Motor Home Mileage

[ALANSD]

I thought the Edelbrock replacements were highly recomended although pricier?

[Chuckles]

I attacked the hot air choke today.

As the gaskets had not arrived yet for the carb, that was left in place. This meant that the plate in the induction manifold could not be removed. SO.... I drilled out the rivets holding the cover in place over the bimetal spring of the choke. That cover could not be moved otherwise, and I needed to know how it works!
With an experiment with a match I could see the spring move to open the choke, that started me off on the correct way to adjust the cap.

The choke is now, as a temporary measure fully open. Its a blighter to start, a few pumps on the gas pedal before and during starting, and continued pumping in the first few seconds, then she's away and runs quite sweet. The tick over is much lower now, indicating that the choke was possibly holding on for quite some time.

I am happy in that I found a possible cause for the excessive fuel consumption, and a few trips will either confirm this or dash everything. I am assuming no air/vacuum is lost throught the manifold plate, and the pipe openings on the choke and the top of the carb are now blocked off. So it's all down to seeing how it performs.

There has been mentions of the electric choke, but I cannot find details of the conversion/kit.

Chuck

[GlenCoombe]

Chuck, make sure you're getting lots of cool air into the carb too. If you're still stuck with the original air filter and horn intake you can do better.
Click on my name and go to my photos for a look at the mod that made a great difference in my performance. Only took a few hours and simple hand tools to make... even got by without giving any blood, which for me is a small miracle.
BTW are you still also using stock exhaust manifolds? Headers will disapate heat and aid in low end torque while offering a modest gain in mpg. I've gone all the way from the motor back using Headman header, 2 and 1/2 inch pipes through Flowmaster mufflers...out via Chevy bowtie tips in front of the rear axle... sweeet sound and nice performance too.

[Chuckles]

Ah! now Glen you are going a bit fast for me!

Saw the air intake, yes that makes sense, so I will have a go on that.

As for the headers, that's a different story. Getting hold of that sort of stuff here will be a challange so I will do some research and see whats available. I will have to do something soon on the exhaust as there is that little rasping noise indicating a pin hole on the manifold.
Chuck

[GlenCoombe]

The stock manifolds are very prone to cracking and even headers require constant attention to torque of the header bolts. I do the "Tight'n up" every two weeks....actually that's about every 7-900 miles for me.
Over there I'm not certain what you'll find or pay so check out www.summitracing.com over here for Headman's and Flowmasters. The Flowmaster mufflers where a big surprise to me as they are VERY heavy. Built to last but a little dear on shipping...
Follow this link to my friend Scott's rebuild site. http://www.picturetrail.com/clubmaxxpch . He developed the remote air intake I copied. His rebuild will make you think you've bought a palace.
BTW I'm of the opinion that Scott never sleeps. I am his National Sales Manager and a very big fan. Check it out.

[swebster]

I thought the Edelbrock replacements were highly recomended although pricier?

Alan, those are very nice. They are not much more than a nicely rebuilt QJet.

Chuck,
I second Glenn's notes on the headers and exhaust. I did the same modification and am very happy with the results. I too had a failing manifold (actually the AIR induction system was failing not the manifolds themselves) and the headers, pipes, h-pipe and mufflers cost me less than replacement AIR manifolds.

[Chuckles]

Well what a disaster.. .... You may recall I disabled the choke by removing the pipes that fed hot air from the inlet manifold to the bimetal coiled spring...... so far so good. It started and ran (vehicle stationary) quite well...considering.

Then we set off a week later, with a full gas tank and water tank to our Country & Western weekend, about 20 miles away! Thank Goodness........

It just about made a 1:80 incline! It coughed and popped; you name it did it, very embarrassing holding up the traffic. I just could not make out what I had done - or undone.

We arrived, had a few jokes about 7.4 litres of engine doing 5mph and settled down for the night.

Then EUREKA! At 3:30 am I remembered, I took off the vacuum line to the auto advance and retard to the distributor to make easier access! Derrrr!

