the motor home would not start.  It was a bad starter.  Now that my memory has been refreshed, it makes me think that the heat from the exhaust (passenger side) probably caused the starter to fail.  It kind of makes sense now (after reading your post again) that the seal allowed the heat to cook the starter.  It made me think also that maybe I will ad some thread lock to back up the lock washers on the exhaust joints.  Wish I could offer help on the vapor lock, so far I haven't had that problem.  I am beginning to think that allot of the problems I have encountered are from the headers and poor sealing at the connections.  The drivers side had worn so badly that the exhaust was to close to the oil filter.  It took me awhile to figure out that when I tightened up the bolts I had pulled it over.  Finally while laying on my back under there one day grumbling it hit me....what changed?  I never had this problem before?  The previous owner evidently never had this problem?  So, what changed?  Then I remembered I had tightened the exhaust bolts.  Once I took the exhaust apart I could see the doughnut seal was totally destroyed.   End of that problem.  That's the reason I put in the original post.  I sure would look at the boots on the plugs for the hesitation..it's very similar to the problems I had and an easy fix.  Good Luck and thanks for your input.  Pete

[Robert J Pollock]

Thanks for the information.
I had the spark plugs and wires replaced last month and the shop used the more expensive heat resistance spark plug wires.
The exhaust headers create a lot of heat near the starter and probably also along the fuel lines so heat from the engine and from summer weather may be causing my "vapor lock" problem.
My RV hesitates when I press the accelerator from a stop. It will also stall frequently if I have to floor the accelerator to get up a long, steep hill to maintain speed. I can chug up the hill quite a ways before the engine starts stalling so it is more obvious on long ascents. Once the engine starts acting up, I let up on the accelerator and proceed at whatever slow speed is necessary to keep the RV moving forward.

[Pete Peterson]

Hello Robert, I just wanted to see if you had curred the problem after the plug wire change.  It was pretty much winter but we are headed the right direction.  Please let me know if this fixes the trouble you had with the stalling.  One word of caution, I replaced the wires and boots at one point and they failed nearly immediately...within less than an hour driving time.  So far so good for me on the fix but I am always a little apprehensive it may return.   May be a little early in the year, we have had a couple of days in the 45-50 range and I told my wife maybe we should pull the cover off the motor home.....

[Robert J Pollock]

The 454 engine in my 1984 Itasca runs really hot but perhaps it is normal for the engine. When it is about 55 degrees outside, then the add-on temperature gauge reads about 190 degrees. When it is 75 degrees outside, then that temperature gauge reads about 230 degrees. I am going to have the radiator flushed to see if that helps.
Since I had the high temperature spark plug wires installed, I have not noticed any misfiring problems but then I did not notice any with the previous set of (high temperature) spark plug wires either. I have one of the spark plug wires tied up to a support so that it stays away from the manifold and the other wires are already somewhat away from the heat.
After I replaced the fuel filter that is located about half way between the fuel tank and the engine, the stalling under load has not recurred. I think that the fuel in the carburetor bowl was being depleted on long climbs because the fuel pump could not pull enough fuel through the partially plugged filter. The real test of the fuel problems will come with the summer heat. I also switched from 87 to 89 octane for good luck. The engine dieseled upon switching off the key sometimes so I thought maybe the higher octane would help stop that. I now apply the parking brake, put the transmission in gear to load the engine, then switch off the key. This seems to have stopped the dieseling but this is another high temperature problem that may reappear in the summer.

[Pete Peterson]

Hello Pat, Robert...Thanks again for weighing in on this subject.  When I was digging into this back in the beginning the fuel filter issue was suggested to me.  I changed both the filter on the frame and the one on top of the engine (that was kind of a pain, for some reason it decided to seep a tiny bit of fuel but finally fixed).  They made no difference in my case, glad that it helped in yours Robert.  For my part, the cooling system seems to function well.  We normally tow either our pontoon boat or our towed all the time.  I watch the heat (just using the original dash meter and idiot light) at all times.  I have noticed that the temperature will climb quickly, to the almost too close for comfort range on longer pulls.  Mind you we live in Montana and we have some pretty good climbs.  We have pulled from Montana though Nevada to California and up the West coast to Seattle and then over the Cascade and Rocky Mountains.  In all cases, and pretty much no mater the ambient temperature the heat will climb to the almost,  OH CRAP range.  It has never overheated, and always returned to the normal range but it makes me real nervous every time.  A very experienced radiator man told me a couple of things to remember.  First, when you pull a grade that a rise in temperature is normal, not over heating but an increase.  Second, when it does rise it should also cool back down within a short time.  I always down shift to a lower gear early on hills and take it easy on the gas peddle.  On the mountain passes I will pull down to the lower gear at about 45 mph.  Most times it will slowly creep down to about 35.  We climbed a couple of passes in Wyoming (the steepest I have ever climbed, made Going to the Sun in Glacier Park look easy), both directions, East and West,  one to the North and the other further South of the Big Horn Range.  They were long climbs, it was summer and no problems.  That has lead me to the conclusion that the spark plug problems were not just overheating.  I am thinking more and more that you are correct Pat, that the problems I had were created by exhaust heat problems.  I have insulated the number seven plug and no more problems for the past three years, (Knock Wood!!).  A previous owner has removed the splash shields on both sides of the engine compartment.  There are no heat shields on the spark plugs either.  Since I shielded that plug I lost the problem, but it gave me a good fight.  The exhaust doughnut seals have given me trouble on two occasions and I am sure that didn't help.  But I can attest that engine compartment and cooling system can use all the things you mentioned Pat.   George answered in this same area about the loss of starters.  I had forgotten that when the exhaust started to leak (second time) and I changed the seal on the passenger side I had to change the starter also.  In my owners manual it indicates 87 plus octane (that was in 1985) at this altitude...they aren't kidding.  Thanks to you folks for your input.  The vapor lock?, I have no answer but I'll bet someone will have some good advice.  Nice to have a forum and participants.  See Ya some time maybe, Pete