Hello,

Been a long time since I've posted here. Always get great advice. I have a CARB (smog) legal engine conversion using a '94 LT1/T56 in a 1982 Volvo 242. Great driver. The engine was from a junkyard and I have replaced all sensors over the years and also had the heads rebuilt at a very good machine shop some years ago. Since the bottom end is stock, and during T56 rebuild it was clear the original Camaro Z28 did a lot of dumping the clutch, I have always driven the motor on the careful side. However, the throttle cable wrapped around the throttle plate while at WOT on the freeway a few weeks ago and the engine redlined for a few seconds before I shut it down. Once I repaired the throttle cable and got back on the road, there was a clear ticking sound consistent with piston slap or rod knock. Lifter quiet did not make any improvement. After draining the oil and cutting the filter, I have confirmed chunks and sparkle. So looks like I have internal damage on the motor.

I am putting together a game plan for doing a mild, smog legal build, that still gets me into the 375 HP range. A couple local engine builders have gone over the scope of work, one in particular has experience building LT1 motors to stay CA smog legal, and has advised me on cam/lifter/valve train package that would give me better drivability over stock, better high RPM pull as well as a decent increase in power across the board.

While dealing with removing the engine, I am going to finally opt for a Painless wiring harness, upgrade the Opti to an MSD/Accel unit with a new ignition coil and properly locate the PCM in the cab. I am also planning to upgrade to a hydraulic throw-out bearing. A bunch of other work with also happen, but not on the GM powertrain.

Any advice from folks here on this plan? Any engine builder recommendations in the SF Bay Area? Time to start learning more about LT1 engine builds, cam and valve train specs.

 

Has the PCM been reprogrammed? The stock rev limiter should have protected the engine from damage due to over-revving. Wouldn't have exceeded ~5,800 RPM.

Do some reading before replacing the Opti. Is there any evidence of problems from the current unit? Is it the factory original? How many miles on the engine? A healthy stock Opti is likely to be more reliable than just about anything available currently. By “MSD/Accel” do you mean an MSD cap & rotor on an Accel base? The MSD cap is usually OK (except for a bad batch about 5 or 6 years ago), but the Accel is not considered the best quality available. Only the Petris unit seems to be problem free, although there was a recent report of a bad batch of optical cam position sensors delaying production.

https://petrisenterprises.com/collec...rk-distributor

May just be semantics, but I would assume that in CA, replacing the cam with one that does not bear the CARB-EO certification is not “legal”. Most likely the builders have just figured out how to use a non-certified part, and tune to pass the tailpipe test.

 

OP

Having danced the CA smog legal thing for the past 26 years with my 96 LT1, now a H/C 383...I can say its the PCM tune that is critical to pass the smog check. I have to get the visual, plug in and tail pipe so there are no offramps, so the tune needs to be solid and the cam not too big. 218/224 would be as far as I would, and did, go

Assuming you have CATS and the other associated emission components (air pump, EGR, PCV) working correctly you will need the PCM tuned for the engine mods you are considering.

Fortunately you have a OBD1 era LT1 and have an 82 car so your emission testing is not as severe as 96 OBD2 cars

Your glitter in motor is likely bearings. Just rebuilding the motor stock with new bearings, cyl hone and rings would not require any pcm tune. Even if you needed a .030 bore and new pistons it would be fine with the stock tune. . Lloyd Elliott would be a source for cams. I believe he has some emission cams and one "may" work well with a stock tune

As Fred notes, do not get rid of your opti if it is an original AC Delco. I believe your opti is a spline drive unless the donor car was a B body than it is pin (newer). Either one, MSD makes a cap and rotor kit which may be needed if yours is original as like any dizzy, C&R are wear items.

Regarding PCM tune, my tuner has passed away, RIP Ed Wright, but I have heard good things about moehorsepower tunes. Injuneer may have a recommendation also.

 

Thank you both, great info. Injuneer, the PCM is on stock tune and did hit the rev limiter. I replaced the Optispark a few years ago with an AC Delco unit as well as the coil pack. There is an issue where the engine lugs a bit sometimes and then snaps into regular power, often during the first 1/2 mile of driving. I have suspected an Opti issue, but sounds like I should re-install the one I have and see if the replacement Painless wiring harness fixes that issue first. Will consider the Petris unit first if I go with replacement.

218/224 from Lloyd Elliot was recommended to me by another engine builder I spoke to a few years ago but I forgot the name, thank you!
LT1 Cam Info «

Will get the ball rolling on a PCM tune as well.

 

Before going to the extent of swapping Opti's, do some checks:

4th Gen LT1 F-body Tech Articles

That procedure checks to see if the PCM is providing the required support for the Opti - a ground, 12 volts to operate the electronics, and 5 volts reference to produce the pulses from the optical cam position sensor. Does not verify the quality of the Opti pulse. But the fact the engine is running indicates the Opti is producing the pulses. You can examine the shape of the pulses (supposed to be a simple square wave) with an inexpensive oscilloscope, but I don’t think I've ever heard of anyone finding a problem. An alternative is pulling the Opti off, leaving it connected, and key on rotate the drive and watch for the 5 volt pulses on a digital volt meter. The 93/94 unvented Opti does have a significant problem with rust forming due to the ozone generated by the high voltage discharge, and the rust can blind the optics in the cam position sensor. That seemed to affect my 94 early in it's life.