Thank goodness the engine hood is inside… there I was in “me rudery” with the doghouse up and yes it was still off – the hose that is.

Well the journey back was better but it still doesn’t like the second stage flaps opening. As soon as the foot goes down,on a hill or whatever, it backfires back up in the carb. I gather reading other posts on this matter it is quite common, something to do with floats and too much fuel, or would it be timing? Bearing in mind our petrol (sorry Gas) is 95Octane and higher.

I now have the gasket set, so soon the learning curve will begin. I must admit this type of carburettor is new to me so “in at the deep end” I must go….

Chuck
Dorset UK

[GlenCoombe]

Interesting.... remember the old curse / blessing? "may you live in interesting times."

Seem you've had some interesting moments lately Chuck.... with more to come as you open that baby up.

Much as I enjoy the work I often leave the "heavy" stuff to my professional.... so I can go home and work.

Check out the tune up thread running for more fun in the engine bay.

[Chuckles]

Glen,
I am trying to select the header and exhaust I need, but have become totally confused. UK and USA terminology differs so much in this area!

I noticed looking down from inside the coach, looking at the back of the engine, that the left side (Drivers side) has the manifold almost bent back on its self to avoid the gear linkage, whereas the opposite side has this preheat valve in the flange between the header and the down pipe. PeterH-79MH and Guy 99 agree that it's a heat riser, which has been totally disconnected, but I dont know if it's open or closed! So it would seem that I need to replace the entire system to ensure compatibility. A flexible down pipe section springs to mind.

The part number gleaned from Hedman is 69126 with a dimension 13/4”, 3” as the tube and collector – what ever that is….

Does anyone who has gone through this route, on an 1982/83 310 have the part numbers handy both for the header and the exhaust system as a whole?

From the Hedman site with the headings year, engine, part number, gasket number, some footnotes and various other codes followed by the Collector and tube size.

68-95; 396-454; 69126*; 27550; 1, 6, 38, 42, 45; Y; Y; Y; Y; N; N; (A); 13/4", 3";

Thanks once again for all the help from the great US of A
Chuck

[GlenCoombe]

Chuck, I'd have to look up the part number from a while back. I actually called them and they sent me what I needed. The motorhome version of the big block Chevy Headmans are "universal" and I'd do away with the heat riser hardware. The dimensions are 1.75" tubes into a 3" collector.
I used Flowmaster 70's with 2.5" inlet/outlet. 3" is too big and the Headmans will come with collector reducers to go from the 3" at the header to 2.5 at the inlet to the tail pipe.
Are you planning to switch to an electric choke?
Of course when you order all this stuff if you're adding new exhaust pipe this all becomes a measure cut bent trial by fire routine.... but don't forget to order the Chevy bowtie stainless tips for the final touch! I have both tips exiting on the drivers side in front of the drive axle. The pass over for the curb side was some trial and error for my muffler guy who bent the pipes.

[dinoburb]

Hi Chuck,

I understand your problem, from a reverse perspective. I restored a Triumph Stag several years ago and converting the English to American was one of the more difficult tasks!

The Hedman part number you have listed is a good number for your application (69126), however, it only has a 1/4" thick header flange. (The plate that mounts to the head.) It is ceramic coated which is excellent. I think you would be happier with Hedman P/N 69820 as it, too, is coated and has a thicker (3/8") flange which shpuld stand up to the heat produced by the MH. Additionally, it is made up of 14ga tubing vice 16ga. Thicker is always better!

I have just listed several parts for sale for the 454 in the parts section of the classifieds. I cannot ship the headers due to cost. Other parts I'd consider though.

Hope this helps, I've spent many hours with my BBC (big block chevy) carbureted version. I have just purchased a 1991 Suburban with a Fuel Injected (throttle body injection) BBC. I'm learning some new things!!

