Hey, whats the most i can mill down my 305 H.0. heads to still run pump gas? I also have a holley high rise dual plain Intake, Holley 600cfm, headers, Mallory distributer with 50,000 volt coil, and crane high lift cam (ya very vauge, but its a budget rebuild, and my buddy had a cam laying around, and all he knew was its a "high Lift"). I also plan to port and polish the heads and intake.

Any help i can get is appreciated, so thanks in advance.

 

Just to make sure you're aware, there are no differences between the HO 305 heads and the non-HO heads. Same casting.

With that being said, I'm not sure how much you can mill them.

But, are you doing anything to increase the lift capability of the heads? Or are they remaining bone stock? If they are remaining bone stock, and even if they aren't, you may just want to find out just how much lift (and duration and whatnot, but lift is the thing in concern) that cam really has. Factory heads have trouble dealing with anything roughly over .480" of valve lift. Anything over that and you can run into clearance issues between the guide boss and retainer. Not to mention, factory springs, in no way, represent a performance piece.

 

it'd help if you knew what kind of pistons you had and how far in or out of the hole they were.

 

Ok, im using stock pistons, and i dont know the cam specs (still)
but i did just look at it before putting it in, and it think its a crane 100052cd. Other than that, dunno.

I thought the 305 and 305 H.O. heads were diffrent? I thought the H.O. had a smaller combustion chamber, and thats what made the compression jump

Well if thats the truth, i may as well just rebuild the heads i got, from the stock 305. they need milled too, but i just figured it would be better to use the H.O. heads from my old engine.

What can i do (Cheaply) to increase lift capabality? I dont have much money left.

Thanks

 

No, its the pistons that make the compression between the HO and non-HO. Non-HO uses dished, whereas the HO uses flat top.

<A HREF="http://cranecams.com/index.php?show=browseParts&action=partSpec&partNumber=100052&lvl=2&prt=5">This is your cam</A>. With that being said, make sure you check clearances. It looks like it should fit under the stock springs. And doesn't appear to be anything to radical.

 

what was the lift on that one? I could not find it on that page. Thanks again.

 

.454 @ valve with 1.5 rocker ratio.

It's in the section labeled "Lift."

 

*oops

 

Are you building a 305 or a 350 ci based motor?

You can (flat) mill 305 heads down to get 50-52cc chambers from stock 58cc. These heads do not lend themselves well to angle milling because of the sparkplug position, but you can flat mill them right down to within a fraction of an inch of the spark plug boss.

More compression is better up to a point.
As to how much compression ratio you can get away with on pump gas, look for a *true measured* compression ratio not over 10.2:1. Anything around 10:1 is good.
Use 92+ octane gas and cooler non projected tip spark plugs. Like champion #RV8C.

You can use different thickness head gaskets combined with the final chamber size to build the motor with the compression ratio you want.
it's up to u to accurately measure your engines specs to deturmine what needs to be done.

Exactly what "pump gas" are you planning to use?
Not going to happen on 87 octane gas.

 

Im building a 305 based motor, i had a good block to start with.
how many thousandths is that, do you know?

I have stock head gaskets, and a pair of slightly warped heads. I just wanted to get a good idea on where to mill the heads at for best performance, because i figured it had to get done anyway.

And i dont put anything less than 92 in my baby, usualy 93 or 94, if im goin to the track. but it sure does suck lookin at the gas prices.

Thanks again kind sirs. lol.