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Old 08-10-2008, 02:00 PM
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350 SBC marine engine sluggish?

I recently put a 350 SBC into a 76 vette trying to bump my hp from about 150 to 270. But I am finding out that the marine engine I put into may have more power it is acting sluggish.
I know the engine is a 78 and was a part of a pair in a boat. Its sister blew up and the boat owner wanted to swap them both out.
My father-in-law has been a heaad mechanic at a marine/boat sales shop and he rebuilt the engine I have now and says there is nothing wrong with the internals of the engine.
So my question, is it possible that the cam in it is set up to be a more torque driven cam, and making it lazy on the street.
If so any suggestions as how to cure the problem and what cam to run with?

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Old 08-10-2008, 02:40 PM
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to help me some with a cam choice I can tell you what little the car has
Weiland Stealth intake
650 holley
Pink Rods
Forged crank

Other than that I think she is pretty mild
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Old 08-10-2008, 02:59 PM
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I doubt the cam is the problem.
Boats need to idle low and slow for docking and pull well around 4500, but marine cams do well in street driven cars and should give you snappy throttle response and good power to at least 5000, maybe more.

I suggest you look at your ignition advance curve and the vacuum can first, then look into carb problems.
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Old 08-10-2008, 03:01 PM
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I actually need to get a new distributor also, right now it has an HEI on it and I was thinking of switching to a MSD with adjustable vac curves...
But I was afraid that the problem was more internal. it doesn't seem to be a "quick rev" type engine and I think I was expecting more when gaining close to 100 hp and it seems to take long to build that power
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Old 08-10-2008, 03:03 PM
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Quote:
Originally Posted by daeble
I actually need to get a new distributor also, right now it has an HEI on it and I was thinking of switching to a MSD with adjustable vac curves...
MSD is good stuff, I really like it.
I would look into Performance Distributors DUI, Memphis, and give them your specs and get a pretuned distributor for your application.
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Old 08-10-2008, 03:04 PM
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I am afraid I am a new era mechanic. I am used to fuel injection and coil packs, the whole distributor and carb thing I have a lot to learn
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Old 08-10-2008, 03:07 PM
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Quote:
Originally Posted by daeble
I am afraid I am a new era mechanic. I am used to fuel injection and coil packs, the whole distributor and carb thing I have a lot to learn
Here, read these, especially the Perf Dist one by owner Steve Davis. They have been in business 34 years so they have it pretty well figured out now.

Computers do all this stuff automatically.

There are 2-3 current threads happening regarding distributor curving and vacuum advance cans, Ill try and get the links and edit here.

http://www.hotrodders.com/forum/dis...-1-a-59033.html

http://www.hotrodders.com/forum/tim...ion-142521.html

Here's a good write up by Steve Davis of Performance Distributors (DUI).
http://www.gofastnews.com/board/tec...simplified.html
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Old 08-10-2008, 03:09 PM
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Hey I appreciate the help a lot, I guess my only last question is what tells you that the cam in this car is not the cause of power or rev loss?

Thanks again
Dev
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Old 08-10-2008, 03:36 PM
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What is the base timing set at? is the vacuum advance connected to manifold vacuum source or a ported source? Have you checked to be sure the mechanical advance is functional and not stuck? Is the exhaust corked up? Answering these questions could lead to the cause of the issue.
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Old 08-10-2008, 03:42 PM
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Wow! the base timing is set at 8 deg. the vac advance is pulled from the intake but shares a vac line with the headlamps.. (not sure if that matters) and the exhaust is not corked because I just replaced the hooker headers and side pipes with glass pack mufflers inside 3 days ago..
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Old 08-10-2008, 03:44 PM
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and the mechanical adv actually is opposite and has some slop in it...I noticed that the pins were pressed and were showing their age..
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Old 08-10-2008, 04:12 PM
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Quote:
Originally Posted by daeble
Hey I appreciate the help a lot, I guess my only last question is what tells you that the cam in this car is not the cause of power or rev loss?

Thanks again
Dev
Marine cams are not that different. They just have lobe separation for smoother idles and spec'd for good midrange torque, and make good street cams.
They are nothin special really.
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Old 08-10-2008, 04:44 PM
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With the vacuum advance disconnected and plugged, set the base timing at 12 degrees before top dead center, lock the distributor down, then reconnect the vac advance and recheck the timing, it should be around 24 degrees, if not the vac advance is ruptured or it`s connected to a ported source, it should pull vacuum at idle. If it checks out okay, test drive.
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Old 08-10-2008, 07:40 PM
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ok, we ran through the vac, system and it all checked out good. It took me a bit longer b/c I didn't have a var. time light. But if the vac checks and the carb just had engine tuner soaked in it, I am running out of ideas. The only other thing that could be making this thing sluggish maybe the gear ratio? But I still would have expected a difference in feel with the upgrade in ponies..
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Old 02-20-2010, 01:40 PM
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350 SBC marine engine sluggish?

Did you change the cam?

Wally
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