vipershark11

iTrader: (6)

ive decided to go the cheap route and port the stock base and suppossedly the stock one is fit for my 305 so might as well use it. ive opened up where the runners meet and rounded all trasitions so airflow will be a lot smoother. i have also removed all casting flash throughout the ports. on the head end ive opened up the ports since they seem to get very small especially on the injector side. basically this side i just gasket matched it then removed some material further in to help it match. here are some picture of my progress let me know how it looks so far. ok seems to me i forgot to take pictures of the runner side which ill get tomorrow. sorry about quality i only have my phone for pictures.

1991 RS 305

I have a TPIS base on my 85 now which I ported when I installed it a few years ago. Now I'm considering removing it and doing 'touch-up' porting, since I'm seeing more about porting the TPI base lately. As time goes on, more thoughts and ideas surface about porting approaches to improve these bases. Sounds like the base is the biggest obstacle for good flow in the system.

Here is a interesting thread link below. Post #15 has a illustration of how the air flow from the runners meets the base, and how to improve the transition at that point. If the illustration is accurate, that appears to be a real hinderance to smooth flow, and an area that could be easily improved. Also, as the air leaves the base and enters the head. I bet the entire 'ceiling' of the base, not just the exit, could be ported to in effect 'raise' it to offer a better transition from the base to the head. Just need to be careful not to go through. Comments?


https://www.thirdgen.org/forums/tpi/...g+ceiling+base

vipershark11

iTrader: (6)

that airflow picture does make sense ill have to check that out and see what i can do to that.

1991CamaroRslow

iTrader: (3)

Viper, look at your bottom picture at the far right, see where the transition is from straight to curved on the inside wall it looks like this 1 / Take the bottom out of that curve to make it look as much like this as possible 1 1 This gives the air an easier transition to the heads port. Be careful not to cut through the material there but you can make it way way better. Look up T moss porting, he's got alot of info on porting 5.0 intakes that are similar to what I do with these TPI bases. Also cut out the injector port to raise and smooth out the roof. I cut that out until the injector port is just an 0 and not the funny shape it has to it. I also run LS1 style injectors that're shorter and won't protrude into the airflow path when installed. Somewhere on here I have basic pics of my porting but I'm not sure how in depth they are. Just ask if you have any questions.

1991 RS 305

Good tips for both areas. Along with what I'm seeing about the F.I.R.S.T. system https://www.thirdgen.org/forums/tpi/...ifold-slp.html , and think when looking at a typical aftermarket 4 bbl intake, its clear any TPI base, including aftermarket, have a roof entry into the head thats too 'flat' due to the low profile design to make these fit the vette and 3rd gen hoodlines. A raised entry to the head would allow the air/fuel better access to the back of the intake valve/bowl area, and then the cylinder, from what I understand.

I bet if you ported the most off the entire length of the roof of the intake possible, it would bring it 'closer' to a raised head entry like other intakes. I know an aftermarket base has more material in this area, but the stock intake leaves room for porting here, as well as the areas mentioned by 1991CamaroRslow. Even if the air never gets as nice a shot as a 4 bbl intake, opening these areas should help any TPI flow more efficiently.

This is interesting because we all talk about porting the base in general, but don't get real get specific about exact areas, and thats whats needed. Does anyone else have more pics of base porting they could post?

Orr89RocZ

iTrader: (20)

the biggest restriction is the pinch point of where the runner meats the head. that area there will yeild the best gains in flow when opened up.

If i were you, i'd siamese the TPI base an inch while your at it.

vipershark11

iTrader: (6)

i know siamesing suppossedly raises the power band up more but im looking to stay in the same power band that im currently at because ill be using 187 heads dont knock them im trying an experiment with these 2 together. basically i ported the pinch you talk about where the runners meet the base theyre just about opened up as much as id want from them which ill take pictures of in bit and post them up either tonight or tomorrow i forgot last time.

1991CamaroRslow

iTrader: (3)

Compare top ported pics to the unported lower pics and you'll see where I knocked out the restriction, also notice how much meat is removed around the injector passages.
https://www.thirdgen.org/forums/tpi/...tml?highlight=

1991 RS 305

Very good, thanks for the info. I did much of what you've shown on your link to my TPIS base when I installed it, but I'm thinking theres more I could do. I too siamesed the plenum to runner openings and siamesed / knife-edged the runners back as far as I dared. It might of shortened the runners 1 inch combined, enough to move the power band up a bit without hurting off idle.

Speaking of plenum, has anyone tried removing the divider at the throttle body opening, while keeping the standard 2-bore t-body? If nothing else, this should add a bit more volume to the plenum, which can't hurt.

jamon8

iTrader: (3)

I was thinking that I wanted to use a brake hone with some more aggressive stones to do some porting

what do you guys think

1991CamaroRslow

iTrader: (3)

It would work for the round portion of the base, and will work wonders in the runners. I did a hand port job on the runners by splitting a sanding block in half and stuffing it into the tubes then using a pair of pliers to turn them. Brake hone may work here but be careful. Really you're better off with a sandpaper flap wheel, long shank double cut carbide cutter bit, and a short rounded tip carbide cutter bit. Also when using double cut carbide bits be sure to keep grease on the tips or they'll clog up like crazy. I've also used a "rotary file" which is kind of like a single cut bit that doesn't tend to clog up with aluminum.

vipershark11

iTrader: (6)

ok i got another picture. BTW i find porting the aluminum to be a lot harder than my cast iron heads. the aluminum has melted to 3-4 of my bits making them useless. to cut the aluminum with my carbide cutters i have to use roughly 12k rpms i think my low speed is, maybe less not sure. also brick stones work well in the middle of the runners. sorry its a little rough theyre not close to being done. its on hold while the heads get finished.

1989GTATransAm

iTrader: (3)

You need to dip the carbide bit into some type of oil. A friend likes to use kerosene. I have seen a variety of lubricants used including WD-40.

1991CamaroRslow

iTrader: (3)

I use wheel bearing grease, you can literally spray out all the scrap with carb cleaner when it's over, makes the aluminum shards more managable.

vipershark11

iTrader: (6)

true but if you use a lubricant i could use my carbide cutters at higher speeds without the aluminum melting?

1991CamaroRslow

iTrader: (3)

Yes it works SO much better, the wheel bearing grease or WD40 or what not also cools the aluminum. I like the grease because it stays on the material and doesn't spray off as bad as thinner material.

Orr89RocZ

iTrader: (20)

i used wd40 and motor oil... both worked well. a grease would probly be better

vipershark11

iTrader: (6)

well that wouldve helped after i used my craftsman on low for many many hours i put into this because of the low cutting speed lol.

385IN2005

[QUOTE=vipershark11;3635209]ok i got another picture. BTW i find porting the aluminum to be a lot harder than my cast iron heads. the aluminum has melted to 3-4 of my bits making them useless. to cut the aluminum with my carbide cutters i have to use roughly 12k rpms i think my low speed is, maybe less not sure. also brick stones work well in the middle of the runners. sorry its a little rough theyre not close to being done. its on hold while the heads get finished.



Use Ferrous carbides for iron, etc...
Use Non Ferrous carbides for aluminum etc...

385IN2005

https://www.facebook.com/pages/High-...62540657151556

Eagle223usa

I used WD40 also on my carbides. You should also check out a set of Cross buffs from Eastwood for a nice final finish. My machinist was impressed!

385IN2005

See here.......
http://www.youtube.com/user/3859c1?feature=mhee