Porting Brain Trust, Help! - ZR-1 Net Registry Forums

tomtom72 · 07-25-2009

Okay, so I'm not the sharpest knife in the drawer....I bought the 91 Plenum & I/H's from Andy that were ported already.

I measured the openings of the ports, as best I could with my sliding scale, and they are 36mm more or less maybe + / - 1 mm.

My first Q is the stock head port diameter on a 90 head is what? 33mm on both ports, on the primary port only, or am I waaaay off base with my numbers? I looked in the porting threads here and came up with the 33 mm number.

I looked in the FSM and can't find a number. I measured a set of I/H gaskets and come up with about 33 mm.

Second Q, as it is obvious even to me the 36 going into a 33 isn't gonna work. My soloution is to use something to re-shape the lower half of the I/H ports so I can get down to 33mm. Maybe starting just below the injector boss? I was gonna use a filler by JB weld. Or make my own epoxy paste from stuff I know how to work with from the marine supply store.

Or, I should just stop now and sell the stuff I bought, because I should have known better! I can't port my own heads, I can't even pull my own heads...it's just not an option for me now.

TIA

Tom

07-25-2009	#1
tomtom72 Join Date: Dec 2004 Location: Jacksonville, FL USA Posts: 4,609	Porting Brain Trust, Help! Okay, so I'm not the sharpest knife in the drawer....I bought the 91 Plenum & I/H's from Andy that were ported already. I measured the openings of the ports, as best I could with my sliding scale, and they are 36mm more or less maybe + / - 1 mm. My first Q is the stock head port diameter on a 90 head is what? 33mm on both ports, on the primary port only, or am I waaaay off base with my numbers? I looked in the porting threads here and came up with the 33 mm number. I looked in the FSM and can't find a number. I measured a set of I/H gaskets and come up with about 33 mm. Second Q, as it is obvious even to me the 36 going into a 33 isn't gonna work. My soloution is to use something to re-shape the lower half of the I/H ports so I can get down to 33mm. Maybe starting just below the injector boss? I was gonna use a filler by JB weld. Or make my own epoxy paste from stuff I know how to work with from the marine supply store. Or, I should just stop now and sell the stuff I bought, because I should have known better! I can't port my own heads, I can't even pull my own heads...it's just not an option for me now. TIA Tom __________________ 1990 ZR-1, Black/grey, #2233, stock. ZR-1 Net Reg Founding Member #316 & NCM member