On my 66 mustang with a 302 I just put a holly 500cfm carb on, and it was a blast to drive... It had as much or maybe even more performance as my 600cfm 4bl on my mav... both engines had a small cam and long tube headers...
I don't plan on keeping it stock, but my budget for this car is pretty small, and its mostly a learning experience. I will have to fix the exhaust system sooner or later, I thought i might as well upgrade while I'm at it. Is putting headers on it really that stupid? Personally, I think the 4 door is a very pretty car, and prefer it over the 2 doors not saying anyone else is wrong, just preference.
I say, build what you like regardless of how many doors! My race car is a 4 door. As for the headers, that's not a bad idea at all. They WILL make a difference, even on a stock engine. If you are going to make any other performance upgrades down the road, you would be needing them anyway to take full advantage.
You guys poo pooing headers on a stock engine don't seem to realize a large part of the loss in HP from gross to net is the fact that '71 & earlier used open headers vs manifolds and full exhaust system from '72 up... Yeah there are other considerations like less compression, leaner carb , reduced timing , all accessories installed, but rating with a corked exhaust was the big loss...
the subject of headers always starts a... poo pooing contest... JMO...they make little difference at W.O.T. on a mild to stock engine.
Just guessing here.. but I think maybe you might need a new engine tuner, Frank. Because that's never been my experience not even once through the years. Retuning the engine after uncorking the stock exhaust is key to maximizing gains from less restriction/pumping losses. And if you do it right.. the gains are quite noticable all the way from idle through redline. Even if that redline is still tractor-like due to the far too short stock style cam.. it gets extended by at least a few hundred rpm before the motor falls over the cliff. Also keep in mind that many stock style single mufflers flow less than 200cfm. Just chopping that damned thing off all on its own will free the engine up for better power and rev range. No carb or intake swap required.
It's not the lack of headers; it's the 2-inch single exhaust and restrictive OEM muffler that's choking it. On a stock engine, a full dual exhaust system with performance mufflers is plenty sufficient. Will headers flow better? Of course, but it's nothing you're gonna feel by the seat of your pants. The additional under-hood heat introduces all sorts of fun new issues.
that's my thinking also. try a set of headers with the stock exhaust and get some #s... headers alone are of little to no gain....carb, intake, heads, and dual exhaust system is what makes...headers work...
And who said the OP wasn't going to install dual exhaust on his car??? You guys seem to Assume a lot... Anyway a with asthmatic single exhaust, it's still the first up grade that should be done so other mods will perform their best...
he really didn't say much about what he was going to do...to or with the car... just asked..."New carb or exhaust?"...maybe headers...
Obviously a few good points being made here but I can tell you for absolute fact that the stock manifolds are a serious hindrance to flow. You guys can speculate all you want to about the "too small to notice" power gains.. but if you really care to learn something about these specific benefits there are tons of dyno and flow bench numbers comparing headers and stock y-systems along with some pretty serious flow drops when bolting on a stock manifold vs typical port pipes used for flow bench. Ever measure the outlets internal opening and look at those pinches, bumps and sharp turns in there? This is why even porting the stock manifolds is easily worth 3-5 ft/lbs of torque everywhere in the power band and slightly more up top if you have anything more than a 1 barrel carb mounted on top of the engine. And also why moving to those hi-po 289 style manifolds gains you even more, especially if they are also ported too. Most but the least sensitive butt dyno's can feel the slight improvements to be had and would be similar to a tune up's slightly noticable gain. The other very serious flaw in the logic being used here is that not only are there immediate gains to be had from reduced pumping losses of headers compared to cast manifolds.. but even a stock y-exhausted single stock muffler restricted motor like the one being discussed here can see substantial torque gains from longer primary tubes. Just study pictures of "high-performance" manifolds and compare them to the average compactly packaged models to see the obvious trend in longer primary tubes when power is of higher consideration. This is because the longer primary tubes act to improve scavenging/resonant tuning of the intake manifold(and that little intake manifold needs all the help it can get in that regard) even when there is a serious cork at the end of the system. So, while scavenging/resonant tuning is surely squashed by fairly large degrees with that cork-like stock type muffler.. it is NOT entirely eliminated from the equation. Which is specifically why I teased Frank about needing a new engine tuner in my above reply. Because if you take a bone stock single exhaust system and do nothing more than install headers AND tune the motor to best use their advantages.. there is an eeaaassy 10+ ft/lbs to be had across a very wide power band. Not to mention that despite that very same heavily restrictive muffler being installed at the end of the system.. rev range and total power will also go up.
...may want to bump up the cam also...stock cam ain't letting any more air through it...it's hard to change just one thing. I put just a 4 bbl. on a V8 once and in the 1/4 it ran...slower...
Very true. But while that's true to a degree(well.. maybe 3 or more).. there are many restrictor plate motors and severely rule restricted classes that are forced to run stock factory numbered parts. The main thing that they all have in common is the use of a well designed exhaust system to capitalize on strengths.. and more importantly.. to crutch the weaknesses. Back to the original question though.. I would ALWAYS(UNLESS.. it's single barrel carb setup that has higher restriction than the crappy muffler causes).. ALWAYS start with an exhaust upgrade for a lo-po daily driver since that's where most of the main advantages will come from. Especially mileage gains(again.. with complimentary tuning). If the exhaust builder has the proper foresight into future engine mods.. the rest of the upgrades will only become that much more complimenary from that baseline flow improvement the exhaust has to offer.
he is asking..either/or... so you think he will get a noticeable difference from his 2bbl. with an $800-$1000 exhaust system? (headers, free flow mufflers, dual bigger exhaust pipes)
Carb would probably need richened for max performance but yes there will be a gain from headers and larger a exhaust... I think this is where the old wives tail of "needs back pressure to run right" started... Could be sort of true if the carb leans out because of better exhaust flow, in reality the carb needs rejetted or CFM increased...
