vendetta

im rebuilding my TPI 350, wondering if i should go with some new head? if so what kind? id like just a lil bit more power but dont wanna kill my mpg?

some input ?

thanks

-Erick

Pwnage1337

It would be a waste if you left the stock TPI on it.

vendetta

well do you mean the heads? you just said the stock TPI

if so what would you sugest?

Pwnage1337

What I am saying is that it would not make much sense to put better heads on a motor equipped with the stock TPI intake.

The intake is restricting the power (at this point), not the heads.

If you upgraded to say a HSR, Superram, Miniram, FIRST, or even big tube runners with a ported base and plenum, then it would be worth it to put new cylinder heads on it.

BigWhiteGTP

Not true. GTA MATT went 12.2@108 with a bone stock TPI intake and stock tune with out of the box AFR 195 Eliminator Heads and a CC305 cam. Then got a mini ram on there and picked up a couple tenths and 7mph.

True, TPI isn't the best flowing intake, but it's hardly the dead zone that people love making it out to be.

300hpse

iTrader: (2)

I agree with bigwhite, it's not like if he put's new heads on, he won't see any power increase because the tpi is totally maxed out.

If I were rebuilding an l98, Id go with a set of new (gmpp) or used (l31) vortec heads depending on budget and also get the tpi vortec base manifold which you will need(~$450). You get a newer head for pretty cheap and it forces you to upgrade part of your intake (which isnt required but isn't a bad idea by any means).

Blackdog36

iTrader: (3)

I agree too that stock TPI can make good power. See this article comparing stock TPI with other intakes on a 383.
http://www.compcams.com/Community/Ar...?ID=1737510521

For a mild build that you are considering I think a good set of vortrec heads, slightly upgraded intake and higher lift cam would work great. SB Chevrolet Small Port Vortec Bow-Tie Cylinder Heads are a great bargain at around $1,000 here http://www.sdparts.com/product/25534...inderHead.aspx
They flow great and can handle 0.53" lift and 0.60" with modifications that scoggin dickey offers too. Heads are PN#25534421 with 66cc combustion chamber at 185cc intake port. Stock is 58cc I believe with a compression ratio of 9.75:1. Since heads are cast iron, you don't have to worry about raising cr too much. You may need a smaller gasket then stock to get compression ratio back up since going from 58 to 66cc's. I think 90-92 5.7 v-8s have -7cc pistons.

Problem with vortecs is that they need specific base as mentioned. Stock base is ok but porting helps. Makes sense to get vortec base since it will flow better than stock. Definetly upgrade long tube runners to bigger size with TPIS runners, ACCEL or other. You might find some good used ones here from members that are upgrading. FIRST is the best TPI system since it flows great and comes with plenum, tube runners and base either in stock or vortec bolt patters. It is $1,000 new and you will need new fuel rails. FIRST makes sense if you can't find used runners or manifold since as these new are $865 vs $1,000 for FIRST. There has been group discounts for FIRST on here at $800. I would be interested in one.

For cams it will cost $300 for new hydraulic roller cam or $100 for a LT1 or zz4 hotcam. Check out this article about scoggin dickey TPI manifold
http://www.chevyhiperformance.com/te...ead/index.html
Scoggindickey sells heads and tpi manifold as kit but seems high at $1,765 http://www.sdparts.com/product/SD806...keHeaders.aspx. Advisable to beef up rear end with new aluminum girdle cover and used aluminum drive shaft that the 4th gens have. Also would be good to add transmission cooler. ECM tune would be helpful to make most of upgrades.

Cost for new parts but see what you can find used.
$1,050 heads
$300 cam ($100 for LT1 or ZZ4)
$390 ACCEL large tube runners
$475 Edlebrock high flow TPI manifold
$160 TA performance girdle
$90 transmission cooler
$50 gaskets
$90 adjustable fuel pressure regulator
$280 higher flowing fuel injectors (recommended)

$2,885 Total

That would make a great street car.

ls six

I have never seen any data to prove it but I keep hearing that the TPI bases flow worse than the standard base because the port is raised to match the Vortec head while the inlet side is at the same relative position as stock causing the air to travel an S shaped path to the head.

I can get Vortec's for $35-$45 each localy and pick a set in good shape my self so I'll see where things sit after milling before I decide on a new base.

Also with Vortec's you should be able to see an actual increase in MPG depending on the tune and the rest of the combo.

Z2887

I had a 84 Z28. I had a L98 out of a '87 GTA. It ran high 12's with a Accel base, and stock runners and plenum. It had TFS heads(When they first came out), and a Lingenfelter 219 cam. Also had a stock TB, stock mass air( with the screen removed),and stock injectors. Summit has their brand of heads now too pretty cheap. Supposed to basically be like a improved version of double humps.

Blackdog36

iTrader: (3)

lssix, good point about manifold. Wonder how much it would affect performance? Maybe not much but you are spending some decent money to get maximum flow for TPI. Has to hurt some.

