just talked to a used vette parts place that has a set of l98 aluminum heads off an 88 vette refurbished for 600 bucks..........he said if i get them ported it will change the combustion chamber size.....i said no i dont want to do that i just want the intake and exhaust ports smoothed out for better flow.....he said oh you want them polished then............i said ok i stand corrected.........he said dont waste my time i wouldnt notice and difference in power............any thought guys? and is he correct? and will a l98 head flow a great deal more than a stock iron 305 head in a firebird if i dont touch them and just bolt em on?

 

you can port the heads for the intake and exhaust, I think they will support 400 to 450 hp if set up correctly. I will tell you, don't polish the intake too much there is a such thing of it being too smooth and messing with the mixture going into the chambers. If you clean up the combustion chambers it will not hurt the compression as much as you will gain by cleaning them up.



Brian

 

Wasp,

O.K. I'm only a little confused. How is opening the intake and exhuast ports going to alter the chamber volume? You will alter the port runner sizes, but that's the whole idea of porting.


Better yet, how are you going to fit L98 heads on a 305 without valve interference and shrouding? Or did I read that question wrong?

 

WASP,

If this guy tells you that porting your heads changes the combustion chamber size, please take your heads elsewhere.

 

Agree, guy sounds like a moron. The only way porting could be considered to change chamber volume is if you include unshrouding the valves, which isn't really necessary on those heads as I recall. There is some chamber work involved in a good porting job, that and polishing the chamber could theoretically change the volume, but typically if done right it's only 1-2 cc's and the improvements are well worth it. Besides, for a 305 get yourself a set of World torquers, they'll fit, and wake up the 305 pretty good. and cost about the same for a brand new set of heads.

 

Through the laws of fluidynamics, there isnt a whole lot of flow to be gaint through polishing the sides of the intake runners. The surface friction between the air and the metal is not as lrge as commmonly believed. 1-3 cfm only. Enlarging them or changing their shape has a far, far greater effect.

Polishing the combustion chamber does increase horsepower noticably, as well as reduce detonation. But thic would hardly increase the combustion chamber size, so I dont know what he was saying there.

 

hey vader, ive been told that the l98 aluminum heads will work on my 305 since they have 1.94 intakes and 1.50 exhausts.........and yeah i was just seeing if what he said was true........i may buy the heads from him but i wont get them done there thats for sure, thats why i posted this i didnt think getting your heads ported would "screw up your compression" as he put it.............as for shrouding im cluless fill me in, its the first ive heard the term

 

are they aluminum?

 

bumpsville

 

Wasp,

You can get aluminum replacements for the 305, with larger valves and no significant shrouding. The valve positions are moved inward slightly on the S/R heads to accomodate the larger valve faces without the heavy shrouding at the outer valve edges. They already have improved port designs, too.

You can fit 1.94 intakes in 305 heads, but there can be some shrouding issues. The spacing on the 350 heads may make the shrouding or even deck interference a real problem.

Measure twice, cut once...

 

sorry vader but i dont understand........what does s/r mean? and what i gather from what your saying is that i can get aluminum heads with bigger valves that will work? noone makes aluminum heads for a 305 that i could find, ive been told my only option is the l98 heads and yes they are 350 heads going on a 305 what is shrouding issues? i thought as long as the valves didnt hit the bore id be ok.............and from what intelligence ive gathered ,hehehehe..........1.94 in and 1.50 ex is as big as a 305 can take..........wrong or right? i want to talk to as many knowledgible people b4 i make a purchase thats for dam sure...dont want my motor apart and find out the heads wont work

 

bump me

 

OOPS! The S/R 305 (stock replacement) heads are only in cast iron, not aluminum.

You can get aluminum heads to fit, but you may have valve shrouding issues (the perimeter of the intake valve is so close to the chamber or cylinder wall that effective flow around that side of the valve is stopped). Anything over 1.94 intakes in a 350 head on a 305 bore could create a clearance problem.

 

ok ill post a follow up to this then thanx v

 

zzzz