gta88 flamered

The title says it all: L98 Heads, Cam & Intake upgrade!

I know we have hundreds of threads from the last ten years concerning this theme with lots of different opinions and ideas. But during this period of time the products have changed, too.
To avoid problems I need some ideas and help.

The motor is a L98 from 1989 with 56.000 miles, the car is a weekend driver only.

The car will be used for weekend driving only, I´m not looking to build a strip or a race car. Therefore a good idle is also important.

My plans so far:
spare plenum will be ported, new intake from Edelbrock/TPiS, new runners from AS&M, I want to keep the stock look as much as possible.

Heads: AFRs, 180cc? 195cc? To be honest I have no idea....
Camshaft: the same

Converter: Upgrade to new converter with higher stall speed, 2400 ok?.

Exhaust: Upgrade to headers


I´m not looking for the ultimate top-end horsepower, but more for the low and mid range torque increase and a wider range of rpms.

Budget for this project is second rate.

Thanks, Jens

vetteoz

iTrader: (13)

Under those conditions if you are going to buy the new intake then you could buy the Vortec version
http://www.summitracing.com/parts/EDL-3817/

and run the cheaper GMPP Vortec cast iron heads
One of the best bang for $$$ heads out there without going to more expensive alum ones .Excellent low / mid range performers capable of making 400Hp with right engine mods
http://www.summitracing.com/parts/NAL-12558060/

You could buy the Vortec intake base and Vortec heads for less than the cost of aftermarket alum heads alone
You could also buy a HSR in Vortec version
http://www.summitracing.com/parts/WND-7542/?rtype=10

gta88 flamered

vetteoz,

thanks for your reply. Changing to Vortec style heads and intake is one object I was definetely not thinking about.

The GMPP heads have an intake runner volume of 170cc and a chamber volume of 64cc, is this ok? Is additional porting of the heads/intake necessary?
What camshaft can be used in this combo?


P.S.: I'm not on a tight budget with this project

vetteoz

iTrader: (13)

I suggested the Vortecs based on how you intend to use engine.Most including my self would say go bigger ; 180 -195cc head ,big cam and make some good Hp but that would be wasted given your stated goals.
Small(ish ) runner heads with good chamber design give good bottom end / mid range power which is what you want for a weekend cruiser.
The Vortecs are so good out of the box they show little gain from porting. If you were after / needed more flow you would consider a bigger port head .
Do search here on Vortec cams; several posts on what works best
Also check out the HSR.
Probably cheaper option than big tube TPI setup and much bigger power range ( with correct cam ) .Many happy users on here ,myself included

MTXaudioSYSTM

get the hsr and a 2800 stall. go big or go home!


i have both and i love the combo. vortec heads coming sooon

gta88 flamered

Ok, thanks for your feedback, guys.

I've searched and found these heads: http://www.competitionproducts.com/p...ber=RHS12407K1

As far as I can see these heads will accept cams with bigger lift and have better valve springs compared to the GMPPs from Summit.

Is this ok?

89fbirdformula

mods in sig, times in sig...

any questions feel free to ask.

also, go to a HSR or something...i regret hanging on to TPI...but ive run some DAMN good numbers with it!

iroc stangs

ya got one question... wheres your sig? lol.

89fbirdformula

hahaha, damn stupid TGO!

robg91z

iTrader: (1)

would the afr 195cc heads work with the vortec HSR?? im also in the process of swapping out some thing from my car

ntomsheck

iTrader: (1)

The vortec intake ports are quite a bit taller than standard SBC ports. You might have to lengthen the head intake ports to use that manifold. That, and the bolts may be different, but someone might have to chime in here.

If you're planning on swapping to AFR 195 heads, I'd just do it now and get the correct ported HSR.

Orr89RocZ

iTrader: (20)

AFR makes 190 cc vortec style head now. It was listed on their website alittle while ago. Thats an option if you already have vortec style intakes, else i would stay conventional port style with either 180's or 195's.

195's are on the bigger side for a 350 but have been proven on many combos here. Although the port size is on the larger side, they have good port velocity for that size so they still can make some low end.

