Can a CC 1971 350Q be rebuilt as a 383?

Hello, I have a 1971 35' Lyman Express Cruiser which came with a par of Chris Craft 350Q engines rated at 325 horsepower. I am restoring the boat and I pulled then engines. While I have them out I figure I will rebuild them. I would like to get some more power out of the engines since I think 235 is pretty low for the boat. Crusader currently offers a carburated 350 rated at 315 horsepower so I figure using a few tweeks I can at least achieve that. I also considered rebuilding it as a 383 stroker. However, this boat being a cruiser I am more interested in fuel economy and range rather than acceleration and top speed so I am not sure which route would better suit the boat. The boat weighs about 13000 LBS and should have a top speed of about 35 kts according to the factory literature. The current engine is the 235 HP 350Q turining a 19X19 three blade prop. Any suggestions or comments on the rebuild/repower would be greatly appreciated.

Regards,
Mike

G'day Mike,

Firstly a longer stroke will give you more low-down torque, but you don't get the benefit of Horsepower till you get to higher revs.

So, as most boat motors don't usually run down low, you mightn't gain that much benefit by a simple increasing of the stroke, because a 383 Stroker Motor won't like spinning as fast as a standard 350, so you might find that your WOT might suffer.

But, as I have always said, there is no substitute for Cubic Inches, or was that someone else that said that?

Bruce.

I'd have to suggest that you not be foiled into thinking that the new 5.7L Marine engines offer a usable 315 HP.
Look at the RPM at which that rating is taken!
You'll see that most are rated at/near 5,200 rpm, or so!
Who in their right mind is going to operate their cruiser at even near 5,200 RPM to take advantage of this horse power?

If you are going to build a 383 for true marine cruiser use, I can't express highly enough on the value in using a Q/E piston, and getting as far away from the full dished pistons as you can!

The increased initial cost is NOT a deal breaker, and the advantages are great..... especially with the 383!
There are as many Q/E pistons available for this, as there are for the 5.7L.
You'll see these as a; "D" dished, Low Compression Quench piston, and/or a Reverse Dome piston. Any of which, when ordered correctly, will give you the correct C/R for your particular cylinder head combustion chamber volume.

Steer clear of the longer rods and short skirt pistons!


As you know, there are some connecting rod clearance issues that have to be addressed. This can be done by placing the 400 crank in the block (after it's re-sized) and prior to the block being machined and cleaned.
Your call!


One other comment if I may..... if these have been raw water cooled engines, I'd forgo using them. You are only a few boat dollars away from a pair of automotive cores that have spent their entire lives with e/g coolant.

Have fun!

.

If the engine box will handle it, you'll be much better off putting in a pair of big blocks. Likely to have better economy, too, unless you plan on cruising over 3200 rpm all the time.

Mark, this thread went as cold as a cucumber...... did one of us say something wrong?

Don't think so Rick.

First time poster so hard to say.....

Mark and Rick,Thanks for the replies, I had completely forgotten that I had posted on this forum. I have been doing a lot of structural wood work on the boat for the last year so the engines have pretty much just been taking up room in the shop. After reading your replies I have a few more questions. First, what are Q/E pistons? Also, yes these are FWC engines but have always been in fresh water with no saltwater use. Are there any trouble spots I should check on the block that are mor prone to corrosion issues? This particular engine is a flywheel forward setup that I am told was done to make it more low profile, so I am not sure if a new big block is an option. I have gotten several books on engine building that had sections dedicated to the 383 stroker, but all have been geared towards automotive engines. If anyone can recommend a resource that would be more marine oriented I would be glad to see it. Also, is a 383 the right way to go, or should I just rebuild it as stock? I know that I will probably need to re-prop the boat with any engine change which is fine since one of the props that came with the boat was chewed up pretty badly anyway.Regards,Mike

Mike, I'm not a big fan of driving from the fwd crankshaft end on these engines.
Remember..... not many drove from the front of the crankshaft.... and when they began doing this, the engines were 283s and 327s... not 6.1s/6.2s.
The Engineers no doubt calculated these loads based on the lower horse power and torque of these early engines.
The 377/383 would make an excellent engine, but again..... this front crank drive would have me concerned.

Point being...... you'd best check to see if there would be any issues with front crank power take-off when using a 377/383!
You sure don't want any issues arising due to this!

As for Q/E..... Q/E = Quench Effect, also known as Squish Effect, and pretty much pertains to (and is limited to) engines that incorporate a "wedge" within the combustion chamber.

It could type out several pages to explain this, but in nut-shelling it..... read this ME.com thread where I just barely touch on it.

There are many many articles out there on the Q/E for the SBC, 235 series Fords, and the Chrysler wedge head engines.
Some are more explanatory than others, some relate to Marine... some automotive!
The principle is basically the same..... however, the quench dimension can be a bit tighter for the Marine version.... of which is all the better.
IMO, it's of particular importance when building the 377/383 for Marine use.

I have NEVER built a SBC without using the q/e build..... and I never will!
I began doing this in the mid 60s (not that it makes a hoot).

Just say NO to these!

Rick,

Thanks for the information, If I do decide to go with a 383 I will probably use a forged crank since I am driving off the snout end I would feel better having the increased strength of forged over cast. I will look into the pistons, I imagine I will first have to figure out the volume of the combustion chamber in my current heads before I choose a piston/rod combination in order to get the right compression ratio. Also, can anyone who has built a marine 383 reccommend a good cam for the application? I have read that I dont want too much, if any intake/exhaust overlap to prevent possible water reversion from the wet exhaust system.

Regards,
Mike