350 auto and 350Q parts interchangeable?

I have a 1973 33' Chris Craft with 2 350Q's my starboard engine sounds if a rod bearing has come loose are the parts for the 350 interchangeable for the 350Q and will my haynes tech book give me the clearances and torques I need?

Jack

Ayuh,... Generally speakin', yes, internal motor parts are the same as pickup truck motors of the same vintage...

Key words; "Same Vintage"!

Questions:
How much of this OEM engine are you wanting/needing to change?
Will this be a complete over-all?
Will you be replacing cylinder heads?
Will you be replacing pistons?
Will you be replacing the camshaft?


The Do's and Don'ts are relative in some of these areas, IMO.

I don't have it apart yet I'll be pulling it out of the water 4 nov so I can start pulling the motor and doing other cleaning and restoration to the boat. As soon as I heard the tapping noise I shut it down and only restarted it to verifiy where the tapping was. I have the Marine Power manual so I can get part numbers but from what I've read the part numbers might not be any good. I was wanting to replace all the bearing and rings on both motors and I will get the crankshaft looked at to make sure it's stll ok. Hopefully I won't have to go any further than that.

Thanks for any help Jack..

Jack, in my humble opinion, if you tear these down for this, you'll be re-ringing them, in addition to the other work.
If you re-ring them, you'll want to look closely at the bores and pistons.
My guess is, that you'll be boring first over as to clean things up.
If you bore first over, it will require new first over pistons.
If you purchase pistons (of which you'll have no choice but to do), you may as well replace with a much better piston selection for Marine use.
Of which leads me to this:
(copy/pasted from another ME.com thread)

*****************
Bill, my hat is off to you!
You're among the few who understand the benefits of a Q/E chamber for any Marine engine using a cylinder head that incorporates a "wedge"..... I.E., the SBC!

It's often a hard sell to those who do not understand it, or who are not willing to educate themselves on it.

And why GM and many rebuilders continue using the Full Dished piston......, is beyond me!

Size the piston dished volume to compliment the volume in the cylinder head chamber, and there ya go!
With the correct piston p/n, this creates no change to C/R and no other mods are necessary!
For a few bean$ more, it can be done easily and correctly, and we reduce Detonation potential!


George, as to what we're talking about, you'd have to do a search re; Quench Effect or Squish Effect, and related this to Marine!
It's all about what's occuring underneath the wedge, and the potential for Detonation in our Marine gassers.
The Full Dish piston does a lousy job at this!

See this image, and imagine the dished portion coming up underneath this wedge area.
The outer ring landing comes to within correct "deck" or "Quench" dimension, but dished area cannot!
The dish is OK in the open chamber...... it's coming up under the wedge area that creates the issue.

(in all fairness, I'd have to say that the full dished piston does not necessarily create an issue, as ignition TA is held back considerably to accommodate it's lack of quench ability and to help against detonation potential............ but it sure as HELL doesn't "HELP" this engine any! )

BTW, for the Marine build, the quench or squish dimension can be tightened up some..... Dennis Moore suggests as tight as .038" due to the lower RPM compared to the hp auto SBC.



IMO, a good choice for the Vortec chamber may look more like this:

The D dished piston works well with the standard Non-Vortec wedge:

You may find some useful info in this thread also.

Jack, if these 1973 engines have been raw water cooled, and in Salt Water, you may want to begin fresh with a pair of automotive cores.
Once salt water corrosion has begun, it's pretty darn hard to arrest it.
You'll be a few dollars only away from two good cores and four correct cylinder head castings.

BTW, the Q/E piston/combustion chamber is not necessarily a high performance or high horse power mod..... it is a mod that makes a much more suitable chamber for SBC Marine Cruiser use.
The gain is performance, but performance that greatly reduces Detonation potential.
Detonation is one of the Marine Gasser's worst enemies.

No need to build back to Chris Craft 350Q specs...... you can better, and with no risk or short-falls!

If interested, ask your local library to bring in a copy of Dennis Moore's Small Block Chevy Marine Performance book for you.