The procedure also verifies the integrity of the electrical hookups for the ICM and coil.

The intermittent lugging could be any one of a number of problems. A Scan9495 data log can often reveal the source. Problem is finding someone to review the data log. I was doing it over the years, but I've given up because most people seeking help don’t want to provide all the details of their build, won't respond to questions, won’t follow up on suggestions and additional tests, etc. Everyone wants an instantaneous “cure”, and it seldom works that way. And sometimes I can’t find the problem.

What is the condition of the MAF sensor? Has it ever been cleaned?

And unfortunately there's only a handful of us left here on this site, maybe a 1/2-dozen that can provide meaningful help.

 

The MAF sensor has not been cleaned since it was replaced a few years ago. Will do, that was a maintenance oversight.

Sorry to hear this forum has less people on it, I've always gotten such good advice and guidance. Happy to take a step-wise approach and follow up if folks here are willing to. The only way I have ever kept this silly project car on the road is with the help of the engine/vehicle community and local gearheads.

 

OP, the point Fred makes about vented vs non vented opti is correct.I am not sure if the early 94 "F" body cars had the non-vented as originally the Y body (Vette did have non vented).

Do you have 2 vacuum lines running to the bottom of yur Opti? if so its vented. Sometimes the check valves (blue and white) on the Opti vent harness get plugged which results in non-venting thus the spark discharge crud builds up inside Opti and contaminates the optical pick up. It can be carefully cleaned. I use a piece of kleenex to slide in the optical pick up. If you remove your cap any crud will be quickly seen inside Opti. Use a skim coat of dialectic grease on the large O ring on cap on reassembly. Use blue loc tite on rotor screws. Also if those check valves are reversed, the opti will not vent. They are one way directional valves.

IIRC MSD makes a vented cap for non vented opti if that is what you have

 

93 and all 94 F-Bodies had the splined shaft/unvented Opti. Went to pin drive/vented for 95 model year and newer. I'm not sure when the B-Body or the Corvette used in 94.

 

I have the spline drive, non-vented Opti.

 

B bodys starting with 94 had vented, pin drive opti.

OP, moving forward you would be better to convert your non vented to vented....if you can find the C&R MSD kit. "If" you have a opti issue and when you take the cap off there is crud inside the opti, that is a clear indicator it is contaminated and will cause issues. It can be cleaned but without vented Opti that cause will return

Since you are doing a cam, get one for a LT1 with pin drive Opti...although that means you need to replace yours. Petris would be a source for one. Keep the old Opti, the Mitsubishi optical sensor is gold

I believe you would need a 95 timing cover though

 

The Petris 93-94 spline drive unit is vented. Also sells the vent hoses with the proper fittings, and new harness.

 

Hey folks here is a bit of an update. Making good progress.

Spoke to a few engine builders in the area, found one I plan to work with. He is planning to break the engine down and assess damage before planning a build up but I have initially scoped a 218/224 cam and am looking at this one from Lloyd Elliot. In addition I have mentioned an interest in 1.6 ratio rocker arms to accommodate stiffer valve springs as well as new valve guides and lifters.

Regarding the lugging issue I mentioned, I inspected the MAF sensor when I removed it. It was recently replaced with an OEM unit, the filaments look clean.

Ordering my a new wiring harness from Painless next, and sending the car out for some frame repair once I remove the interior.

Lemme know if any of this sounds off. Thanks!


Exhaust, accessories, engine wiring removed, and almost ready to lift out the engine.



Front bumper, radiator core support and cooling removed.

 

Hey folks,

Already a year later...but headed in the other direction. Engine was rebuilt by a local shop, I got great advice Lloyd at elliottsportworks.com and went with the following build:

214/222 .511/544 112 LSA Cam
0.600” springs (145 lb seat)
LUNATI 15345 rockers

Putting things back together and noticed the Opti is damaged. This may be the source of a surging/lugging I sometimes had from a stop before the engine went.

Harness connection is damaged with wiring exposed.

Looks like the Petris unit is no longer available or at least not currently. Sounds like the MSD unit is not reliable. Any other recommendation for where to source a reliable Opti?

I also need to make a call on the clutch. This motor should be making 320-340HP so no need for anything performance here. I am thinking the McLeod Street Pro kit? The pic seems to show a hydraulic throwout bearing, need to confirm it is the standard type. Any other clutch recommendations? I have the Hawks Motorsports clutch fork and would like to make sure I eliminate the chatter from the clutch fork when I had the clutch engaged and the transmission in neutral.


All rebuilt and ready to go back in!



Lots of work on cleaning and painting the engine bay. Getting the Painless harness setup and connected.

 

I have never had any "chatter" from a LT1 clutch fork. Clutches, yes. Clutches with "puc" type surface of ceramic, Kevlar are prone to chatter.

A McLeod full face organic clutch disc will be fine for your HP. I assume you are using the "pull" type LT1 clutch?

Stock LT1 was external rear balance so a stock LT1 flywheel will work. If the rebuilt motor was made "internal" balance, then you need a neutral balance, aka zero, flywheel. A machine shop can grind off the weight and neutral balance a stock LT1 flywheel. Aftermarket neutral flywheels are also available but have it balance checked by a machine shop. My McLeod was 25 grams off

 

Thanks Chimera96, appreciate it. Sounds like the McLeod clutch will work well. I sent the flywheel along with the motor and yup the builder balanced the internals to the flywheel as I understand.