Update on the mild 427 tweak for 23' Chris Craft inboard hull

Update on the mild 427 tweak for 23' Chris Craft inboard hull

Paul
Paul

July 19th, 2010, 6:41 pm #1

Okay guys I have been researching the mild 427 build up for the 23' inboard project boat. Here are a few details. Realizing the 427 motor is already a fine marine design, I am not going to a crazy automotive stage here, as it would only toast the motor quickly and there is no point in doing that.

Therefore the build will be a mild tweak this first time around, thinking this is the safe thing to do and also thinking there is no need to go any further than 200 more horses than Chris Craft originally put into this hull. The original power for the 23' inboard Lancer was the 350Q which had a compression of 8.8:1, 235-hp at 4200 rpm, and weighed in at 964 pounds for the direct drive setup. The big dog weighs in at 1143 pounds with the same direct drive, but I am trimming off about 200 pounds so the balance and overall weight of the boat will be generally identical with NO weight premium for the big block.

The 23' inboard hull with 350Q weighs in at 3695 pounds, while the comparable 427 V-drive 23' Lancer Premiere/Custom Super Sport was 4200 and the 427 23 Commander V-drive was 4695. Therefore I am in the same league of 3695 pounds but with nearly twice the power of the original hull. Actual power ratings will remain top secret, and only Jerry Namken or perhaps Gordon Liddy (holding a lit candle under my open hand) would be able to make me talk.

Compression will remain at 8.9:1, heads and rockers will remain stock, but the cam, intake, exhaust and carbs will be upgraded as the first step in speed for the 23 hull.

Limitations will be a 5000 rpm max engine speed. If the heads come off they will be re-used, perhaps in mildly ported form, as these are quite good Ford heads. Going to an aluminum Edelbrock would save weight, but would not appreciably gain all that much power. I like the iron heads. The intake alone will save half the weight of a small person (25 pounds versus 80 pounds for the iron manifold). Exhaust manifolds and risers will be all water jacketed cast aluminum racing NICSON type, which I already have. Therefore the overall weight of the motor with manifolds will be about 175 200 pounds lighter, perhaps a bit more due to the fact that those marine 427 iron exhaust manifolds and risers are VERY heavy.

Comp Cam grind 270S will be used, featuring an operating band of 1800 to 5500 RPM, part number 33-244-4, advertized duration 270 (actual 224 at .050) and lift .540, with 110 lobe separation angle.

This is getting somewhat close to the original PI (Police Interceptor) cam Ford used. It is noted that Holman Moody original c3az-aa at 228-228-114 was the original 427/410hp cam, so this Comp is a reasonable choice. Compression is not going to be altered so this will keep power (and related heat generated within the motor) within reason.

For the record, the Ford 270/290 duration, .481 lift cam, was the stock police interceptor grind, and this was tweaked a bit to Cobrajet specs ie.279/290 duration and .481 lift.

It has been recommended to go with a (205-215) with at least.500 lift and 110-112 degree lobe centers as an improvement to the so-called old tech CJ/GT/PI cams, so this is yet another reason I settled on the Comp 270S. Comp has a good reputation, and everyone I checked with said to avoid the next step up, which would be the 282S, as it was more cam than the motor would be able to use (236 at .050 and .571 lift).

Spring load with the Comp solid 270s is just under 300 pounds, and the unsupported end rockers on the Ford rocker shaft are supposed to be able to handle this. After all, Ford was selling this same rocker assembly on engines rated for 6,000 rpm. To be safe however, I am adding a set of aluminum rocker shaft end supports from Precision Oil Pumps, as a 100% assurance to any thought of failure here. These are quite affordable and would be easy to install.


I have the full closed cooling system, but am thinking that this one will be raw water cooled, primarily for weight control, and the fact that the closed systems seem to run a bit on the hot side. This decision has not been made yet, but will be soon.

