Type 4 Rebuild--Cam Selection

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Re: Type 4 Rebuild--Cam Selection

Post by 72Hardtop » Mon Jul 25, 2011 11:02 pm

Amskeptic wrote:
airkooledchris wrote:If extending the exhaust valve duration hampers the ability to shed heat - wouldn't those 9550 Raby cam's make things run hotter Vs the cooler temps that most report seeing using them?
CHT temps tell you what is happening at the plugs.
Nobody has a gauge that reads exhaust valve face temps.
The combustion temps can be perfectly normal when you burn an exhaust valve,
its failure is a localized trauma that only the valve metallurgy can tell you.
I have not heard of exhaust valve failure in Raby engines due to excessive open duration. But I ask about long duration exhaust valve seat time because I am curious.
It really comes down to the engine combo. With the added intake duration working to help keep the head temps in check. Lets not forget about the exhaust setup without a free flow exhaust it would all be negative.
1972 Westy tintop
2056cc T-4 - 7.8:1 CR
Weber 40mm Duals - 47.5idles, 125mains, F11 tubes, 190 Air corr., 28mm Vents
96mm AA Biral P/C's w/Hastings rings
42x36mm Heads (AMC- Headflow Masters) w/Porsche swivel adjusters
71mm Stroke
Web Cam 73 w/matched Web lifters
S&S 4-1 exhaust w/Walker 17862 quiet-pack
Pertronix SVDA w/Pertronix module & Flamethrower 40K coil (7* initial 28* total @3200+)
NGK BP6ET plugs
002 3 rib trans
Hankook 185R14's

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Re: Re:

Post by Amskeptic » Mon Jan 16, 2023 3:02 pm

72Hardtop wrote:
Sat Jul 09, 2011 8:42 am
vic74 wrote:This is for a 74 westy used as a camping vehicle as well as a daily driver when needed. I would like to use it more in the winter but never got the progressive to work well in the cold. I live in a valley and virtually any trip of more than 20 miles from my house will put the bus in the Cascade, Siskiyou, or Coast Ranges. Loaded down with 2 adults, 3 kids and assorted camping gear more often than not. I'd like to do this while keeping up with the semi trucks--at least the loaded ones. :cyclopsani: Cruising at 65mph on the flats would be fine, I don't need to be in the fast lane. I took it pretty easy on my last engine, took 6 or 7 seconds to build oil pressure on start up--sounded like a diesel at idle. I always drove it with this in mind.

500k+ miles is astounding! If I could get 100k on this rebuild I would be pleased--though I would'nt refuse more. Colin-- I know you advocate stock components and have had much success with them. I also know that you work on a lot of bus engines and have experience with much of what's available on the aftermarket. Between you and your fellow itinerants--I figured I'd get some sound advice!
Keep in mind no matter how meticulous one is you won't get 500,000+ miles out of a T-4 motor. That figure doesn't include the several rebuilds it's had.
Flywheel ................. 588,238 miles
Crankshaft ............... 419,000 miles (should not have replaced it)
Camshaft ................. 146,000/160,000/114,000/168,000 miles
Carburetors .............. 588,238 miles
Distributor ............... 588,238 miles
Alternator ................ 419,000 miles
Heads ..................... 515,000 miles, two sets of guides, two sets of exhaust valves
Oil Pump.................. 320,000 miles, second pump good at 268,000 miles.

The POINT here, 72Hardtop, is that parts can last longer than what "they" say. And we have far more agency over making the parts last than "they" say.
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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