Small Block Chev Heads

I have a 1981 Formula F18 boat with a 5.0, 228 hp, ccw engine. I use the boat in fresh water only and would like to put a set of heads that I have reconditioned, but they are car heads and they are cast iron. Has anyone done this. This is my first sterndrive and I did notice it is a ccw engine. Thanks for any advice you have on this.

If the heads are for a 305 cubic inch motor such as the one in the boat,

Yes they will work fine. No difference from a stock or standard auto/truck heads to marine heads mechanically and the ones on your boat are cast iron.

Marine heads may have brass freeze plugs in them vs steel in automotive... easy to change if needed.

Just make sure the combustion chambers are the same or very close or your compression ratio may change and you may experience pining.......

The heads do have steel freeze plugs and the ones on the boat are brass. I will change to brass. The heads I want to use are 350 chev or 5.7. The chamber size may be large and the water jacket openings have been enlarger to fit the head gaskets to alow for more flow. I will need to open up the water jacket openings on the block so they will all be the same and alow for more flow thru out the engine.

A 305 (aka 5.0L) is a GM SBC.
A 302 (also a 5.0L) is a Ford 335 series engine, such as the Windsor.


Your thread title says Small Block Chevy Heads, so I'll assume that you have a SBC engine.
There are no typical press-fit casting core plugs in the SBC cylinder heads.

SBC cylinder heads are easily identifiable by the exhaust ports being siamese at the center.
Valves will be: Exh/Int... Int/Exh... Exh/Int... Int/Exh.


The above is a heavy casting. Light castings usually have the full scallops at the low side.




If you have casting core plugs in these heads, they are likely Ford heads, similar to these.
(you can see one core plug in this image)





The exhaust ports are evenly seperated in the Ford cylinder heads.
Valves will be: Exh/Int.... Exh/Int....Exh/Int....Exh/Int running down the Port side.
From front to rear, this will oposite for Stbd side.



NOTE: There are several combustion chamber volumes for the SBC cylinder heads, as per the different castings.

I agree with Kghost....... Do Not replace with un-like chamber volumes, or you'll change the C/R.
You'll want to find your existing casting numbers, and search those numbers.
If you use a good casting number data chart, the chamber volume should be listed.


FYI:
Engine rotation direction is always viewed as though from the flywheel end, not from the front end.

CCW rotation is an industry standard LH rotation, same as car/truck as shown here.



CW is Reverse RH rotation.











.

Sooner5151 said:

The heads do have steel freeze plugs and the ones on the boat are brass. I will change to brass. The heads I want to use are 350 chev or 5.7. The chamber size may be large and the water jacket openings have been enlarger to fit the head gaskets to alow for more flow. I will need to open up the water jacket openings on the block so they will all be the same and alow for more flow thru out the engine.

Click to expand...

Ayuh,.... Generally speakin', 350 heads on a 305 result in the valves bein' shrouded, 'n flowin' worse...
'n the combustion chambers are usually bigger, causin' a loss in the compression ratio...
And,....
NO,... Don't open up the block, nor the heads water passages...
Most are closed up abit by the gaskets anyways....
They're restricted for a Reason,... Don't change it....

The following casting numbers are apparently interchangeable between the 5.0L and 5.7L engines. Not all listed show the chamber volume, and most are small valve heads.
12558062 , 10239906 68cc Vortec, 14014416, 14020516, 14102191, 14102193, 462614

Source

The heads have no freeze plugs and they are sbc heads. The one I have are 350 heads designed for 350 to 400 hp engines. I build race engines just for the sport of it. When this 305 dies I will replace it with a 350 300hp just to stay close to the rated hp for this out drive. I have a 350 block 30 over on the bore and it is a bear block. I will need to start from the groud up with it. My boat engine is a CCW engine and that is stamped on the front of the valve cover along with a lot of nomanclature about the engine. This my first stern drive and I am learning as I go. I pulled the water jacketed exhaust manifolds off and found a lot of rust in the exhaust manifolds and will be cleaning on them. The engine ran hot on my 1st. time out and I am looking for the source of the problem. I did learn that when your are 19 to 30 years of age there is a big difference lifting up these cast iron parts than when your are in your sixtys. The parts seam to weigh more or my imagiation is just realy bad. Thanks for everyones help. All advice is very welcome!!!

The engine ran hot on my 1st. time out

Click to expand...

Check/change the impeller. I use a laser infrared temp gun to check the temps. around the engine. Check the thermostat temp. w/it amd replace it if not holding. A water cooled engine probably uses a 140 F. T'stat.

I did some thermography with the space program, but have not tried it on reading hot spots on my engine. I dont know if I can get my hands on the gun and camera but I will try that. Thanks.

Sooner, a few FYI's for you regarding the Marine SBC build.

