Mercruiser 888 (302) Cylinder Head swap?

[ratdude747]

One thing I eventually need to do on my Mercruiser 888 is swap or rework the heads so I no longer need to run lead substitute.

I may have found a deal on some heads that likely have hardened seats... they're Ford D5AE-CA 351 heads that came off an OMC 302 (supposedly includes ARP 351-302 conversion bolts). D5 indicating 1975, which is after the 1974 Ford start of using hardened valve seats.

What I don't know (and can't find) is whether or not these will run right (or rather, what the specs of the under-drilled 351 heads Mercruiser used). For most 351 purposeless they're considered junk (small valves, large chambers), but considering it had already been on a marine 302, maybe they're good for my use?

The heads are very clean and the price is very low ($50), but it's a long drive to get them... probably $250-300 total cost after gas. Is this worth it? Or am I better off to put this off for another off-season and have the original heads re-seated then?

Edit: they're wanting these gone so this is more of an "are these close enough" question. Still a lot of gas to fetch but I've drove longer for less!

 

[Lou C]

I would think a safer plan would be to have yours redone by an automotive machine shop if they are in good enough shape for it to make sense.

 

[ratdude747]

I would think a safer plan would be to have yours redone by an automotive machine shop if they are in good enough shape for it to make sense.

They're perfectly fine other than requiring lead substitute every 3rd fill-up due to having soft valve seats (added cost plus an inconvenience to have to find and buy). I have a lead on a machine shop too (same guy that did the machine work on my 1984 F150's 300 back in 2020)... The issue is that when I do such, it'll likely be pricey and I'll have to have the engine apart the entire time. As opposed to having heads ready-to-install that can just be swapped in one job.

 

[Bondo]

Ayuh,.... What's the vintage of what you have now,..??

 

[ratdude747]

Ayuh,.... What's the vintage of what you have now,..??

1976 Mercruiser 888... Covered in leaded fuel warning stickers and the like. Previous owners ran 100% leaded or (later) unleaded with lead substitute.

Engine is completely stock other than having an Edelbrock performer 289 intake and Holley marine 4160 carb. Swap was done partially by the previous owner (I swapped carbs and cleaned up the install a bit).

 

[Candy Gramformongo]

Unless you just really want to do it for entertainment, hard to justify the effort just to avoid doing the lead substitute thing, which does not sound like much of a burden if you're a typical weekend boater. For sure, driving halfway across the country for some parts that might not work seems a stretch.

 

[ratdude747]

Unless you just really want to do it for entertainment, hard to justify the effort just to avoid doing the lead substitute thing, which does not sound like much of a burden if you're a typical weekend boater. For sure, driving halfway across the country for some parts that might not work seems a stretch.

As long as it is available for local purchase. For now it seems like auto parts stores still sell motor medic brand... But if that drops and lead substitute becomes an online-only purchase, then it becomes a pain.

Btw, the heads aren't that far away... 5 hours (Kalamazoo, MI). I used to drive up that way for work (Holland, MI), so not a completely foreign drive. Still a lot of gas.

 

[Bondo]

Unless you just really want to do it for entertainment, hard to justify the effort just to avoid doing the lead substitute thing, which does not sound like much of a burden if you're a typical weekend boater. For sure, driving halfway across the country for some parts that might not work seems a stretch.

Ayuh,.... As much as most boats get run in a year, it'll be a long, Long time before there's an issue from running lead free gas,......

 

[ratdude747]

Ayuh,.... As much as most boats get run in a year, it'll be a long, Long time before there's an issue from running lead free gas,......

I've also heard that boating is hard on engines and it'd be more likely to fail than a weekend cruiser car. Last thing I want is a leaky exhaust valve burning things down on the water.

 

[Scott06]

Ayuh,.... As much as most boats get run in a year, it'll be a long, Long time before there's an issue from running lead free gas,......

this is exactly what is being recommended to me for my 65 Pontiac engine rebuild. Well known Pontiac engine builder told me that the hardened seats are not necessary. Also can run into issues when pressing them in and hitting water jackets as these older heads were not cast to have inserts. This is on a stroker engine built for some performance.

To the OP- would agree if it worries you just keep putting lead substitute in vs taking a working engine apart. Hapco makes a lead substitute that is sold on Amazon I think its like $65 a gallon last I looked. I use to boost octane seems to work well and a gallon lasts a very long time

 

[ratdude747]

this is exactly what is being recommended to me for my 65 Pontiac engine rebuild. Well known Pontiac engine builder told me that the hardened seats are not necessary. Also can run into issues when pressing them in and hitting water jackets as these older heads were not cast to have inserts. This is on a stroker engine built for some performance.

To the OP- would agree if it worries you just keep putting lead substitute in vs taking a working engine apart. Hapco makes a lead substitute that is sold on Amazon I think its like $65 a gallon last I looked. I use to boost octane seems to work well and a gallon lasts a very long time

Fair enough... If it ain't broke, don't fix it. And if it misfires due to an exhaust leak, then re-evaluate and then look into finding heads that already have hard seats if there is any question about the machinability of the existing heads. Supposedly after 1976 302 and 351 heads converged on one casting from Ford that only differed in head bolt size, which makes later model 302 heads a possible option...

Wasn't super keen on the 1 gallon Hapco... seems like a pain to meter out correctly.

 

[Lou C]

There is a cyl head rebuilding outfit local to me called Machine World NY. I got a pair of GM 4.3 V6 heads from them when I needed to replace the heads on my old 4.3. Worked out well for me. Might consider calling them &see what they advise….

 

[Lou C]

About Machine World NY

machineworldny.com

 

[ratdude747]

There is a cyl head rebuilding outfit local to me called Machine World NY. I got a pair of GM 4.3 V6 heads from them when I needed to replace the heads on my old 4.3. Worked out well for me. Might consider calling them &see what they advise….

Shot them a message. Probably not going to buy anything but an extra opinion never hurts.