How many of you fellers have SLP runners on your car? Can about the same benefit in air flow be accomplished with porting/polishing the OEM runners? At around $350, the SLP's are kinda pricey if I can see similar gains with a little elbow grease.

The reason I ask is I am about to put a set of headers on so I would like to improve the flow of the intake side as well

 

There is not enough meat on the stock runners to adequately port them. Go with the SLP

 

I am not running slps but there is very little that can be done with stock runners because they so thin. Slps can be siamesed very deep, but past that they are not a good choice for runners based on some of the other aftermarket options.

 

SLP runners are really the only runners that allow you to siamese the top end down to near superram length (i.e., 1/2 length dividers). That will raise the TPI WALL a significant amount (by tuning reversion wave to a higher rpm). Over the last couple of years, everyone I've spoken/written to (that's done SLP siamesing) was happy with the result. If you port/replace the base too, results are even better. (Understand though, that this mod will never produce the top-end power of a superram.)

This mod is best suited to stock motors, but it's still an option for motors with head work and/or a cam. I say this to people where their primary goal is to create a TON of low-end TQ -- where 1/4 mile times aren't important. (Heck, there's people running 383's who still opt for a TPI intake. Those people want TORQUE!)

People who want a 1/4 mile car don't like any TPI setup because it limits top end flow -- and therefore 1/4 mile times. The only exception is the FIRST intake that has bores large enough to combat this problem. Even then, the FIRST appears to remain in the category of "almost-as-good-as-short-runner-intakes-for-racing".

I've also seen people siamese the bottom end of the runners, the top of the base, or both. (This version of siamesing can be done with most any runner). The problem I see with this mod is it can/will disrupt reversion waves. Yeah, it does improve top-end but low-end seems to end up worse. (This is one mod I wouldn't do because 1/4 mile times don't seem to go up using this trick. Plus, I've seen 1/8 mile times go down!)

Some people have gone so far as to cut open the SLP dividers and remove the divider -- but that's where you need to pick a short-runner intake because that's what you'd be trying to make! The exception is where inspections require a stock configuration and it has to look stock/near stock.

 

Good Information

 

I think REDTORNADO is elling some ported out large tube runners and intake, not sure, so check the forsale section
here ya go good price to me.
http://forums.corvetteforum.com/c4-p...gm-plenum.html

 

He could use the runners but not the plenum..Its for a 90..

 

whoops, I did not know he had an 85 until you said something, my fault for not checking his profile.

 

Thanks for all the replies and that great bit of info, Gregg. I am going to rebuild my L98 probly punch it out 30 thou, new cam (still researching), hopefully P/P the heads. I will reuse the plenum or buy one of the P/P/siamesed ones from the feller on eBay. Thats where the SLP runner idea came from, he stated that his plenum will work best with them.

A Super or MiniRam is out of the question financially, altho I would really like to have one. I will need that big money for the rebuild anyway. I have already abandoned the stroker idea for the price tag cause I can use the saved money on other needed items.

I am not really concerned with where I top end, just want to get there quickly. I might not be able to kick my C5 buddy's tail but I want to suprise him, like, "Dayumm, that old hunk of iron and 'glass can run", lol.

 

Have you considered a modified LT1 manifold? You can find them for three to four hundred dollars.

Check out Thirdgen.org

 

I had the SLPs on my 86. That and 1.6 rockers got me 13.7s. I felt they were pretty good for the price. The casting is large, takes some care and patience to install. They are very close to the valve covers. Would never give up the Mini on my 87, but it killed me to pay the bucks I did to get it.

 

so..do the SLP's create more torque ? i like the look of them !

 

Now you've changed the rules (from your first post)....

If you're going to refresh the bottom end and put some better breathing head/cam on there too, the package NEEDS to be completed with headers and an intake. That doesn't just mean throwing some SLPs at it. After beefing up the block/heads, NO one here would suggest you install SLP runners w/o doing something to the base too. That's going to cost you another $300ish (used). A matching plenum will add to the final bill. If you bought the whole combo to do the siamesed SLP intake, you'll probably spend as much as a SR/MR (used). So, looking for a used SR/MR isn't out of the question.

I'm not saying that the SLP won't be a viable option after your other upgrades -- just that it might not be much cheaper (if at all). The other good thing is that you could run the runners for awhile -- until you got more money to do an intake right. And, the intake isn't as hard to r/r as the other stuff. (Plus, reselling SLPs can return most of your money.)

To me, your last sentence speaks volumes. If you want a quick car, a FIRST, SR, or a MR will be quicker in the 1/4 mile. Most would say the MR is quicker off the line because it's easier to launch. (The short-runners also help off-idle responsiveness below 2000 rpms.) But, let's talk about how the vaious options would perform.

The SLP intake would provide the hardest pull when you're tooling along and drop one gear to the middle rpm range of your motor. The hogged out SLPs with a base should pull to 5k rpms (and they'll pull hard). This option would burn rubber all day long -- and would do it into the highest rpm/gear with a built motor.

The FIRST and the SR pull higher to ~5.5k rpms -- with a bit less pull in lower rpms. Some of the TQ is traded for high-rpm speed.

The MR will pull to 6.5k or higher. It'll be fastest but smoothest -- because of the wider power band. Higher spinning motors with wide powerbands are simply fastest. That would get you "the fastest car".

