3.2 GHL Exhaust problem

[Evans968]

I know there has been considerable discussion on the subject of "optimal" exhaust configuration on air cooled 911's, but after days of scouring, I have not found an answer. So many different views on "optimal". I have old GHL headers/muffler (2 in 2 out) that, when new, gave dyno readings of 202 max hp, 186 max torque before adding SW chip (haven't dyno'd since). Also provided decent heat to cabin, removable cats, great sound (to my ears anyway).
After several years repairing various cracks in the muffler and failed muffler straps (generally only at DE's), I'm deciding between replacing the entire system or just the muffler. For a mildly tuned 3.2 with any muffler, I'm not sure a new, arguably better, header set (tuned, long tubes) would offer much improvement in power/torque over the GHL from the dyno sheets I have seen on this forum. But I have not yet found a replacement muffler that could reasonably be plumbed into the GHL header outlets without additional elbows in the flow path (probably reducing performance) AND that has not shown a tendency to crack under track loads (e.g. dynomax).
Question: 1) Anyone out there still running a GHL header/muffler system who has whipped the vibration cracking problem (natural frequency issue maybe?)?
2) Will a new tuned long tube header system with a low resistance muffler really offer noticeable performance over my above dyno numbers?
Many thanks!

[Evans968]

Please allow me to bump this as it appears we have no one who’s has tackled the GHL vibration issue.
But I would still appreciate opinions on whether a new long tube tuned header/ muffler system is likely to improve performance significantly over the GHL dyno numbers (202 max hp, 186 max torque on an otherwise an otherwise unmodified 3.2.

[michael lang]

It's been probably the early to mid 2000's since GHL has come up. For whatever reason it really wasn't a popular exhaust, not a lot of guys used that exhaust. I did like it though. When I did my rebuild in '15 I knew I wanted something that could help me get closer to the 250bhp neighborhood so I started looking for a GHL because I thought it would suit my needs and it was one of the few names I knew. The more I learned about exhaust systems the more I realized there were two categories: shiny and noisy giving the impression of more power and the second group being truly functional.

I could have gone with quite a few very desirable options in the second category and I really narrowed it down to two exhaust systems. I had traded emails and spoke with Brian at Rarelyl8 and really liked the results I would benefit from one of his exhaust systems. There was definitely an improvement in bhp with his exhaust over the other because the ID/OD of the pipes was a better match for the 3.2 but the other one gave me the retro look like it was supposed to be there I was going after. Since the two systems were pretty equally priced it came down to one thing...heat. In the 80's as a teenager my '68 bug had no heat and I swore to myself that I'd never own another car again that had no heat. If you've ever gone through a winter in a car with no heat, you know exactly what I'm talking about, just keeping the windshield clear was quite the challenge, especially when it rained/snowed.

My point is if you're goal is to reach a bhp number or some performance spec with a ton of reliability and you're ready to move on from your current exhaust you really should consider the Rarelyl8 pipes. Or you should at least talk with them and explain what your plan is, they may be able to give you an idea that you haven't already thought of.

I hope this helps, best of luck

[Evans968]

Thanks Mike. I can appreciate your VW experience as I had VW buses for several years in the 1970's in Pennsylvania. Always brings to mind one Thanksgiving trip with my kids with a Coleman propane camp stove bolted to a 2 x 6 between the front seats (not very wise, but I was young and foolish). So yes, that was a big part of my choosing GHL for the 911. The heater boxes were not as effective as the stock item, but were OK if I kept the engine exercised (always fun). Also, they had removable cats that gave me some fallback if/when VA went environmental (we're now committed to install full CA requirements soon). Also the primary tubes are 1-5/8 inch OD. Although I can't see much of the primary tubing as they're almost totally enclosed in the heater boxes, but the size of the heater boxes makes me doubt that the tube length matches those nice looking RarlyL8 headers. Thus the question on whether a tuned long tube header set on a 3.2 with muffler will significantly improve on the approximate 10% power gain over stock that the dyno run indicated. I've read many posts that indicate the best gains with good headers are found with extensively modified 3.2's with no muffler, which mine is not (since installing the GHL system I've had the cam timing adjusted a bit and installed an SW chip). Only problem with GHL is the vibration induced failures.
I've narrowed it down to 2 choices:
1) Buy a set of good long tube tuned headers and a muffler that will keep me legal on the noise restricted tracks (DE's and auto-x's) and accept little or no heat and no option on passing emissions test (i.e. track car only).
2) Find a lighter muffler with well designed hardware for supporting it from the engine case and have an exhaust shop fabricate connector pipes from GHL collector outlets to new muffler. Problem here is the muffler should have an inlet on both ends to minimize bends in the new collector pipe, and the best candidate for that seems to be Dynomax which another thread here reported cracked muffler (vibration issue again??)
Hey, thanks for your comments!

[darrin]

evans968 -- potential third option to consider -- IMO unless/until you do more to wake up your 3.2 (higher compression, freer intake, etc.), the exhaust system alone isn't going to provide much of a gain (note how close your dyno numbers are to stock). Like you, I like the modern convenience of working heat AND (as you may well find yourself soon) need to be smog compliant with my '86. I'm very happy with how the addition of rarely L8's active cat woke up my stock factory exhaust system. The active exhaust opens a valve just downstream of the cat that bypasses the muffler (and its back pressure) at / near WOT (when you want it) but behaves as a stock system when cruising along -- also available as a pre-muffler system w/o the cat. Another option . . . here's a link to the 48 state cat version I installed - https://mkexhaust.com/active-exhaust-with-48-state-catalytic-converter/ here's one for the premuffler - https://mkexhaust.com/active-exhaust-with-pre-muffler/