Using a Stock Muffler

[mountainkowboy]

I did a search and either didn't come up with the right term or words.

What is the "real world" largest engine I could build and still use a stock muffler? I was thinking about running a bigger single carb but wanted to use the stock muffler for the better manifold heating. Or is there and aftermarket header that can match the heating ability of the stocker?

[Marc]

What is the "real world" largest engine I could build and still use a stock muffler?...

The RPM/valve & headwork enter into it too, but for a mild engine with a 1-bbl you could probably get away with 1835cc before the stock heater boxes & muffler were a severe restriction.

A considerable amount of the restriction of a stock muffler comes from the tailpipe tips; removing them completely (or replacing them with a "Zoom Tube" AKA "Boom Tube") is just too noisy for most tastes, but you might try taking the baffling out of them first...if that's not too raucous for you, the next step would be to remove them and weld larger-diameter pipes onto the muffler outlet stubs (perhaps with turn-down ends to direct some of the noise towards the pavement)...

[mountainkowboy]

Good to know, thanks Marc. Starting to plan the Ghia for its comeback and am weighing my options. I have a real Weber 32/36 that came on it when I bought it and have been playing around with the idea of using it, but research has proven the manifold heat is imperative to that carb to work properly, hence the stock muffler usage. I have used that carb in the past with great results, but only on water cooled vehicles.

Now that my little shed/shop is almost done, my next project is the Ghia's return to life.

[Marc]

How happy you'll be with the proggy depends to a large extent upon the weather and the weight of the vehicle (and late 'Ghias aren't exactly light). They're horrid about 8 months out of the year up here in Seattle, but might not be too bad in SoCal. Unless you spring for one of the "deluxe" manifolds that provides extra preheat to the plenum chamber area, even with a stock muffler you can expect a pronounced stumble when accelerating from low Rs when it's cool and damp out; fattening the jetting and pump shot help but at the expense of fuel economy - better to fabricate a warm-air box to put around the aircleaner in the wintertime and just learn to live with the flat spot while the engine's coming up to temp.
Another thing to consider is modifying a header so that one preheat flange gets plumbed to a low-pressure point (the collector junction) so there's some net flow as in the stock muffler

[mountainkowboy]

I live basically in the desert, (it was 106* today) and the manifold has the pre-heat ability but wasn't hooked up. I haven't got "into" the engine yet. If the endplay is good and the rods are tight, I may just do a top end with new heads to get her on the road while I build the engine I want.

[Marc]

In your climate the proggy will probably be fine with only rudimentary preheat, so any header that has the flanges will probably suffice (at least ~300 days a year, anyway) even with the non-deluxe intake manifold...

You can sneak the rods off to check the bearings without splitting the case (may as well just throw new ones on if you go that far; if they aren't showing copper it's a pretty safe assumption that the mains are still serviceable - peer in and inspect the lobes & lifters first though). Rather than clean/hone/rering the stock P&Ls, consider a set of AA slip-in thickwall 88s - you'll need to have the heads cut to the "90.5" diameter for them, but odds are that's what you'll be using them for someday anyway.
If you think you may run it as a 1679 for a while, you might want to also fit some HD singles while the heads are off (use .015-.020" steel shims under 'em) - then you'll be good to go if you decide to add some 1.4:1 rockers. Those "wake up" a stock cam noticeably, although you'll lose a small amount of torque below 1800 RPM. With stock springs the improvement's not enough to justify the cost IMO, but the HD singles will make it worthwhile.

1679cc is only 6% bigger than stock, but it's enough to be worth the effort IMO. Just increasing the bore with no other changes will raise your C.R. by ~⅓ point, so it could be borderline on California Regular - depending on the chamber CCs, you may want to toss some .010-.020" shims under the jugs to keep it <8.75:1.
Or, just buy better gas...but honestly, there's only maybe 1 HP gain for a 0.2 C.R. bump, you can realize that by just port-matching the intake and save at the pump.

[mountainkowboy]

Absolutely what I was planning on. I figure as long as I'm not over .010 on my end play......and the rod bearings are ok. I should be able to get 30-40K out of that engine while I build a decent one. I have a set of Kads that I was planning on using for a 1915 or so engine. More interested in it being a "spirited" DD when done, but would really just like to get it back on the road and drive it while I collect the parts to do it right. The wife has put the nix on keeping both the Ghia and the Vert, so the Ghia wins. I may just pull the engine and trans out of the Vert and turn it the way it sits without the FV wheels...undecided right now.