I have an 86 TPI IROC and was looking to buy a 3 inch catback. Is the Dyno max catback 3 inches from front to back. I have heard that it is not but have not been able to confirm this. To be honest I just want something better then stock that is not too loud with two pipes coming out. If this doesnt fit anyone know of any other cat backs in the same price range?

THANX

 

3" till the muffler where it necks down to 2 1/2" IIRC.

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"I don't want to be right - I just want to know if I'm right"
-Einstein

 

Hey Striker, the stock iroc catback is 2.75". If yours is still in good shape you might consider a set of headers and y-pipe first. You could also relace the stock muffler with an aftermarket one. You should see a big improvement. A new 3" catback would be more necessary if you plane on or have mad other engine mods. Thats just my opinion anyway.
Steve

[This message has been edited by steve8586iroc (edited January 01, 2001).]

 

the dynomax cat systems for the f-bodys are 2.5 inch.i have a dynomax syetem and i'm happy with it.for the price it's a good deal.the sound is a little deeper than stock.the the tubing is mandrel bent which means that the bends are smooth all the way around the bend.if you look at stock tubing the inside of the each bend has ridges which if your making a **** load of horsepower can slightly hurt your preformance.now what i did was put this system on then 4 months later i went with a flowmaster.the sound is so much better,alot more deeper,more of a rumble.and that is my 2 cents

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1991 banditt2 firebird #130of#600

 

It's definitely not 3". I ordered one for my IROC and contrary to what JEGS told me I measured it to be around 2.75"



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87 IROC-Z, 5.7, auto, 3.27, leather, !cat, Holley fpr, K&N'S, SLP 1-3/4" Jet-Hot coated headers, SLP .218/.224 .495/.502 cam, Comp 1.5 roller tip rockers, $uperPITAram, Edelbrock lower intake, Holley 52mm tb, Dynomax\Flowmaster catback. Coming Soon(?)- Fasttrack/Accell DFI

1989 Pontiac 20th Anniversary Turbo Trans Am - 161,000 miles, !cat, 9" K&N

 

Guys, it would be awfully hard for a 3" cat to mate to a 2.5" tube. Dynomax® part #17495 - '86-'89, is a three inch tube that necks down to stock muffler inlet size after the bend to the muffler. You can cut off the neck and connect it to a three inch muffler, of which Flowmaster® sells.

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"I don't want to be right - I just want to know if I'm right"
-Einstein

 

2.75, 3" you won't see any difference. The catback is only worth around 5hp to a mostly stock car anyway.

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91 Formula
305 TPI 5speed
1LE/G92/WS6
Custom cold air intake w/K&N, SLP airfoil, ported & polished plenum, TB coolant bypass,Crane AFPR (47psi),94 octane,Crane Extruded Alum. 1.6 full roller rockers, Timing set from 4*BTDC to 10*BTDC,MSD coil,MSD6AL, Holley 9mm Annihilator Laser shot 50 wires, Ac Delco cap,rotor and plugs, Bosch O2sensor, SLP 1 5/8 headers,SLP catback,3:73s,JET 195* fan switch, Macewen white face gauges, Autometer gauges, Zoom hi-performance clutch.
Street legal with stock throttle body, runners,intake manifold,cam, and heads. Coming next..9# Procharger!