The choice is complicated.... You can choose what feels the fastest or you can choose what's really the fastest. What it comes down to is whether you want excess power to pull and peel at lower rpms or whether you want smooth power that get's you somewhere fast.

With the short-runner intake, you should end up as fast/faster than your C5 buddy. If you raced him from light to light or rolling and dropped the hammer, the SLPs would pull out front quickly, but he might have a chance of catching you. One poster with a GMPP 350 short-block, fully ported 113's, headers, large-tube runners, and a hotcam says he can chase down a C5 Z06. So you might not be disappointed with the TPI option either.

 

if you are going to do heads and cam, then IMHO you will need an intake like

stealth ram
mini ram
super ram

to get the real performance you are looking for. those are 1 step above ported out old tpi parts right off the bat, if you open them up then you are in a healthy 350+ world.

 

I am certainly no performance expert, thats why I hang here and do alot of reading and trying to analyzing the information and ask questions. This is what I have absorbed so far. In the dyno results I have seen, max torque and HP are reached along the power band somewhere before max RPM. As I understand it, increasing top RPM will indeed increase the top end speed of the vehicle but is it that important or is the torque at the rear wheels the factor in getting to the vehicle's top speed faster? Overcoming the laws of nature, i.e. gravity, drag coefficients , etc grows exponentially while trying to increase top speed and takes large investments of money when you step outside basically stock set ups and only smaller gains are realized because of these laws.

Gregg, I greatly appreciate your knowledge and help you are giving, but now you’re talking the amount of money in two (3) items that it will take to rebuild the whole motor in the SR/MR and AFR heads. Yeah, if I wait and do a lot of searching and competing for the used items available, I can save some money. I would love to be able to buy these things but its just too far outside my budget. My sled is mostly a road trip car so drivability is more a factor than maximum speed. I am trying to work with what I have, clean it up some add a few extras and stay within a budget. The SLP's were in my price range and I am trying to gain a little advantage in using a few lower cost mods instead of dumping thousands in accessories on top of the thousands in the rebuild.

Like I said, the guy on eBay who does the CNC port and polish of the stock intake recommended the SLP runners to complete the package. That with maybe a 52 mm body would supply what I want on the top end. Using my old cast iron heads with a little elbow grease (read no monetary investment) to clean them up, I will be at my budget level. I then choose the cam to match these humble mods.

The bottom end gets milled, add some flatter top pistons to raise the compression some and/or a thinner head gasket. A little balance work on the rotating assembly and add some good rings and I have pretty much tweeked the stock parts retained as much as they can be. Add the new Exotic Muscle LTH’s to my already modded exhaust and I am being all I can afford to be.

With not going with the stroker, I save at least the extra cost of more milling or a completely new block and the stroker kit, new balancer etc. Then to obtain the full benefits of the stroker, having to buy a quality build kit, MR/SR and new runners, AFR heads, programming, fuel delivery, and more would be more a requirement rather than an option. The costs of the pistons, rings, bearings, gaskets, new cam and even head work are a given with both approaches but now I am saving about $2K by staying “stock“. The engine rebuild costs me $3K instead of $5K+.

OK, so I left 100 HP on the table. Its probly best sitting there rather than under my foot any way! For now, by taking pretty much stock stuff and adding a few extras that had to be purchased anyway, I have increased my HP, displacement and torque. If all this doesnt add alot of top end RPM, There is always the future!

Sorry about being so long winded!!!!!!!!!

 

Here is another thought for you - (I had similar thoughts and issues, doing the much of the same things).

The cost for the plenum porting, slp runners, and throttle body - will run you pretty close to 1000, with the base restrictive intake still there.

That is the same cost for the FIRST -which includes plenum, runners and manifold (all of which in cast form exceeding the SLP and porting) plus larger throttle body is part of the FIRST package . This route will give you a little more RPM- meaning more HP as well.

(almost forgot - with the FIRST - you would need some fuel lines, and am AFPR) - not that expensive.

There are lots of debates of mini / Super / First / LT1

My take is this - I have an auto, that I am not planning on changing gears in (3.07's factory). that said the higher rpms of the short runners are not really going to help.

more to think about anyway....

 

What's your budget? If you can, break it down by intake/headers/exhaust/block/etc....because, for the intake alone, I see you spending enough money to have other choices.

Don't consider the TB as the most important item to replace either. It should be further down your list.

 

So your saying no matter what I do with the plenum and the runners, unless I buy an intake, its all for nothing. And instead of buying plenum, runners, and intake, it will cost the same as buying a SR/MR. What is this FIRST y'all keep talking about? I cannot find anything using the search function but that doesnt suprise me, I am handicapped that way.

Thanks.

 

im afraid of that
that's why i still have the stock tpi
i like the looks of it and i would love to add the SLP Runners,they are on my list,i like the tough look,at first i didn't like them
but i love them polished wow ....but if i buy them....it will be just looks ? will i create more torque with them ???
im more of a torque nut than HP

 

I did the runners, Arizona Speed& Marine $425, Edelbrock base $350 ported it and ported plenum.I had a built motor.I ended up with crap for horsepower and torque.If you go that route you will be disappointed.