Depending on how big you go on the cam, your low end should still be fairly strong. I've recently been in a heads/cam L98 that impressed me. AFR 190 heads (old style head) with comp cams XFI280 cam (230/236, .570", 113 lsa), HSR intake and it drove fine, idled fine although pretty lopey and at WOT it was a blast. Its not even 100% tuned yet. Still on stock converter too, which made that bottom end pretty soggy. A 2800 would really wake up the car.

That may be too much for you, and certainly too much cam for a TPI setup. That motor wanted to go over 6000 so bad but being on stock bottom end, you dont want to push it too hard over 6000.

I think an aftermarket TPI setup on a set of AFR 180 or 195s with a XFI 268 cam would be a great combo. Its been done on these boards alot. That 268 cam is very popular and AFR has the springs to handle that cam. Ask for the 8019 spring upgrade if you go with AFR heads. Its extra insurance to handle that cam.
Thats a very streetable combo that will make real good power. Its best with a stealth ram or similar short runner intake, but still works great with TPI.

gta88 flamered

Guys, thank you all for your replies!

After a lot of reading that's what I'm planning:

- AFR 195 #1040 with 65cc, upgraded to the 8019 springs
- Comp Cams XFI268 # 08-466-8
- Roller Rockers: Comp Cams Ultra Pro Mags #1602-16
- Head Gasket: FelPro Z1003 with 0.041 compressed thickness, is this ok?
- hydraulic rollers: Comp Cams 875-16, is this ok?
- pushrods will be ordered later, when I'm confident about the required length
- the 1 3/4 headers with air tubes will come from Dyno Don

I will stay with the TPI, no way to change to the HSR. I'm definitely not interested in cutting the bracing on the underside of the hood.

So porting the intake, runners and plenum will be the way to go to get the required cfm numbers...

Is this combination ok or did I make some serious mistakes?

I really appriciate your comments!

Thanks.


Edit: what fuel injector size would be best? The 30 lb Bosch Redtop?

Orr89RocZ

iTrader: (20)

You can go with AFR 180's if you like for abit more torquey low/mid range. 195's are best for really ported TPI setups and shorter runner intakes like stealth ram miniram etc. Cant go wrong either way tho.

268xfi is nice cam for this car.

LS7 lifters can be used and are cheaper than comp cams lifters. Usually around 120 a set.

theimpaler68

iTrader: (1)

the first fuel injection intake will fit under hood with no cutting and likes to rev up to 5800rpm for that cam you are looking at. this is the combo i am going to use when $$$ allows.

dhirocz

iTrader: (2)

Heads? Vortec all the way. The vortec intake port was based on the LT1, and will start stalling out where a TPI makes peak torque(which means maximum velocity at tuned RPM in the head before the port stalls). Just make sure the heads are properly prepped and have screw in studs or there is a good possibility you will regret it later. Vortecs will only work well on a 383 if you open up the pushrod pinch accordingly or they will stall torque around 3500 RPM.

Runners? Dont go with AS&M. They are nice pieces, but if you do some engine math you would see they are best suited for a 383 or 396 rather than a 350. If you want to stay LTR, go SLP or Accel( Accel are a little larger, will peak TQ just over 4000 if the rest of the engine is set up right). The AS&M and TPiS units have too much cross section to match the runner length on a 350. Save those for the stroker motors.
Make sure the Edelbrock Vortec base matches the runner tubes (port match only) and check for consistency in the diameter of the passages. Other than that, cartridge roll it only. When people act like they are building a top fuel engine and hog them out is where they loose their power...they loose the tuning effect because the cross section no longer matches the engine combo. To stay tuned, to a point, it will HAVE TO be restrictive (to accelerate incoming air) just work on making your intake more efficient.

And off the shelf comp cam grind like the 212/218/114 would work well in this engine. I'd go with a true roller timing set and LS7 lifters as well. Consider 1.5 roller rocker arms (not roller tip) a good investment here as well.

Ported stock TB with an airfoil, port matched to the plenum is more than adequate here.

Headers? Get the ones with the longest primaries you can find (hooker) and run the 3" collector out at LEAST 12" if you can before connecting to the exhaust. Dont go stepped on the primaries. Do yourself a favor and get header studs as well, not bolts (bolts suck). Try to run a gutted cat 18" behind the collector if you can to terminate wave tuning in the exhaust to help boost torque.

2400 stall is a little high. I'd go with a vette C4 converter. Cheaper too.

