When I go down to get my exhaust done, I'm going to ask them, if they'll cut my precats, and make the front y-pipe 2½" instead of the stock 2¼". Would it be worth the money to do this? I have a high flow cat, DynoMax Rear Y-pipe(with crossover tube) and muffler eliminators.

 

I think that would be a wise move. Our own Vic'89 and 65Z01 are equipped with bolt on mod STOCK L98's. Pretty sure they're both using a bigger front Y and Flowmasters(Jim is, not too sure on Vic's) and they comfortably travel in to the low 13's to high 12's. I think the puny manifolds and complete exhaust is a bottleneck for our cars. Maybe pop a free flow cat in back with muffs(or elims) with a new front Y and you'll feel the difference I'm sure.

Good luck.

 

That's right Vic'89 and I have nearly identical exhaust systems which include a 2 1/2" mandrel-bent front Y with no pre-cats. We also have Random Tech cats and the TPIS custom FlowMaster rear Y. I have ported my stock headers too. We run similar times with Vic in the high 12s and me in low 13s (due to his TC and DRs he pulls about .2sec better 60' times) at similar trap speeds (I may have a slight edge up top).

If you need the pre-cats for visuals, you will need to have a shop gut the pre-cats and open em up to 2 1/2" internally. Then have them mandrel-bend & weld up a front Y and weld the pre-cats back in. Then get a Random Tech 3-stage cat to take care of emissions. If you want a little more, pull the stock exhaust manifolds and port them. Once off you'll see what I mean; the AIR tubes and EGR tube extend into the exhaust tubes and excess weldment tends to block the openings at the mounting flange.

Make sure that the rear Y is also mandrel bent to minimize restriction to flow and it should be at least 3" at the cat and 2 1/2" into the muffler elims.

I think you will realy like the tone. With my FlowMasters I get some resonance but have grown accustomed to it. Anyway the sound at WOT and idle is worth it. I could just turn up the Bose but prefer to listen to the exhaust note on long trips.

 

I think I'm just going to get a off-road front y-pipe that's 2½" without the precats. I will most likely get it put on after I pass the smog test. It's only $200 for it, and I figure with that, it'll be pretty close to headers. (I'm going to port stock manifolds when I get my new heads)

 

Sounds like a plan.

You might also lose the "frisbee" from the water pump pulley for some ponies.

Since you have a Hi energy ignition you could benefit from cut-back spark ground electrodes gapped to .045" too.

 

yeah, get rid of those precats and that wimpy little pipe that goes with them.

 

Yes, the front ypipe is worth it. Every little bit helps. The catback exhaust is where I picked up most of the ET.

65Z01 and I run the same exhaust config, except He has the exhaust manifolds ported also.

Jim ,correct me if I am wrong, but I don't think there was any gain with the ported exhaust manifolds ?

Vic