Logo

New Heads for Old 350

I have a 23' 1971 Chris Craft. The boat originally was equipped with a 307QLV engine and VP 270 outdrive. A previous owner replaced the 307 with a 350 (casting 3970010) and kept the VP 270. When I acquired the boat the engine did not run.

During the rebuild, the machine shop reported one of the 3973487 heads is cracked and unrepairable. It appears replacement "487" heads are available. I know boats but not engines. Can anyone tell me if I should replace the "487" heads with similar or should I take this opportunity to upgrade to a "better" (as in more efficient) set of heads, without busting the bank. Thank you in advance for your assistance.
 
There are many different SBC cylinder heads available........, all of which can be interchanged.
The issue is with the combustion chamber volume and style that needs to work in harmony with the piston profile.

for examples:

If this SBC 5.7L is fitted with F/T pistons, you would stay with the 76cc combustion chambers.
This allows for the correct Static Compression Ratio for Marine use.

If the SBC 5.7L is fitted with the GM style full dished pistons, you would want to stay with the 64/65cc chambers.
And again, allowing for the correct S C/R for Marine use.

If the wrong chamber volume is used, the effective static compression ratio changes.
Too small for the piston profile, and your S C/R will be too great.
Too large for the piston profile, and your S C/R wiil be too little.

In other words, first determine which piston profile was used.
Then and only then, will you be able to chose a correct cylinder head for your SBC!


There are also what we call "light" castings and "heavy" castings.
Avoid using the light castings.


You can find SBC cylinder head casting number ID charts by doing a search.

Check several of these charts as to make sure that the info is the same from one chart to another, and is accurate.


NOTE: not all charts clearly show the combustion chamber volume!

Here is one list.
https://outintheshop.com/faq/casting/heads.html

Here is another list.
http://nastyz28.com/sbchevy/sbch.php

And another.
http://www.jimsperformance.com/headchart.html


You may also need to pay attention to the accessory bosses that some castings have, and/or do not have.


Note that the later Vortec cylinder heads DO NOT perform to the best of their potential with the GM Full Dished pistons!
In order to use these heads to the best of their potential, a LCQ or a Reverse Dome style piston would be a much better selection.


Also pay attention to the Int and Exh valve diameter.

.
 
Thank you very much for your reply. The pistons that are with the engine now are TRW L2304 domed pistons. Because the engine is not original to the boat and, given that I am taking the time (and $) to rebuild, I'm more interested in upgrading, if possible, from the current set up to a more efficient set up than in keeping it as is. However, if the current set up of the 010 block and 487 heads is a good combo, that works for me. Thank you again for your reply and I want to say I've learned most of what I know about marine engines from your site. Most of the info. online is about auto engines, so this site is a wealth of knowledge.

Steve
 
The TRW L2304 piston would be incorrect for a Marine SBC build!


29ce029e-b035-42e9-b043-87a65c828aac
 
Frankly I would not put thousands into this old lump. Rebuilding is never cheap or cost effective. I would go see what your local Volvo Penta or Mercruiser dealer can do for you for a complete power package. Usually the terms are very attractive and you get back out on the water sooner with a reliable system that has far more power, fuel injected and starts in half a turn of the starter. In addition, you make your old boat like new and it'll be far more valuable. If you rebuild the existing you will be "under water" so to speak and right where you started after spending all that out-of-pocket moolah. New heads and a camshaft aren't gonna do much of anything for you speed-wise.
Or take the money that you'll spend on the rebuild and put it towards something newer with the engine you really want.
But if you love your old Chris Craft, then it's time to repower for the next twenty years of the relationship.
However, if you are set on keeping what you have, then install the same old marine heads that it came with or as close to those as you can get. Really, there's not enough performance gain to justify anything else. These are best built with reliability in mind as they are always pushing the boat "uphill". High performance parts may get you another couple dozen ponies but that is only at the top end where the engine is working hardest...you might see an extra few knots of speed but that's about it. Sorry to burst the enthusiasm bubble.
 
Last edited:
I appreciate your comments. As for my enthusiasm, that was burst when I found out the engine was not the matching engine for the boat. Although I understand the original 307 would have been less than stellar, having it all original is what I intended to do when I purchased this boat. Now that I know this 350 was added later, I have no allegiance to this engine.

