Vortec conversion CR and exhaust questions

[jstcrzyengh]

I have an old OMC 305 I/O. Two of the rockers studs are too short, and since the engine is a 77 I was going to pull the heads and rebuild them, but a buddy of mine brought up a better alternative. Vortec heads. They are higher flowing, better fuel economy, and their 1.94/1.5 valves keeps the 305's from valve shrouding, however I am unaware of the current CC of the OMC heads and waht the pistons run as far as CR. I dont want to run higher than a 9.5 or so CR ratio when installing these heads. I am rebuilding the quadrajet, and getting a new intake as well, I was also wondering if I will have to change over to a vortec specific manifolds and risers? I don't mind, but I want to make sure. Also I am looking at a new cam, I am not looking for monster power just a nice ability to cruise 28+ mph to get to the fishing sooner Any help is appreciated.

 

[bomar76]

Re: Vortec conversion CR and exhaust questions

Vortec heads are unbeliveably efficient for the $$$.<br />They WILL NOT fit your existing intake - you will need a vortec style intake. <br />No idea of the chambers of your current heads.<br />Exhaust manifolds are the same.<br /><br />Lot of money to put in a tired old 1977 engine though.<br /><br />I'd forget the whole idea of dropping much $ into this engine and just repower it with a new (or newer) unit....and while I was at it I'd go to a 350 (5.7).

 

[olbuddyjack]

Re: Vortec conversion CR and exhaust questions

Check here for head info:<br /> http://www.mortec.com/ <br />Complements Rainmaker.

 

[jstcrzyengh]

Re: Vortec conversion CR and exhaust questions

Hello,<br /><br />I know about mortec, but there are many 305 heads for that time era. As far as the 350 I have been thinking about it, but didnt want to put too much power through the electric drive until I can switch it out...

 

[Bondo]

Re: Vortec conversion CR and exhaust questions

I know about mortec, but there are many 305 heads for that time era.

The Casting #s on the heads will tell you Which heads you Have........... <br /><br />Also, The Block Casting #s are at the back of the port head, On the block...... This Might give you an Idea as to Which Pistons are in it Now.......<br />Or,...<br />At the Front edge of the starboard head is the Stamped build #s...... That'll give you All the answers for That motor......<br /><br />Either Way,..... I Doubt your motor has the pistons Needed to make the Vortecs Pay Off.........