will i have any problems with running 2.02 int. and 1.60 exh. on 081 heads on my 305? i see alot of 1.94 int. but i havent seen much 2.02 int.

 

2.02 and 1.60 is a tight fit in the 081 chamber and the 305 bore, I would even go as far to say its not really worth the efort unless you open the chambers up some then mill the heads to bring the CC's back down and notch the bores in the block using a head gasket as a temp plate and make you do don't take them down in to the ringland.

 

does anyone know anyone thats ran big valves like this with a 305?

 

Nope. From what I understand those valves are too big and will hit the cylinder walls in a 305 since the bore is so small. Have also heard the 1.94 is the max in a 305 for the most part.

 

since the heads already have the 2.02 valves. what do i have to do to put the 1.94? or am i pretty much screwed.

 

Yes you MAY (not necessarily WILL) have problems.

A valve that large MAY not be over the cylinder at all; but rather, might be above the block deck. A valve smacking into the deck could be considered a problem by some people I suppose, including myself.

Even assuming that the valves fit, physically, there's still the issue of bore shrouding.

Imagine if you will, a head with only one valve, and the same bore as a 305 (3.736").

Imagine that this one valve is located dead center in the bore, and is 2.02" diameter. Open it. See how much space there is all the way around the edge of it, for air to go around the edge and get into the cyl?

Now imagine that this valve is 3.5" in diameter. Should be good for LOTS more flow, right??

OK, now open the 3.5" valve into the 3.736" diameter cyl; and look at how much of a gap the air has, to flow through to get aroung the edge of the valve and into the cyl.

Did you actually improve the OVERALL flow by increasing that valve from 2.02" to 3.5"?

That's exactly what happens (one of the things, anyway) when you put too-big valves in a set of heads. The whole side of the valve that's next to the bore, gets blocked by the bore; so the larger valve actually flows LESS than the smaller valve. Flow bench numbers won't show you that, unless the bench uses a cylinder to simulate the bore.

And even if they do, there's a fair amount of tolerance in where the valve ends up, in relation to the bore, once the head is installed on a block.

You don't actually have to "run" the combo to see why it's not a real good idea.

Try bolting a set of heads up to a 305 block with no pistons in it; and see how much clearance you're working with between the valve margin and the bore. Most likely you'll stop looking for somebody that's "run" that combo, because it'll be REAL OBVIOUS to you RIGHT AWAY, why there aren't too many such people.

 

now heres the question since the valves are to big. can i go a step down put 1.94 in them. to do that all i would have to do is replace the valve seats right?

 

probabily, to grind a new 1.94" seat where a 2.02" seat is now you would have to really sink the valve in the head.

I'd start with another set of 081's and put 1.94's in them for a 305. Sell your set to someone with a 350.

Or bore your 305 at least .060" over.

 

i'm guessing no machine work has been done yet, and they still sport 1.84" valves.

So yea, put in 1.94 undercut valves in, and do a 3 angle valve seat in the heads.

 

Well, there's not much "guessing" to be done there.... if of course this is true.

I agree with F-bird88; those heads sound like they've been sodomized too far for repair, for your application. The correct course of action would be to find yourself a "greater fool" to sell them to, locate yourself an unmolested pair of them somewhere else, and do the right things AND ONLY THE RIGHT THINGS to them.

1.94" intakes are PLENTY for virtually ANY 305. And they are CERTAINLY plenty for any 305 with TBI, or any other stock or near-stock EFI system.

 

 

would it be possible to just put new valve seats in and go from there? id much rather top fix them. because the local junk hard doesnt have any 081 heads in. and when they do get heads they normally leave the engine assembled and sell the whole motor.

 

A picture is worth a thousand words . This IS an 081 casteing with a 2.02 valve set in it . LOTS of shrouding there

 

ok i now realize i made a mistake in buying a these heads. now is there any way i can fix them rather than just sell them. i know of a really good machine shop that i go to when im home. would they be able to do something with them.

 

It's possible that they could replace the seats.

That's not real cheap though.... probably cost more than what it would take to replace the castings.

Somebody with a 350 or 400 would probably pay extra for those "202" heads, compared to what you'd have to pay for other castings. I really think you should try to sell them.

In fact, I'd suggest offering them to your machine shop, as a trade for the right ones. I'd bet they could come up with unolested ones easier than you can, and sell the others to boot.

 

thats a good point. ill see what i can do with them. when i get down the road. or maybe ill save them for when i start building a 350. got to love being a beginner.

 

could i use these heads on a 350 without any problems?

 

Yes ... but.... If you want to see the flow benefit of the larger 2.02
I would recommend doing some deshrouding on the chamber wall mostly on the intake valve side of the chamber near the spark plug. The 081 (305) 's chamber is smaller to suite the small bore 305 and the smaller 1.84" intake valve.

Just installing a 2.02 valve makes the valve edge much closer to the chamber wall actually decreasing the available flow window between the valve edge and chamber wall as the valve opens. So the cure is to lay back and radius the chamber wall near the valve edge.
Does not need to be done equally all the way around the valve. But there are critical high flow areas near the spark plug side that need attention.

Then, you end up with a good head for a 350 or other engine with a larger bore than a 305.

If/ when you go to prepare another 305 casting for larger 1.94" valves you can employ a little deshrouding around the chamber near the valve also. The amount of material that needs to be removed is small but critical.
Not hard to do. All part of porting the head.
But stick to a 1.94x 1.5" size limit for a 305"s bore.
Once you've ported the head and deshrouding a little you'll have a very nice performing head for a 305.

 

Didn't one of the guys here put 1.94 intake and 1.6 exhaust in a set of 305 heads, and it worked well?

 

yah i'm curious about a 1.6 exhaust valve on a 305, i'm planning within the next few years to build a max streetable powered 305. I'll be stroking it and sinking as much compression as i can in to it to still run on pump fuel and going with a fair size cam and ported vortec heads planed for my application and was wondering if a 1.6 exhaust valve is something i should look in to or not..... BTW if this will shroud the valve any that's not a big deal i've got a diegrinder and can take some material out(yah yah i know 305s are dumb to build up and have tiny bores and to long a stroke blah blah blah).

 

Is it possible to only put in 1.94 intake valves, not touch the exhaust, on 305 heads?

 

yes LB9, and very common.

 

There was someone who posted last yr who said he's running them.
You might try a search and PM the guy, if you can find him.
You'd have to grind the top of the block for clearance where the int valve is close to the edge of the bore.
It's pretty easy to do.
Big blocks come that way stock. It's not going to hurt anything.
2.02 valves in a 305 isn't something that a knowledgable builder would intentionally do.
But if you just gotta use those heads...https://www.thirdgen.org/techbb2/sho...hreadid=221370

 

thanks for the link. i think i might try to put these heads on my 305 and see what happens.

 

make th etrip to columbus and pick up a pair of #601 heads(totally bare!) for free!
p/m me
Eric B

 

ohio is a little to far away for me.

 

if i ran these heads with 1.6 rr, what size cam can i run.