Cam and valvetrain longevity....??? low duration high lift...
#651
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M/T - We did put the flame arrestor on mine to see if it made any difference- there wasn't any. I'm running CMI big tubes which might even be bigger than the dyno headers dumping into 5 in. tails dry to the very tip, so I figure there shouldn't be any loss there. I have the 305 heads. I went from 660 hp to 675 hp with the cam change. 675 hp to 705 hp from the intake/ carb change. I was planning on running all accessories and marine exhaust for the final dyno but lost interest and just wanted it finished.
You eventually made 700hp with the complete package. Intake, carb, exhaust, etc.
On another forum, theres a guy there from Long Island, who does some offshore builds. He said he has done some similar builds to your guys. 540ci, RHS 320 iron heads, no porting, dominator, 9.75:1, 730hp at 6200, 700ft lbs at 4500. Hyd roller comp cam grind. Bolt together build. No trickery. Thats in dyno form, no accessories. I asked for the cam specs on those builds. I will report back.
I remember my buddy years back, had a 9.5:1ish, 540, dart 320 heads, mild lift solid roller, dominator, brodix intake , made 720hp at 6200. He installed them in his boat, but could only turn the props he had to 5000ish. He got with bob m, and asked for some smaller cams, that would help make some more low end torque, to help pull those props. Ssm setup. They reduced duration quite a bit, and increased lift a little bit. Went back to dyno, engines made 690ish hp. I dont recall the torque change. Anyhow, the engines went back in the boat, and it gained a big fat zero. They did idle a little smoother. The boat was a 30ft twin vee race style boat, and accelerated awesome with both combos. I think if he had just went to smaller props from the start, he would have picked up acceleration, and top speed.
Anyhow, thats neither here nor there. What we really need, is a guy like articfriends, to do some marine exhaust testing for us on his dyno!
#652
Speaking of exhaust
At the Sprint Cup race this week-end, on Saturday I noticed alot (maybe all ?) of the Modifieds using 4-2-1 headers. Sunday for the Cup race we arrived late, blew thru the garage area, then pit stop row to see all the driver's getting up on the stage, and then going up to the suite it don'd on me...fuk ! I forgot to look at their exhaust. Oh well, will try to remember next year races.
So, talking with a few guys with the modifieds, they said the primaries are sized by the exhaust port, ie same size as port but if tubing not available that size they use size as close to exh port size as possible, then primary about 10 inches or so, stepped up to next diameter. They too, said the collector was really where they found the power. Of course, they all have merge collectors too.
At the Sprint Cup race this week-end, on Saturday I noticed alot (maybe all ?) of the Modifieds using 4-2-1 headers. Sunday for the Cup race we arrived late, blew thru the garage area, then pit stop row to see all the driver's getting up on the stage, and then going up to the suite it don'd on me...fuk ! I forgot to look at their exhaust. Oh well, will try to remember next year races.
So, talking with a few guys with the modifieds, they said the primaries are sized by the exhaust port, ie same size as port but if tubing not available that size they use size as close to exh port size as possible, then primary about 10 inches or so, stepped up to next diameter. They too, said the collector was really where they found the power. Of course, they all have merge collectors too.
#653
Charter Member#568
Charter Member
Yes. Would've been very difficult to run my exhaust and with me having real headers it probably wasn't worth it. As far as front accessories it's the same thing. The hassle of plumbing power steering and raw water to see how much hp it absorbed wasn't worth it as there is nothing I can do about it anyway
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#655
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Bobs Marine Kinetics cams seem like they should work , prove me wrong , swap some different cams exhaust , I cant handle Bobs dateline , call week after week , way of doing biz
#656
Platinum Member
Platinum Member
The interesting thing, would have been, to see what your build made for power with say, a set of Gil's, or the stainless marine standard manifolds. Irrelevent, since you have CMI big tubes.
You eventually made 700hp with the complete package. Intake, carb, exhaust, etc.