If you go with other heads, the C4 aluminum D port heads are ok with some pocket porting...if you go aftermarket, just remember to stay in the 170-180cc range. Flow is not so much what you need, it's velocity. If you port, concentrate on the intake side more to lower your intake/exhaust flow ratio to keep the throttle response and torque up to peak up...but this will also make the engine fall off quicker afterwards so set a lower shift RPM.

Set up correctly with a good dyno tune (mail order tunes are only good to drive to a dyno IMO) you should peak torque between 3900-4100 RPM and keep your driveability and mileage in check. Should also make a perky street motor, but make sure that exhaust flows well...go at least 3" aftermarket if not dual. Get at least 24# SVO injectors that are BALANCED, and make sure the rest of the injection system is up to par. If you can, upgrade your air intake going into the TB (have to make one).

Dont be suprised if your transmission doesnt like this. I did one recently and burned up my stock 60k miles transmission in my '88 GTA. But it still managed to break free up to third and still hauls ***.

gta88 flamered

@ all,
thank you very much for your input :-)

@dhirocz,

there are some interesting points and some basic questions from my side:

I was dealing with this project from the “flow side”: bigger heads/cam and the higher rpms require MUCH more flow compared to the stock combo. The more the better. If there isn’t enough flow, the motor will fall on its face as with the stock TPI....
Thats the reason looking for the ASM runners and the high flow base.

Whats the stall of the C4 converter?

The target of the build is a strong street motor. The car is driven less than 1000miles a year....


Sorry for the - maybe - stupid questions, I’m an electronic engineer with a few mechanical skills....

Thanks,
Jens

dhirocz

iTrader: (2)

The whole point of the TPI engine is torque. Where many people make their mistakes with the TPI engine is that they approach it with the same mentality as they would an engine intended for HP. Thats not what the TPI is designed for. It can be made for that purpose (ie special custom sheet metal intakes) but thats not what we are dealing with here.

TPI engines are 'tuned' due to their runner length and cross section creating a tuned wave effect in the intake runners at peak torque RPM. Since runner length for the most part is fixed, and cubic inches are for the most part fixed, you need to match the runner's cross section to maintain this tuning effect. This will accelerate the air more and compensate for the lack of flow. However, a properly prepared TPI intake will flow enough to meet the requirements for a TPI engine. A 350 TPI at peak torque does not require nearly enough CFM as many people would lead you to believe. A larger intake than needed on a TPI engine would boost flow but kill the tuning effect and therefore the point of using it if the cross section and length are not properly matched to the engine combination. That is the bottom line.

Torque is a measurement. HP is a calculation of an engine's ability to work over time, which is based off torque. If you want to boost HP in an engine like this, concentrate on torque. Make it more efficient, but more importantly, make sure it works correctly. If not, it's not worth using it at all.

Perfect example. The 305 TPI. It's tuned for the 305, both the runner length and cross section peak torque at approx 3900 RPM. The 350 TPI with the same stock intake doesnt even match as well, the cross section limits peak torque to approx 3400 RPM. Why do you think the 305 got the peanut cam? Because in stock configuration, a 305 TPI engine with enough cam has enough potential to outaccelerate a 350 due to the better tuning characteristics in stock form, the lower flow requirement and the same stroke (torque). So to keep from embarrasing themselves, GM installed the 'peanut' to limit peak torque RPM in the LB9 so the 350 could outperform by a wider margin. Good low dollar TPI engine...a cammed 305 TPI, heads with a great intake port and decent exhaust at a 65-70% I-E flow ratio, decent longtubes, and a cleaned up (extrude honed or portmatched and cartridge rolled), stock dimensional TPI intake.

C4 converter stalls 500 RPM over stock.

gta88 flamered

I think I see your point: the tuned wave effect

But: I see a lot of guys here, especially from the SC area, making really big tq and hp numbers with heavily ported TPI systems and big flow numbers. Are they not using the tuned wave effect?

Can you give me an idea of the tq/hp figures my combo (AFR 180, XFI268, hi-flow base etc) could make?

Thx in advance!

Orr89RocZ

iTrader: (20)

Those guys are making TPI essentially a single plane intake. Its a short runner intake tuned for higher torque rpm which translates to higher hp rpms than TPI long runner designs.

TPI is tuned for a lower rpm band while short runner intakes like HSR/Miniram/etc are tuned for higher rpms.