I have a couple pretty qualified speed advisors that will be coaching me to eeek out as much potential from this hull as possible, while still staying safe. They are Curt Brayer, and his son Keith, both of whom run the big block 392/426 hemi in their boats. Mr. Brayer, "Curt", holds numerous APBA records, and was high point man in his class for 7 years in a row. I've been aboard his DANCING BEAR for a personal ride one day, and it left a rather indellible impression on me. Oh did I mention he built the boat too. His son Keith is the one who has the worlds fastest 19' Chris Craft Racing Runabout. It looks stock, but it's not, ha.

As this project unfolds over the next 12 months (or so) I'll be posting engine info and test run data, etc. Stay tuned.

Oh one more thing, a windshield will remain optional !

regards,

Paul
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Randy
Randy

July 22nd, 2010, 2:34 pm #2

Paul,

I am new to this forum. I am impressed with the knowledge among the participants. I have owned a 1969 38' Commander Sedan for 12 years that is powered by 427s. I am the third ower of the boat, the second owner had it for just over a year, and it has always been in fresh water. I love the boat and the 427 engines. I currently have both 427s out and I am doing a complete rebuild. I will send you some pics of the finished product shortly, they are ready to run in the garage and then be installed. I was wondering on your 427 build for your 23 if you plan on replacing the connecting rods? My engines had approximately 1,250 original hours and I never pushed them over 3,800 RPM in the first 12 years I owned the boat. The reason they are out is that the port engine broke a connecting rod right at the location where the I-beam intersected the crank journal. Fortunately, the block was not trashed since I immediately shut it down when it started vibrating. I am an experienced mechanic, mechanical engineer, and drag boat racer. After some research and asking around to several other experienced engine builders, I have the impression that the 60s era connecting rods are prone to fatigue failure due to several factors including manufacturing volume and techniques, and material variation. I too want to rev my 427s to the 4,600 - 4,800 range to increase the power, so I have replaced all of the connecting rods and both crank shafts with Scat components and I had the rotating assemblies balanced with new pistons. The new displacement is around 470 cid with 9:1 compression since I chose to increase the stroke to 4.125" while I was at it. Standard stroke replacement cranks are available and the original cranks are good components. I felt the new rods were cheap insurance to save my original 427 blocks and to provide peace of mind at the higher revs. I also went with new Diamond pistons with a 0.020" overbore to true up the cylinder walls which were at the taper wear limit.

I agree with you on the cam and valve spring specs for your build and that the original heads and rocker assemblies will be fine at 5,000 RPM. The valves in the original CC 427 heads are plenty big for making power at 5,000 RPM. My cam specs are very similar to yours except I went with hydraulic flat tappets. Compare the 427 rocker assemblies to the big block chevy stamped rocker on stud design that Mercruiser specifies can run at 4,800 RPM, which I know they can since I have flogged many of them in both speed boats and cruisers. In my opinion, if you intend to rev a 427 with its original connecting rods to 5,000 RPM you will increase the probability of connecting rod fatigue failure as it is a function load cycling. If you have new valve springs and connecting rods, no other part of an original CC 427 engine should have a problem running at 5,000 RPM. I believe the 4,000 RPM limit was conservative for the 427 engine and it was chosen to allow them to be reliable for a long time. Also, as good as these engines were originally, I don't think CC specified the rotating assemblies to be balanced, which helps things last much longer at the higher revs. The engine I run in our drag boat has a displacement of 492 cid, 16:1 compression (methanol), and it turns 7,200 - 7,500 RPM all season without any problems using the same Scat components I used in my 427 rebuilds. The key is the balanced rotating assembly and valve train.

Keep us posted on your progress. By the way, if anyone is in need of one, I have two original CC 427 crankshafts, one standard rotation and one counter-rotation. The standard rotation crank needs touched up where the rod bearing spun after the rod journal broke, the other one is fine. I also have two sets of original pistons from which someone could probably salvage a good complete set of 8. The connecting rods I would give away, but not recommend using.

