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Intake runners



Hi there,
I'm new in this site. I'm looking to do some modifications to the intake of my '88 but wanted to ask if anybody have instaled SLP siamese runners on a L98 automatic? How do they perform?
I heard it looses some tork but is it really noticeble?
Or how about the Edelbrock stuff? Are they good?
I have read some things about the TPIS, LPE and AS&M but they're pricy.
It all depends on what you want out of the car. I knew a fellow with an 87 auto that went slower in the 1/4 after installing the siamese runners. He later had to change his rear gear, add headers, and a bigger throttle bodyand a big mouth lower intake to get it all to work together.

So, I would say that changing the runners only may not give you much of a kick.

All things considered, the TPiS is an expensive alternative. Here is what I can tell you. Quick blasts up to 6,000 RPM are smooth and very impressive. The engine no longer feels like it wants to increase at a decreasing rate over 4,800 rpm.

Also, bang for the buck wise, by the time you put the bigger runners, bigger lower intake, port and polish the upper, and install a larger throttle body, you are within a stones throw of going all the way.

You might also want to consider that the miniram is a one piece unit and very easy to service, install, etc. No more runners, runner leaks, difficult to access injector rail etc.
Chris , would you put all that on a stock L98? Add maybe headers and thats all. Could you do that if if you didnt want to open up the motor? They do mention some pretty respectable gains.
Well, I have another goodies already in the engine like a crane camshaft, 1.6 roller rockers, LPE headers, Dynomax mufflers, SLP cold induction, air foil, performance MAF and a hypertech chip, and the engine itself was overhouled 23K miles ago, and the list goes on and the wallet gets tin at the same time.
So changing throttle body to a 52 mm and porting the plenum is the next step. I've been playing with the idea of a miniram but really like the look of the long runners and changing maniful of course....and I hope that's it.. for now.
TPiS Mini Ram hands down. So far the best alternative for our L98's. Plus the 95 (Claimed HP ) Gain.

Tie that with some headers, K&N open air box, Performance chip/Thermostat, and mufflers and youll be gained a total of (claimed) around 140 Hp increase

Total bill= 1500-1700$ but well worth it. (Im currently on the TPiS saving spree got the other stuff done :beer )
maxrevs85 said:
Chris , would you put all that on a stock L98? Add maybe headers and thats all. Could you do that if if you didnt want to open up the motor? They do mention some pretty respectable gains.

Providing you have enough rear gear to spin the engine up quick, I see nothing wrong with putting this stuff on a otherwise stock application.

I have heard that the super ram might make more torque, and everybody has their favorites.

One serious negative about the miniram is it is not attractive to look at. There is no where to hide the fuel injection wires, and the distributor looks stupid standing so tall over the manifold.

Too bad we are not all living closer, because I would gladly through you the keys to the 90. It is every bit of the night and day difference right now from driving a L98 to gettting behind the wheel of a LT1 or LT4 equiped C4.
Well BigRed, I guess I have to start saving my pennys...
They claim 95 HP on a stock 350 which is the same as a 6lbs supercharger and the cost difference is $1500 vs $4200 for a Procharger, I like that!

Anyway, my engine is not stock. Is running 257HP at the wheels
+ 20% (automatic) ~ 308HP at the crank, I wonder if I still can expect such a huge gain as 95HP on top of this
I believe they claimed as much as 120+HP with mild mods.

I'm going to go with the porting of all the stock components including the heads under the guidance of my engine builder who is being so kind as to teach me.I've been wanting to do this anyway. Then I will get the 52mm TB. I have the open plenim and the K&N. Engine will be rebuilt . New injectors,I've got the adjustable fuel reg. My plans are to build another engine and do the mini-ram . This way I can drive it untill I can get it done.
I 've been following the progress and suggestions as close as possible to the other members feedback on all this. And reading reading and reading alot of info. This is all new to me working with TPI.
Yup thats right they said WITH Mods (Strokers,ROM's,Headers,etc..) they said 125 gain.

Hell got the cash run them both but dump a 8 lb boost =)
I have heard that the mini ram is hard to get tuned in on the speed density cars. that's the only thing holding me back from putting it on my 90.

Intake Runners


I to am interested in the same mod! My 85 has 175,000 on the clock and now she has a rod knock. I want to rebuild the engine but cant dump a ton of money in the car. I've already done that!

