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I just found a vendor (A+Corvettes) that sells polished (mirror finish) intake runners for the 5.7 1987 engine. The set costs $309.95 and includes all gaskets. It is manufactured by SLP (???). My questions are: do they really work? They claim an increase of 20 HP. Does the plenum have to be ported to take advantage of the increase air volume the runners are supposed to deliver? Will it work if the plenum is not ported? My engine (1987 coupe, auto tranny) is stock except the usual bolt-ons (KN filter, cut lid, throttle body airflow, bypassed t.b. coolant, Hypertech thermomaster chip, cut back electrodes). Anyone has had experience with these runners? Any help will be appreciated.:partyon:
 

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OK, lets take the questions one at a time


I just found a vendor (A+Corvettes) that sells polished (mirror finish) intake runners for the 5.7 1987 engine. The set costs $309.95 and includes all gaskets. It is manufactured by SLP (???). My questions are: do they really work? yes they CAN really work well but to get the full potential youll need to remove the upper 2" of the runner devider and use them on a ported intake WITH a PORTED PLENUM
They claim an increase of 20 HP. Does the plenum have to be ported to take advantage of the increase air volume the runners are supposed to deliver? IN all my testing ,YES, you need to carefully port the plenum and runner entrances
Will it work if the plenum is not ported?
yes but not nearly as well
My engine (1987 coupe, auto tranny) is stock except the usual bolt-ons (KN filter, cut lid, throttle body airflow, bypassed t.b. coolant, Hypertech thermomaster chip, cut back electrodes). Anyone has had experience with these runners? Any help will be appreciated
I ran them before I swapped to a stealth ram, they did very little untill I ported the plenum and intake and removed the upper 2" of runner divider but they did prove to be a good part after minor porting

heres plenum porting info
http://www.eecis.udel.edu/~davis/z28/buildup/plenum/

heres the correct way to port the upper intake RUNNERS


your problem is that the stock base intake and runners flow about 200cfm, porting the lower intake runners plenum and adding the ported SLP runner will bring that up to about 230cfm and will get you about 30hp, now compare that to a stealth ram, it, the stealth ram, flows 275cfm unported, the differance is that all the port work and SLP runners are worth about 30hp and 600 more rpm, the stealth ram has produced in excess of 60hp and an extra 2000rpm

http://www.fasterdeals.com/garageindex.html

keep in mind that both the ported SLP runner combo and the stealth ram will produce potentially much better hp when matched to a better cam, the differance in the rpm ranges, makes the change of cams to match the intakes most effective rpm range a very good idea!
 

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Grumpy: thanks for the info. Now my next question: Since I am not sure I can handle the plenum porting myself, and my car is my daily driver, do you know who sells ported plenums on an exchange basis? I mean to purchase a ported plenum, installing it (That I can do) and returning my stock plenum as a core? If you take a look at the SLP runners I refer to (www.acorvettes.com) you can see they are siamesed as far as I can see, or am I wrong? In Puerto Rico there are no Corvette-specific shops that can do that kind of job and I am leery of having the work done by a shade-tree mechanic who would probably ruin the plenum. Does the custom plenum alone that fasterdeals.com sells for $275 + s/h fit my engine with the SLP runners?
Thank you very much. You sure are knowledgeable in these topics.
PS: the cam is a good idea but it will have to wait a while.
 

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first, you can easily do your own porting work on the plenum, and SLP runners, and yes they do require more work than the out of the box runners have done for best results, all it takes is a few carbide bits and a drill, minimal skill and of course careful measurement and following the dirrections,
now to answer the other question, NO, THE CUSTOM PLENUM for the STEALTH RAM ONLY FITS THE STEALTH RAM BASE and WILL NOT FIT THOSE SLP RUNNERS or anything other than the stealth ram base its designed to work with
if you intend to stay with the basic TPI layout youll want to use the ported SLP runners on a ported plenum and a high flow base like the EDELBROCK or extensively port your factory base
yes the result is a noticable 30 hp,but the STEALTH RAM can potentially produce more!
here read this
http://www.digitalcorvettes.com/forums/showthread.php?s=&threadid=2826

http://www.gmhightechperformance.com/tech/0307htp_holleystealth/
 
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