Alright, before you hate me off the bat, I definitely did search, and came up with quite a bit of information, however, I'm still a bit confused about it.

From what I understand, it is possible, but I need to relieve the cylinders in order to prevent the valves from hitting, could some explain exactly what that means? I have an idea, but I'd like a bit of clarification. I also understand that doing that will lower the compression significantly. Can that compression, or enough to run well, be gained through a different thickness headgasket?

I've got a 305 TPI, it's got a fresh bottom end rebuild, so I'd like to keep it, because I'm not looking for big numbers, and really the only 305 heads I can find are the World Products torquers, which are $1200 for a pair. I work at a GM dealership and can get a pair of fastburn heads for $450 after taxes with my employee discount, so, I'm sure you can understand my thought process here haha.

So, basically, what do I need to do to make 350 heads work on a 305? Is it really worth the hassle? Like I said, I work at a GM dealership, so I have access to zillions of tools, and absolute wealths of knowledge with the other techs that work here.

If it's not worth it, in your opinion, are there any heads you'd recommend? Am I really that inept at the internet that I can't find any decent 305 heads other than the torquers (which is quite possible)?

I appreciate the help guys, like I said, I'm sorry, I'm sure this question has been asked a million times, but my searches, on here and google, didn't really return the kind of information I need.

 

Trick Flow (TFS) has some.
http://www.trickflow.com/partdetail....1&autoview=sku

You really don't want to trim away part of the cylinder if you can help it. Getting the edge of the intake valves radiused may be enough depending on how much lift you want to run. An angle-mill on the heads can also increase clearance between the valve and cylinder wall.
I have some L98 083 heads I could mock up on a 305 block and take some pics and measurements if it would help. I don't have any vortec fastburns in my shop right now.
I think the valve sizes and spacing are supposed to be the same though.

 

Awesome, that would be so helpful. If you had to guess, how much lift do you think would be safe with just the valves radiused?

 

I'll do the mock-up tomorrow with 1.94 valves and measure the lift. Some I've mocked up in the past have went to about 0.600" before touching but that was with milled heads.

 

Hmmmm...well, like I said, I work at a GM dealership, so I have access to all the tools and people necessary to mill the heads.

I really appreciate your help, it'll make it so much easier than guess work haha.

I'm planning on mating it with this cam: http://store.summitracing.com/partde...p;autoview=sku

 

Aren't the fastburn heads vortecs?

If so, they won't match up to the intake right. Requires a 400+ intake to use them, although, the intake is made by GMPP, so maybe that's an option for you.

 

Yea, I'm pretty sure the fast burn's are 8 bolt.

 

Sorry for the delay. I had a set of stock 083 heads from a 1989 L98 350cid engine, and a 305cid block that has been bored 0.030" over. I couldn't find a standard bore 305 in my shop.

I bolted the head on without a gasket so clearance with a gasket will be a little better. I lifted the intake until it touched and measured that, and then lifted until I had a 0.018" clearance to the cylinder wall to basically simulate a standard bore 305cid.

The stock valves from the 083 heads measured:

1.943"
1.505"

At 0.600" lift the intake valve was just about to touch the cylinder wall.
At 0.500" lift the intake valve was 0.018" from the cylinder wall.

The radiused valves I tried next were from a Vortec engine and measured:

1.931"
1.492"

The intake valve went to 0.550" lift with 0.018" clearance to the cylinder wall.
The intake valve went to 0.718" lift without hitting the cylinder wall. That was the limit of travel for the valve with the seal in place and an elastic around the lock groove.

The photos are in this album with descriptions for each. There are pics of other heads in the other albums.
http://s702.photobucket.com/albums/w...20on%20305cid/


photo radiused intake valve @ 0.550" lift and 0.018" clearance:
http://i702.photobucket.com/albums/w...d/DSCF3988.jpg

 

I forgot to say that my mock-up is only for encouragement to go ahead with your project. Of course you should mock yours up to check the clearances to include piston-to-valve as well.

 

Thank you so much, you've been an incredibly huge help. So it looks like with the valves radiused it'll clear 350 heads.

Awesome, like I said, I really, really appreciate the help.

So with a radius job, I should be able to run a mild cam without worrying about the valves hitting at all, correct?

 

Like I said you should still check all of your own clearances before running the engine. Most stock heads need some modification to run over about 0.470" lift.
You'll need to know your spring/retainer/valve combo installed height, the bind height of the valvesprings, and if you're changing springs they have to fit in the spring pockets obviously.
Every combination will be a little different on clearances due to core shift, location of the dowel pins, plus the exact angle and centerline of the valve guides. I would check every cylinder before you start the engine.

If you're using a 0.030" overbored block then it seems you would have a lot of room for lift with radiused valves. Even if you've got a standard bore 305 I think you should go ahead with the project and not worry about relieving the cylinder walls.

If you want to save money on machining the heads for more lift then you could swap to Vortec style retainers. In a lot of cases the smaller Vortec retainers can add about 0.086" to 0.094" of travel before they contact the valve seal. You lose a little installed height with the retainer swap so always measure with the parts you're going to use. If you're very careful about measuring everything and you use the proper valvesprings you may get away with about 0.550" lift without any extra machining.

I do things like this often, but I'd never say to do it without measuring what you've got.

 

Hmmmm...well, I work at a GM dealership, as I've said, so I have access to quite a few people who've been building performance engines for more than twice as long as I've been alive, all of whom are willing to help me because of my situation (defrauded on the car, dealership told me it was a 350, but thats another story) so I'll have to get with them and play around with some configurations.

I'll check about using the vortec retainer, thank you so much for your help.

edit - haha, I just checked the cost of vortec valve spring retainers. 3.62 list price, my employee price is 1.97.