They'll come with bolts/gaskets, but he can buy some other ones if he'd like. I think I have Felpro 1414 or something like that for header gaskets right now and some Percy's dead soft aluminum 3" collector gaskets.

 

Definitely not, unless youve got a SR/MR and a big cam in it already.

20-25 is for the entire exhaust, 15 peak hp is more realistic, but with increased power everywhere

 

I agree, doesn't TPIS or someone make a 1 5/8" set? I also found a set made that size by Stainless Steel Works (I think) out of Cincinnati but they're $899, ouch! The smaller tubes will give better low end torque which is what we street guys are after. I'll bet dyno tests on mildly modified engines would back that up.

 

Its highly unlikely you'll even notice a difference between 1 5/8 and 1 3/4" headers on an L98. HIGHLY UNLIKELY

 

However feeling a difference and there being a difference are two different things. I've always believed in carefully matched components with the entire package and goal in mind.

 

Prove it.

 

Prove they won't.

 

:lol: I was waiting for that, but it only proves the same thing. :D All I can say is that I think the L98 would pickup 10hp with soda straws as headers compared to the factory manifolds. Its pathetic. :D

My own car who is almost a twin to a friend of mine makes more HP and more torque down low and one of the only differences is my 1-3/4" headers to his 1-5/8". Both 350ci.


[Modified by scorp508, 12:11 AM 1/26/2004]

 

i would have to say the 1 5/8 would work out better in that combo
we did a test last season using lingenfelter 1 5/8 against hooker 1 3/4 headers the difference in et was less than 6 hundruds of a second in favor of the lager headers but as we know this was on a very potent 406 running 11.0s at the time so this be known the 1 5/8 would be better for 350 and 383 and some mild 406s
in fact my new 434 motor will still be useing the same 1 5/8 headers for a while before the switcharoo :cheers:

 

C'mon Cork its tough to say what works for a 350 when no testing was done with one. 56ci is a big difference. Just because a 406 did what it did doesn't mean the same trickles down for all things.

 

Well I wasn't planning on starting another argument thread but consider this. I'm sure you know that longer tubes provide better low end power and shorter tubes work better upstairs. Now generally speaking, on mass produced headers optimum length for a street application is usually sacrificed for reasons of fitment. Hence, the smaller primaries become even more critical to retain the maximum low end benefit. Also general drivability and response will be at their best. Since I don't have an L98, a dyno and a couple sets of headers handy here in the bedroom, that's the best I can do tonight. Happy modding to all!

 

Please see my sig. I just had my Hookers (1 3/4") installed last Friday. I too was worried about "low end loss" (after all, its one main reason I bought my L98) before I embarked upon my purchase. In fact, I consulted with a boatload of people here, as well as some other contacts. My input is purely subjective however, I haven't dyno'ed it and I don't go to the track. But in everyday driving, let me guaran-ball-bearin'-tee you that the low end is fully retained, at least from what I can feel. The rest of the RPM band - especially mid-range - is a heckuva kick in the pants.

Please note that I'm doing more mods than just exhaust. Please also note this is a comparison vs. the stock exhaust manifolds, not against another brand that offers 1 5/8".

And Scorp is right - the stock exhaust manifolds are a joke, I literally laughed my AZZ off when I saw them taken off. They are an insult to the L98! So whatever you do, rip them off (like we all should do when it comes to the Blose stereo system) and rejoice :party:


[Modified by bradvette, 10:54 AM 1/26/2004]

 

My '90 picked up 35rwhp with hedman 1 5/8" headers, dual 2 1/2" exhaust (!cats), air pump eliminator and free mods.

 

Just because there was no loss from the stock set up, doesn't mean that the gains were maximized. The too large tubes give breathing ability, that canot be fully exploited by a stock or mild engine. Just when the headers are begging for more, the engine says, Hey that's all I can send you. You end up trading a stronger bottom end for a top end you can't have.

A guy at my local track with a very health, high winding, 383 took off his 1 3/4" headers, which may have been too large already, and installed a set of 1 7/8ths". They made more horsepower. His MPH went up. His ET was slower. They killed his low end torque. His 60' times were slower and so were his overall ETs. Think about it!

RACE ON!!!

 

Yes. You will need to jack the car up pretty high to slide the passanger side header in from the bottom. The driver's side can go in from the top. Good luck.
:thumbs: :auto:

 

:iagree: You do not need it.

 

:iagree:
Go with a 3in. collector gasket set from Percy's. They are aluminum, resuable, and seal better, and won't blow out. They come with better bolts too. I have blown out 2 sets of the P.O.S ones that come with the headers.

FelPro offers an aluminum gasket for between the heads and headers. They seal better and are resuable.
Good luck. :thumbs:

 

Jim, all I can say is I can't feel any low end "loss" at all, and I'll say again that if anything it increased a little. But remember, base timing was bumped up, TPS voltage was re-set to .65v, and although the addition of new Taylor wires and Rapdidfire plugs (ripped out the crappy Bosch Platinum +4's that some dummy put in there before) surely has nothing to do with hp, the whole thing in tandem kicks my azz vs. before (which I could never complain about anyway) As for mid-range to upper end, its significantly stronger. Again, this is subjective, and I'll never care about ET's, DT's or CT's. Before I bought the Hookers, many people posted that the power band moves up a few hundred RPMs, and the effect really kicks in at the mid-RPMs. Guess what, thats exactly what happened!

Yes, I know things aren't maximized vs. the rest of my stock setup, thats a bona fide fact, so you're dead-on there. But I did the exhaust because more will be done. Otherwise, I would have never bothered with anything, and merrily went along in full stock form....and god knows why anyone would do that :lol: But it still won't be perfect, some hp will be left on the table because I'm staying with a LT runner setup and my heads won't be touched (subject to change some time down the road - maybe). But I see no problem with that.

To the original post.....I would get 1 3/4" headers, as long as you plan to do some engine mods for sure. If you're not, then don't even bother with any headers at all.

Are we in harmony now? :D :cheers: :grouphug:


[Modified by bradvette, 11:58 PM 1/26/2004]

 

Close. I used you for an example to illustrate to the origional poster. I didn't say you lost low end power. Re-read my opening sentence. Like too large a cam, you traded bottom end for top end. Maybe you didn't give up from stock, but you DID give up from what you could have had, on the bottom end. You have installed headers that will breath beyond the capability of your heads, cam and intake. That is why you feel most of the increase, as you said. You have the headers to allow for many more improvements. Unless someone has more money than he needs, I don't advocate going to 1 5/8th and later to 1 3/4s, but for the guy that is looking to maximize his set up and not go a lot farther, 1 5/8ths is the answer. That's all.

RACE ON!!!

 

Hey folks , let me give you some food for thought. I have always heard that the header primary tube diameter should be close to the diameter of the exhause valve for best flow. If I calculate correctly. 1 5/8 is 1.625 " and 1 3/4 is 1.75. For those running the stock small valve head on a street engine, the 1 5/8 tubes would theoretically work best . For you folks running the big valve " mega " heads the 1 3/4 primary and possibly larger would theoretically be best. In truth, I believe with a street engine it makes very little if any difference. If you are looking for that last bit of ET and trap speed or you are autoxing. the you better pay attention to the size of the primaries. I'm going to use the 1 3/4 Hookers because they don't make the 1 5/8 s possibly because they know that the 1 3/4 tubes will take care of most of their customer's needs. :cheers: