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It's what we do
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This engine started out as a Mercruiser 502 MAG. We wanted to see what we could do with a semi budget upgrade. I say semi budget because of using the stock block, heads, crank, rods, and pan. We dynoed it with the stock single throttle body top and the dual throttle body top we custom made.
The difference with the two tops was about 20 lb. ft. of torque and 18 HP.

Build was targeted for a Bravo application. Target idle was 800 and max RPM of 6000.

509 CI
SRP Pistons
9.0:1 CR
990 cast iron heads very mild "econo" porting
11/32 x 2.250 Manley SD intake
11/32 x 1.880 Manley SD exhaust
ARP rod bolts
Mel 10770 oil pump blueprinted
Custom Comp Cam
Note: Special Hyd roller lobes....
Comp SBC full body solid rollers
48 lb. injectors

Camshaft is a 111.0 Lobe Sep. Approx .600 lift
Sorry about being so vague about the camshaft. I have spent years working on camshaft design and this one is a home run for this application.

Engine small.JPG

Dyno small.jpg
 

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It's what we do
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Discussion Starter #2
The engines have approx 60 hours run time and no, there is no reversion. :)
 

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It's what we do
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Discussion Starter #4
:thumb: Very nice

Now your just rubbing salt in the wound :|err
Thank you!

Sorry, no salt meant! Besides, you didn't have reversion either! :wink2:
 

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Nice square power on that one. I would call it the HP600.
 

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It's what we do
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Discussion Starter #6
Nice square power on that one. I would call it the HP600.
I am very happy with the linear torque curve. One of the goals was to keep the torque from falling off in the 5000 to 6000 range and have the HP increase up to 6000 to allow the engine to pull larger props to 5900 - 6000.
 

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The engines have approx 60 hours run time and no, there is no reversion. :)
Of course your vaque on the camshaft. With only 200[SUP]o[/SUP]@ .006 and still manage .600 lift I would be tight mouthed too. Otherwise with a 111 LSA and those risers on it the experts would be calling BS on the reversion!:happy:
Of course it never hurts to have installed so far advanced that the exhaust valve completely seated before the piston even its TDC;)

Nice built Brian. The dual throttle bodies may only be worth 18HP on the dyno, but they are worth 40HP + in the visual alone. :thumb:



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It's what we do
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Discussion Starter #8
Of course your vaque on the camshaft. With only 200[SUP]o[/SUP]@ .006 and still manage .600 lift I would be tight mouthed too. Otherwise with a 111 LSA and those risers on it the experts would be calling BS on the reversion!:happy:
Of course it never hurts to have installed so far advanced that the exhaust valve completely seated before the piston even its TDC;)

Nice built Brian. The dual throttle bodies may only be worth 18HP on the dyno, but they are worth 40HP + in the visual alone. :thumb:
hahaha Yeah there might be a little more than 200[SUP]o[/SUP] @ .006. :) The inner pipe goes all the way to within 1/2" of the tail pipe end before it mixes water with the exhaust. Even the cam at the bottom of the last page in the catalogue wont revert. :happy:
 

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hahaha Yeah there might be a little more than 200[SUP]o[/SUP] @ .006. :) The inner pipe goes all the way to within 1/2" of the tail pipe end before it mixes water with the exhaust. Even the cam at the bottom of the last page in the catalogue wont revert. :happy:
That reminds me...
 

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steelcomp was here
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Really nice power. Nice build for sure. How much do you think the EFI contributes to maintaining that torque?
I'd really like to see a build like this with a set of large ovals. ;)
 

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It's what we do
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Discussion Starter #11
Really nice power. Nice build for sure. How much do you think the EFI contributes to maintaining that torque?
I'd really like to see a build like this with a set of large ovals. ;)
I really don't know how the EFI effects the torque curve. It definitely helps being able to fine tune every area of the map optimizing the torque. I think having the long runner intake with the ability to give it as much air as it wants could be a big advantage over carbs. With port injection, the engine will only take the air it wants and we add the fuel. Those are (2) 1200 cfm throttle bodies and are not dependent on vacuum to function or determine the A/F mix.
 

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The inner pipe goes all the way to within 1/2" of the tail pipe end before it mixes water with the exhaust. Even the cam at the bottom of the last page in the catalogue wont revert. :happy:
:thumb: I have always maintained that duration and overlap have nothing to do with reversion, its all in the exhaust system. :happy: Of course that kind of talk can get one banned for life from some boat sites. :no:





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BD - did you study and find what was happening at 5600-5700rpm ? Or any theories/thoughts ?

