I have the taxes coming back soon, and I'm thinking it might be time to upgrade the topend of my 305. Its a crate motor (don't ask why, it was replaced before it was mine) with only 20k miles on it, so it doesn't quite make sense to toss it for a 350, yet. Maybe in a couple of years - but my plans for this topend should go to a 350 quite nicely.

I'm thinking about buying the SDparts Vortec Upgraded Heads/Intake package, specifically the performer air gap combination. I have flat-tops, but I would still have the heads milled to a 56-58cc chamber to keep the compression in the 9.x to 1 range. With that I would go with a XE268H cam. Should make the 305 run along nicely, don't you think? And, in a year or two that stuff would all go with a 350 very nicely, compression w/ those milled vortecs still wouldn't be that extreme, maybe 10.2 to 1, thats workable.

Will the Air Gap clear w/ a stock hood? I have a ZZ3 intake now, and its darn close - with no carb spacer.
Thoughts/comments please...

 

I wouldn't shave the heads. The performance improvement will still be there with the Vortec flow & chambers, and 10.2:1 is pretty high for a street engine. With .040" quench height and 64cc chambers, you'll still need around 12cc dish/relief pistons in a 350 to keep it in the 9.5:1 range. The power difference between 9.5 & 10.2:1 is negligible, but the difference in expense (premium fuel) is significant.

There isn't a Performer Air Gap for Vortec heads. There is a Performer RPM Air Gap, perhaps that's what you meant.

Edelbrock has the intake dimensions on their website. The ZZ3 is a Performer. The difference in height from Performer to Performer RPM is only a quarter inch or so. Many members are using an Air Gap with drop base air cleaner under a stock hood.

In case you were wondering, the RPM and RPM Air Gap are the same height china wall to carb mount.

 

I beleive it would be the Performer RPM Air Gap then - I going by memory from looking at the catelog last night.

Good info on the height difference between the Performer, and Performer RPM, and the lack of difference between the regular and Air-Gap models.

I agree that 64cc chambers are optimal for a 350 in the future, I figured the were pretty big for the 305 - but like you said, most of the benefit will be found in the better breathing, I guess the drop in compression won't hurt too much.

Power/1320 guesstimates anyone? Maybe 240whp/High 13's? (I aprx 200whp/14.6 now)