Poor top end performance/ acceleration?

[91 LTD]

What would cause poor top end only performance/ acceleration? She'll do 100+, but it takes a long while to get there. Clogged cats? Am planning on changing the O2s cause my gas mileage sucks. Also could have sworn I smelled rotten eggs while driving yesterday. Thanks in adv.

[boXman]

What motor do you have? 302 or 351?

[91 LTD]

351w (stock), 2bbl Holley (original equip.). Could the carb need tuning ? Also finally have the time to put in new plugs so well see if they help. Boxman that chick is pretty fine, someone you know?

[boXman]

A 2bbl Holley isn't OEM, it came with a VV stock. They only have 180ish HP...Yes, give it a good tune up. Cats could be clogged.

Thanks, but I don't know her, unfortunately.

[interceptor1985]

rotin egg means bad cats so sorry but they are expencive

[91 LTD]

rotin egg means bad cats so sorry but they are expencive

yah, thats what I thought. Summit has Magnaflow cats for a vic for 70 bucks a pop.

[mrltd]

Cat aren't that expensive, and when replacing the 4 you can replace them with only 2 in most places.

And if your car has a 2bbl carb, there is no point in replacing the 02 sensors....because they are not used.

[91 LTD]

Cat aren't that expensive, and when replacing the 4 you can replace them with only 2 in most places.

And if your car has a 2bbl carb, there is no point in replacing the 02 sensors....because they are not used.

Makes sense. I guess they cant "tell" the carb what to do. Why are they there then and do they affect performance in any other ways? Should I just pull em and plug the holes?

[87mefull]

No offense but try really beating the shit out of your car or taking it on a "high speed" highway run on a tank of 89 or 91 octane and some octane booster. I'm not promoting anything illegal but this will clean up your cataytics. It has worked for me and my car performs very well still with 4 cataytics on it, no problems with acceleration or top end performance. I get a consistent 20mpg and only drop to 16 when having fun with it. :evil:

If the cats are really clogged, then no amount of beating the shit out of your car or long high speed runs will help. The car will have no performance and will probably overheat with possible blow-by past the piston rings. California is the strictest state in the entire US on emissions so I would check which cataytics are legal to use in your state.

Is your car still equipped with an egr valve and all of its emissions equipment? The rotten egg smell can also indicate a lean condition. I had the same problem before with poor top end performance and overall poor gas mileage. Turned out the egr valve was bad and causing the car to run lean at WOT. I could smell rotten eggs after it was running too. Might want to look into cleaning the valve and check to make sure it works properly with a small vacuum pump, you only need a graphite gasket to replace it thats a $1.50 at autozone.

The 02 sensors are a bitch to remove, so I wouldn't remove them if unless you absolutely need to. Is the stock MCU still connected?

[gadget73]

How old is the fuel filter? And I'll agree, if it doesn't have the VV anymore, just leave the O2 sensors. I'm impressed you pass cali emissions with a 2bbl. It should fail visual right away.

[88Vic]

I was gonna say just remove the cats, but since you live in CA that isn't an option. Catco universal cats are cheap, Summit lists them at $43.39 each.

[OneBadLSE]

Unless youre experiencing some hesitation at high WOT speeds, it DOES TAKE FOREVER to get past 100 in these cars. Almost every one i had crawled at 100+. I only think theyre capable of doing 102 mph anyway (i could be wrong). My 1991 T-car was governed at 102 (i know its a 4.6 and completely different, but you would imagine they used the same limits on both cars/engines).

Think about it ... 0-60 with a GREAT RUNNING 5.0 is around 11 seconds. Quarter mile times arent anywhere near sub 16 second range. In fact, i would bet its much closer to mid 17's.

Hope that helped you out

--Lenny

BTW, if anything, the car would be capable of the 5.0 LSC governed range of 112.

[interceptor1985]

Get a 5.0 the cop car has NO problem flying low in fact it cruises at 110 everyday and we had the 140 speedo pegged before, And she will also do burnouts like a champ. Next time we are on the on ramp for the freeway we will time it ..ok?

[gadget73]

351 cars will move a fair bit better than a 5.0 car. The police 5.0 is not any different than the civilian model, the only change is factory dual exhaust. Nothing else special. The 351 doesn't have huge horsepower numbers, but its got more torque, and when running right they will roll down the highway with a fair bit more oomph than a 302 will.

[turbo2256b]

Hows the thermostat? If the engine is running to cold it wont run right and the economy goes down.