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Yeah I only have the catback on right now. Proshop will toss on the headers +hiflo along with a bunch of other bolt-ons in a couple months. There's a ton of sample volumes for 350 irocs on YouTube with these and other combos but imo any clip ain't gonna communicate much vs IRL.
TBH I wouldn't worry about noise and neighbors. Just don't gun it til you're a ways away!
Wow, it's 2018, I can't believe you can still find an L98 with stock manifolds, let alone have a whole entire thread with members still arguing about them lol. I'm only kidding. Dyno Don for the win, order them and be done with it. With how fast luxury cars are today, I suspect you will be moddng your L98 faster than you think, so make the right choice now and be ahead of the game for when the engine mods come. I give it a few weeks after being beat by a new Honda Civic...
- Rob
My thinking exactly. People still arguing headers over manifolds is ridiculous. As noted in the quote, order Dyno Dons and be done.
Wow, it's 2018, I can't believe you can still find an L98 with stock manifolds, let alone have a whole entire thread with members still arguing about them lol. I'm only kidding. Dyno Don for the win, order them and be done with it. With how fast luxury cars are today, I suspect you will be moddng your L98 faster than you think, so make the right choice now and be ahead of the game for when the engine mods come. I give it a few weeks after being beat by a new Honda Civic...
- Rob
My 4,500 lbs boat of V8 luxury car despite a 2.62 rear gear ran 12.2 @ 112 with nothing more than K&N drop-ins, HPS silicone air intake ducts, eliminating the secondary cats and running a 2.5" dual exhaust with a X-pipe in place of the factory Y-pipe that necked down to 2.5" and touched up the tuning to lean it back out. Valve covers have never been off the engine and it still has the stock exhaust manifolds in place.
A 12 second vehicle now days is only quick, definately not fast even looking at factory production vehicles.
Wow, it's 2018, I can't believe you can still find an L98 with stock manifolds, let alone have a whole entire thread with members still arguing about them lol. I'm only kidding. Dyno Don for the win, order them and be done with it. With how fast luxury cars are today, I suspect you will be moddng your L98 faster than you think, so make the right choice now and be ahead of the game for when the engine mods come. I give it a few weeks after being beat by a new Honda Civic...
- Rob
LOL, I can pull out timeslips from the 90's... and I've owned 3 very stock 3rd gens, at least when I bought them. I'm pretty sure that I still have at least one set of the stock HO exhaust manifolds in the basement but it's funny that if you advertize them people will pay real money for them in decent shape.
Originally Posted by Fast355
My 4,500 lbs boat of V8 luxury car despite a 2.62 rear gear ran 12.2 @ 112 with nothing more than K&N drop-ins, HPS silicone air intake ducts, eliminating the secondary cats and running a 2.5" dual exhaust with a X-pipe in place of the factory Y-pipe that necked down to 2.5" and touched up the tuning to lean it back out. Valve covers have never been off the engine and it still has the stock exhaust manifolds in place.
A 12 second vehicle now days is only quick, definately not fast even looking at factory production vehicles.
What vehicle/engine is that?
I know that you've run some impressive times with TBI setups in vans back in the day but I don't think any of them were all that stock...
LOL, I can pull out timeslips from the 90's... and I've owned 3 very stock 3rd gens, at least when I bought them. I'm pretty sure that I still have at least one set of the stock HO exhaust manifolds in the basement but it's funny that if you advertize them people will pay real money for them in decent shape.
.
If you've got an LG4,LU5, L03, etc., with restrictive 2" exhaust manifolds, the 2.25" HO/L98 manifolds provide a real performance benefit, especially if headers are not your thing.
BTW, I bought a pair of L69 HO manifolds for my CFI off of eBay. The seller always has really cool NOS parts for sale, (for lots of $$$$) and had them listed for something crazy like $350. Obviously, no one bought them. When the listing ended, he relisted them at no reserve.
I was the only bidder and got them for 9 bucks. Combined with a new 3" exhaust, really made a difference on my Crossfire.
Well as these cars - stock and modded alike - get slower relative new w/e, they also get better looking and more unique.
Herr Bismarck- was ist die mileage? Personally I wouldn't start messing with a bone stock 350 if it was in collectible territory.
Die Mileage is 170k.. although she looks not a mile over 40k. Interior is basically perfect, exterior she has a couple chips... but she has her original windshield... lol
Die Mileage is 170k.. although she looks not a mile over 40k. Interior is basically perfect, exterior she has a couple chips... but she has her original windshield... lol
If you've got an LG4,LU5, L03, etc., with restrictive 2" exhaust manifolds, the 2.25" HO/L98 manifolds provide a real performance benefit, especially if headers are not your thing.