Randy
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Joined: October 17th, 2008, 6:09 am

July 22nd, 2010, 3:16 pm #3

Impressive! What kind of power / torque do you anticipate after your rebuild is complete?

I'll be curious what kind of WOT speeds you'll see with your 38' after all is said & done.

Thanks!

Kevin Bray
'06 CC Launch 22
FXA-31-4049
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Paul
Paul

July 22nd, 2010, 4:25 pm #4

Paul,

I am new to this forum. I am impressed with the knowledge among the participants. I have owned a 1969 38' Commander Sedan for 12 years that is powered by 427s. I am the third ower of the boat, the second owner had it for just over a year, and it has always been in fresh water. I love the boat and the 427 engines. I currently have both 427s out and I am doing a complete rebuild. I will send you some pics of the finished product shortly, they are ready to run in the garage and then be installed. I was wondering on your 427 build for your 23 if you plan on replacing the connecting rods? My engines had approximately 1,250 original hours and I never pushed them over 3,800 RPM in the first 12 years I owned the boat. The reason they are out is that the port engine broke a connecting rod right at the location where the I-beam intersected the crank journal. Fortunately, the block was not trashed since I immediately shut it down when it started vibrating. I am an experienced mechanic, mechanical engineer, and drag boat racer. After some research and asking around to several other experienced engine builders, I have the impression that the 60s era connecting rods are prone to fatigue failure due to several factors including manufacturing volume and techniques, and material variation. I too want to rev my 427s to the 4,600 - 4,800 range to increase the power, so I have replaced all of the connecting rods and both crank shafts with Scat components and I had the rotating assemblies balanced with new pistons. The new displacement is around 470 cid with 9:1 compression since I chose to increase the stroke to 4.125" while I was at it. Standard stroke replacement cranks are available and the original cranks are good components. I felt the new rods were cheap insurance to save my original 427 blocks and to provide peace of mind at the higher revs. I also went with new Diamond pistons with a 0.020" overbore to true up the cylinder walls which were at the taper wear limit.

I agree with you on the cam and valve spring specs for your build and that the original heads and rocker assemblies will be fine at 5,000 RPM. The valves in the original CC 427 heads are plenty big for making power at 5,000 RPM. My cam specs are very similar to yours except I went with hydraulic flat tappets. Compare the 427 rocker assemblies to the big block chevy stamped rocker on stud design that Mercruiser specifies can run at 4,800 RPM, which I know they can since I have flogged many of them in both speed boats and cruisers. In my opinion, if you intend to rev a 427 with its original connecting rods to 5,000 RPM you will increase the probability of connecting rod fatigue failure as it is a function load cycling. If you have new valve springs and connecting rods, no other part of an original CC 427 engine should have a problem running at 5,000 RPM. I believe the 4,000 RPM limit was conservative for the 427 engine and it was chosen to allow them to be reliable for a long time. Also, as good as these engines were originally, I don't think CC specified the rotating assemblies to be balanced, which helps things last much longer at the higher revs. The engine I run in our drag boat has a displacement of 492 cid, 16:1 compression (methanol), and it turns 7,200 - 7,500 RPM all season without any problems using the same Scat components I used in my 427 rebuilds. The key is the balanced rotating assembly and valve train.

Keep us posted on your progress. By the way, if anyone is in need of one, I have two original CC 427 crankshafts, one standard rotation and one counter-rotation. The standard rotation crank needs touched up where the rod bearing spun after the rod journal broke, the other one is fine. I also have two sets of original pistons from which someone could probably salvage a good complete set of 8. The connecting rods I would give away, but not recommend using.

Randy
Hello Randy and "WELCOME ABOARD".

I'm interested in seeing your photos of the boat and the motors!

We've had some good and some not-so-good stories about the 427 rebuilds here over the years. One fine fellow in the French West Indies rebuilt one only to find out it was admitting oil into the coolant at the location that feeds oil from block to head, needing the tube insert crack repair. In addition, we've had a very nice pair rebuilt in Pacific Canadian waters using modern hyperutetic pistons, which ended up melting those, and needing another complete rebuild, so I am always VERY conservative giving recommendations to people who are going to use these motors in an industrial application (such as pushing a cruiser).

