Offshoreonly.com - Cam and valvetrain longevity....??? low duration high lift...

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I put small props on too, spun to 6000 and went same speeds... 72.3 mph best...

Quote:

Originally Posted by Gimme Fuel (Post 4482111)

I know with my Bob M. 548 combo. (10.2 CR, afr 335 cnc heads, 454-R dom intake with 2100 cft TB. Holley efi. speculated 730-760 hp @6300 by Bob, I never dynoed) it was very touchy with prop pitch. I thought I needed to be somewhere around 25-26p prop with my 253 checkmate...ran it first year, thought it was a dog and was disappointed but was happy to be boating. 73-75 mph struggling to get 5500 rpm. End of that first year found out machinist pooched hone job and bores were quite shiny after 20 hours. Redo .030 over, add a lil extra compression, great ring package...new machinist. Put back in boat, turned the same prop the same rpm......dissapointed. Lackluster acceleration. Even tried a 24p with little improvement.

Now, get a wild hair on my azz to throw a seemingly tiny 23p prop on the boat. Guess what. Instantly screams to 6000 rpm in a heartbeat and climbs past 6300 in short order. Boat passes 80 mph within a mile. Prop was far from ideal (nicks and zero cupping hydromotive qiv) and was just a test, full gear and full fuel tank. Wound up running that prop rest of season with big ole grin on my face. Boat broke 80 mph which takes 700 minimum in that hull plus I keep a ton of gear and supplies in boat at all times, I never run "light." Could scream past friend's similar boat with 600sc merc.

Moral of the story, engine was very sensitive to small change in prop loading and I was my worst enemy. That engine wanted RPM and made its power up there, I wasn't letting it get there with slightly too big props.

Quote:

Originally Posted by MILD THUNDER (Post 4482126)

Test with the professional products intake by paul phaff

Looks like the 53031 is just a polished version of the 53030? Can you find the height anywhere if that's it?

If you really wanna go fast I`d start looking for a Fountain otherwise enjoy what you have. Personally I don`t think a cam change is going to make any significant difference in speed, these heavy cigs aren`t meant to go fast anyway.

I dynoed lower than 2 years ago and my boat goes faster pulls more rpm all with with less boost. Same with Joe so retters dyno is on the low side. I`d stop obsessing on the dyno number.

If you wanna do it for longevity , then don`t think about it just do it, short duration high lift equals an agressive lobe..is that still in discussion???
You`ve seen the chewed up cams from Haxby and others.. no brainer throw something else in there and go boating

I'll agree. If your simply looking for a number, Retters dyno won't do you favors. But in saying that, it's just a number. Look into that 651 cam as mentioned. Many use it with good results. Good luck

I'm not looking for a number but if engines are out why not make them better? Let's face it if anyone on this thread says they can spend 30,000.+ and go slower and just leavening alone is lying.... Not one person would be happy, especially if potential for issues is there

while you switching cams,,might as well do a double swap,go w/ a duration around 258/260 on the intake and add 8-10 to the exhaust,leave lift at or just below .670+/-.should get you to 710-725hp.as for longevity,engines are still running after 6yrs.and thats a few of them.springs,,good springs are key w/ set up.
you have Ti. retainers,I like the added weight savings of them,,helps things out.
I feel for you,,but I never bought into that custom cam crap,,give me the tried and true crane marine series cams.proven to work and last..and not just 20yr old tech,,.as a few members have said.
oh and you can make that power on ls112.:)

What is rest of your build to see that HP?

Quote:

Originally Posted by sutphen 30 (Post 4482274)

What's the height of the intake you're using and are you using a spacer with it?

Having read thru this I feel for the op spending that much and not getting what was expected. With that said is everything right for this combo ? The compression ratio required for the crane 139651 is 10.5 to 12.5 from crane .......knowing that he doesn't have this cam what was comp. supposed to be ?

Is the cam installed advanced or straight up ? With 540 cubic inches it seems like 600 is ballpark for 9.5 to 1 to me but I'm not a engine guru.

Quote:

Originally Posted by Full Force (Post 4481962)

Pistons .010 in hole square decked
Not sure how to figure quench, head gasket is .039 compressed marine gel pro, non figured .030 cosmetics but I went over that way back and decided regular was fine.
540ci dart 9.5:1 flat tops
Cnc afr 325's
Cam 241/246 681/663 on 112 I have to find degree paperwork I can't remember off top of my head I think came in at 107.5? Don't hold me to that been a while lol
Scorpion 1.7
Trend .135 pushrods
Pro comp single plane intakes
Quick fuel 1050's
Gutted 3" flame arrestors, plenty of air to hatch, monitor mid to high 11's to a 12.0 air fuel at WOT
TIMING at 35

Tim, I was just looking at this and thinking about this.

If in fact, you have flat top pistons, with a -3 CC valve relief, a zero decked block, 121cc chamber on the cnc chamber afr 325, .039 thick head gasket, theres just no way its 9.5:1. My calculations put it at around 9.1:1, IF the block was zero decked. If the piston is in the hole say, .010, 9.0:1.

The more I think about your numbers, dyno'ed in full dress with your wet manifolds, only 9:1 static, 4150 carb, its probably not all bad. If that combo was 10:1, a little more duration so it builds a little more power upstairs instead of dying at 5400ish, I could see 700hp or more.

If you were to tear them out, here's what I would do.

First thing, check the piston to deck relationship, and verify what you have. I have a deck bridge and a dial indicator I can send you. If your piston is in the hole .010 or more, you can drop down to a .027 or so cometic gasket. You can have the heads flat milled, probably safely down to around 115cc or so. Install some cams with a little more duration in them. Then you'll be looking at a gain of around .6 to .75 static, getting you in the 9.6-9.75: range.

Here's a good calculator to use. I'd guess your piston's top ring is down around .300 give or take.

http://www.diamondracing.net/tools/

Too much duration, with low compression, can hurt low end power. When the compression comes up, so can the duration.