Thanks for the info Rick. I have it scheduled to pull out of the water next week and I'll start tearing the motor down. Both motors are freshwater cooled and I run them in salt I live on the Chesapeake Bay. I bought the boat in May and been slowly fixing and restoring it. I am looking for good reliable engines and when I get it apart I'll let you know what I found and what I'll do from there. I will look into getting the small- block book and thanks again for the help !
Jack

Jack, you are welcome. I certainly don't want to step on your toes if this is not what you want to hear.
Your engines/your call!

Just an FYI on the engine build:
You'll receive an array of "Nah Sayer" comments regarding the quench or squish effect when you speak with some machine shop owners. These will from the ones who just simply think within the box, and who run with the pack!
So be prepared, and arm yourself with some of the great information provided by DennisMoore, and many others (if you were to research this further).
If you think that this build has merit to it, and if you were want to go this route, don't let anyone tell you differently, and don't let them tell you that the cost is prohibitive.... it is not!
Also best to use a machine shop whos owner has first hand experience and ownership of a cruiser type boat. He will better understand Marine load Detonation potential.


Many of these articles on Detonation have been written by auto enthusiasts, and are not limited to the SBC wedge style cylinder head...., but the principles used to combat this apply even more so for our SBC Marine engines.
It's all about Detonation potential and controlling it best we can.

Again.... this is not to be confused with a high performance mod, in as much as it has to do with Detonation control.

Dennis Moore's info is not web site hosted, so you'll need his book.


This is a great article by Jeff Smith on the Squish or Quench Effect and how to achieve it.

Here's one By Larry Carley

Here is an article by stealthfti, not necessarily pertaining to the SBC wedge head, but he nicely explains squish waves.

Here's one by Bob Hewitt, who does not touch on the Q/E or Squish Zone, but does touch on Detonation and the difference between Detonation and Pre-Ignition.

John Erb writes this article Again, mostly auto related, but nicely applies to our SBC marine engines.




BTW, the SBC full dished piston was a result of the 70's emission control for autos and trucks. Prior to that, the F/T was the common choice.
GM stayed with the Full Dished piston due to their Bean Counters, and combustion chambers becoming smaller/runner size increasing over the years, etc.

The cost to do this better suited build, should be minimal if you use the right suppliers.
No other major changes are required.

Both the SBC Chevy and Chrysler wedge head boys have been doing this for years.


Have fun with it, and good luck!

.

Hi Rick!
I have the boat out now. I work weekends so I can start tuesday pulling it apart, I'll keep you updated, and thanks again for the help and info...
Jack

Jack, you are welcome. I'll try to keep abreast of your progress here.

Hi Rick!
Quick update. I have to work by myself , my boys it seams when I need them "Have to work ", I pulled the galley out and the couch on the port side so I could access both sides of the motors. Right now the right motor is just sitting on the mounts, I'll have to get a spreader bar for my hoist to lift the motor out. Thanks again for the help.

Hi Rick.
I finally got the motor out. Getting ready to start tearing it down. I'll keep you updated on my progress

Jack

I'll be checking in!

Speaking of the quench effect, here's a guy who recently had a 383 built but the shop used f/t pistons in a 383 build with 76cc chambers.
He now has one damaged piston..... cause yet to be determined.
http://www.baylinerownersclub.org/forum/showthread.php?67052-383-problems

Hi Rick! I finally got my motor out of yhe boat and to the house. I pulled the heads and found #2 & 3 pistons missing the top part. I could see part of the top ring. I'll pull the oil pan later today or tomorrow and see what is happening there. The pistons have Z 16 38 stamped on them and just a look and the cylinder walls look good with no scratches or gouges I'll keep you up dated thanks again Jack.

Jack, how about some pictures of the pistons.
I come up with an image for the Z 16 38 as being this.... but I don't know if this is correct.
If it is...... this is bad choice for a marine build.





Pictures would help.

.

I'll get some pictures for you , I kinda figured when I had two with the same failure not good !! I'll have it apart by tommorow after noon don't have to work tommorow

Sorry Rick I miss typed the numbers Z 16 28 is stamped on them I also have pictures

Jack, that is interesting to see those....... those are single valve relief flat top pistons, of which are ideal for a 5.7L when the 76cc chambers are used.


Also, the damage resembles damage from detonation.... no question about it.

Your next task is to get the cylinder head casting numbers.

Could be that you have the 64cc chamber heads.... of which would make the C/R too high for our type of cruiser use.