My own 23' Lancer project will be so over-powered I don't think the motor will be working all that hard and quite honestly I am not real sure why I set the 5,000 rpm limit, as I doubt if I will ever push it that far. My objective with the boat is to get a 23' classic Chris Craft that has the capability to cruise continuously at a relatively high speed, without over-revving or over-taxing the motor. I would say a fast cruise speed would be 3,000, and propped accordingly I think the boat will do that just fine.

I am suprised to hear you broke a connecting rod. Very strange to hear one broke with the easy running your motors have apparently had. Also, even when rebuilt, I would be reluctant to run them higher than say 4200 under the loading they'll see pushing a 38, in my opinion that would be asking for trouble. Just my gut feeling. It would be the equivalent of running a full dump truck at WOT up a hill. In a car all the power can be used, and it is generally used only a short while, as the car can coast, stop at a stoplight, or just cruise easily on the interstate. With a cruiser it is an uphill push all the way.

On my 23' boat, I don't think the motor will be really breaking a sweat, as long as I keep the prop and rpm within reason. That is not the fastest hull in town either, with that deep-v it has a lot of friction, as I am sure you know if you are racing. We always stand to learn, and in my case "a little knowledge is a dangerous thing". Tips and recommendations are ALWAYS appreciated.

Regards,

Paul
forum host

FXA-38-3004-R
original 427 power
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Randy
Randy

July 22nd, 2010, 7:42 pm #5

Paul,

Thanks for the comments. I agree, pushing a 427 continuosly at full load above 4,200 - 4,400 RPM probably isn't a great idea, I just want to cruise a bit faster if I want to and let the engines loaf at a 4,000 RPM cruising speed. I went for the longer stroke to increase the torque curve even more, which equates to more peak horsepower at 4,000 RPM. The transmissions can definitely handle it. I see people pushing modern 40+' cruisers with GM 454 or 502 power to 4,400 - 4,600 RPM and leaving them there all the time. I've done it myself occasionally as a service tech, but I usually pull them back to 4,200 - 4,300 RPM. I know they generally have smaller props, but they also usually have higher gear ratios and similar weight. The 427 can be a much better motor than a GM 454 in my opinion, if controlled correctly. I forgot to mention that I have also installed Holley Commander 950 ECMs with 700 CFM fuel-injected throttle bodies, timing control, and knock sensors on my 427s. That should help keep things in order under heavy loads. I am looking forward to the tuning runs on those.

I expect the melted piston story you mentioned relates to too high of a compression ratio combined with poor timing control. As you probably know, the advance mechanisms of the mechanical distributors can stick and/or wear out and cause big problems. It probably detonated to death, as will just about any stock 427 with old ethanol blended gas and too much total timing. I totally agree with you that the high compression automotive approach is not good for our CCs. In my opinion, pleasure boat motors should not go above 9.0:1 compression with the fuel available today. I believe CC called for 92 octane fuel for the 427 originally. When was the last time you saw that at your gas dock? The fuel situation is another thing I considered in this project, I hate the thought of E-15 or E-20 fuel in my boat. Talk about a hit to power and efficiency and unhappy spring start-ups. I can feel the differnce between ethanol blended fuel and fuel with no ethanol in my V8 truck, original 427s will hate E-15 or E-20.

Randy
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Paul
Paul

July 22nd, 2010, 8:10 pm #6

A couple of thoughts, no real conclusions......

At a given rpm piston speed on the longer stroke motor will be higher than the short stroke, valve train won't know the difference.
You'll be making more torque for sure, so propping up will put more stress on the crank, etc.

