BBC build- Don't tell the Admiral

[Scott Danforth]

No Title

dug out my bin of hose clamps..... acquired these when I worked at West as well as Cummins. about 100 hose clamps, ranging in size from 1-1/4" up to 6" all stainless, some t-bolt.



will come in handy running exhaust, etc.

was playing with the idea of re-making the original formed metal tubing for the fuel feed. added up all the 3/8 flared tubing I would need.....add to that the time to bend all the tubing, de-braze the existing tube fabrication, replace all the damaged tubing (bent, rounded flare nuts, etc) and I was looking at $40 worth of material and 2 hours worth of work. Ebay had a billet aluminum holley fuel feed with fuel gauge for $35. added 10 ft of A1 USCG fuel hose for another $20. should have motor plumbed monday when the parts arrive

Three x-mas parties the next few days. My company party tomorrow night up in St Pete, Tammy's company party Friday at the Sarasota dog track, and a good friend having their annual bash (about 200 people) on Saturday. hope to get the wiring done this weekend so I can then jump onto the interior of the boat. however Sunday may be a recovery day for our livers.

 

[Scott Danforth]

First fire up with fuel, key switch, etc..... Accelerator pump not working, front bowl needle needs replacing......but its alive

make sure to turn up the volume..........

https://youtu.be/PPyOoVaB_p0

 

[Scott Danforth]

you cant see it in the vids.....however the smile on my face you would swear I could eat a banana sideways. Carb kit ordered, will be here after we get back from the cruise.

 

[alldodge]

It's alive, cool

 

[Scott Danforth]

so....had to replace the needle and seats, and the two check valves in the accelerator circuit were stuck..... while at it, change the squirter from a #26 to #28 and changed the secondary jets from #90's to #95's

here is first run after bolting cab back on

https://www.youtube.com/watch?v=SgT1yWtRm6k

here is run after backing idle down from 850 to 650 and setting timing

https://www.youtube.com/watch?v=avc9Dc0sEYU

 

[Maclin]

Nice! Does the admiral suspect BBC vs SBC yet? If she ever heard one of your SBC tuneups she may suspect something is different, just sayin' good job

 

[Scott Danforth]

Ran the motor for about an hour today just off idle. getting a fair amount of reversion at idle with the exhaust elbows I have. just enough that I noticed water dripping from the manifold to elbow joint (didnt have the band clamp tightened).

this has me believing I wont use the selectable exhaust and will most likely need to extend the inner tube a few feet more in the exhaust run to the tips.

 

[alldodge]

I think your tubes are the standard height long risers, with the cam your using I would suggest the +3 up ones. Still may not be able to use selectable exhaust, but need more height

 

[Scott Danforth]

my tubes are 24" long, running back to the transom

yes, standard height, long length. reversion seems to quiet down with idle speed of 900+, at 650 RPM, the reversion wave carries water vapor all the way to inside the manifold.



I believe these

 

[Scott Danforth]

the Cam is fairly mild being only a HP500 clone. Have an email into guy at CMI to get some exhaust elbows and straights. worst case, I build a 3" riser

 

[alldodge]

650 RPM, the reversion wave carries water vapor all the way to inside the manifold

From my understanding and discussions, below 800 is where reversion starts. I had a set of standards and had to replace with 3+ to clear this issue on my motor.

 

[Scott Danforth]

From my understanding and discussions, below 800 is where reversion starts. I had a set of standards and had to replace with 3+ to clear this issue on my motor.

I may just keep the idle high. However since the elbows head to within 6" of the transom, i will be welding a 90 degree elbow on the ends with a 6" tail. Both inner and outer tubes.

Should be about another foot of run

 

[Scott Danforth]

Scored new Stainless Marine +6 risers on craigslist. guy in the keys had twin 454's and ordered new risers to take care of reversion.....then the hurricane took out his boat.

 

[alldodge]

Great, don't need to worry about to high an idle now

 

[Scott Danforth]

Nope, just need to cut-n-weld to get everything to fit. guy drops them off this Friday.

 

[Scott Danforth]

So I got my new +6" elbows. they are quite tall compared to the prior elbows.

they also did not completely take care of reversion at 900 RPM. you can still see the water vapor being sucked in when you slow the video down. it is greatly improved, just not "cured"

they are also about 1" too tall for the bilge hatch.


so...... custom H-pipe exhaust with the cross-over being about 10" up-stream from where the exhaust and water will mix.

have access to a band-saw and a dozen welders that weld stainless all day long.

was hoping to have this issue resolved prior to installing the motor.

 

[alldodge]

I don't see +6 causing a reversion. While there can be some water being sucked in, it would get blown back out with the next exhaust.. I have +3 and runners which go out to within 3 inches of the transom (starboard side) and have no issues

 

[Scott Danforth]

You wouldnt expect it to, however the inside of the elbow was wet, so was the manifold, and there was a bit of pooling in the bottom of the manifold.

I have to bring the RPMs to 1100 to have enough exhaust velocity to keep the exhaust from becoming wet inside the tubes

 

[alldodge]

Something isn't right, what is the LSA on the cam? it should be no closer then 110

 

[Scott Danforth]

114 degree lsa