Exhaust manifolds..

[19Cutlass94]

While my new engine is just sitting on the pallet, Ive been thinking about getting the exhaust manifolds ported. Now my question would be that since Im not able to really tune at all ( 1994 ECM ) would this benefit my new motor? Is it something else that I would have to tune for, or would it help me? Ive got P&P'ed intakes and a 1211 cam.

any imput would be great

Thanks

[rsisbetter]

not worth the effort
if your going to spend that kind of time on exhaust, make headers
just imo

[3100 MPFI]

I agree. There is no real gain you can get from the stock setup. They are just WAY too restrictive. You are better off trying to do something along the lines of headers.

If headers are out of the question, still don't bother porting them. Just get a custom downpipe made (all the way from the flange to the cat). That is the second most restrictive thing about the exhaust system. The downpipe alone will net you some gains, but the porting not so much. Those logs flow about as good as they are going to get.

[IsaacHayes]

S&S headers, see PCGUYs thread.

But if not, forget porting them. Too much work and what little you port them isn't going to help much. But DO replace the downpipe as stated. It's terrible.

[19Cutlass94]

I dont know about headers right now in this point in time. I just got a 2.5" downpipe made up ( from the flange back ) though, so this helps.

But if I got headers then I would probably have to redeign the downpipe then right?

[IsaacHayes]

Still stock motor? how big of a difference did you notice?

I belive the s&s goes down all the way making it your down pipe. You just install a flex and then cat back pretty much. You could sell your downpipe...

[19Cutlass94]

Basically stock motor except for a UDP. So basically stock haha. Even with the exhaust done from what Ive driven it so far, its made a big difference. I havent gotten on it yet ( driving under 3k ), so once I get above 4k Ill let ya know how much better it really is!

Now if I got headers, it shouldnt be something Id have to account for in tuning correct? Not like I can really tune that much anyways.

[IsaacHayes]

oh wow, not even above 3k and you can tell LOL. WOT is when it will really show up!!

Yes headers will lean you out since all that extra exhaust gases that normally are left in the cylinders is now being pulled out making room for more air to come in, thus making more power, and requiring more fuel. Tuning will need to be tweaked yes, any time you free up more air coming in or going out usually.

Something like an UDP, or weight reduction is the only time that tuning won't need to be adjusted.

I'd still do headers though even if you don't ever plan to tune. Until you reach the limit of the BLMs adjustably, you'll still gain power over not having them (but will gain more power with a tune still). With my 3400 lower, and 3500 upper, my computer isn't even richening it up over the stock tune yet, it's still leaning it out. I guess stock tunes are on the rich side. My BLMs are lower than 128 which means it's pulling fuel over the stock tune. It took a while for the ECM to adjust and get more power, and then that's when I scanned and looked at them. So that was the change.

Your cam will screw with the stock tune the most. Everything else will adjust mostly, but not be optimal. Injectors and BLM's can max out. From a 3100 to 3400 it's not THAT huge of a change, but headers and a cam on a 3400 will be a decent change.

[19Cutlass94]

Im not worried too much about the cam. Its not very much more than stock, and Ill adjust the fuel trims so it wont lean out at WOT ( what Im worried about most ) but I just dont want to over do it all at once ya know?

But well see what it runs like when its running good and everything is adjusted to where it should be. Then I might look into headers.

Its strange your stock tune was running rich. last time I scanned mine it was on the lean side. not by much though.

[IsaacHayes]

How are you going to adjust the fuel when you cant tune? You don't adjust the fuel trims, you adjust the VE in the tune..

How old is your O2 sensor? My old stock one was reading lean and it was using a lot of fuel (bad mpg, never was good on the highway since i bought the car), and after I replaced it, the car re-adjusted and was way more responsive, and better mpg, and no more raw gas smell out the tailpipe.

What do you use to scan?

[19Cutlass94]

I know the O2 sensor isnt the original one, but I think its got about 60k miles on it atleast. I bought a brand new one to put on the new motor. I figure this would probably help me out.

What I meant by the fuel is I can adjust the pressure and Ive got several style injectors here as well. Thats about as good as you can adjust the fuel haha

Im not sure of the model of the scanner but its an OTC scan tool. Ill try and figure out what model it is exactly, but I know when it was new it was around $1k. It scans pretty much everything. Different chips scan the different cars.. Im sure you know what Im talking about. OBDI and OBDII. My dad bought it cause he needed it as a tech, and now we've got it here for our cars

[IsaacHayes]

I'd leave the injectors alone for now. Mess with the FPR if you wish, but see where you're at first with the new O2 after the computer re-learns. Mine took a long time, I thought my mods didn't do anything then finally it adjusted and I was like oh wow.

I have definitions for tunerpro RT and scanner pro if you want for the 3100. I've added just about everything available to scan, including a/c pressure, PRNDRL etc. You need an ALDL cable though.

BTW what brand O2?

[19Cutlass94]

yeah for the first couple times running it, the fuel will be stock just to see where we are after its running good. what we plan on doing is scanning the car before the swap, and getting all the system data so we can compare and use that as a reference when we do the swap. But I certainly wont say no to the definitions. Anything that'll help me learn more about the computers!

The O2 sensor is an AC Delco.

[IsaacHayes]

Cool, your O2 will be good to go.

For now take a look :

http://isaachayes.60degreev6.com/aldlcable/

I plan on organizing it and uploading the latest files sometime.

[kprofthestrs]

acdelco is the way to go it responds faster than a others i have had.

saw you mentioned ss headers. and i have read other posts were there have been good remarks which leades me here. i ordered as set of there v6 3400 headers for my 3400 swapped 95 L body. test fitted them on a engine i have at work that i am working to build for my car and they fit great the problem appears to be looking at the rear headder and then looking at the exhaust on my L body there just doest appear to be a way that the rear headder will fit right and not be into the firewall with out modifing or rebuilding it completely. i left a message for there "tech" person friday after i left work. hoping to hear back from them on monday. i was very dissapointed. they looked good just does not appear they will fit in the vehicle right. do know if anyone has had this problem or similiar. posted the pictures i took with my phone and you can get an idea of what i am saying. but they bolted onto a 05 3500 engine i am building so they will fit a 3500.

the pics i took








jim