5.7L rebuild and upgrade to vortec heads

[tfret]

Hi all
The 1984 5.7L in our Dixie stern drive ski boat is closing in on 1150 hours. She still gets it’s done but I know if I keep her the day is coming for the inevitable rebuild. I’ve heard that a decent power gain can be found by upgrading to vortec heads. I’d like to get an education in advance on this and I’m wondering if there is a good thread or “sticky” on this topic. Thanks

 

[Scott Danforth]

No sticky

Swap heads, gain 30hp. Requires vortec intake

At 1150 hours, your motor should go another 3850 hours without an issue assuming you keep up with maintenance

 

[itsathepete]

As Scott said it's just heads and intake. Get a set from the junkyard and go through them yourself or have a machine shop do it. You'll likely find pitted exhaust valves that will need replacement but you might be able to lap them smooth. Machine or lap them flat and put in new valve seals. If your cam is stock, stock valve springs will be fine, but you may want new ones anyway. For a larger cam, the LS6 style beehive springs are recommended. Marine vortec dual plane intake that fits your carb, whether square bore or spread bore and that's it.

 

[tfret]

Any concerns about what year heads will fit? Any 5.7L vortec head will fit my 80’s block? Cast numbers aren’t important?

 

[Scott Danforth]

Any concerns about what year heads will fit? Any 5.7L vortec head will fit my 80’s block? Cast numbers aren’t important?

You are overthinking it. The SBC is the Mr potato head of the motor world

All SBC heads fit all standard deck blocks from 1956 to today. Just get the right combustion chamber

Any 5.7 liter 64cc vortec heads will work

New fully assembled vortec heads are $900, good reconditioned used are about $450

 

[itsathepete]

I don't know if an 84 engine had tty head bolts but I would use new ones regardless. Also, the vortec manifold will require different bolts as well and likely a pipe plug or two to block off unneeded coolant outlets. And the appropriate gasket.

 

[tank1949]

You are overthinking it. The SBC is the Mr potato head of the motor world

All SBC heads fit all standard deck blocks from 1956 to today. Just get the right combustion chamber

Any 5.7 liter 64cc vortec heads will work

New fully assembled vortec heads are $900, good reconditioned used are about $450

Hi all
The 1984 5.7L in our Dixie stern drive ski boat is closing in on 1150 hours. She still gets it’s done but I know if I keep her the day is coming for the inevitable rebuild. I’ve heard that a decent power gain can be found by upgrading to vortec heads. I’d like to get an education in advance on this and I’m wondering if there is a good thread or “sticky” on this topic. Thanks

it seems to me if I was going for VT heads for a little more power, I'd stroke the motor as well, since a rebuild is being considered. BUT, if motor is saltwater cooled, I'd wait and when it finally gave up the ghost, I'd pitch it.

 

[tfret]

No sticky

Swap heads, gain 30hp. Requires vortec intake

At 1150 hours, your motor should go another 3850 hours without an issue assuming you keep up with maintenance

I hope you’re right about those hours. It is very well maintained. However I’m seeing some glitter in my oil when I change it. Don’t know if it’s crank bearings or cam. But something is wearing for sure.

 

[Scott Danforth]

I hope you’re right about those hours. It is very well maintained. However I’m seeing some glitter in my oil when I change it. Don’t know if it’s crank bearings or cam. But something is wearing for sure.

you shouldnt see anything in your oil.

however a simple oil test will tell you.

a well maintained marine motor will go 5000 hours plus

 

[Scott06]

I hope you’re right about those hours. It is very well maintained. However I’m seeing some glitter in my oil when I change it. Don’t know if it’s crank bearings or cam. But something is wearing for sure.

Do an oil analysis as suggested . Blackstone labs was like $40. Do a compression and or leakdown test. If cared fir you should be fine, if not cared fir u know what you’re dealing with

 

[tfret]

it seems to me if I was going for VT heads for a little more power, I'd stroke the motor as well, since a rebuild is being considered. BUT, if motor is saltwater cooled, I'd wait and when it finally gave up the ghost, I'd pitch it.

No salt water. Fresh water lake only.

 

[tfret]

Do an oil analysis as suggested . Blackstone labs was like $40. Do a compression and or leakdown test. If cared fir you should be fine, if not cared fir u know what you’re dealing with

I’ll send a sample for analysis when I change the oil this Fall. I think factory compression is 150? My highest cylinder is 140. Lowest is 115. The others are right around 130.

 

[Scott06]

I’ll send a sample for analysis when I change the oil this Fall. I think factory compression is 150? My highest cylinder is 140. Lowest is 115. The others are right around 130.

115 is getting down there. 130-140 is decent to good. might be worth a leak down on the low cylinder if its valves and you upgrade the heads anyways problem solved Unless u have bearing issues.

 

[Scott Danforth]

I agree, you're down on power with your compression numbers

 

[tfret]

I put reconditioned heads on several years ago but they probably only have 300 hours on them. I expect the valves are ok. That glitter in the oil is telling me something somewhere is wearing. I guess just run her until she gives it up. Could be years, who knows. But I got my answer regarding vortec heads and intake and everything should bolt right on. Thanks for the valuable inputs.

 

[Scott Danforth]

I agree with above. Build a stroker with a SCAT crank and rods, rortec heads, and LCQ style pistons and have it ready to swap when your motor gets a bit more worn

Surprised at your low compression numbers with such low hours. Would suggest a leak down test

 

[tank1949]

I’ll send a sample for analysis when I change the oil this Fall. I think factory compression is 150? My highest cylinder is 140. Lowest is 115. The others are right around 130.

that is not good.

 

[tfret]

that is not good.

Right I know but I guess there isn’t really anything I can do about it.

 

[Scott06]

Right I know but I guess there isn’t really anything I can do about it.

The only thing u can do is a leak down test to see if it is rings valves or both . That coupled with oil analysis to see if bearing material is present can inform u if your short block is good enough to accept new heads or you need a new long block