garkahn90

I am working on converting my L98 exhaust to an LT1 exhaust and need to figure out the best way. I have the pipes (cat back). So a couple of questions: Will LT1 converters bold up to an L98 exhaust manifold? Will LT1 exhaust manifolds bolt up to L98 heads?
Thanks

Corvette Kid

I would be almost positive that you will need LT1 manifolds to make the LT1 cats bolt up. As far as the rest of the system, you'll just need the LT1 hangers and hardware to bolt it up. You can't hardly give a stock set of manifolds away around here. Post in Parts F/S and I'm sure someone will have some LTx ones they'll send you for next to nothing. Yes, they'll bolt up. What year L98 do you have? '88 and up are D-port like the LT1 except I'm not sure if the port is quite as high. Either way, a bit of grinding on the LTx manifold ports will give you a better port match if needed. The bottom of the port is the only place on the manifolds that may need work. The top will already be plenty high.

garkahn90

Looking at the mods you've done to your engine I'd say you know your stuff. My car is a '90. I'll check the FS section for LT manifolds. If I'm going to replace the manifolds would it be worth considering headers?

FD2BLK

Chris is a smart guy but I have had both sets of manifolds and I am fairly sure that you can use your stockers and they will work, the air tubes are the big difference between the two. Look at it this way you have nothing to loose giving it a shot with your manifolds and if it doesn't workout you can always pick up a set of LT1's later. The big problem I see is getting the cat bracket on to the trany, it is a huge PITA Well good luck you’re your project

86Pacecar

On my 86 L98 I have headers that go into an LT4 exhaust. I went straight off the headers into the resonator. So from the resonator it is the stock LT exhaust back to the LT mufflers. Nice quiet sound, zero resonance and still give a nice sound at WOT. I had straight pipes back to stinger mufflers and the system was too loud for my wife to ride with me anymore, now with the LT4 system we can actually talk in the car again. I lost zero performance with the LT4 exhaust compared to the free flowing stuff I had, I would recommend this setup to anyone.

garkahn90

I want to keep things clean so I will need converters. I've seen some pretty cheap aftermarket ones on the web. Glad to hear you killed the resonace problem because mine is bad the way it is; stock back to aftermarket mufflers, they look like flowmasters but can't tell.

I kind of like the suggestion to just trying to bolt up to my existing exhaust manifold, no money lost there, after the cat investment.

Since I'll be doing the wrenching this winter in my garage, I am still wondering if its worth it, in terms of performance gains or sound quality, to purchase headers.

Corvette Kid

Got you fooled, don't I? I've learned as much about my engine mods from reading your posts over the years as I have from anyone around here and it's been a great help at times. I'll certainly defer since I have no L98 manifolds to compare them to. I do believe though from what I've read around here that the LTx manifolds flow a little better than any L98 ones.
Garkahn, if you could use them, I've got a brand new pair of universal 3" cats that I bought from NAPA but never used. I'll sell them for $125 plus actual shipping. Let me know and I'll get the dimensions if you're interested.

86Pacecar

I understand you want to keep things clean so using the stock LT1 manifolds and convertors will do that. Headers will give you a nice performance gain and you can get them with the emission A.I.R. tubes. From the gains I got out of my car the headers are definately worth the cost. From the headers I would go with a set of hi-flow cats. Here is where your personal chice comes into play, you could use the resonator or just go right from the cats to the mufflers. I personally believe that the cats will quiet you down enough without the resonator but I'm unsure about the resonance without the resonator. If it were me I would do the headers with hi-flow cats to the resonator and you will be quiet at cruising and idle but get a nice sound at WOT.

garkahn90

Well you know, sometimes people post questions with the hopes of hearing answers they really wanted to hear. 86, that was the answer [I]I[I] was looking for.
Is it just my perception or does exhaust really sound better through headers?
Any chance that torque will be negatively affected with this set up, everything else remaining stock?
Any suggestions on header brands, important things to look for, tube diameter, long, short, etc.?

garkahn90

I am interested if they are LT1 specific. In other words I want to be able to bolt right in without any fabrication.