Much Happier!

rpengr · **Posted:** Thu Nov 08, 2012 6:00 pm

deafwish wrote:

Thanks fellas!

Will my 500CFM 2BBL supply sufficient fuel to safely accommodate a mild cam upgrade?
If I have to go to a 4BBL & manifold to run a milder cam, the bang for buck will be hard to justify.

Short answer = yes

Long answer is:
500 cfm will support engine RPM of about 4900 or more. Here is the math:
A 4-cycle engine draws it's full displacement every two turns (because it takes 2 turns for all the cylinders to go through 1 complete cycle).
350 cubic inch engine = .2025 cubic foot (350/12^3). .2025 divided by 2 = .10125cf/revolution. 500cfm / .10125cf/rev = 4938rpm
(500cfm at 4938rpm is the maximum theoretical amount of air drawn through the engine. Actual air pulled in is less due to valves/cam/intake, etc.)

I don't have any experience at testing this theory, so other's feedback is welcome.

Your GL engine probably maxes out at 4400-4500 rpm. If the new cam brought you up 500rpm, you would get about a 10% increase in horsepower. Lower end torque would go up as well.

deafwish · **Posted:** Sat Nov 10, 2012 12:56 am

Boat runs flatout at 48 mph at 4500 RPM with 3 adults on board...
Just for my own ego's sake, I would've loved a 50+ mph boat! :oops:

ric · **Posted:** Sat Nov 10, 2012 1:11 am

My little 4.3 does 55 with 2 adults but rides like shit lol

Aussie_Horizon_190 · **Posted:** Sun Nov 11, 2012 5:52 pm

500cfm should be heaps. 4bbl choice would be 600cfm marine - check out VPW in Epping for the best price on these. http://www.vpw.com.au/Category/Index/6469.

For a cam, talk to Crow Cams http://www.crowcams.com.au/.
These guys have a heap of experience and are great to deal with. I raced small block chevs for many years and found Crow Cams consistently delivered more power and torque with less valve train stress than any others. They may also be able to provide some advice re the carb. Talk to Ray - he's a real smart cookie on Chevs.

deafwish · **Posted:** Mon Nov 12, 2012 4:49 am

Hey Alec,

Ray no longer works at Crow Cams, but his colleague was helpful.
They've suggested investing $350 in their '666 Marine' package, which consists of a marine grind cam, lifters & springs.
He mentioned that my Holley 2300, 500cfm 2BBL would be sufficient for this upgrade & mentioned that the 2BBL is far from a bad thing...
$350 for a mild power increase seems much better bang for buck than a 4BBL & manifold!
p.s. Might anyone know any spec's of the cam that's standard in my 5.7GL?

ric · **Posted:** Mon Nov 12, 2012 8:32 am

deafwish wrote:

p.s. Might anyone know any spec's of the cam that's standard in my 5.7GL?

Not far off from a pretzel being shoved in there. All GM 'marine' cams are automotive camshafts, so look for a 220hp carb'd 5.7 used in a car and that's it. Looks like early 80's truck.

rpengr · **Posted:** Mon Nov 12, 2012 8:34 am

deafwish wrote:

Boat runs flatout at 48 mph at 4500 RPM with 3 adults on board...
Just for my own ego's sake, I would've loved a 50+ mph boat! :oops:

I agree with the Cam upgrade posts, if your willing to put in the work to install it. A lot more $100s if you pay somebody else to do it.

However,
48mph at 4500rpm does seem a little slow for your 180 and a 220HP engine. I would still check the condition and proper size of your propeller. Minor dings can take a lot out of your top end. Just having your prop reconditioned might bring you to 50-51mph at 4600rpm. A new SST prop might do better than that?

For reference, my Horizon 240 (250hp GS 2-bbl carb) was able to hit 46 mph at 4800rpm this weekend with 4 adults, lots of baggage, and 65 gals of gas. Prop is 14.5" diameter x 19 pitch SST.

ric · **Posted:** Mon Nov 12, 2012 8:42 am

All depends on the hull and an H180 hull is short and steep. A larger boat would be faster with the same HP.

rpengr · **Posted:** Tue Nov 13, 2012 4:41 pm

ric wrote:

All depends on the hull and an H180 hull is short and steep. A larger boat would be faster with the same HP.

