7.4l tune-up

[ALANSD]

Good photos ....I also went with the Accel wires, and then even wrapped a couple that were very close to the manifolds. These still seemed to need extra protection. The Jacobs ceramic wires are the way to go, but not cheap.
Mine has had the wire looms and guides and I always check to be sure they are routed right.
If you haven't yet protected your starter wireing I would also consider doing that. You can get the thermal wrap from Ebay or a parts house and protect those critical wires from stranding you with a dead starting system.
I have had trouble free starting for three yrs now. Ahhhhhh...

[swebster]

Excellent point on the starter wires. Mine burned through on a trip and I spent three hours under the Moho in a very hot rest stop in Florida one June rigging it up to start and run.

I have had trouble free starting for three yrs now. Ahhhhhh...

You know you just "put the whammy on yourself" with that one.

[FrankR]

The pics are great. You may have waited too long to check your engine. You mention all the parts replaced but there is a few "tricks" for a good job.
The distributor is best removed from engine. Reinstalling is not a difficult task. Some times the distributor can be rusted/corroded in place. Better to free the unit now than on the hiway.
It is a good practice to check and oil the mechanical shafts and linkage for the advance mechanism. A vacuum test of the vacuum advance diaphram is required for performance and economy. When replacing the ignition modual, the smooth machined surface in the distributor should be very clean. It is very important that heat sink silicone be placed onto back of ignition modual. Heat will destroy a modual. Setting the timing on a gas engine is mostly a personal preference. I have installed many ignition controls that can alter ignition timing at drivers seat. The timing can be changed about 15 degrees either before TDC or after. Low octane fuel with advance timing is not a good situation 3especially on long hills.
Silicone spray or WD40 is good to use on plug wires into cap and onto plugs. These sprays allow for easy removal at a later time. It is a good practice to put anti seize on all the spark plugs before installing into engine.
And all engines need a compression test to determine engine internal compression/condition. Replacing parts is good but for the most bang for a buck, care and workmanship is paramount. Frank

[ALANSD]

Originally Posted by swebster

You know you just "put the whammy on yourself" with that one.

"Maybe its the good whammy" as my smooth running had been very pleasurable for quite some time.

[outofcontrol]

Originally Posted by FrankR

The pics are great. You may have waited too long to check your engine.

Thanks Frank, I've had this coach for 5 weeks now, and I've spent every weekend in it! So much to do/improve/update. I have some hi-temp wrap, I think I'll wrap some wires this week.

I did all the things you said, even anti-sieze on the plugs. I didn't test the vacuume advance or pull the whole distributor. I think I have a vacuume hand pump for testing the advance. Do I have to set the timing if I pull the whole dist. out for inspection/lubrication?

Originally Posted by swebster

The good news is that you already have headers on there so the more you do to improve fuel/air/spark the better the performance/mileage improvements you'll see over a stock exhaust.

I thought the PO said these were aftermarket headers, but when I saw the air pump and leads off the header, I assumed it was stock. Is there any performance gains by removing the air pump and plugging the header leads?

Next winter I want to find a donor motor 87-89 454 TBI system and convert to FI. I figure at that time, I'll employ some sort of variable timing system. I'd rather spend my time learning EFI than how to tune this carb. Although I'll most likely dive into it before then. I'm getting about 8 with my 2500lb. 6x12 enclosed trailer, and about 9 without, so I think I'm in the ball-park. I have 61k miles, and I think she's throwing around her weight pretty good.

-Kevin

[swebster]

Kevin,
You will need to re-time if you pull the distributor. One note, you can time off of number 5 using the timing marks on the bottom of the engine (they put them there as you can get to the stock position). You can check the advance and vacumm without removing it but if you want to check everything then a pull is pretty easy....just mark everything. I replaced my distributor in an AutoZone parking lot one night...no biggie.

I've not seen headers with the AIR injectors before. In fact, I didn't even think the AIR systems were on your year moho. They are either a very good upgrade specifically for your application (Gibson? Banks?) or they were customized. I had the injectors in my stock manifolds. They looked like cigar tubes and entered the head stopping just short of the exhaust valves. I ended up removing all of the plumbing when I went to aftermarket headers.

I would have to say that removing all of that turbulence in the exhaust improved performance. I get a consistant 8 - 9 mpg on my 345 since making all of these changes and I'm running a stock (rebuilt) carb.

[outofcontrol]

I'll pull the dist. tonight after I buy a timing light.

I'm thinking that the air pump has to put some sort of drag on the motor, and those tubes sticking into the flow right out of the head has to disrupt the flow in the headers. Isn't the smooth flow of exhaust through the header critical to the performance benefits of the header? It seems counter-intuitive to have a big straw disrupting flow in such a critical area. I wonder if it was added to correct a problem, or to meet EPA standards for a particular state.

Do you think removing this whole system will have any adverse effect on the performance of my motor? The purpose of it is to help burn any unburned fuel in the exhaust right? This system is not used anymore?

This seems like a free performance modification to me.

-Kevin

[swebster]

Yes on everything...but you may find it easier to replace those headers with aftermarkets rather than try to remove and re-weld those tubes.

Got mine from Jeg's for about $150. Made for the 454 in P30 motorhome applications.

