350 SBC Vortec Conversion

[Bondo]

Re: 350 SBC Vortec Conversion

Ayuh,... You're Learning something........<br /><br />Now you've got to get Off the compression Ratio issue.......<br />The Vortecs can be run with considerably More than the old heads,.... Without High Test Gas.....<br />With the semi-dished pistons you Have,... You'll be lucky to get the Comp. Ratio Up to where the Maximum Potential can be achived,.....<br />You'll be running Better,+ Stronger,..... But, There'll Still be more Possible Power with Lower end changes.......<br />

What about going to 1.6:1 rockers?

Not necessary, Nor recommended,......<br />Although the vortecs Do use a Self-Guided Rocker,.. It's still a 1.5 ratio.... <br />

Which head gasket should I use?

As I said before,... You'll need to measure how Deep the piston sit at TDC, below the Block Deck..........<br />Then find the Fel-Pro gasket that gets you as Close as Possible to the Golden .040 Quench............<br />If the Block Hasn't been Decked,.. I'm Guessing that you'll be using a Shim Gasket..........Which will be No Problem with your Closed Cooling System.............<br /><br />Go back to that Google search,.... All the answers are There........

 

[FreeBeeTony]

Re: 350 SBC Vortec Conversion

OK Bondo......I am going to measure the depth of the piston today.........<br /><br />What is "Quench"?<br /><br />I will also check Google.......

 

[Bondo]

Re: 350 SBC Vortec Conversion

What is "Quench"?

It's the distance from the Very Top of the piston,...... <br />Too the Very Bottom flat area of the combustion chamber of the Head.........<br />In other words,.... The Clearance between the Head(the lowest part when installed),+ Piston(the highest part, when installed),....

 

[FreeBeeTony]

Re: 350 SBC Vortec Conversion

And the quench wants to be 0.040?<br /><br />Just enhanced my education further.........sounds like 0.040 is kinda close....<br /><br />Am I asking for trouble if I get it that close?

 

[4.3sunbird]

Re: 350 SBC Vortec Conversion

.040 is not too tight .<br /><br />Im not sure it'll really give you much for results in the boat application for the trouble<br /><br />for higher hp engines or alum rod engines you have to have more piston to head clearence <br /><br />I have run as tight as .020 piston to head but in a low rpm torque build-up<br /><br />I've had a sb chevy that would still hit the heads with the pistons with .060 which was a combo of piston to wall clearence allowing the piston to rock along with crank flex and rod stretch ... that engine had a power range from 6300 rpm to 9400 ..I dont think you'll have that problem

 

[Bondo]

Re: 350 SBC Vortec Conversion

The late Smokey Yunick also recommended a quench clearance of 0.040 inch as a safe but critical clearance. With all other variables being equal, this contributes to creating an engine that is less prone to detonation. <br />Tightening the quench area often results in the reduction of ignition timing requirements. This can then lead to a reduction in negative work. This often is evidenced by a gain in low- and mid-range torque.

Keep Reading,.............<br /><br />With those semi-dished, valve reliefed pistons you've got,............<br />No Problem...............

 

[FreeBeeTony]

Re: 350 SBC Vortec Conversion

OK......I measured the top of the piston to the deck......looks like ~0.025"......will do it again tomorrow.<br /><br />If that's right I should be looking for a ~0.020 compressed head gasket?<br /><br />Also measured the original head gasket....~0.040" (uncompressed)...how much do they compress?

 

[Bondo]

Re: 350 SBC Vortec Conversion

I go by what's printed on the package,........... <br /><br />A Gasket is compressed at the torquing of the head.....<br /><br />Your used gasket is probably very close to it's compressed thickness.......<br /><br />I think Fel-Pro has a website listing of their SBC gaskets,..... Somewhere.....<br />I'll look around.......

 

[FreeBeeTony]

Re: 350 SBC Vortec Conversion

Thanks alot bondo........<br /><br />next w/e I plan on pulling the block out of the boat for an inspection.......think there is an oil leak.......maybe the rear main seal......I understand it can be replaced w/o removing the pan.<br /><br />this week I plan on odering the heads and manifold.....am going to try and put it back together before the winter (already see a little surface rust!)........at least the heads and manifold.......will probably replace the exhaust manifolds and risers in the spring.....

 

[lowshovel1]

Re: 350 SBC Vortec Conversion

Tony, you may as well replace pan gasket along with rear main seal-----if it turns out to be leaking pan gasket,your going to kick your self for not changing it. Buy the one peice gasket --

 

[FreeBeeTony]

Re: 350 SBC Vortec Conversion

Good idea low..............I was kinda thinking the same thing!<br /><br />Not getting much response from the hot rod forums.......how about the push rods? Can I go with the orig?

 

[FreeBeeTony]

Re: 350 SBC Vortec Conversion

Measured the piston to deck again.seemed to be~0.025 again.does that sound right?<br /><br />So I should be looking for a 0.025 head gasket?

 

[Buttanic]

Re: 350 SBC Vortec Conversion

That sounds about right for a stock undecked block.

 

[Bondo]

Re: 350 SBC Vortec Conversion

Originally posted by FreeBeeTony:<br /> Measured the piston to deck again.seemed to be~0.025 again.does that sound right?<br /><br />So I should be looking for a 0.025 head gasket?

I did a quick seach last night,.... I see .016 shim gaskets,+ .018 composite gaskets available......<br />MrGasket,.... Cometic,... Fel-Pro....And a few others I forgot.....<br /><br />You're shooting for .040,...... Not .050.......

 

[FreeBeeTony]

Re: 350 SBC Vortec Conversion

I know it's 0.040.but what if my measuremant isn't right and it's only 0.015.......I would rather be safe than sorry......

 

[Bondo]

Re: 350 SBC Vortec Conversion

Forget the Safe Than Sorry,...............<br /><br />Be Right,....... Not Wrong...................<br /><br />I think the .018s are the 1s you're looking for............