An H240 would be faster than an H180 on the same horsepower? I don't think so.

By that logic, I guess I should get an H310 so I will only need a 4.3L :roll:

ric · **Posted:** Tue Nov 13, 2012 4:53 pm

rpengr wrote:

ric wrote:

All depends on the hull and an H180 hull is short and steep. A larger boat would be faster with the same HP.

An H240 would be faster than an H180 on the same horsepower? I don't think so.

By that logic, I guess I should get an H310 so I will only need a 4.3L :roll:

well, not if one weighs 2500lb and the other 4500lb.

Example:
2012 H180 with 3.0 liter engine. Top speed? 42-43mph.
2012 Stingray 18ft with 3.0 engine. Top speed? 50-51mph.

They weight about the same, it's the hull. Now my buddies 2004 H220 with the 4.3 is actually faster then my Stingray 195CS with 4.3 by a few MPH. Rides better too.

TX H210SS · **Joined:** Thu May 27, 2010 9:10 am **Posts:** 1488

Many things affect speed on the water....how much weight you got in boat...waves...wind...I have some buds that could hit payload pretty quick.

Do you have ss prop or aluminum....aluminum ones will flex under load...so you will gain a little speed with ss...also I am not ensenuating anything but hate to assume too..are you trimming out the drive once on top of the water?...also is that 48 MPH on the speed or GPS??? You may be kicking along faster than you think.....didn't you have the faulty spedo?

deafwish · **Posted:** Tue Nov 13, 2012 10:38 pm

What Ric is saying holds quite alot of truth (did I just say that?! :lol:

).

Would someone please be able to confirm what cam is in my 1997 5.7GL, 572BPLKR?
I've found 2x potential cam's but am struggling to decipher which one I have!
Part number: 3853159
http://www.marinepartseurope.com/en/vol ... shaft.aspx

or
Part number: 3856119
http://www.marinepartseurope.com/en/vol ... shaft.aspx

Once I know the part number, I'll try find some spec's of the cam!

<edit> Alloy 3 blade, 21 pitch prop and it was trimmed just before cavitation. Speed was via iPhone GPS application!

fiznuka · **Posted:** Wed Nov 14, 2012 9:08 pm

I think this is a link that would be helpful. I am pretty sure this is your engine judging by the block #. It covers the LK model.
Hope it helps.
http://boatinfo.no/lib/volvo/manuals/lk ... .html#/202

deafwish · **Posted:** Thu Nov 15, 2012 1:54 am

Thanks fiznuka!

I've spoken again to my local camshaft manufacturer (who has 30+ years experience in auto & marine V8's) and has suggested I go with the 1666 cam:
http://www.crowcams.com.au/media/catalo ... %20all.pdf
How does this compare to the 'hot' Mercruiser cam?

He also stated that my Holley 2300 (500cfm) 2BBL will not be worth replacing with a 4BBL (600cfm) kit, as the RPM's/ airflow (4600 max) is not sufficient to warrant the upgrade. Interesting!

rpengr · **Posted:** Thu Nov 15, 2012 8:57 am

deafwish wrote:

He also stated that my Holley 2300 (500cfm) 2BBL will not be worth replacing with a 4BBL (600cfm) kit, as the RPM's/ airflow (4600 max) is not sufficient to warrant the upgrade. Interesting!

tag from 2000 VP 5.7GS

I would suggest that your cam upgrade will increase your maximum allowable RPM. With the new cam, there is probably no reason you could not run the same WOT RPM as the Injected model of your engine.

The picture above, shows the maximum allowable RPM for my 2000 5.7GS (Vortec Heads and 500cfm 2bbl) as 4400-4800. (and I am getting good performance hitting 4800rpm with a 19pitch SST prop). The GSi version was 4600-5000.

So in my opinion, with your cam upgrade, I don't see why you could not shoot for a WOT of 4700-5000. Can you ask your CAM Expert what he thinks of this?

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