What I am trying to do now is salvage what I can from the existing 350 or, as you recommended, start with a fresh motor. I certainly have enough to do just refreshing the hull, electronics, fittings, etc. I don't want to expend time and money into an engine that is not worth the time or money.

I know that most boats are money pits. I am hoping at the end of this project to have a fun, reliable boat that my family and I can enjoy. It's starting to sound as though the 350 it has now may not serve that purpose. Thank you again for your suggestions.
 
Originality is only an issue if you're restoring a Hacker Craft triple cockpit or a famous rumrunner. Put in a power package that will make the boat enjoyable, reliable and marketable
 
quote_icon.png
Originally Posted by socalboatr

quote_icon.png
Originally Posted by Rick

The TRW L2304 piston would be incorrect for a Marine SBC build!




I am not surprised. I'm guessing there are quite a few "issues" with the existing engine.



I did a search and that piston comes up as a domed piston.
In other words, the TRW L2304 piston's dome is raised above piston deck, of which consumes combustion chamber volume, of which increases the Static Compression Ratio.






quote_icon.png
Originally Posted by socalboatr
I appreciate your comments. As for my enthusiasm, that was burst when I found out the engine was not the matching engine for the boat. Although I understand the original 307 would have been less than stellar, having it all original is what I intended to do when I purchased this boat. Now that I know this 350 was added later, I have no allegiance to this engine.
You will be better off with the 5.7L SBC.

What I am trying to do now is salvage what I can from the existing 350 or, as you recommended, start with a fresh engine.
I certainly have enough to do just refreshing the hull, electronics, fittings, etc. I don't want to expend time and money into an engine that is not worth the time or money.
Learn what you can regarding the proper way to build a SBC Marine engine.



I know that most boats are money pits. I am hoping at the end of this project to have a fun, reliable boat that my family and I can enjoy. It's starting to sound as though the 350 it has now may not serve that purpose.
My point was/is..... the 5.7L with domed pistons, and no matter what size combustion chamber you use, it is going to produce a static compression ratio that is too great for Marine Cruiser use.

Thank you again for your suggestions.




quote_icon.png
Originally Posted by socalboatr
In the event I don’t want to abandon the time I’ve spent so far on this boat, can you recommend a good f/t piston for this 010 block & 487 head combo?



Mortec claims that the 3973487 castings are a 71-72 LT-1 350 application, with 75cc chambers.


One forum suggests this:
they are not LT-1 heads as far as i know. they wouldn't have come off of an Impala if they were. i've had a set or 2 of them, actually being the best performing open chambered head i used on a small block. they just have 1.94/1.50 valves and 76cc chambers though. but they have hardened exhaust seats i believe. they are a fairly good all around head that really doesn't do anything real well, other than help keep compression low.

A Chevelle forum suggests this:
The 487 heads are of the large chamber versions. They are probably the best choice of the 71-later low compression heads from the early 70s. In the 1.94/1.5 version, they were the more or less standard 350-4bl version.





Keep in mind that these guys above are SBC car enthusiasts, and are not necessarily SBC marine enthusiasts.



.
 
I've reengined two different 1969 23 ft Chris Craft Lancers over the years, both of which had the 283FLV ( 185HP) RWC engine. Both times, I did the analysis and since I liked the hull, decided to install brand new factory "crate" engines with FWC cooling kits. The first reengine ( circa 1985) was with a Chrysler LM318. The second ( circa 2007) was with a Mercruiser 5.7MIE ( 260 HP w/TKS 2 bbl carb) and an aftermarket FWC kit. Both times the decision came down to...
1) Quality time on the water vs. $$$ and effort.
2) An enforceable warranty on the engine.

On the second (current!) boat, I replaced the original 250 drive with a 280 as the 280 drives are stronger and quieter. Note per my several posts on the subject, that I also on both conversions went with thru transom exhausts with mufflers as the exhaust passage on the 200 series drives is severely inadequate for 350 CID/5.7L class engines.
 
Last edited:
I've reengined two different 1969 23 ft Chris Craft Lancers over the years, both of which had the 283FLV ( 185HP) RWC engine. Both times, I did the analysis and since I liked the hull, decided to install brand new factory "crate" engines with FWC cooling kits. The first reengine ( circa 1985) was with a Chrysler LM318. The second ( circa 2007) was with a Mercruiser 5.7MIE ( 260 HP w/TKS 2 bbl carb) and an aftermarket FWC kit. Both times the decision came down to...
1) Quality time on the water vs. $$$ and effort.
2) An enforceable warranty on the engine.