I have heard and do believe from personal experience, that CC over-propped their boats for performance bragging rights, and that we might all do well to back off just a bit on the pitch. Mark Weller and I have discussed on a couple of occasions and he may well be right. I wish someone had told me that before I spent a thousand dollars each on new 4-bladed props that are pitched too high, as I have discovered the motors won't reach 4000 now and it just adds more stress trying to maintain a fast cruise. For some reason I didn't reduce the pitch enough when I changed from 3 to 4, but now I know so I'm passing the warning along. It's going to cost me some bucks to fix it and get em repitched.

I'm backing off the 23x24 4 blade I'm presently running to a 23x23 4-blade perhaps, and maybe even to a 23x22 in a 4 blade, as the 23x25 was the original 3-blade spec and that might have actually been backed down to a 23x24 3-blade? I'll have to consult with the prop manufacturer about that one. I think the motors would rather be spinning 3000 rpm continuously (for instance) with a little less pitch.

One thing about the 4 blades, you just touch the throttles and the boat jumps out of the water. I suspect it is putting a lot of stress on that 1-3/8" shaft

Right now at 3000 rpm I'm hauling the mail !! (Get the lifestock off the river-bank............I'm coming through!!)
Here's a few photos of our TRADITION on the Cumberland.










Here is an old video with a really crappy camera, but you can see what it's like blasting down the Cumberland River.
This is with the 4-blade props too. I don't do this very often but I keep the boat tuned so it will.
<object width="480" height="385"><param name="movie" value=""></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="480" height="385"></embed></object>


Regards,

Paul



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Randy
Randy

July 22nd, 2010, 10:14 pm #7

Paul,

Your boat looks great, I have been looking at your pictures as I get familiar with the site. I currently have 23x23 four blade props and 1 1/2" shafts. The boat was no slouch with these props before and the 427s would turn 3,600 RPM fairly easily, and 3,800 RPM was about all I ever tried to get from them. I do not intend to change anything with the pitch of the props with this engine rebuild. What peak RPM and speed does your boat run now? Just curious for prop spec comparison purposes.

Randy
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Paul
Paul

July 23rd, 2010, 3:54 pm #8

From the archives.........

2200 RPM 8.3 GPH x 2 = 16.6 GPH

2400 RPM 9.3 GPH x 2 = 18.6 GPH

2600 RPM 10.5 GPH X 2 = 21.0 GPH

2800 RPM 12.O GPH X 2 = 24.0 GPH

3000 RPM 14.9 GPH X 2 = 29.8 GPH

3200 RPM 16.6 GPH X 2 = 33.2 GPH

3400 RPM 18.1 GPH X 2 = 36.2 GPH

3600 RPM 19.4 GPH X 2 = 38.8 GPH

3800 RPM 23.6 GPH X 2 = 47.2 GPH

4000 RPM 25.0 GPH X 2 = 50.0 GPH

On occasion I commute between Commodore Yacht Club on Cheatham Lake where TRADITION is docked (near our primary residence) and Cedar Creek Yacht Club on Old Hickory Lake, where our lake house is located.
This is 18 miles to downtown Nashville, 45 miles to the Old Hickory Locks, and another 18 miles to Cedar Creek YC. Running at 2600 to 2800, which is VERY comfortable for a 38, that trip would burn about 90 gal of fuel, and at $4 per gal thats a $360 4-1/2 hour trip, or about $90/per hour of fun figuring a half hour getting through the locks.

In the 427 powered Lancer, I think I can prop the boat to run at 30 mph around 3,000 RPM, maybe not that fast but I think she will be a 50-mph boat on top end with the hull and power combo, so 30 seems like a reasonable fast cruise. At 3,000 rpm that's about a 30 gal burn, again figuring a half hour at the locks, or a $120 cost ($60/per hour fun factor for fuel only). More likely be running a little slower, because if I'm in a hurry I can make that trip in 45 minutes by car.

