Earlyest 351W
Cargo Master
Joined: May 2007
Posts: 2,071
Likes: 36
From: British Columbia
4V marine intake manifolds
Hi Arctic Y,
In a car or truck a four barrel carb will usually give better mileage than a two barrel IF the driver is conservative and is almost always only using the primaries. This is because the 4V's primary venturis are typically smaller than the venturis of a two barrel.
Then again, with Holleys and early Autolites this isn't so obvious...it certainly is with Rochesters however.
It could also be because under moderately heavy load, the secondaries are open a little but power enrichment is low, vs. in a two barrel the power enrichment would be on full.
As for the 351W 4V (not) being available in 1970, I stand corrected.
The marine 4V manifolds presumably were factory installed on marine engines, but I don't really know. I know there are ones with D1JE casting prefix and D5JE prefix. Except for casting numbers and being attached with only 12 bolts, both of these are identical as far as I can tell to the C9OE cast iron car intake.
In a car or truck a four barrel carb will usually give better mileage than a two barrel IF the driver is conservative and is almost always only using the primaries. This is because the 4V's primary venturis are typically smaller than the venturis of a two barrel.
Then again, with Holleys and early Autolites this isn't so obvious...it certainly is with Rochesters however.
It could also be because under moderately heavy load, the secondaries are open a little but power enrichment is low, vs. in a two barrel the power enrichment would be on full.
As for the 351W 4V (not) being available in 1970, I stand corrected.
The marine 4V manifolds presumably were factory installed on marine engines, but I don't really know. I know there are ones with D1JE casting prefix and D5JE prefix. Except for casting numbers and being attached with only 12 bolts, both of these are identical as far as I can tell to the C9OE cast iron car intake.
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Post Fiend
Joined: Sep 2006
Posts: 14,325
Likes: 14
From: Island Southeast Alaska
Merc and OMC may well cast there own as they do intermediate housings and heat exchangers. In most harbors here ya can find several 4V 351W's. This may well be a place to get 4V's for our trucks for little or nothing used. This is why I brought the subject up.
I agree on the better mileage with a 4V in a boat as well. When at cruse speed The engine uses less fuel than a 2v for the reasons mentioned above. Next question. I had to use 302 exhaust heat exchangers and am wondering if the port size on the 302 is smaller or not. Now would be a good time to port them if so before launching for the season. If necessary.
I agree on the better mileage with a 4V in a boat as well. When at cruse speed The engine uses less fuel than a 2v for the reasons mentioned above. Next question. I had to use 302 exhaust heat exchangers and am wondering if the port size on the 302 is smaller or not. Now would be a good time to port them if so before launching for the season. If necessary.
Hotshot
Joined: May 2004
Posts: 12,170
Likes: 5
From: The hills of No. Calif.
So I presume that at your typical cruise speed you're not running WOT?
Most of my boat experience is with smaller 4-cylinder I/O boats, where you typically run at WOT all day long, which, with the all the drag, winds up topping out around 3200 RPM. I would suppose that such is not the case with the 351 in there and you're running about 1/2 or 2/3 throttle at cruise?
Most of my boat experience is with smaller 4-cylinder I/O boats, where you typically run at WOT all day long, which, with the all the drag, winds up topping out around 3200 RPM. I would suppose that such is not the case with the 351 in there and you're running about 1/2 or 2/3 throttle at cruise?
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