Re: How fast does your 4.3L V6 push your boat?
Lookin good!!! (would far prefer to be looking at that than my office right now...)
The (absence of) balance shaft is worth another 10 - 20 horsepower depending on who you listen to, so if starting from scratch on building a 4.3 suitable for every day marine use, you're better off to start with a non-balance shaft block / bottom end that is late enough to have the marine roller cam in it (not a bad cam, but clearly became the horsepower limiting component in my v-6 with touched up vortec heads, intake and carb set-up.
Unfortunately, if you already have the balance shaft block, there's not much of a market for performance parts and so there is very little in terms of cam offerings for that lower end. There are a couple of "mild" cams available for the non-balance shaft engine so tere are options of you want to go further thanthe 220 - 240 hp you can get with a little higher compression (shaved heads, thin gasket), well tuned 600 cfm carb, edelbrock performer intake, a few degrees more timing advance (mine ran best a couple degrees past the factory spec, picked up 100 rpms or so wot there), good flowing air cleaner, etc... The caveat to going with a bigger cam is that to get much of a performance gain, pretty soon you're into head work and springs, a performance exhaust, etc... The stock heads are limited to well below .500 lift (more like .460 to be safe from what I understand), AND you start to lose torque on the bottom end of the rpm range... pretty soon you're dealing with a dog out of the hole. When I go to that point, was going to cost as much to wring another 50 horse out of the 4.3 as it would to replace it with a mild 350. of course, like many others on here, I couldn't stop there....
ps. I think I've got specs for the factory cam(s) in my notes somewhere at the house from when we were playing with the 4.3. I'll see if I can dig them up tonight... Someone else on here may have it as well. I remember there being several people on here who had clearly done some major homework on 4.3 builds for marine apps.
The factory, marine, roller cam in the non-balance engine (don't remember if any different from the balance shaft version) is actualy a pretty decent cam for all around performance, and is more agressive than most people realize. but of course could be improved on - especially if the heads were touched up a bit and running a more open intake.
On exhaust, my impression was that there was little to be gained there - perhaps with custom tubular headers, but the cost / benefit would be redicluous... but I did not run aftermarket performance exhaust manifolds and factory set-up side by side and so can't verify that assumption.
cheers!
Lookin good!!! (would far prefer to be looking at that than my office right now...)
The (absence of) balance shaft is worth another 10 - 20 horsepower depending on who you listen to, so if starting from scratch on building a 4.3 suitable for every day marine use, you're better off to start with a non-balance shaft block / bottom end that is late enough to have the marine roller cam in it (not a bad cam, but clearly became the horsepower limiting component in my v-6 with touched up vortec heads, intake and carb set-up.
Unfortunately, if you already have the balance shaft block, there's not much of a market for performance parts and so there is very little in terms of cam offerings for that lower end. There are a couple of "mild" cams available for the non-balance shaft engine so tere are options of you want to go further thanthe 220 - 240 hp you can get with a little higher compression (shaved heads, thin gasket), well tuned 600 cfm carb, edelbrock performer intake, a few degrees more timing advance (mine ran best a couple degrees past the factory spec, picked up 100 rpms or so wot there), good flowing air cleaner, etc... The caveat to going with a bigger cam is that to get much of a performance gain, pretty soon you're into head work and springs, a performance exhaust, etc... The stock heads are limited to well below .500 lift (more like .460 to be safe from what I understand), AND you start to lose torque on the bottom end of the rpm range... pretty soon you're dealing with a dog out of the hole. When I go to that point, was going to cost as much to wring another 50 horse out of the 4.3 as it would to replace it with a mild 350. of course, like many others on here, I couldn't stop there....
ps. I think I've got specs for the factory cam(s) in my notes somewhere at the house from when we were playing with the 4.3. I'll see if I can dig them up tonight... Someone else on here may have it as well. I remember there being several people on here who had clearly done some major homework on 4.3 builds for marine apps.
The factory, marine, roller cam in the non-balance engine (don't remember if any different from the balance shaft version) is actualy a pretty decent cam for all around performance, and is more agressive than most people realize. but of course could be improved on - especially if the heads were touched up a bit and running a more open intake.
On exhaust, my impression was that there was little to be gained there - perhaps with custom tubular headers, but the cost / benefit would be redicluous... but I did not run aftermarket performance exhaust manifolds and factory set-up side by side and so can't verify that assumption.
cheers!