Take care,

[GlenCoombe]

Yup, Dinoburb gets it right... 3/8" flange and thicker tubing is the way for the BBC.
Why not email Summitracing.com and see what they say about shipping over there?

[Chuckles]

Originally Posted by swebster

Seems like it's plumbing all related to the choke. I doubt that any of this is opening a vacuum leak in the manifold but I've never actually seen a hot air chock on the 454 before. I suspect it's just a plenum not open to the intake plenum which allows hot air from the intake to open the choke. You may consider converting to an electric choke (there are a number of kits available).

I took this picture, with a camera that is failing fast! (it started to play up a few days ago!) As you can see it’s a very amateurish design, but it works! The pipe that goes inside the induction manifold was OK but from the flared connections on the top of the flange it just came away in a cloud of rust.

It is impossible to see how big this plenum is but it appears quite cavernous. I had some 8mm brass nipples that take instrument airlines, handy, and with a little persuasion (Girt big ‘ammer!) they fitted inside the pipes. I tried to braze and solder but there was no bight, plus the difference in thickness of the metals didn’t help, and... well.... its not my trade!

The saga on the carburettor is, I hope, closing now. I rebuilt the carb with a standard gasket kit set, cleaned the metering needles, that had a crust forming on the tips – particularly the secondary’s, and Hey Presto! … the popping, banging and back-fire has gone. I took her up to 5500 revs slowly then straight open, no hesitation or misfire. The choke remains disabled for the time being as I don’t want to push my luck, besides which, the new seals on the choke bimetal spring chamber has made the operation a bit stiff and sluggish. I could see that casuing the same original problem ... again!
The engine will start with a couple of pumps on the gas, and within 30 seconds or so, will settle to idle.

The test will come in a few days when I am off to London (185 Miles each way) on a business trip and will be staying in the Airstream at a site (Campground) by the Thames. That should give me some idea on how the mileage is going.

Thank you very much in clearing up the mist over the headers, that is very much appreciated.

Chuck
Dorset UK

[Chuckles]

Just come back from a "Blast-up-road" in other words, really pushing it.... and found naturally enough …. the problem has only partially gone away!

First. The Choke Hot Air pipes do not take their heat from the induction Manifold. The gasket blew out under the plate and low and behold ...its exhaust! How on earth does the exhaust get into the inlet side of the engine 'V'?

Am I right in thinking this is something to do with this reheater or heat riser, the valve flap in the right side exhaust pipe first after the manifold or header. After all the hot air chamber and the heat riser are on the same side.

Second, if you want to disable this choke don’t do as I did, short circuit the pipes so the air is drawn from the carb to the bimetal spring chamber, bypassing the heat chamber pipes. I thought is was being clever in keeping the "air moving" so to speak but the choke thought otherwise and found the air being pulled in, not being heated... well you guessed it, the choke closed, there was a smell of petrol (sorry gas)... the rest is history.
Silly me thinking I had a fuel (better?) leak due to the petrol (Doh!) smell.

I will get there. I hope before the London Trip….
Chuck

[Chuckles]

Well I’ve done the London trip...... and..... its better, better than 5.7/9 miles to the gallon that is.

It ran like a dream, apart from a droning noise from, what I think may be the UJ's or some where on the drive shaft, I digress..... Yes it ran well, there and back on less than a tank full of fuel. That equates by guestimate to about 9.5-9.7 MPG.

However after a good run (50-55mph) and you then hit the traffic it starts to cough and splutter a bit, or, if after slowing down you increase the throttle considerably, then there is a strong smell of pet..... Sorry Gas.... and what feels like a misfire. On the last legs of coming home it sounded quite rough, I can only assume that as I haven’t done anything ignition wise, that the plugs are due to be replaced, and possibly the leads (wires?).

One reason I did not attack the plugs yet, I can’t find a socket to fit them! I have most plug spanner sizes but are these different? Any ideas out there what size socket to use – silly question I know but puzzling just the same.

I have some new plugs and Ignition leads on the way so we will try that.

