I know that there was a thread about this somewhere in the past but I cant find it, basically I need to know what the mods are to get the aluminum heads from the L98 to bolt up to the 305, thanks.

 

Well the D-port (113?) L98 heads use the pre 87 bolt pattern so your going to need an intake to fit.

 

Yup also dont forget that there is no provision for EGR built within the head, so either you have to change the PROM or use an external EGR setup.

 

The combustion chambers are a little bigger than your stock ones. 64cc compaired to 58cc so your compression will drop a bit.

 

IIRC, Al L98 heads have 58cc combustion chambers.

 

you are correct, 58cc. good head for the 305 IMO.

 

Only the aluminum L98 heads were 58cc. The cast iron were 64cc.

https://www.thirdgen.org/techbb2/sho...n+chamber+size

 

he is talking about alum. heads, he said it right on the second line of the first post.

so yes, the heads in question do have a 58cc combustion chamber.

 

Al = aluminum

 

My bad I read that wrong. I thougth he was talking about the stock cast iron ones.

 

Yeah but do you have to make any machine modifications to the heads to use them, or are they bolt on? Thanks.

 

Yes the heads are a bolt on. The only modifications you have to make are to the inner four bolt holes on your intake manifold (if you use the stock or a 87 and up intake). You will need to elongate them so the bolts will line up correctly. If you plan on using an aftermaket intake then just get one for a 86 or older sb chevy.

Steve

 

Does anyone have the specs on the limitations of the valve lift before the valves would interfere with the cylinder bores? I'm hoping to use a zz4 or similar cam in my build. Thanks.

 

I Do know I have been told that a larger than stock (ie. 202/160) valve will not work with a 305 bore on the 113 heads. Any imput?? Ive never bothered to check it out myself.

 

Do the heads with a performer (or EPS) intake (needs adaptor plate), and an lt1 cam or slightly larger roller.

 

i beleive that 1.94/1.5 valves will work on a 305.

BUT, i have a VERY long conversation on valve sizes with Harold Brookshire from Lunati (and formerly UltraDyne Cams) when we were picking cams for my 305 build-up, he told me with his cams, to stick with 1.84's on the 416 heads, he said there would really be no gain, and maybe even a loss from going to 1.94's. he said it had to do with the actualy flow of the ports vs the valve size, and the exaust flow. said with the 1.84's on mildly ported 416s will keep the intake velocity up, and having the valve not so close to the cyl. wall, it should actualy give me better real world HP numbers than the 1.94's. especialy considering most of us 305 guys are not trying to make our power at 7k, we are generaly looking to keep our torque up.

 

Valve size depends on a few variables but the single most important one for measurable differences is the matchup between port cross sectional area and valve diameter. Then comes the cam lift, yes, too much lift won't hurt but you can't gain anything if the port is already small. Then comes the shrouding, it's very small. Take a look at any new engine with roof (4 valves per cylinder) style heads and tell me about this "shrouding." I seriously think it's a myth, no hard evidence has been presented to me to prove otherwise... unless somebody has some reasearch? So yes, smaller valves can be fine. Just look at vortec heads. They've been tested very frequently on countless dyno flogs and guess what, size doesn't matter if stock ports. Open up the ports and then open up the valves. A good way to understand it is that a poppet valve will flow ~ 80% of the cross-section of the port. So if you have large 200cc + intake runners it's safe to assume you'll benifit from large valves, 170cc and less, likes the 1.94/1.50 combo, although 1.94/1.60 is usually better just because the exhaust ports on sbc's suck.

 

They will work. I've mocked up a bare 305 block with 2.02/1.60 heads (TFS 23*). Valve-block interference will roughly occur at lifts of .600"+, however the TFS heads do have better valve centerlines than a GM casting 2.02/1.60 I would imagine.

 

So basically what I'm getting from this is that I can use any small block heads I want so long as they have around a 58cc combustion chamber and the valve sizes dont exceed 2.02/1.60, however I would probably benefit from staying with the valve sizes I've got now except maybe for a slightly larger exhaust valve, right?