has anyone tried siamesing and radiusing the plenum ports with stock but ported runners? (seen it with slp's but not stock ones, looks like possibly better velocity on the stockers but a lot of work) and how about the same with the base runners? sounds/looks feasible as long as you radius the runner openings on both ends as well. just wondering if anyone tried this and what was the outcome? more power? or did you get ses codes all over the place? not a new idea but everyone seems so quick to spend tons of cash on bolt on cure all's, instead of working with what they have. maybe i just stick to the old ways too much? thanks

 

We're in the same boat, I could probably afford a $400 pair of runners and another $1500 for a set of heads etc. No way, I don't plan on a 11 second monster but I will go the fastest I can using stock components (modified of course.) I also plan on porting the hell out of everything and getting larger valves, I will then be satisfied AND my car will hold high appreciative value a few years down the road. I am still curious how much difference the porting on stock components actually makes. It sounds like a good idea to me either way, go for it man!!

 

hey at least someone else is thinking. i figured if you port the hell out of everything, then maybe the biggest TB you can get, a cam and maybe some better (still oem) heads . a 305 should be respectable until you either build something else or you decide your happy with what you have. gee from responses i dont think too many people have even gotten into these motors to see whats possible with mostly stock parts. they seem to go with the "it's good or it's crap" crowd and dont take the time to learn things for themselves. but then again it's a board for ya. i know some have and either they arent talking or most people think their full of crap so their tired of preaching. we'll see.

 

If you do not do a big head and cam change as well as in take I wouldnt waist the cash on a big TB if the ram jet 502 can use the stock TB then that will be plenty for what you are doing got Andria Skuliet hope Ididnnt goof his name up to bad and he does porting for tpi sytems and gives his performance gains with just porting the intake and doing the free mods. As far as heads go I would look in to that hard before you spend the cash on bigger valves and a three angel valve job if you do the porting and polishing of the heads your self and then pay some one to to the valve you can almost guy a set of good aftermarket heads or at least a set of L98 vett heads used from some one most people doing what you are doing just have a three angle valve job done here that will cost 150 buy its self and then port and polish them your self and if you do go to a bigger cam and you have to change springs that $75 to have the spring seats cut. Try dan burks sit for the head porting on a 305 he has lot of info for this along with more info on intake porting wish I was at home so I could give you the links to their sites. Hope this helps tha tis how my firt engine was built I used a stock 350 with a fresh rebuild and a take of zz4 cam from SDPC I used a set of 305 heads off of a 87 transam I had a three angle valve job done on them bought a set of comp cams springs that would work with that cam and I didnt have to have the spring seats cut and I did the port matching and polishing my self I also ported all the tpi stuff the car did vary well compared to stock but it wasnt long and I wanted more so I changed to l89 vet heads and did the same to them. Then when that was no longer enough I changed to what I have now.

 

You hit it square on the head, my friend has a CFI '84 vette with all stock engine components (except for ignition) and can get real nice numbers like low 14's, I'm talking cross-fire injection!! So more air in & out can only mean more power. People would rather brag about how much money they blew on their motor and put the vendor sticker in their windows. Quality is a strong word, you can have an aftermarket head with CNC porting etc. by machines on an assembly line or you can talk to some folks and go to an experienced, respectable machinist that does it by hand, and cheaper even.

I love my GTA and I wouldn't have bought it if it had all that aftermarket junk on it. Use conservative intelligence--> it is impossible to have a perfect set up, and dipping into the aftermarket only complicates things and makes it harder for an efficient balance. I understand GM had it's short comings but any gains in one place is a loss at another. To me 5-10 HP gains for over $400 on new runners is insane, the stock runners will never go bad! They're the same material, just don't port through 'em! If a strong port job can't give you 7HP then aftermarket can't either.

I think F-bodies have tremendous potential, you don't have to go to extremes to realize it unless your car's only life goal is speed, then screw it: pull your lumbar seats, A/C, radio, carpet, power luxeries etc., drop a 454 in and go nuts.

Sorry for going off, it's great someone else gets the picture and not the "magazine ads", I respect that.