From reading all of the reply post I think I will just port and polish the intake track bump up the compression, stab in a good roller cam, roller rockers and port the stock heads. My plan is to make the car re-saleable so that when I get ready to up-grade I will be able to sell it easy.

The car ran great in stock form but,I want that little bit of extra ZIP when I drive the 85. If I want to really play, I have a 98 Coupe that I can go crazy with.

Can any one tell me what the difference is between a stock TPI base and a big mouth base? Can you do a little bit of porting and polishing to a stock base and get (some what) the same effect???
I've never seen a big mouth base so I would not know.


Bill Curlee

Welcome to CAC. Yes, you can port the stock base. The fellow I sold my 85 to ported the heck out of the base unit. He is now working on aluminum welding the runners together, then hogging them out to build his own siamese runners. The upper plenum has plenty of little bumps and extra metal you can port out.

Will it make a big difference? Who knows, but you will achieve your goal of keeping it all looking stock, low buck, and having fun.

Keep us posted of your progress!
Thanks for the welcome!
I'm very happy to be here with you all!

I too have already ported the H#** out of the upper plenum. I removed all of the bumps and most of the EGR hole vent dam just behind the main opening. Yes that alone made a huge difference.
I also ported the stock throttle body. There is work that can be accomplished there too. I did the mods when I changed out the EGR valve.

I just didn't know if the base porting would make that much difference.I still would like to sit a stock base and a big mouth base side by side to see what they did to make a difference.

I wonder if porting the stock exhaust manafolds makes a difference? I know if you extrude hone a stock exhaust manafold it makes a huge difference.

I hope my budget rebuild turns out for the best. I know it will mechanicaly but I dont want to screw up anything compatability wise.
Bill C,
The TPIS Insider Hints book has the two pictures you're looking for and the difference of the ports is very noticeble, but it looks the same as the Lingenfelther or Edelbrock manifold and the price difference is big.

It mentions that a fully ported stock manifold can get you about 14 HP and the Big Mouth gets you 22 HP and can still be ported for a little more

When I got mine overhauled I got hypereutectic pistons and a mild cam, Crane Powermax 2032, and installed a K&N, open the air filter box, fuel regulator and Hypertech chip and it was running good but after I got the SLP cold air intake and 1.6 roller rockers it really made a big difference. When it reaches 2000 rpm on the feeway it feels like floats over the pavement, like spreading butter over warm bread. The only down side is that now has a strange noise like a diesel engine rattle coming out from the rockers, maybe because it has the stock springs.

Total bill ~ $4500

Well,, someone just offered me a used big mouth and SLP runners for $375. Is that a good deal??? Im not going to go hog wild on the rebuild. If I were going the aluminum head, forged piston route I might jump all over the deal. I just might port what I have and save the bucks for other stuff that needs fixed. I will go the same way you did. Hyperutetuc pistons and a good cam and 1.6 roller rockers. :) Is the ZZ9 cam still the hot ticket or is there something out there that is better?

Did you do your own rebuild or farm it out to a shop? Im hoping to be well below $4K :0 What is your 1/4 mile time and horse power?


Bill C
Bill C,

That's a very good deal, maybe the SLP runners will not help that much from what I heard in previous posts but for that price you have nothing to lose, just the manifold worths more than that, plus you can always get another runners.

I did not rebuilded the engine by myself, took it to a shop and I was very pleased with their job. I got the performance parts that I wanted and they put it together

If you're building yours in the mild side a good option is the hypereutectic pistons, they're much cheaper than the cast aluminium or steel ones and they're good up to 450 HP. The 1.6 roller rockers are a must and I believe the zz9 cam is the better option in the market for your car.

Hp in my engine is 308. Last time I took it to the track was before getting the cold air induction, rockers and headers and my best time was a horrible 15.3 I believe now it should run low 14's. I can't wait to take it to the track again but I have to convince my wife to take a long trip to the closest drag strip.
I have a late '86 with stock alum heads. When I bought it 4 years ago it had 98,000 miles and that intake oil leak that all 350's seem to have. After having the greatest time in my life driving the heck out of it that summer and fall I went to fix the leak that winter.

