5.7 vortec conversion

[ckgreenman]

Re: 5.7 vortec conversion

The vortec haeds don't allow as much lift (.488 max IIRC), but if you are running the stock cam, or any cam that doesn't excede .488 (at the valve, not lobe) then no need to change it.

I had heard .470 at the valve so that gives a little more room than I thought. However, the cam I'm looking at putting in has a max lift of .451 (I think) with stock rocker ratio.

So from what I'm seeing the vortec conversion shouldn't be too much of a big deal as long as I can get a good set of heads and an intake. I'm actually considering grabbing some heads off mid 90s truck in a local salvage yard and fixing them up.

 

[John_S]

Re: 5.7 vortec conversion

Did the cam have to be changed? or was it as straight forward as heads/intake (w/ supporting parts for the change over)?

No, you can leave the marine flat hyd cam. It makes the same HP as the roller. Many people believe the roller cam is part of the vortec engine. It is, only in that by the time they went to vortec heads, they all had the roller cam.

FWIW, I did change mine to a roller, but that is only because I got a good deal for the cam and all related components from an iBoats forum member. It does make for a more difficult in-boat replacement. Sealing up the timing cover / front oil pan caused me to contort my body in ways that hadn't been done in years. And my boat has very good engine access.

 

[ckgreenman]

Re: 5.7 vortec conversion

No, you can leave the marine flat hyd cam. It makes the same HP as the roller. Many people believe the roller cam is part of the vortec engine. It is, only in that by the time they went to vortec heads, they all had the roller cam.

I thought the roller did ad a few HP. Oh well.

To add to your point, mine is a non-vortec and it already has the roller cam.

Which cam you use is more a function of the block you have not the heads. One thing I WAS told, however, was that the spring pressure needs to be higher on a roller cam.

 

[John_S]

Re: 5.7 vortec conversion

hi there I been reading here trying to learn what type of heads are you using for that and how much did you paid for them are the heads marine app or automotive if they automotive thanks.

I would have to go back and look at my notes. There are two main GM casting numbers for the 350 vortec heads. I used the ones that were recommended by the prformance car gurus. Since then, I have seen it posted that the other one is prefered for marine. I don't know for sure.

I paid about $500 for the pair with free shipping from Jegs. I haven't priced any recently.

 

[ckgreenman]

Re: 5.7 vortec conversion

I would have to go back and look at my notes. There are two main GM casting numbers for the 350 vortec heads..

Are they 906 and 082?

 

[Bondo]

Re: 5.7 vortec conversion

I'm actually considering grabbing some heads off mid 90s truck in a local salvage yard and fixing them up.

Ayuh,... Late 90s,... 96 is past mid..... Late-90s til the end of the Run,....
Btw, on a side note,... Anybody know what year Chevy quit puttin' 350s in pickups,..??

Sealing up the timing cover / front oil pan caused me to contort my body in ways that hadn't been done in years. And my boat has very good engine access.

That's why they make it relatively Easy to pull the motor,...
Cam swaps are Much Easier on a stand.....

Are they 906 and 082?

It's 062, ain't it,..?? 906,+ 062....
The 906s have bigger exhaust seats,+ some Hotrodders think it impedes the flow...
They're perfect for marine in that the valve gets better cooling...

 

[ckgreenman]

Re: 5.7 vortec conversion

Ayuh,... Late 90s,... 96 is past mid..... Late-90s til the end of the Run,....
Btw, on a side note,... Anybody know what year Chevy quit puttin' 350s in pickups,..??


That's why they make it relatively Easy to pull the motor,...
Cam swaps are Much Easier on a stand.....

It's 062, ain't it,..?? 906,+ 062....

yeah that's what I meant

 

[John_S]

Re: 5.7 vortec conversion

I thought the roller did ad a few HP. Oh well.

To add to your point, mine is a non-vortec and it already has the roller cam.

Which cam you use is more a function of the block you have not the heads. One thing I WAS told, however, was that the spring pressure needs to be high on a roller cam.

If it did add a couple hp, it wasn't enough for Merc to change the engine specs. The roller has higher lift but shorter duration that the flat hyd cam.

Cam should be choosen to go with the whole package. For example, the stock marine cams compensate somewhat for restrictive exhaust system.

The roller lifters have more mass and as such would cause valve float at a lower rpm. Not sure how much that comes into play on marine engines that don't go over 5K rpms, but springs should be matched to whatever cam is being used.

 

[John_S]

Re: 5.7 vortec conversion

That's why they make it relatively Easy to pull the motor,...
Cam swaps are Much Easier on a stand.....

"Boat" and "Easy" are contridictions I thought. I guess my point was, it was not worth the extra work just to change from flat to roller. Otherwise it was a simple in boat swap.

 

[270win]

Re: 5.7 vortec conversion

Ayuh,... Late 90s,... 96 is past mid..... Late-90s til the end of the Run,....
Btw, on a side note,... Anybody know what year Chevy quit puttin' 350s in pickups,..??...

1999

It's 062, ain't it,..?? 906,+ 062....
The 906s have bigger exhaust seats,+ some Hotrodders think it impedes the flow...
They're perfect for marine in that the valve gets better cooling...

They're both really good marine heads, the valves can be upgraded in both. I've run both in sbc motors and they will both support 400hp in a street car.

Max lift is .470 but you can have the spring pockets massaged to accept up to .550. My last one was .492 lift w/1.52:1 rocker. They also use press in studs fomn the factory so I would recommend screw in studs for a higher lift cam. I've ran Cammotion springs to match the cam specs and have had great results...

 

[FreeBeeTony]

Re: 5.7 vortec conversion

I think it's 906 and 062......as far as I know they are both the same. At one time it was said the the 062's were better than the 906's but I don't believe it's true.

Edit: I missed the 2nd page to this thread..........guess I'm a day late........

 

[270win]

Re: 5.7 vortec conversion

I think it's 906 and 062......as far as I know they are both the same. At one time it was said the the 062's were better than the 906's but I don't believe it's true.

Edit: I missed the 2nd page to this thread..........guess I'm a day late........

I wasn't going to elaborate, but yes, the 062 and 906 heads are exactly the same head. And it's very common, even with guys who know their stuff to be wrong about this. Somehow one of these heads got confused with the old swirl port heads...depending on who you hear it from both of these heads get a bad rep. In reality, you can use either one and get good results. They make excellent low and midrange torque and still allow up to 6000 rpms...of course that many rpms is unnecessary in this application....

The bad reputation of either of these heads was made worse because the rumors about them were spread by some very well intended experts in the hotrod industry. Chevy High Performance did an article about them and later did a follow up article admitting their mistake...