Was the intake a 500EFI or 525EFI ? Did you use the top from Tyler Crockett ?

What do you think the outcome would be with using a good hydraulic roller lifter in place of the solid roller lifter ?

BTW: I'd take the IMCO's (you used) hands down over the Gills (especially the 'shorts') any day. Very decent exhaust. Just not Db legal around here unfortunately. :cry2:
 

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BD - did you study and find what was happening at 5600-5700rpm ? Or any theories/thoughts ?

Was the intake a 500EFI or 525EFI ? Did you use the top from Tyler Crockett ?

What do you think the outcome would be with using a good hydraulic roller lifter in place of the solid roller lifter ?

BTW: I'd take the IMCO's (you used) hands down over the Gills (especially the 'shorts') any day. Very decent exhaust. Just not Db legal around here unfortunately. :cry2:
Everytime I see something like that I have ask did the computer see a voltage anomaly it didn't like or a solar flare. Whats up. What does the oil pressure have to with the intake tract or the valve train, yet it steady as a rock, went down 3/4 lb and came back.



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It's what we do
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Discussion Starter #15 (Edited)
BD - did you study and find what was happening at 5600-5700rpm ? Or any theories/thoughts ?

Was the intake a 500EFI or 525EFI ? Did you use the top from Tyler Crockett ?

What do you think the outcome would be with using a good hydraulic roller lifter in place of the solid roller lifter ?

BTW: I'd take the IMCO's (you used) hands down over the Gills (especially the 'shorts') any day. Very decent exhaust. Just not Db legal around here unfortunately. :cry2:
We did 6 pulls and it only did that on one. I noticed that, and also saw the oil psi, and the bsfc (which we weren't even monitoring) Pretty sure it was some electrical spike or something. All the other pulls it was between 606 and 612.

It was a 500 EFI intake and NO the top was not from him. We made them over three years ago. Can you tell it's a sore subject with me

intake.JPG


I have built a couple of similar 509's only with alum heads and the same camshaft with Morel hyd roller lifters. The engines are not identical and the boats are completely different so I don't have any factual data to compare. However, they all have the same characteristics. Meaning, they accelerate like crazy from 2000 on up. I don't see a real advantage to the solid rollers for the majority of the customers out there. My OPINION is that with the solid rollers it will pull better (slightly) above 5000. With the very tight lash in this situation, it might not be for the average "change your oil and go" type of guy. Although, it has 2 full seasons on it and this is the first winter I will run the valves. No issues, just think I should.
I did it to answer something I was curious about. When it comes time to replace the lifters, I will put Morels in and will see.
IMCO builds a nice manifold. I built the tail pipes here in the boat. It's a 28 LP Daytona and even as low as they rise off the manifold, they are only about 1/2" from the gunnel. And they are FAR from sound legal here too. Just been lucky. :happy:
 

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It's what we do
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Discussion Starter #16
:thumb: I have always maintained that duration and overlap have nothing to do with reversion, its all in the exhaust system. :happy: Of course that kind of talk can get one banned for life from some boat sites. :no:
Somewhat true.... You can have a tail pipe that does not revert with a "stock" camshaft. Install a cam with more duration overlap and it will. Extend the inner and outer pipes and it wont.

They go hand in hand.

When upgrading power in a boat engine, the first question is; what kind of exhaust do you have? If it wont work with what they want for power, change it. It's not an option.
 

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steelcomp was here
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I really don't know how the EFI effects the torque curve. It definitely helps being able to fine tune every area of the map optimizing the torque. I think having the long runner intake with the ability to give it as much air as it wants could be a big advantage over carbs. With port injection, the engine will only take the air it wants and we add the fuel. Those are (2) 1200 cfm throttle bodies and are not dependent on vacuum to function or determine the A/F mix.
I'm sure the curve is much better with the EFI, There's really no "transition" to be tuned. My thought on the smaller ports was better cyl filling, better VE, more power under the curve.
 

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It's what we do
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Discussion Starter #18 (Edited)
I'm sure the curve is much better with the EFI, There's really no "transition" to be tuned. My thought on the smaller ports was better cyl filling, better VE, more power under the curve.
Exactly! I thought you were referring to the complete torque curve as far as would it make more or less torque. It is definitely a more linear "smooth" torque curve with EFI.

I have used good oval port heads in the past with good results. In our applications, I believe the rectangle port heads, massaged properly, are better for 500 CI and above, especially when you need it to work hard in the 5000 to 6000 range. Also the cam design takes the cylinder head into consideration. Obviously, a different camshaft would be used for oval ports.
Just what I've found that works for me.
 
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