Well, I got carried away (again) and stripped her down to the short block. $2,000 in parts later, I had installed a big mouth intake, TPIS runners, ported plenum, 52mm throttle body, TPIS stage IV chip, attacked the MAF with a knife and removed the screens, opened the air filter lid, K&N filter, TPIS 24 lb/hr injectors, adjustable fuel pressure regulator, 160 thermostat. Took the heads to a local shop and had new valves, seals, springs (LT4) installed and had them pocket port, and intake gasket match them.

Wanted to install a bigger cam, but when I measured with a old cam I had laying around, the air conditioning condenser looked like it was in the way and I hadn't had it evacuated. Didn't want to just vent the freon so I installed Comp Cams roller tip 1.6 rockers. I had TPIS raise the converter lockup to 45 mph and the cooling fans come on at 185.

It fired right up and has A LOT more power! :J

It had so much more power that I had to be very careful when the engine was above 185 and the throttle body would stick and make me grab too much throttle. I'd just smoke the Goodyear GSC's. I haven't bypassed the throttle body cooling lines because I drive it in the winter and thought I might get throttle iceing. The solution was Michelin Pilot xx3's - sticky. It was also shown a problem in the fuel system at 1/2 tank or lower. It launches so hard that the fuel pressure drops and the engine cuts out. I think the fuel pump sock is clogged - next project if I can bring myself to not drive it for a day.

Best money I've ever spent. :dance


I have the exact fuel tank problem. I think it is just a crappy pump that cant keep up.

This is the rebuild problem that I face. I already have a ton of cash invested in the car replacing things just to keep it on the road. The engine going South didnt help "AT ALL"! :( Well ya got to make lemon aid out of sour lemons! :) The good news is I can do ALL of the work (except head and block machine work) so I save a ton of money there. Almost ALL of the bolt on stuff is new or reworked sooo,,, I save money there too.

I would give my right tes (well you know ) to be able to do the super duper 383 ci, 450 HP deal with all of the go REAL fast parts BUT,,, as cool as the 85 is, and as much as I enjoy driving it like I stole it, I just want to fix her up with a decient engine drive it for a while and at the end of the summer, sell her and up-grade to a 96 "OR" sell it and get the FIRST model year new Vette to shoe horn in a 427, 450hp small block! Be it a C5, C6, Tiger Shark or what ever they are going to call it! :) . If I sell the 85 and the new Vette doesn't come along for a while then I want to add some performance goodies to the 98!

It sucks to have all of these options! :)

Not wanting to go all of the way on the 85,L98 what do you think I can get out of porting the dickens out of the plenum, runners, base manifold and heads. Then adding a 52mm TB, headers, 1.6 rollers, 9.5:1 hyperutetic pistons, ZZ9 cam and cold air induction????

Whats your recommendations??

Bill C
When my engine breaks, I'm going to do something like what I did to my son's '70 Camero. It's now scarry fast, and can beat my Vette! :cry

Use a '97 Vortec truck block because it comes with a roller cam. I got mine for $500 and sold the heads to the machine shop for $250. I used Keith Black hypereutectic pistons (12cc dish for iron heads, flat top for alum heads), zero deck the block, full rebalance.

Heads - the choices are endless. On his I used iron Vortec, modified by Scoggen-Dicky for 0.550" lift and bigger springs for $550. They just came out with a TPI big mouth base manifold for Vortec heads - great for a Vette. Since you have a handle on a big mouth manifold and runners at a steal (buy them now!) and I have a set, then the hot ticket is Air Reseach Alum 195 heads. Put this together with the roller short block, 1.5 roller rockers, a ZZ9 cam or better (check out TPIS's latest, Crane and Comp), ported plenum, bigger injectors, TPIS chip, 52mm throttle body, ported MAF and K&N filter. You can do this for around $4K to $4.5K depending on your deal making ability. Did my son's for $3K.

The down side? You'll need better tires, you'll get tickets. BUT - you'll have a grin that'll look stuck on your face!:eek :Twist

And as for my son Nate.... :booty



I'm more afraid of breaking other drivetrain parts :0 than tickets :) Did you say you had parts for sale??? If so what are they? Your set up sounds fantastic. I can't go that deep but I will get the pistons and the cam. Whats better than a ZZ9 cam???? I have'nt kept up with the new stuff. Ive been traveling alot but, now I'm ready to crack that engine open and get it fixed up. What do you think works best. I can cet a set of Crane 1.6 rollers for $100. Is that good or should I go with the Comp Cams rollers. I herd that there great!!

Bill C

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