Holley 450 marine carb on 4.2 - JeepForum.com
 
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post #1 of 7 Old 08-12-2017, 10:00 AM Thread Starter
waynaferd
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Holley 450 marine carb on 4.2

Just come across one on Craigslist for a good deal and want it for my 258, albeit a bit too big...not terribly tho

I know marine carbs are more for keeping backfires and spilled gas from burning up boats, but any reason it wouldn't work on a land locked vehicle?

TIA!!


A 55 '5 and a 77 '7
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post #2 of 7 Old 08-12-2017, 10:28 AM
swatson454
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This statement gives me a little pause for use in a vehicle but I don't know exactly what it means:

"All Holley Marine Carburetors are designed to meet Coast Guard specifications. A marine carburetors fuel metering system is calibrated to compensate for unique engine loads found on boats. The J-style vent tubes direct fuel/fumes back into the carburetor for safe operation while on rough waters."


Shawn

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post #3 of 7 Old 08-12-2017, 09:08 PM
gunsanddaisys
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I've got some experience in the marine carb world, so let's give this a try!

I'm assuming the carb in question is a 4160 style holley (vacuum secondaries), correct? The quoted statement above is true, but only applies to the secondary metering plate. It's metered orifices are permanently set and are most likely tuned for constant engine load in marine application, though I will admit i'm not sure of how different it is. I don't really see why it wouldn't run on your engine due to the marine aspect. Marinized holleys differ only in: the vents being J tubes to redirect floods, bushingless primary throttle shafts with grooves to prevent fuel from seeping past, the altered metering block, and the lack of a fast idle cam.

The J tubes I actually think are kind of beneficial so long as you know how to clear a flood. The throttle shaft isn't really that big of a deal; there just may be a slightly larger vacuum leak there. If the secondary metering plate is any sort of trouble, it can be changed for a full metering block with a longer fuel crossover tube. Finally, the largest issue with a marinized carb is the lack of a fast idle. They were shipped with zero fast idle system aside from just a choke butterfly and electric choke coil. This was due to the throttle on a boat being non sprung. If you needed a faster idle, you just opened the throttle a bit in neutral. Of course this can be changed, but you just need to know the correct part numbers; it's a bit tricky to find.

Your largest issue i guarantee is going to be the rated cfm of that carb. It's pretty large for the 4.2. If you do go for it, i would almost suggest a restrictor plate to keep some low speed performance and throttle response.
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post #4 of 7 Old 08-12-2017, 09:14 PM
Rtracy2001
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Quote:
Originally Posted by swatson454 View Post
This statement gives me a little pause for use in a vehicle but I don't know exactly what it means:

"All Holley Marine Carburetors are designed to meet Coast Guard specifications. A marine carburetors fuel metering system is calibrated to compensate for unique engine loads found on boats. The J-style vent tubes direct fuel/fumes back into the carburetor for safe operation while on rough waters."


Shawn
The engine compartment in a boat is much more sealed than in an automobile. They are even equipped with fans to ventilate the compartment and remove fuel vapors before starting. The J-shaped vents should prevent fuel from sloshing on the trail, and direct any vapors into the engine to be burned. kind of a nice upgrade.

Special fuel metering on boats does seem to be slightly problematic. Boats are often run at or near full throttle, with periods of hard acceleration in-between, and are generally not held to the same emissions standards as automobiles. They are also not expected to last as long. (a marine engine with 1000 hours is an old timer and 100,000 miles takes nearly 2000 hours @ 60 mph the whole way.) Expect the carb to be metered richer than a comparable automotive carburetor and it would likely have a larger accelerator pump. Tuning it to an automobile engine would require re-jetting and adjusting the accelerator pump at a minimum.

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post #5 of 7 Old 08-13-2017, 10:15 AM
swatson454
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Based on those posts, I'd shy away and see if I could find a 390.


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post #6 of 7 Old 08-13-2017, 11:56 AM Thread Starter
waynaferd
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I figured with vacuum secondaries I could get away with 450 cfm easy enough

This carb is $200 and comes with a rebuild kit.....not much difference than an eBay carb after looking

Still haven't decided 100%but shying away from the marine carb ATM.....

And thanks for the details about marine vs street carbs....learned something new today lol

A 55 '5 and a 77 '7
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post #7 of 7 Old 08-13-2017, 12:16 PM
gunsanddaisys
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For $200 you'll be disappointed for sure. Keep your eyes out for something else.
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