Hello Jet Boat Fans,

I am new to the forum.  I'm hoping to get some help with my problem child.  This boat has been my never ending project.  I applied mostly new gel coat (except the deck flake), new wiring, underwater led lights, floor, stringers, reconditioned all aluminum and polished, and started on the interior. 

Before I can fix the interior I need to get my mechanicals sorted.  The motor is the original 1976 Olds 455-4 Berkeley Pack-a-Jet.  I've done a cosmetic restoration on the engine, installed a new Edelbrock Performer intake, Pertronics marine HEI disti, and polished the sand cast Berkeley logs.

My problems with this engine are many.  I'll start with intake manifold sealing issues first.  I am using Mondello gaskets, heat riser block off plates, Mondello valley tray, and Street Demon 750 carb (converted to marine).  My problem is getting the front and back of the block to seal with the manifold.  Using these gaskets I am seeing about a 1/4" gap between the top of the front/back of the block and the bottom of the intake.  I thought I had a really thick bead of Ultra Black RTV there.  At idle it was fine.  When I cruised and did a couple 40-50 mph bursts it leaked lots of oil all over the front and back of the motor.  I was having this same problem, although not as bad, with the orig intake manifold too.  I am not using gaskets at the front/back of the block.

Any tips on a leak free install would be greatly appreciated. 

What type of silicone? I have always had good luck with the “Right Stuff” by permatex. Also I will put some dimples in the block and Intake with a center punch so the silicone has something to grip to and make sure the surface is clean with acetone or brake parts cleaner. Let it set up for 24hours before starting engine, never had an issue with leaking at end rails.


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Hello Jet Boat Fans,

I am new to the forum.  I'm hoping to get some help with my problem child.  This boat has been my never ending project.  I applied mostly new gel coat (except the deck flake), new wiring, underwater led lights, floor, stringers, reconditioned all aluminum and polished, and started on the interior. 

Before I can fix the interior I need to get my mechanicals sorted.  The motor is the original 1976 Olds 455-4 Berkeley Pack-a-Jet.  I've done a cosmetic restoration on the engine, installed a new Edelbrock Performer intake, Pertronics marine HEI disti, and polished the sand cast Berkeley logs.

My problems with this engine are many.  I'll start with intake manifold sealing issues first.  I am using Mondello gaskets, heat riser block off plates, Mondello valley tray, and Street Demon 750 carb (converted to marine).  My problem is getting the front and back of the block to seal with the manifold.  Using these gaskets I am seeing about a 1/4" gap between the top of the front/back of the block and the bottom of the intake.  I thought I had a really thick bead of Ultra Black RTV there.  At idle it was fine.  When I cruised and did a couple 40-50 mph bursts it leaked lots of oil all over the front and back of the motor.  I was having this same problem, although not as bad, with the orig intake manifold too.  I am not using gaskets at the front/back of the block.

Any tips on a leak free install would be greatly appreciated.

Welcome to the site and beautiful float...i also have a 455 olds and had the same problem...had and have the same gasket set-up....i tacked the intake gaskets to the heads...set the intake manifold on i have a rpm air gap....measured the gap from the block to the manifold.....i multiply 1.5 the gap let it sit for about a hour and to tack up...then sat the intake manifold on the block/ heads and finger tightened then manifold bolts...then after 24 hours/ next day i torqued them to 25 lbs and havent had a problem since....hope this helps

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Forgot to add the step at the beginning to dimple the block and intake across front and back.

Be careful with dimpling. Cast iron can crack.


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Very true you can also just get a little emery cloth and rough it up a little as well

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Entertain taking a files edge and scoring it instead.


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Never thought of that one...thats way better than the emery cloth

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Thanks for the additional inputs.  Engine is old and has never been rebuilt.  Compression is very good so I am going to be conservative.  No dimpling.  I will rough up block edges and bottom if intake.  If my gap is more than a quarter inch I will use some old cork gaskets I have from the old Turkey tray set with the Right Stuff 1.5 times remaining gap.  I think roughing up the bottom of the intake front/back edges will help.  I'm stripping the paint on the intake and heads now.  Hope to have repainted Saturday and do my install on Friday.  Public ramps here are closed on the weekends so I hope to test next week.  I'll post me second headache soon (leaky log seal to exhaust ports).  Hope you all can help there too.

I tried the cork gasket and silicone before didnt work ended up pushing the gaskets out you should be fine with the silicone....like anger said seal it and run it

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Your boat how much $$$ do you want to spend?


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If the compression is good just make sure the valves/ rockers are adjusted seal it up and run it. Spend your money on a second engine from scratch.


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Thanks for the inputs.  I'll try to seal it up, adjust the valves and enjoy.  It's just so easy to think about all the things you want to do when it's partially broken down. 

What type of fittings on the hoses?


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I don’t use anything on my AN’s


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