[wanderingeye]

We bought Hedman headers from Summit Racing. There were only two brands that have a 3/8" flange. These things are hell for stout and fit perfectly. The ceramic coating cut down the heat in the dog house considerably. One unexpected benifit was the noise reduction. Free-flowing exhaust gasses make less noise than the original restrictive castiron manifolds. Cheers Tom

[ralley]

I, too bought some hedman's a few months back, but haven't put them in yet. Looks to me like I will have to re-plumb the exhaust to make them work, and I haven't done my homework about where to buy exhaust fittings and which ones to buy. Maybe at my next tune-up when the plugs are out....

Is there a proper thread about doing this job--? I may have missed it.

Rob

[wanderingeye]

Ralley It might be worth your time to check your headers with the manufacturer's web site, Hedman.com. Under Hedman Elite (extreme duty/ motor homes) you will find your engine and chassis year. The reason for caution is that these headers are one of only two brands that I could find with a 3/8" flange. I cannot remember another automotive product that rated so high on the cost/benefit curves. They fit perfectly and fortunately all the original bolts came out. We threw the cast-iron manifold and air injection in the dumpster. The original manifold was spauled, like crumbling concrete from excessive heat. Depending on elevation changes and wind speed (it's hilly and windy here in the NE), we're getting up to 11 mpg. Our headers were $275 from Summitt Racing with $10 shipping.
Cheers, Tom

[GlenCoombe]

Tom, if you think the Headmans are stout wait till you pick up a Flowmaster 70 muffler. I was very much surprised at how heavy and well constructed they where. They really "round" out the sound too. At normal throttle opening they are quite tame, however when you dip a bit deeper the big block signature sound is very nice indeed. The temptation is to drive a little more with the drivers window open and your foot a little deeper if you like that kind of sound.

[ralley]

Originally Posted by wanderingeye

Ralley It might be worth your time to check your headers with the manufacturer's web site, Hedman.com. Under Hedman Elite (extreme duty/ motor homes) you will find your engine and chassis year. The reason for caution is that these headers are one of only two brands that I could find with a 3/8" flange. I cannot remember another automotive product that rated so high on the cost/benefit curves. They fit perfectly and fortunately all the original bolts came out. We threw the cast-iron manifold and air injection in the dumpster. The original manifold was spauled, like crumbling concrete from excessive heat. Depending on elevation changes and wind speed (it's hilly and windy here in the NE), we're getting up to 11 mpg. Our headers were $275 from Summitt Racing with $10 shipping.
Cheers, Tom

Thanks very much. I'll check this weekend. Headers are still in their shipping box under the bed in the Zeppelin, so will requires some excavation to get to the paperwork for model #, etc.

Rob

[ralley]

The Hedman part number for my configuration is 69820. It is the "elite" with the 3/8 inch flange.

Thanks for the heads up............

R

[swebster]

ralley,
You'll have to "marry up" the old exhaust to the new headers but I'm with Glen, this is a good time to consider replacing everything. New free flow mufflers, an H pipe and 2.5 pipes will help those headers do their job.

I use flex connecters to transition the 3" header outputs to the 2.5 pipes, then into a three foot pipe, back to an H pipe kit from Jegs. From there two more 4 foot pipes lead into Jegs mufflers then more sticks to the back, two 90 degree mandrel bent pipes then out the sides. I also added SS exhaust tips for that extra 5 hp!

Went and used all new hardware, handers, everything. My exhaust was a mess from the manifolds back so this complete replacement made the decision easy. I have to think the replacement process would be easier than trying to connect up to your existing system.

[dinoburb]

Greetings,

I have a recommendation that is slightly counter to most of the previous suggestions. If you are going duals than the 'H' pipe is a must, however, a single 3" or 3.5" pipe will provide the necessary flow improvement at towing RPM (with a slight torque improvement over duals) but not quite as much horsepower at 5000 rpm (which you'll probably never hit)! Remember, most items designed to improve HP usually do it at the expense of low end torque. Even most torque improvements claimed by dual exaust proponents are at a higher RPM than the original numbers. When Gibson exaust talks torque and towing in the same breath they talk a single pipe system ex: Summit Racing Parts (This example is for my R-2500/454 Suburban). Quality headers such as the Hedman 69820's are also a must. If the vehicle requires a catalytic converter you'll also need a high flow converter to match the improved breathing provided by the headers and large exaust.

Hope this helps.

Take care,

Sean

[ralley]

Gentlemen: Thanks very much for the sage advice. Duly noted and saved against the time that I need a new exhaust system.

For the time being, I will install the headers and join up with the existing 3 inch pipes, and await failure of the existing system (which appears in very good condition). I can lay up parts against the inevitable.

Best,

Rob

[joewinfield]

I want to join Rob's post, this is very helpful. My engine work is complete except for distributor and headers. Searching now for the right Hedman. Thanks for the usual great forum help. joe

[wanderingeye]

Alansd, Peter-79MH, FrankR, OutofControl, Swebster, GlenCombe, Ralle and Dinoburb
Gentelmen, Your posts on this forum have made owning an Airstream more pleasant than it might otherwise have been. I am not a mechanic! My wife says I have a 51% success rate of dissassembling something then reassembling it and having it work again. She may be right....my orphan parts jar is as full as my spare change jar. Our '84MH is in magnificent shape considering it's age. I beleive in renewing rather than repairing. For instance, I have completely replumbed the fresh water system. We have 77,000 miles and I am looking toward the day when I may have to reengine. This (attached) engine has been offered to me at a reasonable price. This would be a preemptive maintenance. What do you think? Tom

[outofcontrol]

You might have to cut a hole in your doghouse for that blower.

You might as well just remove the doghouse so you can look and listen to that jewel while you punch it.

-Kevin