Mongoose

iTrader: (2)

After doing some extensive reading of past posts this morning I'm left with a question or two about these runners. First, are the current design (second design from what I gather) actually better than the original design released by SLP in regards to airflow and potential performance improvement? Second, I intend to do some port work on my plenum when I put these runners on so would "siamesing" the ports on the plenum to match the runners instead of just gasket matching them be the better way to go? I'm also planning to install an Edelbrock base (3860 I think) when this all happens so my last question is subjective at best, what kind of improvements(not hp numbers, just how the car will react) can I look forward to considering a stock TB, peanut cam 305 with headers, SLP CAI, free-flowing exhaust,etc.? Before "350" is brought up I intend to swap one in but not until the 305 expires.

1989GTATransAm

iTrader: (3)

Here in So Cal we are converting the 2nd design to shades of the first design. The 2nd design has some restictions that the first design does not have. For a high flowing runners the first design is the better one to start out with. It will be a lot less work.

Problem is the first design has not been made for a number of years now and and they are a lot harder to come by. I do see them for sale from time to time.

86 IROC

iTrader: (3)

I'm going to say the car will seem a bit lazy due to the lack of cam & gear in your car. I've seen a few threads where even 350 cars didn't pick up after swapping runners. I have a set that have been extrude honed, and am hesitant to install them w/o changing the cam - or at least 1.6 rockers.

Mongoose

iTrader: (2)

That's something I'm considering doing at the same time(the 1.6 rockers) just to try and get a little more out of the cam without having to swap it due to the car's mileage. I've also got another 9 bolt rear with 3.27 gears (car currently has a 9 bolt with 2.77) waiting to be assembled so that could help matters. I'll probably wind up replacing the valve springs when I do the rockers just to be on the safe side, any recommendations with stock heads?

86 IROC

iTrader: (3)

Stock 69' Z28 valve springs should fit w/o machine work and handle the extra lift. I've seen them fairly cheap in Summit/Jeg's.

customblackbird

iTrader: (15)

your 305 does not need a intake upgrade, the least thing you should be worried about is the intake on your 305. the 305 was GM;s flagship motor and they designed the TPI to work for the 305 not the 350. the TPI is not all that restrictive on a 305... u put a TPI on a 350 and it becomes restrictive.

without a head and cam upgrade you dont need to touch your TPI intake. u could prob still get away with it with the heads/cam done. dont waste your money on that. the motor will benefit more from the heads/cam.

as far as the SLP's i have them on my 350tpi and you should definitly siamese the intake, and gasket match them. it will be a huge restriction if you dont and theres 10-15hp in the porting. the stock 48mm TB will be good for 400hp and you def dont need to upgrade that even with a head/cam/intake upgrade. 1.6rr might help alil with the stock 305 peanut cam. still its the heads that dont flow, even with the extra lift of the 1.6rr.

Mongoose

iTrader: (2)

No arguement on the Tb as I don't intend on switching it.

jack harrison

i noticed a big drop in bottom end torque, but a bit more upper bhp. i supose its a good thing, it doesnt fry the tires off the lone. oh, and you should deffinatly siamese the plenum.

Mongoose

iTrader: (2)

Maybe I'll put them on ebay.......

jack harrison

why?

Mongoose

iTrader: (2)

Seems like they'll do little to nothing for my 305 and could very well hurt it's current performance.

SDTransAM

iTrader: (5)

How much do you want?

Arent the SLP runner's and the edelbrock base, more expensive than going with the HSR? and dont you get more HP from an HSR? So which way would be better route?

customblackbird

iTrader: (15)

hsr would pro produce less HP on a 305, the HSR flowssss wayyyy to much air for a 305, 350's loose low RPM hp/tq with a HSR... imagine that on a 305 lol it would be such a dog, i wouldnt get rid of the SLP runners, they are a good runner and when u build the 305 up with heads or cam u will have to increase runner dia. as well as base.

u could get some $$ for those from members here but if u go to a 350... u will def want to keep those runners if u keep the TPI setup.

i'll be putting my SLP runners on sale prob in the spring when i drop my motor in the car... since im getting rid of the TPI and going with a 383 HSR. i'll be selling the runners... midly ported at the top, a ported, siamesed, portmatched plenum to the SLP runners, good 22lb stock injectors, with fuel rail, BBK adjustable fuel reg, 48mm TB with SLP air foil. prob sell it cheap so let me kno who wants in... willing to let go with out base or TB if not wanted.

SDTransAM

iTrader: (5)

I would be interested, I forgot to mention that I have a L98, It just seems for the money of the SLP runners, and an edelbrock base, the HSR would be a better, and cheaper route to go. If the whole stock setup is to restrictive for a 350, why would I want to go that route?

customblackbird

iTrader: (15)

the stock setup is restrictive but its easier to tune a TPI LTR setup vs something like the miniram/HSR etc. not to mention they arent EGR equipped so they arent emission complient so dont try to pass inspection. a hogged out TPI can perform very well with a L98 or 383 or even larger cubes 400... on. they are street machines. they build lots of low RPM tq and HP so driving around town is a blast, also i dont need a higher stall converter due to a cam that a TPI likes so your gas milage would and could also be better. some ppl just plain like the look of it.... and yes im one of those ppl. i hate how the miniram and LT1 are so low, the TPI just looks like a B@D@SS intake. but im willing to compromise with the HSR.

also the HSR has modifications that has to be done, fuel fittings to the fuel rails like the fuel lines have to be custom made. and theres other things, like the custom chips and tuning, no cold start injector, no VATS etc, as well as no EGR, increased RPM usually requires better flowing heads and larger duration cam, decrease in lower RPM power etc. the HSR is bascially just more work to get it right and when u do a HSR swap it usually requires much more upgrades to take advantage of the HSRs abilities.

the TPI is a great performer if its upgrades. upgraded runners, ported plenum and aftermarket base are great steps and can really bring your TPI to life. the costs are not all that huge in diff prob cheaper than HSR.
TPI...
runners... 250-300$ 150-200 used
base... 400$ 200 used
plenum.... u just have to port it thats a few hours if u can port.
total... 650-700 new and 400 used. thats worth 30hp and more tq on a stocker not to mention increase in RPM powerband to 5200-5800 depending on your porting work. thats with a stock chip and on a stock L98

HSR....
HSR base/runner and plenum.... 310$
HSR fuel rails...225-250$
fuel regulator bc holleys stamped non adjustable or adjustable ones is poop... 100-150$
custom chip...150-300$
new radiator water neck bc stock TPI wont work... 10$
fuel line fitting modifications to HSR fuel rail... id say prob at least 50$ if u do it yourself (thats fuel AN fittings and fuel stainless flex hose) expect to pay more if somone else does it.
TOTAL... at least...935$ lol see i kno they say only 600$ but theres other things that have to be incorporated. stock chip could be used but it wouldnt run well. im sure it could be alil cheaper if u could burn your own chip but its still gona cost u, as wells as doing something with the fuel line routing or taking your chances with the Holley stamped regulator... even tho its cr@p. u can expect 30hp with a HSR intake on a stock L98 as well as a good bit of less tq than stock... seems that the TPI is better on a stock motor. untill better heads/cam is used... but even then a TPI would benefit from a head/cam upgrade as well. not to mention the TPI would be legal.