Repowering ’62 Connie from 427 gas to 6BTAs

[bwanaf111]

Hi all!

I’ve got a ’62 45′ Connie that I am repowering from 427 gas to 6BTAs (JWAC). I am spit-balling that the performance should be acceptable, as I don’t run her hard at all, and don’t plan on changing that. I would love to hear what the brain trust thinks.

Current setup is (2) 1969 Chris Craft 427s with Paragon 44s, 2.5 to 1 gears. I am swinging 22 x 22 modern 4 bladed wheels. Her weight is listed at 28000 pounds. I usually run at about 2500 rpm (1000 shaft rpm) producing 9-10 kts.

the 427s new were supposed to produce 432 FtLbs of torque and 207 Bhp at 2500. at 2900 their torque peaked at 438 and 242 HP. Max was 4000, 393 and 300 HP. When I first got her, I seem to remember opening her up to 3400 ish rpm getting ‘about’ 20Kts.

I am dolling up a pair of ’89 6BTAs (JWAC) with 2 to 1 ZF 220As to drop in her this spring.  I am hoping they will turn at least 2000 rpm to get me to a comfy cruise, and not be over/under propped. 

What thoughts do we have on how close we’ll be?

Thanks so much for any input you’all have!

Cheers

Tom C

Topic

[Tony Athens]

“Aftercooler looked clean, so passed on that…  What does that mean? You must have x-ray vision?

160F Hi-flow thermostat is a must for this engine to get the temps  safe

Mounting–front of the engine and the side on the transmission

Seaboard Founder

Go here for the latest stuff we put together and share for all to see:

[bwanaf111]

Upgrades for sure!

Tony,

Thanks for the input! I will definitely up size those hoses! I wondered when I saw the reducer coming out of the head…why would they do that?!?!? I think I found all the rerouting instructions, but am planning on installing temp and oil pressure alarm system, and seem to remember you had optimum locations for the sensors, but I can’t now find it!  I think the lower temp thermo might be a good idea too?

I had oil analysis done on the gears, and they came back good, (2 year old oil looked clean like new). Is the filter below the pump like the 280? I was going to check the Torsional couplings, but decided it would crush my budget. on that note, I am going to have to Fab new aft motor mounts, are there any downsides to attaching to the block verses the gear? (would simplify Torsional coupling replacement if required).

Aftercooler looked clean, so passed on that…

I really appreciate the help, please don’t let me do something stupid!

TC

[Tony Athens]

2:1 gears will be close with your existing props..  You can fine tune that later– Transmissions have been check, gone  gone thru,  or tested?  Same vintage as the engines?  Torsional coupling is new or ??

Paint job  looks great BUT with that said, these are super early 6BTA 5.9 250’s (over 30 yrs) and need to have  the engines coolant circuit re-plumbed / upgraded for long term safety.  IMO,  it would be shame to do all of this and not do these changes as this coolant plumbing design  had ZERO tolerance for error or even a simple/quick overheat…………..There is stuff on the web site to guide you on this

Aftercooler serviced ??  This is a non-acid “hot tank” job… 

Seaboard Founder

Go here for the latest stuff we put together and share for all to see:

[bwanaf111]

EIDs 442560 and 44278571 showing about 2000 hours on non functional hobbs meters. They ran well for the three days I ran them (28 hours) no smoke, started every time without hesitation.

TC

[Author]

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