Mercruiser Tempest

[GeneD]

Hey, ever hear of one?
Well...I picked one up today. $100!
The guy at the machine shop told me properly set up, it's good for 500 HP!
What do you guys think? Is 500 reliable HP attainable?
He told me I will have to change out the pistons to flat tops. He also said, and remember I'm reporting the news, not making it, that the Keith Black pistons (hypereutectic) are just fancy castings, and not worth the money!
One not so good thing about this motor is that it is bored .030 over, making it 407 CID. I'm pretty sure that is the limit on a 400 casting.

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GeneD
007
Melbourne, Florida

[PaulO]

Gene,
The Tempest was only available for a few years from Mercrusher and was a 350 C.I.D. motor. As far as I have heard, nothing too fancy; Higher compression, high rise manifold, I thought that they were based on 2 bolt main blocks. Anyway, originally rated at 300 flywheel HP.

Basically, you could modify that motor the same as any SBC. If yours has a 400 crank in it, then you have something that has already been modified and you might have a head start on an economical stroker.

Let us know what is in it.
PaulO

[Murphy]

GeneD,

What a buy! I've got the Tempest 300 and those of us who do love'm.

Here are the specs out of Merc. Service Manual #9:

CID: 350 (5.7) Production Performance
Heads: Aluminum high rise
Block: Cast Iron (4 Bolt Main Bearing Caps on #2,3,4)
Rods: Forged Steel
Pistons: Forged Aluminum
Crank: Forged Steel
HP: 300
Bore/Stroke 4.00 in./3.48 in.
Comp. Ratio: 9:1
Comp. Pressure: 150 PSI
Idle rpm: 750-800
Max RPM @ wot: 4800-5200
Oil PSI: 30-60
Firing Order: 1-8-4-3-6-5-7-2
Plug Type: AC-MR43T, Champion RV8C, Autolite 144, NGK-Br6FS
Plug Gap: .032
Timing at Idle: 8 BTDC

If you decide to work it over please let me know. Mine is ready for an overhaul this winter and I could really use your advice on how to go about it.

[GeneD]

Whoops!
Me thinkist, I do not have a Tempest.
This is what I was told.
It IS a 400 CID motor, that much is certain, I know a 400 when I see it. When my bud told me it was a Tempest, I didn't argue or question him.
I think I am in trouble.
If the Tempest was a 350, then where in the world am I going to get marine head gaskets for a 400?
Maybe I shouldn't have gotten rid of that 350 4 bolt?
Me thinkist, I screwed up!
Oh, and it's got 2 bolt mains with nodular crank. Really deep dish piston tops.
Heads are nothing spectacular. "D" chambers with the 1.98 intakes. More than likely I'll go with bathtubs hopefully with 2.02's with a stock type camshaft. My roller won't work I don't think.

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GeneD
007
Melbourne, Florida

[This message has been edited by GeneD (edited 08-11-2000).]

[GEOO]

Gene, You should be able to get a reliable 500hp out of a 400ci. GEOO

[GeneD]

Forrest,
Make a post on this subject.
Also,
I know where there are two more of these things.
Both are bare blocks, and they want $100 each.

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GeneD
007
Melbourne, Florida

[GeneD]

Ha!
See connections pay off!
I have located the hard to find 4 hole Chevy motor for the truck.
Donzi Dave Pitt (GearHead99) found me one in Orlando for a bargain basement price and I can't wait!

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GeneD
007
Melbourne, Florida