what is th emaximum lift on a set of heads off of a 87 305 with a carb? I know that's not super specific, buty its the best I can currently do. I'm looking to put a cam in and port the heads and thinner head gaskets. It's a super low budget job since the engine is coming out in 2 months.

 

could be anywhere from .45-.55

God only knows...

A casting number off the head may help a bit to narrow the playing field but on the same head without any work done to them you can find large variances in the valve guide heights. you will have to pull a head apart and measure EVERY guide to make sure you will clear.

 

so the guides hitting the retainers is the first limiting factor?

 

the only factor.


unless you plan on using them on a 305 again, in which case your valves are going to smack the cylinder with too much lift.

 

if you're upgrading the cam, and that's why you're asking this, pick a cam below .5" lift. (probably the area you're in anyway). Somewhere in the .470" range.

assemble it all up, measure clearance between retainer and guide boss. .060" I think is the accepted safety margin. Then you can either chance it, if you have less than .060", like .040" probably wouldn't be life or death, or you could just get .050" offset locks. May need to re-shim your springs. Cheap, easy solution.
oh yea, get new springs with a new cam.

 

vortecs have a retainer to guide interferance problem aroud .45 other wise the pull out studs become a problem around .47 as do the spring seat diameter at .47-.5. regardless of waht lift you go to you should get rid of the pull out studs and the factory springs, retainers, and rotators.

 

Okay, I'm looking to keep all of that stuff- as I said this is a budget project for 2 months- the only reason I'm doing it is to teach my brother how to port heads and install a new cam and intake. I know this is being cheap and cheap almost never equates to good performance, but its a 305, not worth spending money on when I have a 350 Olds engine being rebuilt to drop in.

Basically I want to know if something like the summit 1103 can absolutely needs new springs, if so I'll go smaller.

 

you need new springs if you do anything. factory springs aren't good for much and used factory springs are even worse. if you're teaching someone to port heads you don't need springs at all, use a spare set or spare head and just throw the heads away when you're done or save them for a later project

 

I understand your way of looking at porting, but since this will be his first major car project I would like to give him some fruits of his labor to enjoy, besides installing the heads and intake and cam or a POS 305 would really e a good way for him to learn the ropes- no risk of loosing anything of value and still has some visible results. I've got a few other engines to chose from which will replace that 305, but for now I'm wanting to just give my little bro a place to start, and for the expierence I consider a $50 set of springs, a $60 cam and $50 worth of gaskets to be a good investment- besides I'm sure I could always sel the engine for $200 or throw it in something else.

 

Before you do anything.. the right way to do things is get you heads flow tested. Again what do you want to do with it? By geting your cylinder heads flow tested you can see max cfm flow for intake and exaust at what lift.
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Bowl blending is fine for porting. Be careful when you really start cutting in. You can reduce flow.

 

ap, I know exactly what you mean.

I think some people can grasp what you're going for now, and give advice on that, a learning experience is the best way to do it (you always screw up your first one, best to not waste a ton of cash.) Your time is free/cheap, so spend more time than $$$


read f-birds posts in the past, he doesn't like to throw good $ away, and has many good tips. hint: $3 outside caliper (the old school caliper), is good to measure wall thickness. A garden hose (free) will help show you where to port more, and where to not waste time. A 5/16" rat tail file ($5) can help smooth out surfaces etc. Use a 6" long, 1/4" ball nose cylinder carbide cutter, if you're only getting one. (carbidebur.com)
Sharp tipped ones don't cut well on the nose of it, which you'll need to use, and a 6" long one will get into all the deep places. The thinner end 1/4" vs 3/8" helps you get the sides of your guide boss. Try hand back cutting your old valves for a extra few CFM. Pin your rocker studs (drill bit and roll pins are cheap, and give peace of mind, PM me your address if you want me to send you some, i've got gobs of them).
if you want any more tips just ask.