PS- a slightly better cam isn't a bad idea either, lol
Also with a quality, customized chip your mods will be best utilized and should get no codes/lights

 

I burn my own chips. I wish I would have got in to it before when my car was stock. I used a hyper chip for a long time be fore I started to burn my own. Burnning chips was probly the best performace investment I have made yet just wish I was a little better at it but hay Im learning.

 

Ed Maher from here has done that, check it out:
https://www.thirdgen.org/techbb2/sho...threadid=47098

I went way beyond that:
https://www.thirdgen.org/techbb2/sho...threadid=47263

 

awesome madmax, just what i was talking about. accept yeah you went WAY further into the base than i was thinking. hey, your first dyno run didnt look right. your HP/TQ dont cross at 5252 rpm like they should. but the second looks right. i was thinking about siameseing the base to about 1" in but figured i'd hit water soon after, good to know otherwise. are your runner tubes stock? or have you since done them also? (got tired and confused reading numerous posts and links) i was thinking of opening the runners and plenum even further and radiusing the ends (making my own gaskets with rvt) then leaving the base side of the runners stock to bump up the velocity, but still siamesing the intake of the base into about 1" (now maybe 2" lol) i'm thinking with the healthier cam and the rest of what i plan to do the 305 should be fun to drive. great links, tons of what i was looking for. on a side note how do you like your g-tech? does it seem even remotely accurate? i'm looking into getting one to have something other than the butt dyno to tell me if things are going like i want. makes me wonder, if you were to siamese the base all the way to about 1" from the opening to the head (or as far as you can possibly go) would that make your intake set up act more like a dual plane intake, a velocity stack, or a single plane intake? or maybe a combo of 2? humm...... either way, thanks just what i was happy to hear. long live the people who think

 

Actually it does cross in the right spot, its just that the scales for the TQ and HP are not in the same spot. One of the scales is on the left, the other on the right.

The car still has the stock runners on it, and I dont really think that a larger set is going to do much but of course thats a guess and without checking it I could be really wrong

Theres no water passages in the intake base besides up in the front where the thermostat is, so hitting water shouldnt be a concern. I think that Mike Davis (one of the links on that post) at first siamesed his base about 1-2", but it looks to me like after he tore his motor apart he cut more out of the base from the pictures. I would have to guess that the intake still acts more like a dual plane than anything, but not exactly like one. Its certainly not a velocity stack, the runners in the base are just too flat for that to be happening. Its kinda in its own realm really, mix+match.

The G-tech is a nice tool, but you need a place to use it. The road needs to be straight and flat, otherwise it can throw off the readings. Its pretty close on time, usually about .1 or at most .2 faster than what I have run at the track. The MPH is a different issue, its generally about 2mph off but sometimes it has been as much as 5mph off from what info I have on what the car runs at the track. I think that the ones I had that were off alot were because of where I ran the car. It does great vs. itself though, very useful for comparison purposes.

 

thanks again , good info to know about the g-tech. 5 mph is still better than the guess-o-meter. and thanks for the info on the intake

 

I've still got my TPI apart and with all these stock bases being siameased I'd like to do the same with mine. I can't afford an aftermarket base so this should help me out quite a bit. I alreadt have the SLP siameased runners and thought about removing some more of the divider.

I have a custom burned TPIS Level 5 chip burned for a 355 with modified 87 MAF TPI. TPIS said if I don't change heads or cam that this chip would still control a 383 just fine. Now for my question. If I did remove this much of the dividers, would it require a differant chip? I *think* it would be ok since this is a MAF system but I'd like to ask before I get my tools out.

Thanks!

 

Would removing the dividers in the base and the SLP runners like has been described in previous posts require any mods to the chip? I have an 87 MAF setup so I'm kinda hoping I'll be ok...I hope I hope.

 

If you read the post I linked to, you'll find I am running a MAF setup and did no tuning whatsoever between the two runs. It had definitely gone to the lean side at WOT and had some knock that it did not have before. I messed around a little before I reprogrammed, and backing off the timing a little seemed to help. Maybe with an increase in fuel pressure it would take care of that as well.

I'd hope that the TPIS chip you have would be closer than the ASM chip I was running, for what you paid.

 

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