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repower 283 w 350

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mike backstrom
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repower 283 w 350

Post by mike backstrom » Mon Oct 14, 2013 5:03 pm

can any one who has done this please offer advice on physical block, heads ,crank nose, flywheel etc. can i use a truck 350 w/ a cam change for marine use. can i use a one piece rear main seal crankshaft 90s vintage? this will be fresh water only.

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mfine
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Re: repower 283 w 350

Post by mfine » Mon Oct 14, 2013 5:33 pm

Mine was an improperly built 350 when I started but... You can use a regular 4" bore block. The crank and flywheel are not special marine parts. For heads, I went with new heads from Summit with new valves and seats etc. pre-installed rather than rebuilding the old ones. They needed minor modification for the 283 water flow, machining the end flat and drilling and tapping a water outlet on the end of each head. Cam choice is going to be application specific. Pistons, rods, lifters, rockers etc were all automotive products.

The starter, alternator (or gen), distributor, fuel pump and carb need to be marine specific, and obviously the water pump and exhaust manifolds. The stock accessories should work but there are some opportunities for upgrades here if it does not need to look 100% factory original.

I did not have a transmission/reverse gear to deal with, but on some you will need to get oil to them.

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Re: repower 283 w 350

Post by mike backstrom » Mon Oct 14, 2013 5:39 pm

mostly i am concerned with both ends of the block and crank bolting to the chris craft accessories and the cylinder heads w/ water ports on one end.

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Re: repower 283 w 350

Post by mfine » Mon Oct 14, 2013 6:32 pm

The flywheel end of the block was not an issue for me. The flywheel end of the heads needed the water ports added, but that is a rather basic job for a machine shop.

The aft end on mine was "special" because it is a jet drive with no transmission, and because Chris Craft's original design to keep the oil in was pathetic, like something Harley Davidson would have done. You will have less of a chore.

I think CC drilled a hole in the crank to allow oil to flow to the manual gear but I will leave specifics to someone with direct experience with that.

I will say my block is a late 60's casting, and I don't know what issues need to be tackled with later year blocks.

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Re: repower 283 w 350

Post by quitchabitchin » Mon Oct 14, 2013 7:46 pm

If you have access to a "truck" 350, chances are it has the 3896929 cam, which is a good choice for marine use. It has lots of low end torque. It was the stock cam in the Q series engine and tens of thousands of pickups and RV's. I chose a Lunati cam with a little more, .030", lift and slightly more duration. The stock "151" cam would also be a great choice with a slightly more lift and duration than the 929.

The basic block is the same, you should have no problem bolting any of your parts on. The only thing I found was that my original 327 crank had not been tapped for a bolt in the snout since it uses a press on damper and flexplate. This only made a difference to the guy I sold the crank to since he will need to have it tapped to accept a crank pulley in an automotive application. I am not sure of your transmission, but mine has it's own fluid supply. Some applications may have an oil passage drilled in the crank to supply oil to the transmission.

I do not have water ports on the heads, the Q uses the stock water pump outlets adapted to the Q cooling system. Later heads will have accessory ports (drilled and tapped) on the ends where the older heads will not.
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Re: repower 283 w 350

Post by Peter M Jardine » Mon Oct 14, 2013 7:47 pm

The original 283 and 327 from CC has a forged crank, but other than that, it was nothing specific. Personally, I would use a 327 if you can find one. You can still find lots of 283 CC's around. Within 2 hours from me, I know of at least 6 for sale. If I was going to build a 350, I would do as Matt said and get heads and the whole works. Now..... how much horsepower can you put through those old paragons before you need a heavier tranny... I honestly don't know the answer to that question.

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Re: repower 283 w 350

Post by quitchabitchin » Mon Oct 14, 2013 8:15 pm

Not all 327 cranks were forged, just the early, small journal ones from 62-67. Anything 68 or later in a 327 stroke is a cast, large journal.
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Re: repower 283 w 350

Post by mike backstrom » Mon Oct 14, 2013 8:27 pm

How do I know if my trans needs oil from the crank nose? It's a 61 ski boat

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Re: repower 283 w 350

Post by quitchabitchin » Mon Oct 14, 2013 9:18 pm

What model transmission is it? Does it have it's own dipstick?
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Re: repower 283 w 350

Post by Peter M Jardine » Tue Oct 15, 2013 5:08 pm

quitchabitchin wrote:Not all 327 cranks were forged, just the early, small journal ones from 62-67. Anything 68 or later in a 327 stroke is a cast, large journal.
So F's and not Q's or some of the Q's?

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Re: repower 283 w 350

Post by mike backstrom » Tue Oct 15, 2013 7:48 pm

I checked the trans, no dipstick to be found

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Re: repower 283 w 350

Post by kjhoffman » Wed Oct 16, 2013 9:50 am

I have a 350 truck engine in my 1941 34 ft Deluxe Enclosed Cruiser with a 283 conversion. This allows use of original gauges and controls. I used a 350Q oil pan but did have to do some redrilling and taping on the pan, heads and crankshaft for oil to the manual 2XE transmission. Crankcase ventilation was done using 350 valve covers. If you use a 350 with 283 pan you will have grind the pan to clear the large journal throw's of a 350. A 62 to 67 small journal 327 will bolt together with no pan ginding. It is advisable to use a windage tray if run at more than 4,000 RPM. The 62 to 67 also has the same crankase ventilation as the 283 if you want it to look original.