There is a point in which too much velocity can choke a port. There is also a point where you can have too little flow to make a certain power. High hp high rpm motors need a large enough port area to pass the required airflow for that power and rpm range, while keeping velocity in the port to a certain limit. Total engine is a system and it all works together.

Not all got the peanut cam and they still were not quite as fast as the 350. The 45 cubic inch advantage really makes a difference in hp and torque production which translates in the 350 L98 being much faster even tho its handicapped slightly with the 700r4 compared to a T5 LB9.


If you stick with hiflow base and your typical big long tube runners, that combo is known to be in the 330-350whp range depending on state of tune/tires/dyno/weather conditions etc. If you went with a short runner design or siamesed the TPI to shorten the runners, its capable of 360-380whp.
Burnout91 did the HSR swap from TPI on that combo but with 195 cc heads. Went from 330whp to 380whp with just the intake swap. That seems unheard of but shows you the cam is capable of much more with the right heads/intake manifold.

To note, I've never seen a motor make less power with more flow. If you went with aftermarket TPI system that flowed 240 cfm and your heads flow 280, and made xxx whp, then switched to TPI system of same runner length but the package now flows 280cfm like the heads, I would expect a BIG increase in power at the same RPM ranges. I would not consider the large TPI runners out there including FIRST too big for 350 motor if you have the heads/cam to support the flow they can provide which I believe is up in the 260 cfm range per runner. If that was the case, then why do L98's respond well to intake bolt ons with big runners on stock heads/cam?

gta88 flamered

Orr89RocZ,

thanks for your feedback, some interesting points.

Ok, another question from my side (I hope one of the last questions before placing the order with Summit...)

With the 180cc AFR's I think the #0919 are the right ones, correct?

"These cylinder heads are a L98 based geometry. Not compatible with self-aligning rocker arms. Two center bolts at 72 degree angle for 1987 and up engines. Exhaust port is raised 0.100 in. over stock."

Thx, Jens

BadSS

I agree. You can not port a set of aftermarket replacement TPI runners "too large" for a "performance" 350,,, which would still be smaller than the box stock FIRST.

gta88 flamered

Looking for the flow numbers (someone measured 300cfm without porting) the FIRST is a great solution and the price is ok.

There are a few things I don't like:
- the round throttle body opening
- the attachment of the TPS
- the solution with the fuel lines and the Fuel Pressure Regulator, I prefer the stock fuel rail design with the integrated pressure regulator

We have a car inspection here in Germany every two years, and the L98 type of engine is known from the Corvettes .... and I'm definitely not willing to wake up sleeping dogs.

dhirocz

iTrader: (2)

There are other differences you aren't taking into consideration. Heads are different, as are exhaust manifolds. Even the factory tune is different. I'm not saying the 350 takes a backseat to the 305, but purely from an intake only standpoint, it will work better on a 305 stock for stock than a 350. 305 require less air and the runner length and cross section both match better on a 305 (3900 RPM) than on a 350 (3900/3400). RPM is required to make HP, and the 305 in this instance, if it were as capable via the camshaft, exhaust and heads as an equivalent 350, would be capable of more power in that aspect, because of the intake's tuning advantage on the 305. Stroke is the same between the two and is the mechanical leverage that creates torque (which is why strokers make more torque, longer mechanical advantage like a longer prybar) They are not equipped from the factory well enough for bore size to make that big of a difference between the two. These are very similar engines after all, using much of the same hardware. This isn't even taking the wave tuning into consideration. However, the difference in how these engines are factory equipped does hold back the 305 some in relation to the 350. The moral of the story is the stock TPI intake works best on a 305 if the intake were kept stock. If you start changing things with the intake, it's a different story. I know, it's complicated to understand, but tuned intakes work alot different from the typical untuned ones so the same rules do not apply.

I'd be interested in puttin a 305 and 350 equipped identically otherwise up against one another to see what they would do.

When I am referring to cam, I am referring to something of a decent size but not overkill for a LTR TPI, like a 212/218/114 HR. Also keep in mind that factory tunes also come into play...there are alot of variables here. But the guys who know how to set them up are the ones who have the 'couldn't be a 305' engines. You know the ones, there are a few on this board.