Summit heads are $650 a pair http://www.summitracing.com/parts/SUM-151124/ Not bad but valves are smaller at 1.94"/1.50" with 170cc. GM bow-tie vortec are 2.00"/1.55" at 185cc. I think the extra $400 would be worth it. I would get best heads you can afford.

vetteoz

iTrader: (13)

$1000 gets you a set of TFS heads .Takes std TPI intake so save $$$ there

175cc / 56 cc chamber to bump the CR a bit for more power
http://www.summitracing.com/parts/TFS-30300001/

Or for same price something that will beat any of the others mentioned

195cc/ 62 cc chamber.Allows for future upgrading
http://www.summitracing.com/parts/TFS-30400001/

vetteoz

iTrader: (13)

Have to run a Vortec base on Vortec heads. Bolt pattern is different (4 bolts at different angle instead of 6 ) and the ports don't match up

Z2887

good advice

TigerVette

Yep - it's all about where it flows and makes power. I've found TPI to make a great street car, feels like a bigger motor and does well on mpg for an older setup. Didn't even mention the low setup costs.

Saabster

iTrader: (2)

So glad I own a TBI car. $200 for an intake and you're ready to rock and roll.

ls six

The bolt pattern can be re-drilled by hand but more importantly that picture is a lie.

Especialy with the TPI base. It's got more material than non port injection manifolds but what ever the manifold the mismatch will almost certainly be better than what that pic would have you believe.

Also if you are planning a mild street motor and MPG is a real concern realise that the cheaper aftermarket heads that compete with the Vortec do not have modern chambers and MPG will suffer.

vendetta

well i do plan on porting everything and usging some SLP runners

vendetta

how about this? or am i totally clueless here
SLP runners
http://www.summitracing.com/parts/SLE-20002/
Vortec base
http://www.summitracing.com/parts/EDL-3817/?image=large
Vortec heads
http://www.summitracing.com/parts/SUM-151124/


does that setup go together well? seems to be alot of different ones ....

ls six

I havent tried it yet but a few members on this forum had good results with the stock runners and a ported and siamiesed base. I dont remember for sure but I assume they did the typical plenum porting aswell.

From what I saw in the dyno graphs it appeared that the motors ran nearly identical to a typical lightly ported TPI combo but was able to suppoer power at higher RPM's. I suspect that when the individual runners began to peak the ports were able to "borrow" flow from the neighboring port.

This only works on the non-paired cylinders pressumably but the overall effect is greater output and a broader power band.

If nothing else it's free if you have the time and if the results are less than what you want you can still get the base and runners with no lost coin.


I have a spare IM so i'll be trying this when i can get to it.

vendetta

so with the vortecs id presumably get better mpg if it was setup right and thats all i did? im going to do more but that would obviously help it from going down to mych yes?

ls six

It can fall to either side of stock depending on what your total package ends up being along with the tolerances you build the motor too but I would guess that with only the vortec's on an otherwise stock short block and intake that you'll see a healthy bump in both HP and TQ from off idle to stock redline and possibly a few MPG better mileage.

danziger

Great post! This touches all the bases for what I want to do with my L98 Formula. I want a drivable street-car that is reasonably dependable with good-manners and like the options in your post! Thanks!

Blackdog36

iTrader: (3)

NP. I've also been thinking about building up my 350 for a strong street car. Recipe seems similar in that you get good heads, cam and choose what intake you want (LTR, miniram, HSR, carb). Tough part is that once you increase power a little, you have to start looking at transmission and rear end. I might splurge on a set of AFR 180's although vortecs look good. I'm hoping to keep stock bottom end and beef up drivetrain a little. I've read good things about Comp Cams XFI-268. Has rpm range of 1,800-5,800 rpm and you can use stock converter. Just need heads with good lift to take advantage of aggressive cam ramping. Also need to tune ECM but it shouldn't be too bad with a lobe seperation of 113 degrees.
http://www.jegs.com/i/Comp-Cams/249/12-466-8/10002/-1#. I'd love a 383 but $$$ keep climbing for that combo. Maybe someday when the 350 gets tired...

ls six

I wouldnt wory about the trans or rear unless you plan on racing a lot or your eventualy going for something more potent than a TPI 350 or 383.

Both units are only as good as the up-keep you put into them.

Your 700 may need to be rebuilt depending on it's current state but it's pretty good up to 400-450 WHP. You can also use the GM 4.3L V6 converter with no issues, it's a bit higher stall than stock and should work good with most TPI builds.

The rear has been run in low 11 second cars so unless you intend to spray or boost the car it'll be fine.


Do any work needed to bring the two up to par and be happy.

vendetta

I just had the a new 700r4 put in with heavy duty parts and everything

ls six

Just make sure the TV cable is set right and it should serve you well.

vendetta

What???

ls six

TV cable, throttle valve cable. If it's not adjusted right you will be eating that new trans in short order.

Double check it after a few miles anyway cause they can and do go bad, Mine kept slipping after the rebuild and I'd have to pull over and re-set it or the trans would have burnt up.