Reman 305 Engine with 2 different heads, and open cooling ports?

Walleye4Days said:

So, we ordered a new marine reman engine from a major rebuild of GM engines... But, I noticed that the 305 we received has 2 different heads on it. One side is a 416 head (which I know tons about and fully understand) but the starboard head is a 450 casting head, which I know NOTHING about...
Any re-builder who would use two different cylinder head castings on the same SBC would qualify to be in this year's junk-yard shop 12 month calendar.

Note the difference in combustion chamber volume and in the valve diameters.
The valves can be made to match, but to enlarge a 58cc chamber to be 76cc is not doable.
Also, the 18cc difference in the combustion chamber volume would require different pistons on one side.
For a Marine build, in order to achieve the correct S C/R, 76cc chambers would typically be paired with Flat Top pistons, and the 58cc chambers would typically be paired with dished pistons.

Here is what I found.

12506450: 1987 through 1994 350ci, 76cc chamber, 1.94/1.50-inch valves.
14014416: 1980 through 1986 305ci, 58cc chambers, 1.84/1.50-inch valves.

(Source = https://www.enginelabs.com/engine-tech/cylinder-heads/small-block-cylinder-head-id/)



Are having two different castings going to make a difference,
If my info is correct...... Yes!

or is there anything I should be worried about?
I would return it and either ask for your money back, or if comfortable after learning about this, have them correct it.
While at it, find out what cylinder head/piston profile combination they are using for a Marine application.

Also, if you do have them install the correct castings, make sure that they use the 8 stop cam follower adjustment procedure, and NOT the 2 or 3 stop!
I also noticed that on my original AQ225D I stripped down, the 2 furthest cooling ports are sealed with lead,
In all of my years, I've never seen nor heard of anyone having done that.

and on the new reman engine they're open like they would be on an automotive setup...
Is there a preferable way to seal these, or do I just use a gasket that blocks them off and not worry about sealing them off with poured lead/aluminum like the old heads on the now defunct VP 305/AQ225D..?
The rear of the intake manifold does not allow for any coolant cross-over.
Just use good quality intake manifold gaskets.

If you use the RTV silicone sealant at the front and rear (in lieu of a front/rear gasket), give it a few hours to begin setting up before you do a final tightening of the bolts.

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Walleye4Days said:

The head casting I'm seeing is #378450 on starboard, and the atypical 416 casting on the port head.

The pistons I see on both sides are flat on top with a slight raised profile around the edge of them. Not sure if this is considered full fished or flat top, as I'm not too familiar with the piston profiles (they look identical to the pistons in my current VP engine that I pulled though).
You have just described a GM style Full Dished piston.
That piston may work with the 58cc chamber head, but it will NOT work well with the 76cc chamber head.
From what I'm reading here, this shop DOES NOT know what they are doing!

I called in to get an explanation on the heads, and the answer I got was this: with the heads on this particular engine, being an H.O. engine, the starboard head from the core engine wasn't up to par with what they wanted to machine, so they pulled a head off of another 305 that had the opposite head not up to par. Then, ported and milled the head to match the existing 416 head (as they claim the only difference is how much is hogged out in a 416 head vs the 450, and that all else is identical aftprevious to machining, but then that ALL is made identical via after they machining, match, and balance them out internally to each other on the flow bench (it's a "Blueprint Engine" btw. Not sure if that matters in respect to the heads).BS.... you cannot port an intake or exhaust runner, nor mill a head in order to change the combustion chamber volume from 58cc to 76cc or visa-versa.
Besides, no one mills only one cylinder head for the same V-8 engine!

As for the blocked coolant passages, I definitely mistakenly explained it wrong. The passages on the head are fine, it's the from passages on the intake manifold that are sealed/not open. It looks like two cooling ports (or where they'd normally be) are just sealed up with lead or just weren't machined out or something. Is this because of the different kind of thermostat housing or 'water in vs water out' setup on a marine engine vs automotive and the likes?

You would need to go back quite a few years to find a SBC intake manifold that had a rear coolant cross-over.

I'll see if I can shrink a picture to get it on here to better explain. For some reason, this forum doesn't like the pictures from my phone and doesn't allow them to post (maybe file size or conflicting coding or etc?). But, I'll try.
Pictures would be great!