BTW, I bought a pair of L69 HO manifolds for my CFI off of eBay. The seller always has really cool NOS parts for sale, (for lots of $$$$) and had them listed for something crazy like $350. Obviously, no one bought them. When the listing ended, he relisted them at no reserve.
I was the only bidder and got them for 9 bucks. Combined with a new 3" exhaust, really made a difference on my Crossfire.
A Crossfire car should have had the HO manifolds on it. Mine did and the 2 others I've seen. They were essentially HO motors with a little more compression (9.8:1) and the CFI on them.
A Crossfire car should have had the HO manifolds on it. Mine did and the 2 others I've seen. They were essentially HO motors with a little more compression (9.8:1) and the CFI on them.
I can assure you that the factory manifolds that came off the car were 2". In fact, I still have them in my attic.
I can assure you that the factory manifolds that came off the car were 2". In fact, I still have them in my attic.
No HO manifolds on my Crossfire either. I did like Chuck did and swapped them on, along with a HO replacement exhaust. It definitely made a difference.
No HO manifolds on my Crossfire either. I did like Chuck did and swapped them on, along with a HO replacement exhaust. It definitely made a difference.
Yup, HO manifolds and full 3" exhaust really woke that car up.
I ran low 14's with my stock '89 L98 Formula.
After adding a Crane 2032 cam, ported alum L98 heads, 1.52 rockers, Accel base and runners, ported plenum, 52 mm TB, cold air intake, 3" SLP cat back (from factory dual cats), SLP chip, adj FPR, 2,400 converter, SLP shift kit I ran 13.7's with the 3.27 9 bolt and 26x10 slicks.
I was expecting much more improvement so I called all the vendors and asked them why only .5 second improvement. You know what they all asked???
What kind of headers are you running?
I told them I ported the factory manifolds (cause I heard they weren't that bad) and had them jet hot coated too!
Some held back the chuckles and some did not and recommended I put on some headers. The problem was I had improved breathing on the way in and the CI manifolds were the bottleneck.
I didn't like what I saw with long tubes as far as ground clearance was concerned so I went with shorty Hookers and had a custom dual 2-1/2" to single 3" Y-pipe made to hook up directly to the 3" exhaust. You could really hear the cam now! Revved easier and much quicker too.
First pass at Englishtown was a 13.19 a gain of HALF A SECOND!!!
I was now happy. Over a second quicker than stock. Stock mph was 98-99 and now I was at 106-107 mph.
With a little tweaking of fuel pressure, timing and a little unleaded race gas I was in the low 13's.
i have an lg4 bird too,i just picked up an excellent running L31 vortec and am currently going through it and have added an edlebrock rpm intake,
holley 650 ultra dp,sp350/357 cam(baby lt4) and ill probably do beehive ls6 springs,new timing chain,new felpro blues everywere,maybe
some .02" head gaskets to bump up the compression/quench.i have a b/n set of flowtek shorties and y-pipe(yeah ,i know they suck,cheap cheap) and a set of 91 tpi exhaust manifolds,which do i use?ive got a decent cat back already...
any other recommendations?
currently ive got a t5 currently and 3.08s in a 10 bolt lsd rear,
umi torque arm,loop and independent torque arm mount,umi sfc's,edlebrock lca's
iroc wonderbar,strut tower brace and the car is a super low option stripper.
you are doing 12.8s? i think i should be pretty close to that when im done,thats wicked
i have an lg4 bird too,i just picked up an excellent running L31 vortec and am currently going through it and have added an edlebrock rpm intake,
holley 650 ultra dp,sp350/357 cam(baby lt4) and ill probably do beehive ls6 springs,new timing chain,new felpro blues everywere,maybe
some .02" head gaskets to bump up the compression/quench.i have a b/n set of flowtek shorties and y-pipe(yeah ,i know they suck,cheap cheap) and a set of 91 tpi exhaust manifolds,which do i use?ive got a decent cat back already...
any other recommendations?
currently ive got a t5 currently and 3.08s in a 10 bolt lsd rear,
umi torque arm,loop and independent torque arm mount,umi sfc's,edlebrock lca's
iroc wonderbar,strut tower brace and the car is a super low option stripper.
you are doing 12.8s? i think i should be pretty close to that when im done,thats wicked
Since you have the Flowtechs and y-pipe already, I'd certainly use them.
You'll have trouble touching 12's with a manual, and probably never do it with 3.08's.
3.73's would be great for that car. The T5's .63 OD ratio will make them very pleasant for cruising also.
02-26-2018, 07:20 PM
Combined with a new 3" exhaust, really made a difference on my Crossfire. 
