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Old 05-24-2007, 02:02 PM   #1
76 Silver Argosy
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1975 26' Argosy 26
Fallbrook , Southern California
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502 to replace knackered 454 engine

G'day folks.

Although I appreciate my engine replacement saga has gone on way longer than can really be considered respectable, I feel I am moving toward ending the sorry saga at last.

I had a good chat with my local engine rebuilding guru last week, and during discussions I mentioned I was tempted by having him rebuild my busted 454, but was also seriously contemplating investing in the HT 502 (see example here). Turns out he reckons to build an engine suitable for mounting in Ethyl would not save me any money. He says the biggest problem we 'classic owners' face is the build up of heat in the engine compartment as there is no easy way to duct the heat off.

The HT 502 is purpose built for towing and high torque applications, such as inside an RV, and would, obviously not the excellent GM warranty. So, to cut a long story (if not a long saga) short, this is the route I plan on taking.

My questions to you, esteemed 'Streamers are as follows:
1. What carburetor will I need?
2. Which inlet manifold?
3. Will the standard engine mounts be OK?
4. Will I need change the bellhousing?
5. Do I need change water pump?
6. What's the best source for a HT 502 - I live in Southern California?
7. Any other changes required?
8. Is this enough questions for one posting ;-)?

I plan on switching to a dual electric cooling fan setup (see here)to make sure this beaut does not over heat, and will also switch over to electric fuel pumps - anything to try and reduce the 'drag' on the engine. Any other suggestions I should consider while spending the kids college funds?



1975 26' Silver Argosy MH: Ethyl the Never Ready!
Fallbrook, Southern California

"Experience is something you never have... until just after you need it!"
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Old 05-24-2007, 02:37 PM   #2
Desert Fox
1985 31' Sovereign
Tucson , Arizona
Join Date: Jan 2004
Posts: 250
Smile Hi,

Hi Andrew,
With the price of 502 I would rebuild the old 454. It is a work horse and it is proven out by being in the service for many years. Do the following.
1. replace water pump with a new one no rebuids.
2.Put decent headers on.
3.Electric fuel pump O.K.
4.Put oil cooler on the engine as well as on the transmission.
5. Install a new fan cluch on your engine or two electric fans.
Your unit probaly has a 4 barrel cvarb. Have it rebuild. This way you save on intake manifold as we as on the exhaust manifolds.
Your trany schoukd be a 400 s speed with straight cut gears for better take of in 1 gear.Good trany.
Regards from Russell in sunny Tucson Az.
P.S. How is your trany?

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Old 05-24-2007, 02:44 PM   #3
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2000 34' Excella
Tucson , Arizona
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If you are hard over on the 502 then Scoggin-Dickey has the some of the best prices for GM crate motors. I have bought heads from them and other parts and have always found them to be first rate.

Frankly, I'd go with the 454 you had in it. A good rebuild will be the cheapest route and the power difference is marginal on a good torquey 454 rebuild. It's all in the cam.

Scoggin Dickey at Sdpc2000: Performance Parts, Racing Engines, Racing Engine Parts, Race Engines, Race Engine Parts - SDPC for scoggin-dickey.
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Old 05-24-2007, 03:29 PM   #4
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1984 31' Airstream310
Dunsmuir , California
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Originally Posted by elolson
... It's all in the cam.
Is there a trade-off between power and other desirables and fuel economy?
If you want others to be happy, practice compassion.
If you want to be happy, practice compassion - The Dalai Lama

1984 310 Limited Motorhome
Courtesy Parking (W/S/E/Wi-Fi) on I-5 in Northern California, 70 miles from Oregon border
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Old 05-24-2007, 03:32 PM   #5
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Altoona , Georgia
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When my time comes, hopefully far in the future, I plan to get a factory rebuild from Nappa or the likes there of. At the same time I will exchange the tranny, carburetor, alternator. and starter. A radiator rebuild and a good set of headers to finish the job right.