On the second (current!) boat, I replaced the original 250 drive with a 280 as the 280 drives are stronger and quieter. Note per my several posts on the subject, that I also on both conversions went with thru transom exhausts with mufflers as the exhaust passage on the 200 series drives is severely inadequate for 350 CID/5.7L class engines.

Thank you for sharing your repower experiences. The boat I'm working on was modified to through hull exhaust by a previous owner, most likely when it was modified from 307 to 350. I was initially going to revert it back to an outdrive exhaust but that was before I tore it apart and confirmed it is a 350, not the original 307.

I'm set on keeping it a 350 and, based upon what I've heard, including your feedback, inclined to keep the through hull exhaust. Now I'm trying to decide whether to rebuild the 350 that it came with or do what you did, purchase a crate engine with a warranty. Can you tell me if you had to modify the transom to accommodate the Merc during your 2nd repower? Thank you again.
 
The reason I got the MIE (Mercruiser Inboard Engine) version of the engine is that the Lancer hull uses an extended "Hollman Moody Style" housing with the Volvo Outdrive. Most sterndrives use a configuration (non H/M) I/O housing flange at the transom which has the starter motor mounted to the housing, whereas "bob tailed" engines have the starter mounted to a bell housing (flywheel cover in marine world parlance) as part of the ENGINE. This H/M style housing allowed ChrisCaft to use Chriscraft marine branded engines ( same as inboard engine boats) which are "bobtail" configration.

If your boat has a early 200 series drive, i.e pre 280, it is likely that the engine is also a bobtail to H/M housing setup like mine. In other words, the Merc engine should bolt right in.

The quick check is.... is the "bolt circle" of the engine to transom mount circular, or an inverted "U" ??? If circular, its a H/M style.
 
Last edited:
Tit is likely that the engine is also a bobtail to H/M housing setup like mine. In other words, the Merc engine should bolt right in.

.

i.e..... a MERC inboard (MIE) engine should bolt right in...

Also.... pay attention when getting a replacement engine (if carb) as to the presence of a "wedge" under the carb.... Many "inboard" engines have one, most sterndrive ones do not. In my boat at least, the proper setup is a spacer, not a wedge.
 
Just to help clarify..... when a Holman Moody, Eaton, Donzi or other make Borg Warner -slash- Volvo Penta PDS adapter housing is used with an AQ series drive, it:

.... requires a Borg Warner flywheel cover.
.... moves the engine forward by 3 1/8".
.... adapts the Borg Warner F/C equipped engine and the PDS directly to the AQ series transom shield.

One draw-back would be that the AFT end of the PDS was available in the course spline only.




socalboatr said:
Can you tell me if you had to modify the transom to accommodate the Merc during your 2nd repower? Thank you again.

I may not be understanding you on that one..... but if you are considering going with a Merc A drive, I would suggest NOT.
Stick with the AQ series Volvo Penta.
It will be stronger, offer smooth cone clutch gear engagement and it will be easier to service and to work on.

Also, any of the AQ series drives (250 and on) lend themselves to the addition of the Duo Prop lower gear unit.
 
Just to help clarify..... when a Holman Moody, Eaton, Donzi or other make Borg Warner -slash- Volvo Penta PDS adapter housing is used with an AQ series drive, it:

.... requires a Borg Warner flywheel cover.
.... moves the engine forward by 3 1/8".
.... adapts the Borg Warner F/C equipped engine and the PDS directly to the AQ series transom shield.

One draw-back would be that the AFT end of the PDS was available in the course spline only.






I may not be understanding you on that one..... but if you are considering going with a Merc A drive, I would suggest NOT.
Stick with the AQ series Volvo Penta.
It will be stronger, offer smooth cone clutch gear engagement and it will be easier to service and to work on.

Also, any of the AQ series drives (250 and on) lend themselves to the addition of the Duo Prop lower gear unit.

Think he is referring to my MERC engine, not the drive.
 
I was referring to the Merc engine. I wasn't sure if it was compatible with a volvo outdrive. Having said that, I've decided to make the best of what I have now, rather than repower. I will save a new engine for another boat.

