Does the smog system affect a car's performance/horsepower? Bought a second '71 LT-1 (the new one has the original smog and the other doesn't), and notice a pretty significant difference in power between the two cars. The car with the smog has noticeably less pep.

 

The cars with the smog equipment still intact have an extra parasitic pulley for the pump as well as running off of ported vacuum advance instead of manifold vacuum advance and the CEC advance restrictions which limit advance to 3rd gear, 4th gear and WOT. and about the first 30 seconds after startup.

cc

 

The smog pump only uses about 1HP and does not affect performance in any other way.

 

Maybe power steering and power brakes has something to do with it also? The car with more pep has neither, the other has power both.

 

The equipment typically regarded as "smog" equipment really doesn't affect power much. However, compression ratios dropped in 1971 in order to lower emissions, and this compression ratio drop will affect horsepower along with the more conservative cam profiles. The distributor advance curve is slower on the emissions engines, and total timing is limited. This is easily corrected by setting the total timing correctly and running some softer advance springs.

Other comments:

• The A.I.R. pump pulls insignificant power (about 1 hp).
• The EGR is operated by ported vacuum, so it only functions at light throttle cruise - no effect on WOT performance or idle.
• The vacuum advance controls on the emissions engines limit vacuum advance under cold conditions, under some cruise conditions, and at idle - they have no effect on WOT performance.

Overall, the emissions controls themselves have little effect on WOT performance, but engine design (lower compression, cam profile, and advance curve) does have an effect on power output.

Lars

 

Be careful comparing the two; too many variables. #1 might feel strong if it's had a recent rebuild; #2 might be unmolested stock and showing her age.

Whatever you decide, LT-1 smog equipment is nearly priceless. If you pull it off, you certainly want to hang on to it.

 

Hi,
I'll second Mike's point about the value of complete systems. It was taken off so many cars that to put a complete system together for a particular engine and model year is very expensive. $$$$
Finding the proper hoses, fans, pulleys and brackets, etc, drives people crazy.
Regards,
Alan