On another forum, theres a guy there from Long Island, who does some offshore builds. He said he has done some similar builds to your guys. 540ci, RHS 320 iron heads, no porting, dominator, 9.75:1, 730hp at 6200, 700ft lbs at 4500. Hyd roller comp cam grind. Bolt together build. No trickery. Thats in dyno form, no accessories. I asked for the cam specs on those builds. I will report back.
I remember my buddy years back, had a 9.5:1ish, 540, dart 320 heads, mild lift solid roller, dominator, brodix intake , made 720hp at 6200. He installed them in his boat, but could only turn the props he had to 5000ish. He got with bob m, and asked for some smaller cams, that would help make some more low end torque, to help pull those props. Ssm setup. They reduced duration quite a bit, and increased lift a little bit. Went back to dyno, engines made 690ish hp. I dont recall the torque change. Anyhow, the engines went back in the boat, and it gained a big fat zero. They did idle a little smoother. The boat was a 30ft twin vee race style boat, and accelerated awesome with both combos. I think if he had just went to smaller props from the start, he would have picked up acceleration, and top speed.
Anyhow, thats neither here nor there. What we really need, is a guy like articfriends, to do some marine exhaust testing for us on his dyno!
You eventually made 700hp with the complete package. Intake, carb, exhaust, etc.
On another forum, theres a guy there from Long Island, who does some offshore builds. He said he has done some similar builds to your guys. 540ci, RHS 320 iron heads, no porting, dominator, 9.75:1, 730hp at 6200, 700ft lbs at 4500. Hyd roller comp cam grind. Bolt together build. No trickery. Thats in dyno form, no accessories. I asked for the cam specs on those builds. I will report back.
I remember my buddy years back, had a 9.5:1ish, 540, dart 320 heads, mild lift solid roller, dominator, brodix intake , made 720hp at 6200. He installed them in his boat, but could only turn the props he had to 5000ish. He got with bob m, and asked for some smaller cams, that would help make some more low end torque, to help pull those props. Ssm setup. They reduced duration quite a bit, and increased lift a little bit. Went back to dyno, engines made 690ish hp. I dont recall the torque change. Anyhow, the engines went back in the boat, and it gained a big fat zero. They did idle a little smoother. The boat was a 30ft twin vee race style boat, and accelerated awesome with both combos. I think if he had just went to smaller props from the start, he would have picked up acceleration, and top speed.
Anyhow, thats neither here nor there. What we really need, is a guy like articfriends, to do some marine exhaust testing for us on his dyno!
#658
Platinum Member
Platinum Member
Im getting ready to start soon on my 540 NA project on dyno using efi, at one point maybe ill pull my dyno headers off and substitute on a set of manifolds and dump the water on the ground , my hp goal is 700 btw with sub 9-1 compression, not saying its going to make it but thats the goal
#659
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In the testing I've done over the years a good manifold like stainless marine, or imco gives up around 15 - 30hp on a build that makes 625-650hp with decent headers. I run 1 7/8 primary headers with full length 3" exhaust into magna flow mufflers on every engine during initial testing and break in, so I can monitor 10 O2 sensors and egt's. It's also easier to hear the motor during initial run up. This setup is very close to what a set of cmi e-tops makes for hp in the 600 - 650 range; the e-tops give up a bit of torque, but no hp. Once you get in the 700 - 800hp range, e-tops start to lose a bit, nothing major, but a set of big tubes or lightnings could be a benefit if you're chasing every last hp. One very important note is, cams with a bigger split on the exhaust show far less power difference between exhaust systems then the ones with the tighter split. This is why we run 8 to 10 degrees even on heads with good exhaust ports. Underperforming exhaust is a reality, and should also be part of the design criteria. The same way a crappy intake port needs more duration to carry the rpm. If you spec a cam based solely on flow numbers you could be giving up quite a bit of power. Not that it applies to this thread, but blower motors literally dont give a chit about exhaust in terms of hp percentage. It's amazing to see on the dyno
#660
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COOL Haxby nice to have you on board subscribed