Hey guys, hope everyone is having a good day. Looking to start up a new conversation to see who is still active on the forum. It's been a while since I've been active but I recently got the urge to get back in the garage and work on the 'vette. Got a '85 z51. No huge mods, just some FIC fuel injectors from John, TB foil (lol, came with the car when I bought it), 3" DMH cutout, and a TPIS BigMouth base.

So I have a stock plenum, and runners. I have a spare set of stock runners looking to do a trial run on matching the base ports to the stock runners. Just need some guidance on measurements and tools. Been checking google and yt for some vids on how to port. But was wondering if any of you guys have any input on porting stock runners and plenum. Not in any rush to buy a set of $500 runners if I can potentially do the job at home.

Heres a list of tools I have seen can do the job
- die grinder with a carbide open flute and 80 grit cartridge roll attached to a 6" mandrel.

Any thoughts? Take it easy on me lol, im a noob but always looking to expand my knowledge on wrenching.

 

my 2-cents -- you are somewhat limited with a stock (85) TPI. best you can do - pocket port and gasket match. that will provide minimal results. not much you can do with those long, stock runners. you would also need to address those iron heads and maybe install a set of long tubes. maybe a cam upgrade - but nothing requiring a custom tune. if you're looking at you tube videos - checked out a series by "Darin Dochterman."

 

Stock runners dont have any meat to port..you can clean up obstructions on the plenum or cut the port divider wall out but you wont feel any difference.
The base needs tons of work, spend enoguh time youll get a real gain. There is 30-(40cfm if youre ocd) you can go after takes time though.

 

I used a powerful sand blaster to clean out the aluminum runners and it smoothed them up inside very nicely. I tried different grits inside of my Sandblasting cabinet and you could see the difference after a few hours of material flowing through it at high pressure. Porting and polishing is something best left to those who do it for a living as they know all the mistakes that we would have to learn. I match the gaskets and do the very best I can but I hesitate at trying to grind material away when they was not much material in the first place. I used to clean up the heads on my motorcycles with a Die grinder and the Eastwood kit with the proper parts and sandpaper rolls but those were air cooled and had more "Beef" to work with and they were aluminum. I have not tried this on any cast iron heads yet as I don't have any spare ones laying around to practice on.

I had two Cast iron heads ported and polished and they really did some beautiful work without any boo-boos. I hate to think what might have happened to them if I had tried to do it myself. "A Man has got to Know his limitations" and that is beyond MY expertise!

Best Wishes for a successful project!

 

When I did stock runners & plenum:
-smooth out plenum intake
-flute plenum opening into runner tops
-carefully knock "dimples" out of runners
-port match runner openings to intake base openings
-open up all intake gaskets so they don't intrude into air flow path

Since I used OEM base I machined into the base so each intake would pull through two runner tubes. Don't recommend that since you have a BM base already.

Main thing is to have fun with the mods.

 

I agree with Cuisinartvette....that porting stock runners seems a waste of time. If they don't still, they used to make a ball kit where you could force them thru the runners to slightly expand their diameter -- and, more importantly, remove dents. Not sure how one could apply that much force to the ***** though?

If you were really interested in gains, bigger aftermarket runners is a better bet. I know many are getting expensive (even in used form) for the gain you get, but at least you'd really be moving more air. Porting the mouth of a plenum probably has a small benefit as does any port-matching to whatever runners you choose. Porting the base is also good.

A lot of us have been here 10-20 years. We can tell you no one really tries (or has tried) to do much in regard to the stock runners. Even in testing and publicized upgrades, runners end up being replaced with something bigger/better. Porting or extrude honing a base was an option "in the day". But they also make larger-tubed aftermarket bases....even those are often ported. Plenums are about the only reused stock TPI item when looking to upgrade that config.

I'd be surprised if someone didn't encourage you to consider swapping to a completely different intake. In doing so, they wouldn't necessarily be wrong (depending on your goals).

 

Just sent my my mechanic to do the porting.
Already have AS&M runners (41mm). going to port match the plenum and the stock intake base to 41mm.
Going to smooth the ports using Brush Research BC15818 Flex-Hone 1-5/8 (41Mm)

 

I would go with siamesed AS&M runners if at all possible, then attack the base manifold and try to match the plenum to the runner inlets. Theres not much meat on the stock runners