At least starting at the carburettor end was the right way. In the end I cut the hose between the air inlet at the top of the carb and the choke hot air pick-up, and inserted a simple auto fuse, which fitted directly. It blocks off the airflow both ways. To make double sure (belts & braces), I removed the choke flap altogether!

After all this it will definitely be the exhaust. (…. just can’t find that credit card….)

[overlander63]

Originally Posted by Chuckles

One reason I did not attack the plugs yet, I can’t find a socket to fit them! I have most plug spanner sizes but are these different? Any ideas out there what size socket to use – silly question I know but puzzling just the same.

Spark plug socket size is 5/8", or 16mm, whichever you have in your toolbox.

[Chuckles]

Thank you Terry, I ended up with a 16mm plug socket - new one by George!

And what a job.... spark plug removal is not a quick fix is it... Having to remove the front wheels was certainly a bit of a pain ....

On the drivers side there is this panel that extends from the front cross panel and blocks off all access to the front plugs. Has any one removed this altogether? does it actually do any thing, apart from making it very difficult to get at the plugs. And those heat shields around the plugs ... are they really necessary? I would have thought that without them air would pass more freely around the plug. On the front one drivers side I had to remove the bolts holding the AC pump bracket so I could move it to get at the plug. Who thought that one up!

Any way (any road-up; as we say) the plugs were all the same biscuit colour indication a good fuel mixture after the London trip, and apart from burnt out leads on two plugs, all seem quite well. The fuel fill up confirmed a figure nearer the 9 MPG.

On the question of plug leads, any experiences out there. I have been advised to stick to copper core rather than the carbon fibre and silicone types. Any thoughts on that

Chuck

[GlenCoombe]

Chuck, good to hear your mileage figures.... I'm not sure I can say this without hurting feelings but here goes....you're doing it wrong! Did you attempt to extract the plugs from the top side? I do all my top end repair work from above. I regularly tighten up my header bolts and distain removing the wheel well inner panels as you've figured out. Once the air cleaner is out of the way you can actually reach most of the stuff down there.
It may be that you've yet to shed some of that stuff on the top of your engine related to the factory manifolds ... headers really do clean up the operation.
As far as the wires go high temp, high performance wires are worth the investment. Sixty degree plug boots keep the boots away from hot manifolds. I prefer MSD.
I had lots of trouble with my original 454 due to manifold leaks that just cut the boots in short order. Think high temp, pin hole exhaust leak against rubber....or anything for that matter??
Headers..high temp wires...lots of cold air.... good tire inflation... all measure up to happy Airstream.

[Chuckles]

Glen, I did make a start from the top, but I needed to be made of rubber for the front ones drivers side. I think my 310 may be a slightly different around the dog-house as there has been some modifications done in the past. The drivers side is very tight, but there is bags of room t'other side, so it was not so much of a problem to remove those plugs.

But in the end it became quicker to take off the wheels, Thank goodness for levelling jacks! ... (yes I do realise that they are for levelling and not for changing wheels but.... when needs must.) ... I am the lazy type, at least that's what my mentor told me during my apprenticeship "..you will be a good worker because the lazy ones aways find the quickest and easiest way to do things" This was in the days before 'Health & Safety' issues!

When I change the spark leads (sorry wires) I will photo these. two look like the plug caps exploded! certainly burnt beyond use. Its surprising how they have deteriorated, as I think the PO,or at least someone had within the past 6000 miles replaced them. They looked good where you can see them. Just goes to show....

[GlenCoombe]

Chuck, I agree the DS is a little tight. While laying almost on top of the motor I'm just able to get my arm along side the (cool) header tubes. From there I can actually reach the front 3/8 bolt at the front of the motor with my wrench...(sorry, spanner) I wear a 33 inch sleeve... metric I can't do without a book and calculator anymore.
Heat and high voltage can do wonders to these so called high temp wires. Exhaust leakage around the gaskets can cut them like a knife.