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Cooperative Motor Works

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You are here: Home / The Daily Pose / GMC Motorhome: Don’t fall in the crack…page 2

July 11, 2018

GMC Motorhome: Don’t fall in the crack…page 2

So getting the intake out, this is an original…….non rebuilt motor.  Othere than the outside looking about as grody as you can imagine, It was the carbon cookies……there were too many of them inside the “turkey tray” not to be building for 40 years.  You can see the intake where I chipped off some of the “cookies’    What is that black stuff?  Don’t worry, the actual metal is under there somewhere……well it’s oil that had been cooked by the heat from the exhaust crossover    Here’s another cookie I just pulled off….don’t eat it!!!! 

The machinist will have to chip all that mess off before it goes in his tank…that much crap would contaminate to cleaner……. while he’s doing that, we will clean out the cookie residue.  Remember just one small chunk of that mess will clog up and oil passage and the motor will go away.  I’ll show you a pic of the cleaned valley tomorrow….it was vacuumed out then a quart of oil was poured on all the surfaces in the valley to try and wash any cookie crums down into the oil pan and out when we dump that oil.  A normal……non-concave intake motor does not bake cookies as bad as this….sure there will be some but man…our intakes should be nicknamed “The Easybake Oven”!

Anyway, we will get the intake back hopefully today and I’ll let you see it all go back together.

Mel picked up his dechromed yellow pimple yesterday    A good older restoration and custom body, it needed a little sprucing up    The thing I like is it’s a 2 door coupe….. makes for a slick rake   and I love that roofline!  We brought in extra exterior people to push this job out….kinda out of what we do but not really……..thanks Mel for putting your faith in us.

A unique exhaust system we’ve been building up over the year sports 2 tailpipes out of a single pipe system  Standard 2 1/2″ pipe, we join the 2 header pipes together without mufflers.    This allows the motor to better balance it’s outputs without having mufflers in the way.  Like an old Ford Mustang with it’s “equalizer” crossover pipe between their dual exhaust pipes…….bringing the pipes together like this helps offset the stainless steel blockoff plates stopping GM’s original “balance thru the motor” idea.  Blocking the intake as we do, blocks off this important balancing feature.  This is why mufflers usually take a hit when your coach backfires…I know you’ve seen blown up mufflers…….

I feel using the original diameter pipes allowing for the 3″ insulator silocone bracket donuts to isolate the pipes from the frame.  If you install a 3″ pipe exhaust system the 3″ pipes are in direct contact with your frame….more transferred vibration and heat.  Those spacers were put in there for a reason.

The single pipe comes back to a single “1 in/2 out” stainless steel muffler   which acts as sort of a free flowing “megaphone”.  Less restriction coming out means relief of backpressure.  The back pressure of the exhaust system (a good thing for a low RPM torque situation is set by the diameter and length of that 2 1/2″ pipe.  I could sit here and tell you those specs were scientifically designed to maximize engine efficiency…….Naaaaaaa, it just kinda worked out that way…..at @ highway speed (60-65) the system opens up and reduced in noise……the noise is energy lost in sound………like a 2 cycle motor with a chamber exhaust….this set up seems to do the same.

Anyway, we’ve done many of these……it puts the noise and heat of the muffler out from under the front floow and in the back…sounds kinda like a pusher diesel……all the sound is “back there”    Phillips son is here for his summer visit with Dad….had to take this pic…….no one told him to get up there!  Phillip has some future problems I would say    The spiked helmet he wears everywhere is a hoot!

Finally, to prove how OCD Drew is, out engine assembly guru is………yesterday he came by at lunch just to show us how perfect this valve covers for Susan’s next motor being built came out……OK, awesome man…that’s the detail we want!    That’s the guy you want on your side…look his up……..  he was further excited when we switched our roller cam motors to original metallic Oldsmobile blue…hey, color matters!

Great…it’s only 7:30……..that gives me a 30 minute head start on the day…….I have a new suspension compressor to install….under the 4″ aluminum fresh air duct….can’t pull the wheel liner without big work…there’s a wheel flare in there…….BTW, never take those out if you can help it after they are in there nice……..I’m just sayin………….they’re so packed back there they got the ole man out there….Damn it’s hot out there!

See ya tomorrow……Oh and with that exhaust project done…Scott, you go up on the lift for your Monster transmission, FiTech fuel injection and an all new fuel delivery system…..Bet you’ll stay tuned!  We’re pushing hard…stay tuned

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Article by jimbounds / The Daily Pose

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