When installing your new engine, pay careful attention to the routing of the plug wires. Heat is the enemy!!!
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Old 05-25-2007, 01:54 AM   #6
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1989 34.5' Airstream 345
Heart of Dixie , Alabama
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You are right on about heat removal.
Look at the later AS MH, they have a pair of vents to let some heat out.
See it just above wheel opening...

You could add something like that, or one from a Trans Am or Z28.
A spoiler directly below radiator base, angled slightly forward at bottom, will create a vacuum behind it, drawing more air thru radiator.
It would also prevent air flow from bypassing and slipping underneath.
It must be below base of radiator, not on front bumper, or anything with a air gap between it and radiator.
You will be pleasantly surprised at how well air flow works.
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Old 05-25-2007, 06:35 AM   #7
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1977 31' Excella 500
Berkeley Springs , West Virginia
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How about a 496?

How about a 496? That is the modern replacement for the 454. Same basic block but enlarged. Look for a wrecked pickup truck. I'd score the engine, the transmission, the computer and EFI system. Just buy the whole thing.

That'd get you a modern engine with electronic fuel injection that would run better than any carb. Get yourself a new aluminum radiator and call it good. Maybe cut some louvers into the fenders as they showed above.

It's at least worth looking at.
- Jim
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Old 05-25-2007, 02:41 PM   #8
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1975 26' Argosy 26
Fallbrook , Southern California
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454, 496 or 502?

Thanks guys.

Given the difficulty I've had in removing the damaged 454, I am really anxious not to repeat this procedure, so would rather spend the extra cash and get a new/remanufactured engine that will, hopefully with a little TLC, last us many years. The 496 is a possibility, as is a 502 or Jasper's 'purpose built' RV 454 engine.

Having looked under my mattress and confirmed a total lack of a large pile of cash, any purchase will not happen quickly, so in the meantime I am having the three-speed (Hydromatic?) rebuilt, have had the radiator recored and assorted other coolers pressure tested. I will also see about rebuilding the front suspension and steering, rewire the front coach electrics and recore the water heater. All this in the (vain? I hope not) hope of making Ethyl run reliably and smoothly for many years to come... am I niave or what?!

Then there's my assorted electrical woes to sort out as well. Thank goodness I realize this is a longterm hobby and not an instant vacation.

Happy Memorial Day everyone.


1975 26' Silver Argosy MH: Ethyl the Never Ready!
Fallbrook, Southern California

"Experience is something you never have... until just after you need it!"
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Old 05-25-2007, 05:21 PM   #9
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Belleview , Florida
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Andrew, good to see you back at it.... even if you're not progressing at a rapid rate.

Tranny rebuild: Low RPM lockup torque converter!! Tow and go is the terminology I've seen and heard. Did you ever find out the rear end ratio?

Engine.... how many miles are on the present mill? If the block is sound I'd strip it down and bore it out. Look for deals. Use new parts for all accessories. Start hanging out with the motor heads, they're always buying stuff they don't need and selling off later cheap.

Engine mounts are easy to do and cheap when the motor is out and a real bi%c^ to do later so the choice is yours.

I like the electric fans idea. New core or new rad if you can find a good buy.

You've got time on your side....if not money so hunt for the deals. Those deals will steer your project.

How's the interior coming along?
Glen Coombe AIR #8416
1984 28' Funeral Coach
Former Rolling Showroom & PuttLab (now party bus)
"I'm not an expert. But I did sleep in an Airstream last night."
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Old 06-22-2007, 10:19 PM   #10
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1979 28' Airstream Excella 28
Bakersfield , California
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I have been looling at upgrading my 79 Excella 454 to something more power. I have found out the following:

