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305 power rating

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floater1

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"As you may have read here I h

"As you may have read here I have a '78 OMC 305. The valve covers say 225 on them. Now its my understanding that means 225 horsepower rather 225 lb ft of torque. So if thats the case, how does this engine make those 225 horses? This engine came factory with a 4 barrel carb but even on there best day most carb'd 305s in automotive applications never made more than 175 hp. Did OMC specify from Chevrolet that they wanted say for example flat top pistons which would yield a higher compression ratio, therefore allowing for higher horsepower in some of there 305s? What 305 marine camshafts did OMC run that were different from automotive applications?"
 
"The pistons, heads and entire

"The pistons, heads and entire long block is the same 305 that was in a 1978 Pickup truck or van.
The main difference is the unrestricted exhaust of a boat, and the camshaft. The cam is a chevrolet 340284, which is marine specific and has a grind similar to an RV or mild street performance camshaft.

This is why in the 70's and 80's when I was a young lad, we learned quickly that swapping a cam and adding low restriction exhaust can make a family car a semi-muscle car for cheap.

this article is very informative about how the 305 can make plenty of power with bolt on parts and reduced exhaust restriction:
http://www.goingfaster.com/spo/325_horsepower_305_cid_chevrolet.html"
 
"" When I was a young lad.

"" When I was a young lad. " Those where the good old days.
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"
 
"Hy Stat, would these be the c

"Hy Stat, would these be the cam specs for the marine 340284 cam?

"Stock Marine Specs - Flat-based lifterGM Part No: 340284, Merc Part No 431-5943Duration @ .050: 200 intake, 212 exhaustValve lift in inches: .400 intake, .410 exhaustLobe centerline degrees: 108 ATDC, 112 BTDCLobe Separation Angle in Degrees: 110""
 
"Very interesting link on the

"Very interesting link on the 305 upgrades, Hy Stat. 305's have always been lethargic, but like any small block, they can make power!"
 
"smae with the old Chevy 307 o

"smae with the old Chevy 307 of the early 70's.... one of the first smog motors in cars, it could make good power in a boat..."
 
"I once built a Chevy 302 &#40

"I once built a Chevy 302 (came originally in 68-70 Camaros). Not sure how much power i was making but it took my steel body tubbed 70 Nova SS to 10 second quarter miles with a 2 foot wheel stand coming out of the hole. Shifted at almost 10k RPMs. You haven't heard a small block whine till you get it past 9000 RPMs. Of course, it didn't make any power until 4K. Those engines are capable to say the least."
 
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