Right now I don't really know my fuel consumption with the big 4-blade props on the 38. I do know it responds instantly to the throttle, gets up on a plane very nicely, and will back off on power down to around 2500 and still stay on a plane. I'll verify that this week-end. Top end with the 4-blades has to be suffering as 4-blade props just DO NOT achieve the same top speed on any boat, when compared to an equivalent 3-blade (or two blade as your racing experience may prove). Never saw a 2-blade on a Commander, ha, would be expensive in a 23 x 25 eh? With my 4 blades I am not able to get much over 3700 RPM max, and you can see why I'm not happy with them on top end, as they lug the motors too much. I therefore don't run at WOT very often, never really did anyway. The 4-blade props are just fine at cocktail speeds, and they seem to do very well at my cruising speed of around 2600 to 2800, knowing the 427 puts out 438 footpounds of torque at 2900 anywhere near that range is running pretty easily on the max torque curve.

It will be interesting to see the difference between theory and practice

What is your time frame for testing the big fuel injected strokers?

Regards,

Paul





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Randy
Randy

July 26th, 2010, 8:05 pm #9

Paul,

From your numbers, it sounds like our boats are very similar in performance with stock 427s, which they should be. I typically cruised at 2,700 - 2,900 RPM with 23x23 four-blades. My boat will start to fall off plane when pulled back to or just below 2,600 RPM and would top out at 3,700 - 3,800 RPM, where the hull looked and felt really good on the water. I believe you said you have 23x24 four-blades, which may be the slight difference in the minimum planing RPM. My Commander is the Sedan model with the slightly longer enclosed helm area and the full sized sliding glass rear door. I am not sure if there is any significant weight difference between the Commander models.

As part of the project, I am replacing the original flathead 6.5 KW Kohler genset with a new and much lighter 5 KW, 1,800 RPM, Westerbeke. I am also putting in a smaller plastic fresh water tank in place of the original 75 gallon steel water tank to gain some extra storage space in the back. The weight difference of that stuff is fairly significant, but in the overall weight of a 38 Commander, not so much. I have a running 6.5 Kohler avalaible as a result. It would be best for parts as it really needs valves and springs.

My goal with the new stroked and fuel-injected 427 motors is to be able to cruise in the 3,700 - 4,000 RPM range or slightly higher if I want to, but not have the engines at or near WOT while doing it. I often take trips with guys with modern gas powered cruisers who can just stay ahead me. I would like to screw with them and have the 40+ year old CC pull away from them just for fun. I have been delayed a little with the project this season due to high water conditions at the marina where I keep the boat. The boat is kept on the Mississippi River near Grafton, IL, north of St. Louis, MO. We have had repeated high water conditions this season, combined with a busy work and race schedule. Both engines are fully assembled with the rebuilt transmissions on, one is ready to run, and I need to finish wiring the other. I am waiting for the water to go down so I can get the boat in the lift well to put the engines back in. The marina has rack storage, so I can put the engines in complete with the transmissions on using the rack storage forklift. It will probably take a few weekends to get the initial break-in time, the fuel mapping dialed in, and the bugs shaken out of things. That is the fun time of such a project for me, compared to hours and hours of bead blasting, wire brushing, and painting. Don't get me wrong, I like that time as well, and the details are what make the project. I can see there are many others out there that have spent countless hours doing the same.

By the way, I don't think I have ever seen a 23x25 two-blade prop, it would be cool but maybe not such a good fit for the CC hull. I run two-blade props on the drag boat, maybe I can do a little photoshop work and get a pair on the CC for a laugh. I not sure I am good enough to reverse the rotation it photoshop though. I have attached a photograph of my Commander to see if I have figired out the photograph posting thing for this site. I'll see if it works.
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Paul
Paul

July 26th, 2010, 8:33 pm #10

Here is what I just received on the email:

If the 4 blade propellers are bronze, cost to pitch change is: $306.00 per propeller
If the 4 blade propellers are nibral, cost to pitch change is $340.00 per propeller
If the 3 blade propellers are bronze, cost to repair is $ 251.00 per propeller
If the 3 blade propellers are nibral, cost to repair is $279.00 per propeller

Deltaprop.com
(877)238-8214 toll free
(513)467-0601

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