I bought my 72 comet gt a while back and felt it was definitely not performing the way I thought it should. almost as if it was just plain lazy. with no get up and go. you could floor it can it would shift down and not really go anywhere in a hurry. well we adjusted the timing all over the place with no real gain in power then we even changed the dizzy to an hei style it seemed to help a little but not much. well today I drove bills 74 comet and it felt the same way kinda lazy is the best way I can describe it. my question is whats the deal? what do you guys think is going on? I thought maybe the motor in my gt might just be tired but after driving another car just like it and it perform the same way I dont figure its just my car
Low compression and terrible gearing. There is one other possibility, does it still have a cat and is it original?
my 72 doesnt have any smog equipment and I dont believe his 74 does I know his 74 has long tube headers and dual exhaust
X2 on the low compression and terrible gearing. Get the compression up to where it was in the mid 60's which would be about 1.5 more than what you have now and go with at least a 3.25:1 gear
a couple of sure fire things that always work on those old smog motors 1. Install a bigger free flowing muffler. And remember that just because the inlet/outlet is 2.5 inches doesn't mean that the internal core is as large. Choose wisely and that stockers measily 200 cfm cork can be eliminated from the "biggest choke" list. Next would be the Y-pipe.. then onto the single exhaust pipe sizing. 2. Get rid of the factory air cleaner with restrictive snorkel. While it's always best to have fresh cool air.. the far less restrictive design of an open element is still a big plus. 3. Recurve the disty to get rid of the ultra conservative "we figure you won't maintain your engine very well" smog era advance curve. Flip the shaft 180 to use the tighter reluctor side. 10L reluctor is best for performance applications. 4. I''l bold this one to get the point across for level of importance. DO NOT RUN PORTED TIMING!!! Always use a manifold vacuum source and change the vac pot diaphrams "initial pull" to best match the new mechanical curve. This is where some of the largest gains in idle/off-idle torque can be found if dilaed in correctly. 20+ ft/lbs is very common and I've seen far more on some ocassions. Always best to tune for premium fuel when power/torque is concerned. When dialed in corrctly.. the gains in mileage achieved from fatter ignition curves(less throttle required at cruise/steady state speed) can easily help offset the increased price at the pump. If you can keep your foot out of the new found power. 5. Get rid of the choke plate and retune the carb for the new ignition curve. For best result and to avoid possible engine damage.. you MUST go back and forth with the ignition and carb during the tuning process. When getting more serious with carb and ignition mod's it's also quite common to start messing with air bleeds. Trimming throttle shafts is easy and worth a few cfm too. Usually best to find the largest carb that manifold will accept(the actual venturi size is the largest restriction point.. not the bore size itself) with Holley obviously being the most tunable. 6. Hotter coils are fairly cheap and offer greater tuning flexibilty and can affect final timing curves. Best to have them installed before spending too much time on everything else listed above. Some will say that the carb will never flow enough to make these mod's worth while.. but they are wrong. A small carb can be made to flow much more air than its rating would indicate and many vec secondary 4bbl setups don't even add much in the way of additional air flow when you calculate what the engine will consume within the stock engine/cam size/rpm parameters. This is why it's possible to completely shut down the secondaries and see very little loss in total power. Also why it's possible for 2bbl pro-stock and class racing to make WELL over 500 horsepower on a double barrel setup. Not all are using 500 Holleys either.
Doing steps 3-6 on my 74 when I first bought it was enough to make it go from meh to WOAH on the ol' butt dyno. Heck ever since I wrecked it my brother-in-law won't leave me alone about just caging it and doing some dirt track racing since his team totaled their Datsun last season. Although I didn't go open element, I just put on a bigger snorkel until I get around to making the scoop functional. Open element has been scary to me after I watched a guy leaving a car show accidentally suck soggy air cleaner into a carb, get REALLY unlucky, and blow his engine on the spot. Another thing, when I did that flipping around the distributor shaft thing, I had a serious issue with the placement of the hard fuel line going to the carb and the vacuum port on the distributor. For some reason my engine REALLY wanted those to exist in the same space, and it wasn't happening. I probably did it all wrong... but at least I got it to finally run without pinging.
Good for you and you definately "get it". The trick is to allot as much initial timing as the engine will tolerate and then divy up the rest to achieve proper sweep and total timing requirement. Which usually mean.. much more initial, tighter sweep, and limited total. Many of these old smog motors will easily tolerate above 40 degrees because mixture motion/quench is so poor. Dual snorkel mod's used to be very common and some even came that way from the factory. All you need do with the disty is to clock it into a postion that best suits clearancing and then rewire the cap to place the firing order in that new location.
So, junrai.. you gonna try to nix that old tired smog tune or not? 25-35 ft/lbs or off-idle torque, enxtended rpm range,and better MPG awaits your decision.
well at some point Ill get back to working on it but for now since I dont drive it Ill just leave it the way it is
