L-88 Emissions - Results, if anyone's interested

[Jon S.]

In case anyone was wondering how this worked out, 3 failures and several $$$ later, I was able to get the car passed! It wasn't easy. The first shop was a complete waste of time (and it darn near cost me the car when it backfired and caught the air cleaner element on fire - the result of a TDC timing effort). The second shop was great (Howard's Corvettes/Reno Racing, for those of you in the Phoenix area) and they came up with the recipe for success: 1)change carb jetting, 2)remove/plug power valves in carb, 3)retard timing to 6 degrees, 4)loosen the valves to .030 intake, .032 exhaust (cold), 5)increase idle mixture 1/4 turn, 6)install hotter Champion N12YC plugs and index them.

Set this way the car actually sailed through easily, so it's possible that it may not ALL be necessary. Next year I'll try it first without adjusting the valves (an expensive process). It didn't run worth a darn down to the test facility and back, but that's beside the point.

Of course now spring and summer are coming, and so are the 100 plus temps here in Arizona, so I probably won't be able to drive it anyway...but hey - it became a matter of principle.

Thanks to all for the great advice.

[Joe Scafidi]

Re: L-88 Emissions - Results, if anyone's interest

I was very interested. Congrats and I was going to post a response to your earlier question but someone had come very close to my response so i didn't bother. The only thing I wouldn't have bothered with is the valve lash. I believe you accomplished almost the same effect with the timing retard. I am very glad you didn't take all the advise and go out to buy yourself a trailer and destroy that great driving sensation. I drive my top flight 67 435 hp coupe all day in 95 degree weather. Have fun!!! Joe

[Joe L.]

Re: L-88 Emissions - Results, if anyone's interest

Jon----

I expect that the jet change, timing modification, and idle mixture change accomplished most of what worked for you.

[Duke W.]

Re: L-88 Emissions - Results, if anyone's interest

Jon - I hope you plan on reseting the valves back to the recommended lash, which is .024/.026 inlet/exhaust according to my Chevrolet Power Manual. Running the valves loose means the lash is not taken up prior to the opening part of the cam lobe,and this will shock load the valve train every time the valve is opened. Your actually better off with the valves a mil or two tight rather than loose. Plugging the power valve may result in a dangerously lean mixture at wide open throttle. I really don't understand why this was done. Assuming you ran on a dyno, the engine load would be so slight that the fuel is probably going through the idle and off idle passages with little if any coming through the main jets. In any event, the secondary throttle bore jets would certainly not come into play. You should consider reconfiguring the car to its OEM setup, but keep the new parts and install them when you require emission testing. I still can't believe that AZ requires testing on a 31 year old car. California recently exempted everything through '73, and '74 and up are now on a rolling exemption when they reach 30 years?

One other question. What kind of fuel do you have to use to keep that 12.5:1 compression ratio out of detonation.

[Duke W.]

Follow-up L-88 question

I guess this one's for you, Joe. When looking at a '67 L-88 on a site Jerry referred me to, I noticed it didn't have a PCV system, just a breather and road draft tube. I always thought L-88s could theoretically be licensed, but "closed" crankcase ventilation systems were required on all US cars in '63 and California cars since '62. The '69 L-88 on the same site DID have a closed PCV system. What's the deal?

Duke

[Joe L.]

Re: Follow-up L-88 question

Duke----

You're correct on all scores. 1967 Corvettes with L-88 didn't have a PCV system. They did, indeed, have a breather type cap on the right side valve cover and a road draft tube on the left side valve cover.

You are also, of course, correct as to the PCV requirements beginning in 1962 for California. I'm not sure about the 49 state requirement beginning in 1963, but it was certainly about that time.

I do not know the reason that L-88s were allowed to be sold, and as far as I know registered, without emissions control of any kind. I can tell you this, though: in these early years of smog controls there were some sort of exemptions for certain low production, hi-performance cars. In 1966, for example, all California-delivered Chevelles had the California-required A.I.R. system. I bought a 360 hp SS396 brand new which had it. However, I had a friend that had a very rare(for 1966)L-78, 375 hp SS396 and his car did not have it, even though they were both originally delivered to the same dealer in California. For 1966, the L-78 engines did not have the A.I.R. systems, even though they were required on all other California Chevelles(and other Chevrolets). Also, for 1966 Corvettes delivered in California with the 390 hp L-36 engine had the K-19 A.I.R. system installed. However, the L-72 engines did not. I worked with a fellow that bought an L-72 brand new and brought it to work the day he took delivery. I clearly remember looking at it and being surprised that it didn't have the A.I.R. As far as I know, though, 1967 Corvettes with L-71 engines originally delivered in California did have the K-19 A.I.R. system.

In any event, I strongly suspect that this "hidden" exemption, perhaps an inconspicuous loophole in some pre-USEPA governmental regulation, was the reason that 67 L-88s don't have PCV or anything else with respect to emissions controls. 1968 and 1969 L-88s, on the other hand, have the full bevy of emissions controls of the time, including PCV and A.I.R. 1969 ZL-1s, too.

[Jerry Clark]

Road Draft Tube

Joe, Duke and all:

A short side note regarding that road draft tube, I have a friend here who built a 67 L88 clone, he did it as correctly as I have ever seen it done. One of the major problems was finding a correct L88 draft tube assembly, he did finally find one at $2,000.00, I would have given serious consideration to an old beer can and a piece of tubing, the price of these toys is getting ridiculous.

jerry

[jeff chester]

Re: cost of these cars

Yes, the price is rather high, but you and I know that if we had say an extra $50- 100 G's laying around we would buy one.--They were/ are the KING of the hill, in a stand point of the 60's and of a collector car to day.. Like a Yenko Camaro.. Rare never see one, yet (I) drull when I just see pics of them let alone see one up close..Wait I have nerver seen ONE. Saw a L88 hood once. jc

[Jon S.]

Re: L-88 Emissions - Results, if anyone's interest

Hi Duke, You're absolutely right. We made the tuning changes just to get through emissions, nursed it to the test lane, then it was right back to the shop to set everything back to stock.

As for the plugs, we did that last. We put in 3.5 power valves, but there wasn't enough vacuum at idle to keep them closed. Correction, there was enough vacuum at idle (1000 RPM), but the 'idle' test in Az. is now done (on automatics) in drive with the brake on, which dropped it down to about 750-800 RPM. At that engine speed, the power valves were burping open and running the HC reading up.

Az law requires emission testing of all vehicles 1967 and newer. I found out this isn't a sliding window, but a fixed date. I guess it looks like this is something I'll have to do every year, so I did save all the parts.

As for fuel, I haven't driven it much yet, but I so far I've used Union 76 100 octane low lead (a local station sells this). The mechanic who got the car through emissions (also an L88 owner) suggested running a 3 to 1 mix of that and 110 octane leaded racing fuel to bring up the octane rating and the lead content, so I'm going to try that next. My driving will be light, with no racing - just driving to shows, etc.

Jon NCRS # 10673

[Duke W.]

Thanks...

...for the update, Jon. I'd suggest contacting your elected state representatives to see if they're willing to support some rational and reasonable emission test legislation. I've received some support from my local California Assemblyperson, but it did not involve new legislation other than obtaining their support for CA SB 42 a couple of years ago, which called for a 25 year exemption, but some last minute gerrymandering bumped it to thirty before it was passed the Assembly.

In the meantime - HAVE A BALL WITH YOUR L-88!

Duke