Port Runners/Plenum??
Thread Starter
Burning Brakes
Joined: Jan 2006
Posts: 859
Likes: 8
Port Runners/Plenum??
I'm looking to add some extra horsepower but I don't want to modify the stock intake. I don't really care too much about upper end power, but if I can gain some upper end without losing any low end torque, I wouldn't mind doing that. Right now the car is mostly stock except for headers, true duals, and cut lid. I'm thinking of porting the runners and plenum for some extra air flow. My question to those who've done this is, first of all, will I feel any significant gain? And second of all will I lose much, if any, lower end torque?
I'm not looking to get into the 12's by building a high rpm monster, my goal is to get into the mid-low 13s, and maintain all of the lower end torque that the L98 is known for.
I'm not looking to get into the 12's by building a high rpm monster, my goal is to get into the mid-low 13s, and maintain all of the lower end torque that the L98 is known for.
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
I got no measurable gain from porting the plenum & runner flanges.
For quicker throttle response try bumping the TPS base idle voltage to .65Vdc.
A 160deg T-stat & fan switch will add some power as will cut-back stock AC Delco spark plugs.
Of course deleting the spare & jack will drop about .05sec off the time slip at the traps.
BTW, what is your current ET, trap speed and 60' time??
For quicker throttle response try bumping the TPS base idle voltage to .65Vdc.
A 160deg T-stat & fan switch will add some power as will cut-back stock AC Delco spark plugs.
Of course deleting the spare & jack will drop about .05sec off the time slip at the traps.
BTW, what is your current ET, trap speed and 60' time??
Thread Starter
Burning Brakes
Joined: Jan 2006
Posts: 859
Likes: 8
I got no measurable gain from porting the plenum & runner flanges.
For quicker throttle response try bumping the TPS base idle voltage to .65Vdc.
A 160deg T-stat & fan switch will add some power as will cut-back stock AC Delco spark plugs.
Of course deleting the spare & jack will drop about .05sec off the time slip at the traps.
BTW, what is your current ET, trap speed and 60' time??
For quicker throttle response try bumping the TPS base idle voltage to .65Vdc.
A 160deg T-stat & fan switch will add some power as will cut-back stock AC Delco spark plugs.
Of course deleting the spare & jack will drop about .05sec off the time slip at the traps.
BTW, what is your current ET, trap speed and 60' time??
I have no idea what my current et time is since I've never taken the car to the track. However, after I do a few more mods, I will get to the track this Spring and see where I'm at.
Thread Starter
Burning Brakes
Joined: Jan 2006
Posts: 859
Likes: 8
Quick question, I am planning on getting the march underdrive pullies, but is there much of a performance difference between the steel and aluminum pullies? The aluminum ones are $100 more. Also, should I go with the power and amp series or the performance series?
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
I have the steel March Power & Amp series, running only the crank & alt pullies, and didn't see any gain in trap speed though the engine seemed to rev quicker in 1st gear. The overdrive alt pulley is needed to assure charging at idle.
In retrospect I think the Al pulley set would be better due to the lower rotating mass of the Al pulleys.
In retrospect I think the Al pulley set would be better due to the lower rotating mass of the Al pulleys.
Le Mans Master
Joined: Jun 2006
Posts: 5,642
Likes: 5
From: One day you're a Comet...the next day you're dust... Arkansas
I'm looking to add some extra horsepower but I don't want to modify the stock intake. I don't really care too much about upper end power, but if I can gain some upper end without losing any low end torque, I wouldn't mind doing that. Right now the car is mostly stock except for headers, true duals, and cut lid. I'm thinking of porting the runners and plenum for some extra air flow. My question to those who've done this is, first of all, will I feel any significant gain? And second of all will I lose much, if any, lower end torque?
I'm not looking to get into the 12's by building a high rpm monster, my goal is to get into the mid-low 13s, and maintain all of the lower end torque that the L98 is known for.
I'm not looking to get into the 12's by building a high rpm monster, my goal is to get into the mid-low 13s, and maintain all of the lower end torque that the L98 is known for.
Burning Brakes
Joined: May 2006
Posts: 857
Likes: 1
From: Morrisonville Illinios
I bought a set from ASP of billet steel under drive for less than $200 for all three. The weight saving would be not much the Aluminum ones are shinny when polished up (steel can be painted).
wro87
wro87
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Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
I didn't see any change in top end nor short time after porting plenum & runners so no change in torque. But doing the siamese base mod did cost a little low end but flattened the torque curve so that my shift points are not in the high 5k RPM range.
To do 1.6:1 RRs properly you need to install new valve springs. This requires holding up the valves while releasing the old springs. Some use compressed air but I use the "rope trick" to hold my valves up.
In any case it really isn't difficult; I would say a day or two max would get the job done.
On my '88 I had to grind down the drip tabs and narrow the bolt towers inside the stock valve covers. Neither was a big deal with a Dremel.
Since my valve covers were brown, it was a good opportunity to sand and paint them too.
To do 1.6:1 RRs properly you need to install new valve springs. This requires holding up the valves while releasing the old springs. Some use compressed air but I use the "rope trick" to hold my valves up.
In any case it really isn't difficult; I would say a day or two max would get the job done.
On my '88 I had to grind down the drip tabs and narrow the bolt towers inside the stock valve covers. Neither was a big deal with a Dremel.
Since my valve covers were brown, it was a good opportunity to sand and paint them too.