The FIRST is a great intake. It moves alot of air and makes good power. Why? For one, it moves more air. Two, the runners are shorter, enhancing upper RPM capability while still being long enough to deliver a good amount of torque through a cleaner casting. Does this mean it's tuned? No. The combination of runner length and cross section prohibits it UNLESS the peak torque RPM is 4800 and runner length from the valve to the plenum is 17.36". The problem doing this with another intake is that the runner length and peak torque RPM must meet at the RPM range you are building the engine for. TPI runner length on stock style intakes is longer than that of the FIRST, meaning it's hard to 'hog it out' and retain it's tuned characteristics.

Keep in mind that the FIRST, which is a much better, cleaner out of the box intake as far as ports matching up and casting flash. This makes a large difference on a tuned engine as well (turbulence at peak torque RPM). The FIRST is light years ahead of the stock TPI intake in that aspect, and that improves port efficiency which in turn is more torque. Why do you think extrude honing works so well on TPI engines?

What makes matters more complicated is that the required CSA of a TPI intake to be tuned differs with the size of the engine. However, runner length is a function of RPM and does not change (much, depends on the parts you use and if you change runner length during porting). This is why the 305 is better suited for a stock TPI intake, and this is why porting should be planned and thought through carefully. This is also why runners like the AS&M are larger and longer than those of the ACCEL and SLP line...a 383 or 396 needs to maintain correct runner length with larger passages to feed the extra cubes. A 350 does not need runners of that size if you are going tuned.

So no, you can't port a set 'too large' unless you are planning on keeping the tuned characteristics of the intake. If you are, then you most certainly can go too large OR too small. Very small margin of error there. If you are looking past wave tuning and are trying to free up some more HP than by all means, go as large as you want... make sure you feed those heads the cfm they can flow as long as you dont go so large as to kill velocity, butcher to create turbulence, or go too small as to stall the port. There is still plenty of runner length to make decent torque. But that kind of defeats the purpose of the TPI intake when you can save money and go with an untuned intake like the HSR or single plane, dont you think?

Orr89RocZ

iTrader: (20)

Yeah I know the differences in the tunes and heads. Smaller valve heads are needed on the tiny bore 305's. But yes the stock TPI intake are best suited for 305s since they were designed for a 305 motor...if you believe the history behind the TPI intake setup. GM Engineers were planning on dropping the 350 for the 305 but last minute decision brought the 350 back and they stuck the TPI on top. Worked out ok. Now I dont know what you want to base the "work better on the 305 than 350" part on because certainly with same cam and intake, the 350 still outpowers the 305. Better suited to 305? Certainly. Works better on the 305? Thats subject to what exactly you are comparing.

And all intakes are tuned for a certain rpm range on a motor. Its the wave tuning formulas behind intake manifold and runner design. An intake runner will have a certain required length to be optimal for the desired rpm range. Alot of engine parameters will effect this, so the same intake can be tuned for different rpms on different displacement motors. There are some real good software packages out there that can simulate this and calculate optimal runner length and cross-sectional area. PipeMax is one of the best known.

Sounds like GM wanted 3900-4000 rpm peak torque in the 305 and when that intake moved to a 350, it dropped to 3200-3400 rpm.

88fastgta

iTrader: (9)

here is the reciepe for 330+whp and 410+WTQ using and 355 block and tpi.. there secret is all in the tpi

fully ported and siamesed plenum... grind down egr walls..

slp runners and edelbrock base(get them welded and ported by DR. J in california.. he opens both of them up to flow around 320cfm expect to pay 700 for this) with this done this will make the tpi out flow a hsr out of the box and spin to 6 grand....

afr 180 or 195 heads or even ported 113 heads....(195 heads would be better suited for the new welded tpi)

gm hot cam with 1.6 rockers at least or bigger cam

fully built 700r4 with at least a 3000 stall converter(thats what im running... there are other running up to 3600 yank coverters)

decent headers and exhaust like dyno don headers.

nice custom tune..

do this and you will be well over your 300WHP goal... there are plenty of people on thirdgen including myself who have over 300whp with this setup... alot of people in california are up in the 360+WHP range... there is one person by the name of 1989gtatransam thats darn near 400whp range with tpi... it can be done but it will be expensive.....

mikesanto70

looking for 400-450 hp from my 92 5.7 z28 HSR or the new bbk what heads too, 11.29 would be great for me