Porting Brain Trust, Help!

[tomtom72]

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.:redface:

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
:cheers:
Tom

[LGAFF]

Primary in the head if 33......2ndry in the head is 36. Why not port the top of the head tp match? Bolt on the IH to the head, use a highligher marker attached to another hightlighter marker to reach down into the IH and mark the head port entry....it should be a cresent shape.

Tape off the area, buy a grinder or if you are really patient use a Dremel to match the port.

Regardless if you port match or not, you are going to flow better than the 31MM that the base of the IHs were as stock. You are gaining 2ndry flow as well. You can always come back later and have the heads done.

Let me know if you want to call me......Nothing to fear but fear itself. If you are going to epoxy the IHs, use the Morso product....not JB Weld.

[LGAFF]

http://www.moroso.com/catalog/categorydisplay.asp?catcode=22001

[tomtom72]

Lee, thanks for helping me out. :thumbsup:

I wish I could do as you suggest in the first part of your reply. I would take my time and enlarge the head ports' opening to match the I/H ports 36 mm diameter....but I don't own a home, so no garage and the garage space I rent I can't do anything except park.

The I/H's that I bought have been opened up to 36 mm at the openings and they look fairly consistant all the way thru the both ports, 1* and 2*. I just couldn't find any info in the FSM on what the stock size of the ports are so I could figure how much I needed to close up the bottom half of the ported I/H ports. I know that is the 1/2 a$$ answer.

Thanks for the link to the Moroso product! That may have to be the way I go if I want to use the stuff I bought. I should have thought this out more completely before I bought the stuff.

Thank you very much for your time!
:cheers:
Tom

[Ccmano]

Regardless if you port match or not, you are going to flow better than the 31MM that the base of the IHs were as stock. You are gaining 2ndry flow as well. You can always come back later and have the heads done.

:iamwithstDon't bother to re-narrow the IH's, use them as is. Not ideal, but you will still be better off than stock. Then just go back and port the heads later.
H
:cheers:

[tpepmeie]

Way back on my '91, I had Greg port the plenum and housings and used them on stock heads. There was clearly a step at the head/housing interface, which is not desireable. Nonetheless, the ill effects were not significant, as the car still did 380 rwhp in that configuration. Bottom line... it'll work. Do the heads later on.

todd

[XfireZ51]

:iamwithstDon't bother to re-narrow the IH's, use them as is. Not ideal, but you will still be better off than stock. Then just go back and port the heads later.
H
:cheers:

During one of our FBI Pizza nights Marc H. asked if I had port matched the heads when I did the P&P. I told him I had and he mentioned that it was worth about 5 rwhp by doing so.

[tomtom72]

:worship: to the Porting Brain Trust for helping the port-challenged among us...namely me!:mrgreen:

I want to make clear that I know beans about the science and art of porting an intake system. I just figured that with so large a miss match at the head port, that I actually would wind up with a net hp loss because of me not thinking this purchase thru to it's logical conclusion.

Thank you Gentlemen very much for your assistance to the non-cognicenti!

:cheers:
Tom

[Pete]

Tom,road trip to Lee's house next weekend :)

You can meet the FBI group.

Pete

[65ZR1]

I wouldnt use any product to narrow the ports back down. Except for welding, there is now way I would trust the filler to stay there with the gas, air, heat and vibration. Just think of what that stuff would do if it ended up in the cylinder.

[Paul Workman]

I wouldnt use any product to narrow the ports back down. Except for welding, there is now way I would trust the filler to stay there with the gas, air, heat and vibration. Just think of what that stuff would do if it ended up in the cylinder.

Amen! :iamwithst

Fer sher, I wouldn't use JB or anything else but welding. But, you will end up with a net gain regardless. If you have a die grinder, you can radius the edges of the primary ports on the heads - take less than an hour, and it might be worth a few extra ponies to boot?

P.

[Locobob]

I agree with pretty much everything that has been said here. Using metal filler would be a huge/ugly job and would likely result in pieces flaking off and falling into the cylinders - don't do it. If you can find someone to help you out the best bet would be to port match the top of the heads. If not then just bolt up the ported intake and be happy - it will still be a big net gain.

[tomtom72]

I want to thank you all for showing me the light. :handshak:

I'm not going to close up anything using filler.:redface:

I may just bolt on the stuff I have and see how the motor behaves.


Pete, that would be a sweet weekend road trip. I'll have to do a mapquest and see what I can figure out....it would be sweet to see how the FBI does things and meet all of the brothers out in that neck o' the woods.

Again, thank you guys for saving me alot of potiential grief down the road!:thumbsup:

:cheers:
Tom