Cracked Intake Manifold 351W - 1988 Supra Comp

[Petersen51]

Hey all, new to this forum, as I just purchased a 1988 Supra Comp. I have a cracked intake manifold, and was curious if anyone has any tips on finding a replacement? Should I only go through a marine site, or can I use Summit, Jegs or the like? Try to stick to OEM specs?

Also, there is a stainless bump out on the bottom of the manifold under the carb, does anyone know what that is.....and do I need to find a manifold that has that installed? Any advice and tips are appreciated, thanks!

Cracked 1.jpg
Cracked 2.jpg

[cadunkle]

You can use any 351w intake manifold. Nothing is really marine specific. Some manufacturers lined water jackets with brass or other metal, but it's not necessary or a significant consideration for marine use. For an otherwise stock 351w I'd probably go with an Edelbrock Performer, well suited for low RPM torque and good through 5000 RPM.

The stainless sheet metal pan under the intake is for the exhaust crossover. It warms the air/fuel charge in cold weather to atomize the fuel better and help prevent carb icing. Not really an issue or consideration for how you use a ski boat, but most lower RPM intake like the Edelbrock Performer have an exhaust crossover passage, though it'll appear different.

Your intake cracked from freeze damage though. I would be concerned about freeze damage to the block. With the block you can get lucky and freeze plugs may pop out. If you're run it and there are no external water leaks and no water in the oil, you may be fine though.

[michael hunter]

+1 looks like freeze damage to me ? Any water in the oil?

[Petersen51]

Thanks for the information! Yes I do have water in my oil, that is how I got to this point in the troubleshooting process. I am also pretty certain I have a crack in one of my exhaust manifolds, which I am replacing, however Skidim is on back order (1-2 weeks). Any other reputable sites out there for marine parts? I pressure tested the exhaust manifold with pressurized air in the water jackets and water in the exhaust manifold....it produced bubbles.

The plan is to replace the intake and exhaust manifolds and see if that cures the issue.

[Mischief IV]

You can try a few of these.
Marinepartssource.com
Nautiqueparts.com
Bakesonline.com

[Petersen51]

Thanks for those. Checking multiple outlets right now and everyone is on back order do to foundry issues at the factory. Apparently the manifolds were breaking in half and everyone had to send them back. Hopefully I find one before the season ends!

[Petersen51]

Found one through Basic Power Industries. bpi.ebasicpower.com

Pretty solid selection.

[angus2112]

i have a intake you can have just pay shipping as far as the exhaust drill the end of the cracks v the cracks and use jb weld did it pop any soft plugs
Weak spot on a sbf right side front lower block look for rust

[Petersen51]

Would you all consider this a conclusive test? I attached a hose (city water pressure) to the exhaust manifold, capped the riser port and turned the hose on. Water started pouring out of the exhaust ports. Curious what you guys think about this test. I have a video, but I don't think I can attach it.

Exhaust Manifold.jpg