ok, heres what i'm looking at. i have an s10 blazer with an otherwise bone stock l03 in it. over the last month i've been searching this site exhaustively for any and all information i can get on the l03 in stock form. the numbers are sickening. i have the stock manifolds on the truck now and i somehow managed to get another set of stock manifolds off of another l03. no idea how i got them, but i got them.

i read in a few older posts that theres 2 different size exhaust manifolds they put on these motors, the 2" collector versions and the 2 1/4 versions. so i measured the collectors on the set i got down in the basement. 1 7/8".

thats beside the point. i can get a set of the better flowing manifolds for next to nothing. so when i do get them i plan on porting the everloving snot out of them. so my question is how far can i port these things out and not have them crack?

yes, i know the manifolds suck. problem is, i'm limited as far as exhaust is concerned. i have a t5 installed in the blazer and headers just wont work without alot of modification. the LH collector on the header will run right into the slave cylinder. that being said, manifolds are $5, i already have the tools, and time is free.



smith

 

IMO, i would go through the hassle and get the headers.. i'm assuming that longtubes are the ones that interfere with the slave.. go shorties.. summit has some that are $140.. the performance gains will be worth the trouble.. and later in life, if you decide to get more performance, the headers will already be there.. if you really want to do the manifold way, i would say port them no thinner than 1/8th inch.. make sure the flange is large enough to prevent warping when/if you take them off..

 

Because of the heat that these things endure, I don't know if it would be safe to be taking away too much material here. I know guys that have cracked the manifolds without porting.

Besides, you have to look at it this way. The amount of 'safe' porting you could do would NOT warrant the amount of time it would take to get any 'gains'. Really, cast iron is a pita to port and you will eat away at a few carbide bits easily on each manifold. I say save yourself the headache and just put them on as-is. I really don't see you putting out much more power by opening each port 3/16".

Either that or find a way to get a set of headers. You said that you didnt want them hitting the slave cylinder, would a set of block huggers work with a custom fabbed exhaust thereafter?