At 08:33 PM 3/6/06, John Greenlee wrote:
>".... will be fitting a new exhaust and am interested in fitting a header as well. My 1600 is mildly tuned with a .030 overbore, aluminum ‘B’ replacement head milled back to standard compression ratio, and Moss ‘fast street’ cam."

That sounds like a nice mild upgrade street engine, maybe a smidge over 100 BHP.

>"I am looking at your site at the header EXL99 and exhaust systems ES060 and ES060T".

With a quick web search I find these part numbers on the APT web site here:
    Part No: EXL99 = http://aptfast.com/item/5460547-mga-lcb-ex-header?keyword=EXL99

Pictures on the APT site do not necessarily represent the actual exhaust pipe bending profile for the MGA.

The original MGA pipe goes under the rear axle. If you lower the ride height for racing the stock exhaust pipe might get very close to the ground, but it won't interfere with the axle. If you raise the ride height with improper new leaf springs, there may be a problem trying to route the exhaust below the rear axle (and problem with length of check straps and travel of shock absorbers). The APT systems should go under the rear axle in original style. The resonator (if there is one) should not be positioned under the rear axle. It can go just ahead of the rear axle or under the floor (not too close to the plywood please). I would ask about these issues before buying any non-stock exhaust system.

>"Are these a good solution for a normally driven road car?"

Yes, with some reservations. See EXL99 headers here:
http://aptfast.com/ShowItem/102516%20MGA%20Long%20Center%20Branch%20Header.aspx
Similar headers form Moss Motors here:
https://mossmotors.com/performance-exhaust-header#

The Moss header design has changed more recently, now a one piece welded system (picture at right).

The trick with installation of headers is that the pipes must clear the steering column on a LHD car, and it's a close fit with the MGA. I know the Moss headers clear nicely. I'm not familiar with the APT headers. This is probably okay, but not guaranteed (yet). Some MGA headers made in the UK or in Australia do not fit a LHD car. There is also some concern that the original carburetor heat shield may not fit with the headers, but so far I have no experience or feedback or pictures.

>"What size tubing is used in these systems?"

I don't have the spec's on any of these headers, but would guess 1-1/2" for the large bore header tubes and either 1-3/4 or 2" for the single outlet tube. The APT Maniflow exhaust system used 1-3/4 inch pipes after the collector, which is plenty big enough for street use, even with a warmed over engine. Original MGA exhaust pipe is 1-1/2" so there is not much benefit in fitting the headers with the standard exhaust. The Maniflow headers have welded construction to eliminate lap joints and any possible leaks at the extractor to collector pipe joints.

The APT Maniflow exhaust system uses glass pack silencers, which are perfectly functional as delivered, but give me some cause for concern. My MGA has the Falcon stainless exhaust system (from Moss Motors) in stock configuration with 1-1/2" pipe but with glass pack muffler. I takes me no more than 40,000 miles of driving to blow the fiberglass out of the muffler, after which is becomes irritatingly loud with raspy pitch. I have installed a new muffler a few times (previously provided by Moss under lifetime warranty). I have recently endeavored to re-pack the fiberglass. This worked well for a short time before blowing out the new random fiber packing. I might try it again with tighter packing (whenever it irritates me enough to get motivated again)..

Definitely avoid the big bore headers for a street engine. The larger header tubes are good for 140+ bhp and engine speeds above 5000 rpm (race engine of course). But at lower engine speeds (below 3000 rpm) the big bore tubes do not scavenge as well and would result in reduced low end torque (less power for normal street driving).

"Is this a ‘bolt together’ proposition?"

Yes, or at least it should be. You will need all new pipe hangers, as the original ones only fit 1-1/2" exhaust pipe. Check to verify that the proper MGA hangers are supplied with the exhaust system.

Note: This picture does not represent the correct configuration for the MGA. With the "two box" system the small muffler goes under the floor up front, immediately after the 2-into-1 collector.

"Which of the two (single box or twin box) is better for this setup and to give a sports car sound that is not ridiculously loud?"

The larger pipe and straight through muffler is substantially louder than stock exhaust (even though the original muffler is straight through glass pack). Some people like the adrenalin rush, some not. With the muffler in back it doesn't exactly set off car alarms, should be street legal, but can be an attractive nuisance around cops. The additional small muffler in the middle makes a decent resonator to cut sound volume noticeably and should have almost no additional restriction. A race car wouldn't want the additional weight, but otherwise it may be only a matter of cost. The MGA is enough of an attractive nuisance around cops, and I prefer to keep a lower profile, so I think I'd go for the two box system for a street car.

If you do this, take picture and make notes, as I would like to post the feedback.