would i see any improvements if i ported the stock plenum, intake and heads if so how much horsepower over stock.... is it worth the hassle, i dont want to buy a new intake and heads because i want everything original execpt for the cam.... it would be going on a nearly stock 350 gta with stronger springs, AFPR, slp intake, crane 2032 cam, hedman long tubes, full flowmasters catback with high flow cat... also would i loose any bottom end power... cause i dont want to loose that...

 

Do a search! This has all been talked about many, many times.

 

haha in a nutshell.... porting the plenum/base will help slightly, take out the EGR walls behind the TB. but u wont get alot outa it unless u really port the hell outa it and upgrade the runners etc.
porting the heads will give u prob 20 hp maybe and add 1.6rr and thats like 10, porting the heads will help along with the intake but the heads will limit your power along with the intake. ur peak hp will peak at 4800 even if u port alil u wont increase it much.

 

well im just tryna get the most i can get out of the stuff that ive got... 20 horses doesnt seem bad at all from just porting...... if i port all of that stuff would i feel the difference....

 

Seems like an easy place to gain knowledge, but the bottom line here is that many people have different opinions, and the combinations of components are endless. Not just a specific pair of ported heads, but how they were ported. how much is going to be removed, will pocket porting be done, 3 angle valve grind? are you going to port match, are the inner exhaust runners being radiused? People will try to give you a general rule of thumb, and that's usually the best anyone could hope for. There are too many contributing factors.
I agree that removing the form walls behind the TB (inside the front of the plenum opening) is a good idea. Doing one thing isn't going to amount to much, it's once everything is done (porting the entire plenum i.e. obstructions behind TB, raised beams in between runner ports, matching the port openings, to the plenum, port matching the intake base to the ported and polished heads etc etc.) I will say that the intake base is known to be restrictive for a 350. Sounds like the vortech heads and matching intake base is a good start, then port match all that. I know the mini ram plenum and runner design suffers a bit down low, where the vortech base and heads do very well. Mini ram does better up higher in the rpm range BUT the TPI wasn't meant to be a high reving machine.

 

aS 1987camaro... said it really depends on the port job, the money u would spend with the heads, porting, portmatching, 3 angle valve job and prob a fresh set of springs... ur basically rebuilding the head and therefore $$$, as much as it costs for rebuilding stock heads u can basically almost buy new heads, u have alot of posts goin on here and all are wanting or asking something different. there are too many contributing factors, whos porting the heads? how much are they porting, etc

the base of the TPI is the most restrictive part of the TPI for a 350, the base was not designed for the 350 but the 305 which doesnt flow nearly as much as the 45 extra cubes 350. the base and runner upgrade on stock heads will net 20-25hp, of course porting the plenum helps when the runners/base have been upgraded.

20hp u could feel but its not gona be seat of ur pants, its gone feel like its got more pep.

mini rams are INSANE CRAZY REVERs, those things are meant to be pushed to 7000rpms and beyond, they have no low end bc of its incredibly short runner design, even shorter than LT1's. and upgraded TPI is good to about 5200, then porting u can get 5700 maybe 6000 if its heavily moddified and ported, the next step is the HSR which will pull to 6000 no prob and the runners are long enough to keep a good percentage of the low end torque that makes the TPI so much fun.

 

I appreciate your desire to keep everything stock looking; however, you have already lost that with the modifications you have made. Nevertheless, if you want to stay with the heads you have - if you have the swirl port heads it is probably not worth taking them off to port them. Also, what is your skill and knowledge level in doing machine porting work to engine heads? While there are lots of good articles out there to guide you it is easy to remove too much material and ruin the heads or break through to a water passage.

I recently posted my experience and the costs to port the TPI intake on my 5.0 litre. I thought of going down into my heads and hiring someone experienced in doing this to port the heads. Once the heads were off he was going to charge about $150 per head, which I understand is quite cheap. I came to the conclusion the added expense to remove the heads and hire someone who knows what he is doing to port the heads was not worth it. It would have been more cost effective to buy new heads.

There is not a lot of porting available to a stock intake manifold and runners and they are a little under designed for your 5.7 litre engine. Porting out the plenum is definitely worth it. There are at least three articles around on how to do this. Then if you want to install new heads, intake manifold and runners later it will build on what you have already done.

I noticed a large difference when I had my plenum ported, but then I had a Holley AFPR regulator installed and replaced the original injectors which had over 200,000 km on them.

You mentioned you have installed an AFPR, how are your injectors? Maybe time to get some new ones like I did. However, you would not want to replace them with the stock GM injectors so your car moves just a little further away from being stock.

 

There are lots of heads available, especially for the 350. BC GTA made good points about the effort and expense to have your stock heads machined. between removing the heads, having new valves, springs, retainers, keepers, seals, etc replaced, all the machining for a shop to port and polish the heads, it's not usually worth the bother and expense. The aftermarket head manufactures know this, and have their heads priced well to discourage peeps like us from machining our stock heads. Don't get me wrong, it's a great experience to do a DIY head work over, but do you really trust yourself in the machining. I've read that differences in flow between runners could hurt performance. I've done porting and polishing before and i can say that i had no idea how close i was in flow #s between the intake and exhaust runners. I'd have to have someone test it on a flow bench for me, and I don't know anyone that could do that for me without charging. I guess more reason to consider aftermarket performance heads. I'm considering the 305 torquer s/r WP heads. I wish they had an aluminum version with the same 58cc chambers.
ANyway, back on track here. I think you would have to know your car very well, to notice a 20 hp increase. That's at the begining of the noticable (seat of your pants) range I think. There are lots of great articles out there that GMHP and CHP has run. Do some searches.