Okay here it is,
I have seen posts about 2.02's not working on 305's without cyl.wall work and couldnt understand because I have been running them for 4yrs in a standard bore 305. Here's the info,
casting # 3998993
(mortec description ....72-73...307/350......75cc chambers
....current..350.........Goodwrench crate motors,"Hecho en Mexico",75cc chambers)
I am using them on a blown motor so the 75cc is good for me. I bought them used and with the machine work already done but this is what I know they are opened up to 2.02/1.60 ported and pinned and they work in a standard bore 305 with no machining to the block

 

How much lift are you running. If your running low enough lift there is no potential for interference because the valve never reaches past the deck.

 

I dont have the exact specs for the cam, I installed it in 1986 and it was the B&M blower cam for over 7lbs of boost, I do know it was around 500/500. I also checked the valves before I installed the heads and without the spring installed you could push the valve in well past any coil bind

 

lift and squish would be two big parts of the equation you're

 

ede, care to finish the rest of your thought on the matter?

Steve

 

Even if you get he vavles to work you will have major shrouding problems. A Smaller 1.94" valve will work better and probably male more power.

 

Ok I will try to make this more clear, it isn't if they will work, they have been on the car for 4 yrs and I agree about the shrouding but I had a pair of (3927186....69-70...302/350......Camel hump,64cc chambers,accessory holes) 1.94/1.50 that had manley s/s valves, on it before the 2.02's and it is making much more power now even though I went from 64cc to 75cc must be pushing more volume past the larger valve

by the way I was waiting for ede to finish too, figured he must of needed a nap lol

 

Two words - Perimeter Shrouding.

Not to even try to put words in ede's mouth, but I believe what he was trying to convey was that if the chambers are large you may be able to operate the larger valves in a smaller bore engine, since the valves ar maximum lift are not interfering with the block deck. A 76cc head just might make it on that engine. If the engine was built for blower duty, you would likely want larger chambers to control ultimate compresion pressure.

With smaller chambres, provided the deck has been relieved properly to prevent interference, you could run the larger valves but would likely suffer serious shrouding.

To answer your question more thoroughly would require more information from you. Head castings? Peak valve lift? Chamber modifications? Valve installed height?

 

ede is talking like Yoda again.

"Not if lift the valve is too much engine for your"

 

I have a head shop 4 doors down and have been over this with him a few times in the past, here is what i have learned from his 30+ yrs of doing heads.


350 heads any valve size (i didnt ask about larger than 2.02) will work on a 305 as long as the max lift isnt over .490 ish (cant remember exact number offhand) or the valve will hit the deck since the 350 chambers are setup for a 4 in bore and you have a 3.75 basicly.

305 heads can handle max 2.02 intake valves and he has installed them into 305 heads , but he says it weakens the head in his opinion and he would prefer not to go over 194/160.

 

A long time ago in a galaxy far, far away...

Somebody posted a picture looking up the bore of a 305 with 2.02/1.60 heads bolted onto it (no crank/pistons installed, obviously). You could see the entire valve of both the intake and exhaust.

However...

The shrouding of which Mr. Darkside spoke was certain perceptable.

Now, on the other side of the coin...

Back in the old days, our good friend the General notched the top of 396 cylinders so 2.19" intake valves wouldn't wack the cylinder wall. Somehow, nobody worried about "shrouding".

I'm sure there's a technical explaination why BBC valves aren't affected by shrouding, but SBC are.

 

i have a junk 305 block with some junk castings on them.... i donno the valve size (this is just a mockup block/heads) but the heads are assembled.

the valve smacks the cyl bore...

i should take some pics to show.

 

You should.