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Re: repower 283 w 350

Post by kjhoffman » Wed Oct 16, 2013 9:55 am

The early oil pan's 283 or 350Q will not bolt to the 90's 350 block.

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quitchabitchin
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Re: repower 283 w 350

Post by quitchabitchin » Sun Oct 20, 2013 11:09 am

Peter M Jardine wrote:
quitchabitchin wrote:Not all 327 cranks were forged, just the early, small journal ones from 62-67. Anything 68 or later in a 327 stroke is a cast, large journal.
So F's and not Q's or some of the Q's?

I would assume this to be correct but you may find some early Q's that could be small journal, forged cranks because CC could have had inventory left when they started the Q series. You would have to look at the casting number on the block to see if it was a small or large journal block. www.nastyz28.com has a great online resource for anything related to Small Block Chevy regarding blocks, manifolds, cams, cranks, etc. It is complete with casting numbers, timelines, models, HP, etc.
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Re: repower 283 w 350

Post by mike backstrom » Mon Oct 21, 2013 5:29 pm

has anyone actually done the crankshaft drilling to get oil to the trans? from what i have read that seems to be the gray area, depth and hole size?

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Re: repower 283 w 350

Post by jim g » Tue Oct 22, 2013 5:30 pm

I've done it 15 to 20 times. Its easy but it can be scary. 1/8" drill bit. Drill back to the main journal stay 90 degrees to the crank and drill from the oil hole in the main journal to the hole you just drilled. Clean crank out well. The scary part is if you break the bit your well {you know}.

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Re: repower 283 w 350

Post by Russ Arrand » Wed Oct 23, 2013 5:28 pm

I have a 283/350 flywheel forward in my boat Blue-BY-U that most of you have seen or heard about. I started with a 1974 350 truck engine std bore 2 bolt. I had it bored 20. Had the oil pan relieved for rod clearance, had the crank drilled for oil to the manual trans (you have to do that). We drilled and tapped the CC sloped aluminum intake for water to come out of the heads-there are boss's for that. I put a set of Dart heads on it am able to run 87 oct. I put some Glen-L aluminum exhuast manifolds on it to save some weight and maybe breath better. I run a magnetic Mallory dist with a mechanical tach drive. I have a Holley 650 marine four barrel. I run a 13x15 3 blade cup prop. I put on a Leese-Nievile one wire alternator.

If have GPS'd this boat at 50 MPH with just me in it with not much gas. CD's did the engine and thinks about 260-275 HP.

This is a great conversion for our old boats. Other than some modifications to the engine stringers for the fuel pump and water pump it is bolt in. A lot easier than a new Crusader. I like the feel of a manual tranmisson. Hope this helps.

Most of the conversion info was from Gordon Millars articles in Classic Boating in the early 2000's.
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Re: repower 283 w 350

Post by mike backstrom » Wed Oct 30, 2013 1:25 pm

Russ, what issue of classic boating? maybe i can find an issue.

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Re: repower 283 w 350

Post by cc-woodboats » Sat Nov 02, 2013 7:04 pm

Te other thing you will have to do is make a new bolt for the nose if the crank. the 283 is fine thread and the 350 is course.
the bolt is drilledthru the center with with a #31 drill from the end of the threads towards the head, stop about half way thru the head of the bolt.then from the hex end drill a #55 hole till it breacs thru to the other hole. then drill thru one of the flats on the hex with a #53 bit
The crank is drilled with a #1 drill .228 and the main journel is drilled the same size about 90degrees from the feed hole to the rods.
I use a grade 8 bolt. be sure and deburr the hole on the main journel.

I had a 350 crate engine in a 61 ski boat with a change of cam,carb and intake turning a 13x14 prop to about 6,000 rpm. the paragon lived with no problems.
The only recurring problem was bearings! should have installed an oil cooler on the engine. the later Chris Craft 350s all had coolers.

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Re: repower 283 w 350

Post by Russ Arrand » Sun Nov 10, 2013 5:30 pm

The article is in Classic Boating in the Sept-Oct 1996 issue # 73. This is what I have done in BLU-BY-U. You have to some mod's but they are not hard. Instead of tapping the front of the heads I tapped the CC intake manifold where the water comes out of the block. I can send pic's if you want.

I am going to this again this winter for a customer that wants modern power and a manual trans in a Gar Wood.

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Re: repower 283 w 350

Post by BULLGR » Tue Dec 06, 2022 8:14 am

Hi there - hijacking a conversation you were having and you mentioned Classic Boating Magazine #73 - Where can I get a copy of this article on drilling Cam in 350 conversion

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Re: repower 283 w 350

Post by BULLGR » Tue Dec 06, 2022 8:43 am

I found a copy of that article in my old paperwork .... seems like he might have read it too! Cheers

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