MILD THUNDER

iTrader: (3)

Not bad. Seems about right on par with the 502s with afr heads and 741 cams I've seem posted here over the years.

I bet a little more cam and it would wake up in the 5400+ range

TylerBurich

Take a loot at cam part # 139671 in the link... It looks like a mark 4 version of a 741 but it is on a 114.
http://www.cranecams.com/120-125.pdf

I currently have part #139771 which is similar to 500 EFI cam. I'm almost set on the Crane 139671. Should make power on a 522 well past 5500 which is as fast as I would ever spin it. Thanks for all the input guys!

TylerBurich

Head Flow data as cast ... I'm not sure what Teague did to them if anything but they are a good starting point.

BMP 310cc BBC Aluminum Head Flow Data
Valve Lift -- .200 --.300 --.400 --.500 --.600 --.700 --.800
2.300 ------- 148 -- 218 -- 278 -- 320 -- 352 -- 372 -- 375
1.880 ------- 120 -- 155 -- 185 -- 215 -- 242 -- 263 -- 280

MILD THUNDER

iTrader: (3)

Thats basically the same cam Mike Tkach used in that build he was talking about. He said it peaked at 5900 I think.

I try to look at more than the peak rpm horsepower takes place on the dyno sheet. You really wanna look at what the engine is doing, in the higher rpm range that you will be running in. Assuming you want to keep it at 5500rpm at wot, I'd focus on what the engine is doing between 5000 and 5500.

'Lets say, the smaller cam, that peaks at 5500, is making 598HP at 5500, and 585HP at 5000. Then you go to a little bigger cam, that peaks a few hundred RPM higher, but now the engine is making 622HP at 5500, and 597HP at 5000. Even though its making its "peak" power outside your rpm range, its still making MORE power, than the smaller cam, at the RPM range, you will be wot.
'
Looking at the torque numbers can tell alot as well. Using the above example, the smaller cam version, is making 615 FT lbs at 5000, and 571FT lbs at 5500. The larger cam, is making 627FT lbs at 5000, and 594FT lbs at 5500. Over this 500RPM, the smaller cammed setup dropped 44 FT lbs of torque. The larger cammed version, dropped 33 FT lbs. HP is a derivitive of torque. Guys are always assuming that upper rpm horsepower means less torque. It doesnt work that way. If youre making more HP at 5500RPM, youre also making more torque. You just cannot change that.

Whats my point? My point is, where peak HP rpm takes place, is not the end all imo. Making big torque numbers in the 3000-4000 range, usually means small torque numbers in the 5000-6000 range. I myself, would probably go with the 139681 crane, 240/248 112 LSA stick in that build, over the 236/244 114 LSA cam. But it all depends on what you want from it.

MILD THUNDER

iTrader: (3)

Something else to keep in mind, a set of stainless marine manifolds , or other similar style manifolds with short runners , will give up around 40hp and 30-40ft lbs of torque in the midrange on a NA 600ish up build vs a full length header. Sometimes the cost for an exhaust upgrade is a better bang for buck than heads, cam, intake, carb...

in the car world first thing we do is exhaust upgrade , in marine world, it' usually the last . Sucks marine exhaust is so expensive though. Although the car world isn' that far behind . A set of kooks longtubes and green cat midpipes are almost 2 grand for my Challenger .

hogie roll

why would anyone buy stainless marine over the thunder and lightning manifolds? Cost the same and they make more power than anything

TylerBurich

I already have the IMCO Powerflows with the longer risers for TRS. They were about $5500 from teague when I purchased them 10 years ago, still look new! My thought for leaning towards the milder cams is that I won't be wasting power because of the style of exhuast I have. I have absolutely no clue where the powerflows become a problem with a NA build. I know a true long tube header would have the best flow characteristics that a 600hp NA build would need but as everything is a compromise i'm going to stick with my powerflows. That being said, If the bigger cam makes the better number in that 5000-5500 range then that is what I will be installing. Thanks man! Did you run those #'s in your software or were they from your wisdom bank?

TylerBurich

Did anyone go to PRI this last weekend? Since the snow has started to fly I have been looking into short travel lifters. I really like the stuff from Isky, especially the bushed lifter they offer. Any thoughts on the longevity of a bushed short travel lifter in a marine engine?
link to article
PRI 2017: Isky Racing Cams HPx Hydraulic Lifters Handle the Pressure

TylerBurich

Leaning towards the Crane 139681 MT mentioned earlier or similar for this build. Would this be a mistake given the use of my imco powerflows? Have been looking at the Johnson slow lifters as well. Also, any reason to not go 4.600" bore? Merlin 4 block is same price in 4.595". Trying to maximize overall power across the 3500-5800 range.