Mercury racing 502 efi- head work- valve springs
09-02-2015 | 03:18 PM
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Mercury racing 502 efi- head work- valve springs
Pulled the heads on my 500EFI's at 200 Hrs. I know that valve springs should be replaced. Should a valve job be completed? Anything else ? What are the best replacement valve springs ? Anything I can do while the heads are off to get more power without spending a ton of $?
09-02-2015 | 10:44 PM
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From: Tennessee
At a minimum, you need to change the springs, retainers, locks and seals. While they are apart, have a good look at the rocker arms, lifters and valves. These parts may or may not need to be changed. You should not only have a valve job done, but also surface the heads and put them back on with Cometic head gaskets.
There are a few things that can be done for more power. All of them will require some ecm work. There is a little to be had just with some fine tuning of the stock ecm calibration. A little cleaning up of the fuel tables will not only clean up the transom (I bet it gets at least a little black), but it will save some fuel and add a little power. If you don't mind running some better fuel, we can add a little timing and raise the limiter.
If you want a little more, then while the heads are being surfaced, cut a little more, run a thinner head gasket, and raise the compression a couple of tenths of a point. You can get them to 9:1 (from the stock 8.75:1) pretty easily. While the heads are off and apart, a little clean up in the bowls and throats is a good way to find a little power. You also aren't real far from changing the camshaft. The exact route to take really depends on you. It depends on how much more power you want/need, what your budget is, etc. You can easily add 50+ hp to that engine. However, you WILL need to change the throttle body in order to really reap any benefits from the above mentioned upgrades. The stock dual blade throttle body is not large enough.
Just upping the compression a little, cleaning up the heads runners and bowls, changing the throttle body and tuning it will get you a good 50 hp. Depending on the boat, you could see anywhere from 3-5 mph.
As for parts, ISKY 8005A springs, Comp 10* steel retainers and locks, and PC seals will work great and are what we use. We have done a ton of 500's like I described above. Some boats are worse then others as far as the tune goes. We have had a few that would soot up the transom pretty badly after only 30 min of running. We can eliminate all of that with some tuning. Give me a shout if you have any questions at all or need any help.
Eddie
There are a few things that can be done for more power. All of them will require some ecm work. There is a little to be had just with some fine tuning of the stock ecm calibration. A little cleaning up of the fuel tables will not only clean up the transom (I bet it gets at least a little black), but it will save some fuel and add a little power. If you don't mind running some better fuel, we can add a little timing and raise the limiter.
If you want a little more, then while the heads are being surfaced, cut a little more, run a thinner head gasket, and raise the compression a couple of tenths of a point. You can get them to 9:1 (from the stock 8.75:1) pretty easily. While the heads are off and apart, a little clean up in the bowls and throats is a good way to find a little power. You also aren't real far from changing the camshaft. The exact route to take really depends on you. It depends on how much more power you want/need, what your budget is, etc. You can easily add 50+ hp to that engine. However, you WILL need to change the throttle body in order to really reap any benefits from the above mentioned upgrades. The stock dual blade throttle body is not large enough.
Just upping the compression a little, cleaning up the heads runners and bowls, changing the throttle body and tuning it will get you a good 50 hp. Depending on the boat, you could see anywhere from 3-5 mph.
As for parts, ISKY 8005A springs, Comp 10* steel retainers and locks, and PC seals will work great and are what we use. We have done a ton of 500's like I described above. Some boats are worse then others as far as the tune goes. We have had a few that would soot up the transom pretty badly after only 30 min of running. We can eliminate all of that with some tuning. Give me a shout if you have any questions at all or need any help.
Eddie
09-03-2015 | 01:20 PM
#7
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Joined: Jun 2011
Posts: 2,169
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From: Henderson, KY
Oh, ...and he's good at this $hit too !! :-)
Highly recommended
Highly recommended
At a minimum, you need to change the springs, retainers, locks and seals. While they are apart, have a good look at the rocker arms, lifters and valves. These parts may or may not need to be changed. You should not only have a valve job done, but also surface the heads and put them back on with Cometic head gaskets.
There are a few things that can be done for more power. All of them will require some ecm work. There is a little to be had just with some fine tuning of the stock ecm calibration. A little cleaning up of the fuel tables will not only clean up the transom (I bet it gets at least a little black), but it will save some fuel and add a little power. If you don't mind running some better fuel, we can add a little timing and raise the limiter.