I'm starting with the 4.00 010 block and two good 487 heads. Due to some pitting on a few cylinders, I'm going to see if the machine shop can bore the cylinders .030. If so, then I will buy some new flat top pistons, and whatever else I need due to the larger piston size.
 
If the 487 castings have 75cc chambers (as thought to be), you should be ok.

FYI..... a .030” over-bore is only .015” off the walls.
You should not need to anything out of the ordinary to the cylinder heads.


.
 
If your boat has a early 200 series drive, i.e pre 280, it is likely that the engine is also a bobtail to H/M housing setup like mine. In other words, the Merc engine should bolt right in.

The quick check is.... is the "bolt circle" of the engine to transom mount circular, or an inverted "U" ??? If circular, its a H/M style.
To me, it appears the engine to transom mount pattern is circular. Here is a photo of the transom bolt pattern. I'm interested to know what crate engine I can use, if I decide to go that route. Thank you.
 

Attachments

  • transom.jpg
    transom.jpg
    170 KB · Views: 84
..............
To me, it appears the engine to transom mount pattern is circular. Here is a photo of the transom bolt pattern.

That would be your "transom shield" mounting/bolt pattern. The transom is the AFT most hull component that the "transom shield" mounts to.

I'm interested to know what crate engine I can use, if I decide to go that route.

The AQ series lends itself to an array of engines either by way of the Volvo Penta flywheel cover, or with Borg Warner components such as a Borg Warner pattern flywheel cover with the Borg Warner -slash- Volvo Penta PDS adapter housing.

The OEM GM V-8 flywheel cover provides a standard engine placement.
The Borg Warner F/C and Borg Warner -slash- Volvo Penta PDS adapter housing places the engine forward by 3-1/8".

AQ series flywheel cover types.jpg

With the right BW flywheel cover, this combo can be used for the Ford and Chrysler V-8 engines also.
 
Here is a photo of the existing connection between the sbc 350 engine and the VP 270 outdrive.

View attachment 22800


ChrisCraft was known to do the Flywheel Facing Forward installations. This means that the front of the crankshaft, crankshaft key way and key are being asked to perform the PTO (i.e., power take off).
The SBC crankshaft was never actually designed for front of crankshaft PTO.


I would suggest going with a conventional engine installation.
Since the engine has the deep oil pan on it, I would assume that the engine could be turned around, and you'd have enough space underneath it to do so.

Here's what I'd do if this was my boat:

I'd pick up a Borg Warner pattern flywheel cover for the Volvo Penta application (no I/B style rear starter motor mount).
It will be similar to this one but without the I/B style starter motor mount.


I would pick up a Borg Warner drive coupler and three of the correct "exposed shank" grade #8 bolts.
(six shown here... only three are needed)

I would pick up a Johnson F5B-9 seawater pump. You can find these on sale for around $160.
No side load from belt tension, tried and proven to be a superior seawater pump.


Pick up an AQ series AQ 260 style T-stat housing.
images



Show me the front of your PDS adapter housing.
If it offers the B/W splines, you will mate the PDS adapter housing to the Borg Warner pattern flywheel cover and B/W drive coupler.
When mated together, the components will resemble this order.

AQ series flywheel cover w extended PDS housing .jpg

Now the front of the engine will be facing forward with good access to the crankshaft style seawater pump, the engine circulating pump, T-stat housing, alternator system, drive belts, hose plumbing, etc.
This will allow the coolant hoses to be plumbed in a more conventional manor, simplifying your cooling system.
(much better than what ChrisCraft did back then)

AQ series flywheel cover w extended PDS housing 2 .jpg





But that if it were my boat!



Your call on that!


.
 
ChrisCraft was known to do the Flywheel Facing Forward installations. This means that the front of the crankshaft, crankshaft key way and key are being asked to perform the PTO (i.e., power take off).
The SBC crankshaft was never actually designed for front of crankshaft PTO.
.
I dropped off the block, heads, etc. at the machine shop to see about having the block bored. The owner of the machine shop was perplexed as to why the engine was backward.

I suppose I need to decide what direction, literally, to go next with this engine. Thank you for all that information. It may be time to tally up what a rebuild of this block will cost versus a crate engine.
 
The fly wheel facing forward engine’s block configuration is the same as the one that you want to over-haul.
Its the ChrisCraft oil pan and front housing that makes it appear to be different.

You would not be using those parts if you do as I suggested.


.
 
Last edited:
Back
Top