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Walleye4Days said:

Oooookay... So, just got off the phone with them again (this is a large reman company well known in the marine industry, so I'm refraining from putting their name out there until we know for sure they screwed the pooch so to speak, haha. (Don't want to bash anyone unless I'm for certain of course).
Understood.
However, consider that you may save someone else from having the same issue with this company if you were to mention them by name.
It would also give everyone a chance to see how well or NOT well this company resolves your problem.
Problems can and will arise......... it's how well they are resolved that counts the most!

Anyways, this is what came of the conversation and discovery of what all they said went into the build and their explanation of the head inquiry:

- The number I listed as the starboard head was incorrect. The head number on the port side is a 416 head. The head on the starboard side was a 376450. They said it's 60cc and they ported the bowls out to match the flow of the 416, because the 450 head weren't reamed out as much from GM for smog purposes. The difference between a 416 and 376450 head is that the 416 heads got an extra valve remaining by a bit that hogged out more of the excess around the intake tunnel around the valve stem on the intakes. And the valves seats were re-ground to accept the larger valves like the 416 head, and new brass guides put in on both heads.

They claim when they were referring to porting and milling, they're referring to port-job they did on the 450 head in order for it to flow at the same numbers as the 416 head, and milled the decks down a to flat specs (on both heads) Nothing on the intake manifold side of the heads was touched as far as porting goes, but they did shave the intake manifold seats on the head, in order for the manifold to still match up perfectly at the same geometry because of decking the heads down lower on the block side.
That would appear to be quite a bit of extra work when you consider that a major and reputable re-builder would typically have a stock pile of cylinder heads to chose from. Something smells rather rotten to me!

They said they'll happily take the engine back and send another one with number specific heads matching if that's what my complaint is, but that I'd have to pay the return freight since there's nothing wrong with the engine and "that it is completely normal for reman engines to have same style/year/flow heads with different casting numbers, so long as they flow equally as good on the bench after all machining and before final install"...

Suggestion:
Contact several other major engine rebuilders and run this by them.
See how many of them would agree or disagree with the cylinder head combination that you ended up with.
See if they would also mis-match casting numbers, and/or go to the extra trouble of re-working the castings like your supplier did.


After looking around the internet, I've noticed others have had remans sent to them with different casted heads as well, including a couple I found that received one straight from Mercruiser like that they claim... So, I'm not really sure what to think of all this!? Lol. It seems a little odd too me, but I also really am not wanting to eat the freight.

But, I digress. It's a 60cc head (originally from factory) on starboard side - all completely redone - and a 59cc head (originally from factory) on the port side... Does this sound like it's going to be problematic, or something I honestly won't even notice as I only fish in Lake Erie and never take my engine above 3500rpm..?
With those combustion chamber volumes, and using the bore/stroke values for a 5.0L SBC, you will see an approximate 8.85:1 Static C/R on the port side, and an approximate 8.76:1 Static C/R on the starboard side.
To top that off, you will have a 5.0L SBC engine that was built with GM style Full Dished pistons with the intent of using it in a Marine application.

This is all a little overwhelming to understand (the head numbers, valve numbers, how it all works and affects one another, etc). So, I really thank you guys for taking the time to try and help guide me, it means a lot.

Would it be ok to take my matching 416 heads on my current engine and just swap them over to the new reman?
Unless they have been modified, the 416s will have the smaller intake valves.
Also, you would likely void any warranty.


Or does that completely defeat the purpose of having the reman to begin with? I just recently went through and put in new valves, new valve seals, and re-lapped and seated the new valves of course. So, I know the existing heads I have don't leak, but I'm not sure if that's all I need to be concerned about or watching for. I'd hate to switch em over if I'm just overreacting or maybe nitpicking about something I'm not really well versed enough in to truly understand fully.
With a correctly built Marine version SBC, all of the details are very important. In fact, the details are what make for longevity.

Sorry for the dictionary, just trying to figure this all out.
Understood!

I do have a question..... why did you go with a 5.0L when a 5.7L is typically less expensive and will produce more torque?

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