.

Rick I found these numbers 23
GM 3970010 cast into the block

Rick I also found GM40 3998993 on both cyl heads

I found a few sources of mixed bag info.
Some were made in Mexico and apparently some in the US.
The Mexico castings are apparently known for cracking according to some people.
Since these are not scalloped at the area of the lower bolts, some say these are the heavy castings.
(see my image below)


Here's some info:

thin, crack prone, big chambers 76-80ish

The 993 casting is a heavy casted head that came on the following:
3998993....72-73...307/350......75cc chambers
3998993....current..350.........Goodwrench crate motors,"Hecho en Mexico", 75cc chambers
They aren`t that great for performance, being they have a large chamber and a not so good intake port. These are the basic smog heads.

The answer is yes you can get 300 rwhp out of these ! HOPEFULLY your machinist
has more time than you do money! The heads will need 2.02 ,1.6 valves , screwin
studs and guideplates ,bigger spring pockets,downcut guides ,it would be smart
to open up the pushrod holes, and THEN THE 30HRS OF PORT AND BOWL WORK!!
Those heads were used with the target crate engines, and are one
of the better (heavy weight) heads chevy made in
the 75-76 cc range.

350 small block heads with 3998993 casting number.
From MorTec.com:
3998993....72-73...307/350......75cc chambers

What comes up consistantly is the 75cc and 76cc chambers.
Perhaps the 1cc difference in chamber volume, is between US and Mexican castings..... I don't know.
76cc chambers should have worked beautifully with your F/T pistons, so something else must have caused the detonation... perhaps too much ignition advance for the fuel's octane rating.


See attached image at the page bottom.
Within the red circles are what people call the scalloped areas.
The scalloped areas suggest the light castings that are more prone to cracking.
The light castings should not be used for Marine.



This is the 3998993 and is minus the scalloped areas, so this would indicate heavy castings.
Not a high performer for the auto guys... but may be OK for mild marine build.
Nice thing is.... in a 5.7L (3.480" stroke) w/ f/t pistons, the c/r is just about right..
And with a compressed head gasket thickness that renders a total .038" -.040" squish band..... you get a Quench Effect!
Dang near perfect for a Marine Cruiser build.

Rick thanks for the info I'm at work now so when I get home I'll get pictures of the heads for you. I found a decal that said to use 91 octane the marina I got my fuel only had 87 maybe that caused the problem

Rick here are some pictures of the heads

Well, the problem appears to have been from detonation which is entirely different from Pre-Ignition.... although excessive pre-ignition may lead to detonation..... tuff to say after the fact.
Detonation causes:
Poor combustion chamber design.
Excessive cylinder heat.
Excessive ignition lead.... aka advance.
Lean F/A ratio with too much advance.
Lean F/A ratio leading to excessive cylinder temperatures.

Too much load for lower RPM operation with one or more of the above.
Good reason to stay out of the 2k to 3k rpm range when loads are heavy. We're likely pushing water at this RPM, and we're likely not fully up on step yet!

Like said.... the 76cc chamber size is good when used with the flat top pistons in a 5.7L build...... particulary the single valve relief pistons.
Build a quench dimension into this, and you'll have a good combination.

But you definitely want to do your forensic work, and learn what caused the problem in the first place.

.

Thanks Rick again !!! I talked to a friend of mine who races alot and he has a machine shop where the guy is good and does quality work at reasonable prices. So I'll get everything together and go see him, I'll keep you updated Thanks again !!!
Jack .

You are very welcome, Jack.

That's excellent. Perhaps let him see posts #5 and #7.

I'm not doubting his automotive High Performance experience at all... Nope... no way! But often the Auto enthusiasts aren't fully up to speed for a Marine
cruiser SBC... not small boat SBC's, I'm talking Marine Cruiser SBC engines.

Take the Quench dimension for example. We want to squeeze this down to approx .038", whereas the HP Auto guys want in upwards of .050" + or so.
They also love longer rods and shorter piston skirts in some applications.
We have C/R limitations that do not necessarily align with HP Auto.

Bla bla bla and so on.

Just say'n.... that's all!

I will show him these posts and my friend I talked to said the guy would work it how we want it to go, I'll be careful to let him know what I want before I let him start. Thanks again Rick !!