If you want a little more, then while the heads are being surfaced, cut a little more, run a thinner head gasket, and raise the compression a couple of tenths of a point. You can get them to 9:1 (from the stock 8.75:1) pretty easily. While the heads are off and apart, a little clean up in the bowls and throats is a good way to find a little power. You also aren't real far from changing the camshaft. The exact route to take really depends on you. It depends on how much more power you want/need, what your budget is, etc. You can easily add 50+ hp to that engine. However, you WILL need to change the throttle body in order to really reap any benefits from the above mentioned upgrades. The stock dual blade throttle body is not large enough.
Just upping the compression a little, cleaning up the heads runners and bowls, changing the throttle body and tuning it will get you a good 50 hp. Depending on the boat, you could see anywhere from 3-5 mph.
As for parts, ISKY 8005A springs, Comp 10* steel retainers and locks, and PC seals will work great and are what we use. We have done a ton of 500's like I described above. Some boats are worse then others as far as the tune goes. We have had a few that would soot up the transom pretty badly after only 30 min of running. We can eliminate all of that with some tuning. Give me a shout if you have any questions at all or need any help.
Eddie
There are a few things that can be done for more power. All of them will require some ecm work. There is a little to be had just with some fine tuning of the stock ecm calibration. A little cleaning up of the fuel tables will not only clean up the transom (I bet it gets at least a little black), but it will save some fuel and add a little power. If you don't mind running some better fuel, we can add a little timing and raise the limiter.
If you want a little more, then while the heads are being surfaced, cut a little more, run a thinner head gasket, and raise the compression a couple of tenths of a point. You can get them to 9:1 (from the stock 8.75:1) pretty easily. While the heads are off and apart, a little clean up in the bowls and throats is a good way to find a little power. You also aren't real far from changing the camshaft. The exact route to take really depends on you. It depends on how much more power you want/need, what your budget is, etc. You can easily add 50+ hp to that engine. However, you WILL need to change the throttle body in order to really reap any benefits from the above mentioned upgrades. The stock dual blade throttle body is not large enough.
Just upping the compression a little, cleaning up the heads runners and bowls, changing the throttle body and tuning it will get you a good 50 hp. Depending on the boat, you could see anywhere from 3-5 mph.
As for parts, ISKY 8005A springs, Comp 10* steel retainers and locks, and PC seals will work great and are what we use. We have done a ton of 500's like I described above. Some boats are worse then others as far as the tune goes. We have had a few that would soot up the transom pretty badly after only 30 min of running. We can eliminate all of that with some tuning. Give me a shout if you have any questions at all or need any help.
Eddie
09-03-2015 | 09:08 PM
#8
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Joined: Oct 2005
Posts: 1,078
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From: Waldorf, Md
Chris,
First question would be why are you pulling the heads ? Head gasket issue or some other reason.
I am going to go against the grain here and say that if you have the springs checked and they measure in specs, then leave them alone. I have seen more new springs break than ones with 200 hours on them. I very rarely see a retainer that needs replacing either. I automatically replace locks every time. Mercruiser uses an unusual Crane lock on a lot of their Big Blocks. If you do decide to replace the springs, why would you not go with what has been on there and working well for 200 hours ? Most of Mercruiser's valvetrain is Crane. Your machine shop should be able to determine exactly which springs are on the engine and get the correct replacements.
I have three sets of Big Block Mercruiser heads in the shop right now. One set needs everything, another set needs springs, intake valves and a touch up on the valve job and the third set really does not need much at all other than a good cleaning, touch up the valve job and put them back together. Just depends
Probably would not hurt to touch up the valve job and maybe do a little bit of port smoothing. Unless you are going to do a camshaft change or do major engine work to up compression, nothing else is really going to gain you a lot of power.
That's my opinion,
Bill Koustenis
First question would be why are you pulling the heads ? Head gasket issue or some other reason.
I am going to go against the grain here and say that if you have the springs checked and they measure in specs, then leave them alone. I have seen more new springs break than ones with 200 hours on them. I very rarely see a retainer that needs replacing either. I automatically replace locks every time. Mercruiser uses an unusual Crane lock on a lot of their Big Blocks. If you do decide to replace the springs, why would you not go with what has been on there and working well for 200 hours ? Most of Mercruiser's valvetrain is Crane. Your machine shop should be able to determine exactly which springs are on the engine and get the correct replacements.
I have three sets of Big Block Mercruiser heads in the shop right now. One set needs everything, another set needs springs, intake valves and a touch up on the valve job and the third set really does not need much at all other than a good cleaning, touch up the valve job and put them back together. Just depends
Probably would not hurt to touch up the valve job and maybe do a little bit of port smoothing. Unless you are going to do a camshaft change or do major engine work to up compression, nothing else is really going to gain you a lot of power.
That's my opinion,
Bill Koustenis
Last edited by BillK; 09-03-2015 at 09:12 PM.