Don't confuse yourself with the CCW -vs- CW .
In other words.... don't confuse "Counter"-Clock-Wise with "Counter"-Rotation.

As said, a Standard Marine engine is typically CCW or LH rotation, (when viewed from the flywheel end) just as what you have.
Your decal showing CCW rotation may be a result of this engine having been a take-out from a twin engine application (they perhaps labeled both engines).
Most people will assume that a single Marine engine will be a "Standard" CCW or LH rotation, until we get into twin engines.
And even then, not all twin engine applications use one Counter-Rotating (i.e., CW or RH rotation) engine.

Rest assured that you have a very standard CCW LH Rotation engine..... same rotation as Car/Truck engine.


As for cooling. There is no need to modify the SBC heads or block.
Keep the OEM sea water pump and sea water path, T-Stat housing, Exhaust manifold/riser "Transfer Ports", etc, up to snuff.
These engines do not over-heat unless/until there is an issue with something within the this system.
These systems require periodic maintenance, and more so than the Automotive cousin.


All SBC cylinder heads began as automotive heads. What separates the Auto from Marine, is often the castings.
There are some "light" castings that should be avoided for Marine use.
Do a search for one of the SBC Cylinder Head casting number web sites. Not all list complete data, but it's a place to start.
The Mortec site is down, but somewhere you can find archived data.


Then we have combustion chamber volume.
The piston profile selection determines which size chamber should be used as to avoid HIGH or LOW C/R's.


Then we have a "quench" that should ultimately be discussed, but perhaps not in this thread.


.

Sooner5151 said:

The heads have no freeze plugs and they are sbc heads. The one I have are 350 heads designed for 350 to 400 hp engines. I build race engines just for the sport of it. When this 305 dies I will replace it with a 350 300hp just to stay close to the rated hp for this out drive. I have a 350 block 30 over on the bore and it is a bear block. I will need to start from the groud up with it. My boat engine is a CCW engine and that is stamped on the front of the valve cover along with a lot of nomanclature about the engine. This my first stern drive and I am learning as I go. I pulled the water jacketed exhaust manifolds off and found a lot of rust in the exhaust manifolds and will be cleaning on them. The engine ran hot on my 1st. time out and I am looking for the source of the problem. I did learn that when your are 19 to 30 years of age there is a big difference lifting up these cast iron parts than when your are in your sixtys. The parts seam to weigh more or my imagiation is just realy bad. Thanks for everyones help. All advice is very welcome!!!

Click to expand...

Ayuh,.... You keep mentionin' it's a CCW motor,....
We Know that, it's a Standard Chevy 305, dressed as a Mercruiser....

The 1st thing to do, in Any overheat situation is to change the raw water Impeller, which in yer case is in the lower unit of the drive...

I have a large learning curve for these marine engines. I think probably the best bet is to rebuild the existing heads. I am going to take the boat to a mechanic,s shop and have them pull the engine for me so I can check the exhaust becouse the boat will fill with water even when not running. I did pull the stern drive off and am in the process of rebuilding the water pump. I checked the rubber boots for the drive unit area and they look new.

At this point, all we know is that you have a 1981 Formula F18 boat with a 5.0, 228 hp, ccw engine.
We really need more information from you.

Is this an I/B or I/O?
If I/O, which drive?
If I/B, which style transmission.

Sooner5151 said:

becouse the boat will fill with water even when not running.
I checked the rubber boots for the drive unit area and they look new.

Click to expand...

Assuming that this is an I/O, if the drive shaft bellows are OK, and if your garboard drain plug and fitting are OK, this could be anything from a failing shift cable bellows, to an exhaust Y-pipe-to-transom-unit seal failure.

Be willing to pay for complete diagnostics that truly identify the problem, and ask for a firm "quote", not an estimate.



.

10-4 I plan on a sollid quote, and the stern drive is pre Bravo, I think I was told it is an MR stern drive. I looked at the bellows for the cables and the exhaust and the rubber is soft not cristilized and I found no holes in any of the bellows so that is why I have turned to getting someone to pull the engine and check the flange to transom and the y pipe and exhaust. Thanks for the info and advice.

I didn't see anyone welcome you aboard...

Soooo welcome aboard !

It appears you have the knowledge but no garage and tools to " pull " the engine.

That's not a slap at you,

Where are you going to take this engine down ?

You going to farm out the build ?

Be gentle now i'm a old dog but i have been known to bite.

thanks for the welcome, and yes I have built several small block chev motors. I am going to let a marine boat company pull the engine and check out the exhaust y fittings due to the boat taking on water when I put it in the water. I pulled the sterndrive off and the bellows for the shift and exhaust look good with no holes, so I need them to look at the other parts. I like the old boat an it has a new interior, and I am putting a new instrument cluster in the boat so I can see them. Grandkids and wife just like to ride and fishing is my pass time. 3 more years and it may be my full time.