1. Torque is more important that horsepower. I am installing a set of Thourley "Y" headers that should add about 30 HP in the low end for torque. These run about $600 ceramic coated to keep heat out of the engine compartment. If you are interested I can tell you my source for buying the headers, but make sure you get ceramic coated to keep heat out. My exhaust geru tells me he gets more torque from both 2 1/2" pipes going into a single exhaust, drivers, side than the dual that I have currently. This did suprise me. I will let you know next week after I get it put on.
2. I have seen you can get more low end torque by adding a Eldebrock intake, cam and right carb to get about 35 more HP in the low end. I am strongly considering this, but you have to add the cam as well as intake to get the full benefit. If you rebuild you can make this change and install a system. Elderbrock has this on thier web site.
3. Beware of 454/502 hot rod engines. I have installed a few of them and they do generate more heat as they run at 200 to 220 all the time compared to running 180 with the old 454's. Make sure you get a truck engine not a car or hot rod engine, different animal. You want your horsepower in the range of 1800 to 3200 RPM for the motorhome, at least that what mine tells me expecially with the Gearvendor overdrive unit. I may install the intake after the exhaust and see what impact it has. What is good is the headers and intake would work on a new engine as well as a rebuilt.
4. My motorhome does not have a snorkle for air cleaner fresh air. I have been told that I can a few more horsepower by running a snorkle tube to grab fresh air for the intake. I will keep you posted.
Chris Addington
Central California
1965 Tradewind Trailer
1979 Airstream Motor Home
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Old 06-22-2007, 11:08 PM   #11
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2007 25' Safari FB SE
Suburbia , Sunny So Cal
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Slight detour

Hey Ranchmink, You joining us at the CalStreamers summer Rally? Its around the corner from you up near Gorman.

Check out the "California Streamers Summer Rally" thread on upcoming rallies page.

Hope to see you there.
I'd rather be boon docking in the desert.

AIR# 13896
CA 4
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Old 06-23-2007, 12:41 AM   #12
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2003 22' International CCD
Whittier, California , Depoe Bay, Oregon
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Posts: 358
A great source for GM Crate engines is New everything and 50 more cubic inches is 50 more lb-ft of torque compared to the 454.

2003 22ft CCD Int'l
2005 GMC Yukon Denali
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Old 06-23-2007, 08:58 AM   #13
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2004 25' Safari
. , Illinois
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I know it's more costly, but have you considered putting a diesel in it instead of another gasser? Reason I say this is that you seem to want to hang onto this long enough to not want to do it again (at least for some time). A gasser, though powerful enough, mostly gets about 200k on the high end before needing an most cases, even sooner than 200k, whereas a diesel, 100k is really just breaking it in, plus the slight mileage increases, etc.

The 502 is a great engine, but it too has it's share of issues. Piston slap was an issue, as is oil consumption. If you didn't think diesel would be a good option for you, then I might lean toward a rebuilt 454, but if it were me, I'd have bitten the bullet and taken on the drivetrain upgrade to diesel. They can fit, there was a factory 280 turbo diesel out there.
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Old 06-24-2007, 09:50 PM   #14
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1990 33' Land Yacht
Jacksonville , Florida
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Posts: 112
454? 502?


Whatever route you take with the engine, start looking for and purchase a Gear Vendors overdrive unit. I installed one in my 1990 Land Yacht (three speed Turbo, same tranny as yours), and at 60 MPH, the RPM decreased FRom 3,000 to 2,400. Engine is quieter, runs cooler and 2,400 RPM seems to be its "sweet spot."

You just may be able to get a quality rebuilt 454 and a Gear Vendors for the same price as that high dollar 502. I guarantee you'll like the Gear Vendors!

PM me if you have any questions.



Frank and Susan Davis
Jacksonville, Florida

33' 1990 Airstream Land Yacht: Edelbrock, Banks, Gear Vendors, MSD, Taylor wires, Super Steer bell cranks, Bilsteins, Roadmaster sway bar, Safe Steer, Pressure Pro, Crossfire, Bigfoot levelers, Rickson 7.5" rims & 245/70 R19.5 Bridgestones on steer axle.
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