Help! My new motor's not right!

[Torque]

This is complicated to put into a thread, but I figured I would give it a shot. I have an LT1 with GTP ported heads (new valves, springs etc. whatever his highest stage is, flowing almost 300cfm), ported intake, large TB, hooker longtubes with dual 3" going into mufflex y-pipe into carsound 3" high flow cats and then into single mufflex 4" exhuast the rest of the way out, Custom ground cam (similar to 306), 1.6R roller rockers etc. etc., Ed Wright custom programming for this setup, all the normal bolt ons like cold air etc.

I ran this motor 3 years ago and without much effort was in the 12's with 118-120 trap speeds prior to it letting a valve go. I finally got around to picking up another motor, had the heads re-done, and slapped it all together. After a couple mishaps (blown fuse that controls some sensors, bad water pump) the car runs without throwing any codes.

Symptoms are as follows. Pulls fine (as much as can be expected with this big of a cam at low RPM) up to about 3k, then trails off sharp power wise at 4500RPM and then it will rev up to 6-7k but lacks power. Sometimes Idle is good, sometimes it needs to be feathered to keep it running. Typically, it idles around 1200 which is where it is programmed to idle.

I am not getting any codes at the moment, no strange noises, almost all the components ran fine on the stock motor I slapped all this stuff into. It seems like it is acting like a timing issue or fuel ratio issue.

Any other tests I can run or any suggestions? My next steps are to do compression (was good on this bottom end with the stock heads) and check the plugs. Any help would be greatly apprecaited, I have spent a ton of time on this thing.

Thanks!

Eric

[tabahr]

Check your fuel pressure. I'd recommend watching it during a run by temporarily fastening a guage to the shrader(sp?) valve and duct taping it directly to the windshield. I'd bet it falls off when the symptoms occur.

[Torque]

I did check fuel pressure at idle. Good idea to check when I get in it. After talking to Craig at GTP, he suggested that I replace the Optispark. I hate doing this but I guess it is also worth a shot.

I am going to do some research on the symptoms of a bad optispark to ensure they are the same as what I am seeing...

[FRMLAV8]

What about springs? I know you said you replaced them before, but worn out springs will cause power to fall off in the upper RPM's.

Randy

[Torque]

Good thought, I was wondering myself if the valves were too tight causing them to float ect, but I did adjust them and if anything they are probably too noisy/loose right now.

I do have all new springs with spring pressure to match the lift of the cam. The same setup worked fine with my old motor.

Anyone ever loose an optispark? Will do a seperate post but wondering if they simply cause power to lapse at high RPMs or if they just flat out stop working. Also, do they throw a code?

[FRMLAV8]

I have lost an Opti, but the symptoms are usaully more pronounced.
Such as: sputtering or cutting out at around 3000 RPM (sometimes lower), backfires under heavy acceleration, hard starting, and eventually the car won't start at all.

The opti usaully doesn't throw a code, but it is supposed to. There are actually 5 codes associated with the Opti, so you may want to get it scanned and see if anything is in there. Even if the SES isn't on you may still have a code.

Randy

[Torque]

Thanks for the feedback. That helps to hear from someone that has lost one of these things before. Mine does seem to be coughing/possibly cutting out around 3500/4000 and then running rough above this so this might be it. Now it's time to decide whether I risk trying one of the ones I have in the garage or buying a new one!

Looks like you built a solid 383. Did you degree your cam when you put it in? The other thought I had was that when I degreed this cam (108 centerline, went in at 105 so I had to degree it) it could have changed the timing charachteristics on the opti. and confused the computer. I would think that the computer would adjust accordingly, but was wondering if anyone else has successfully degreed a cam with an opti.

[N20LT4Bird]

Have you gotten it on a scanner and watched the air/fuel ratio, timing advance, etc?

[Torque]

I just bought a scanner. No codes are being thrown, have not tried to read on the fly, I will read the manual and see if it can do this. It is a actron from Autozone. Probably a piece of crap but just wanted to pull some codes as quickly as possible. Any suggestions on better scanners?

You look like you have built a pretty solid motor. Did you degree your cam? I put a seperate post on this. Wondering if its related....

thanks for the info...

[Sean 94z28]

I am doing my opti now, it is the 3rd one in 156k. Unfortunately my symptoms have always been the same and are only slightly like described above.

Stumbles and cuts off idle to 2100 rpm. Still runs very strong from there to redline. Can't hold cruise in 6th at 65mph due to cutting. Mine has always been a low RPM issue. Keep in mind everbody has seen slightly different sysmptoms.

All three of my dead opit's have been on the "hot" (cap and rotor)side of the part. I have never thrown a code related to opti because of this. Opti generated codes come from the "sensor" side of the part (from what I understand).

I have had hard start too, when it is really on its last breath.

Except for this latest failure, the first 2 did not die from any contamination (water or oil) on the internals. There was VERY heavy build up (carbon?) on the terminals and rotor. Much like you would see on a normal cap and rotor after 60k.

Like I mentioned in another post this latest failure (only 35k) was due to oil leaking from the opti drive shaft seal and getting into the cap and rotor seciton (carbon tracking everywhere). Still never a code.

Sorry to ramble so long, it's fresh on my mind.

Sean

Search the site on "opti", you get mucho info.

[Torque]

Thanks Sean for the info. I did do a site search on Opti prior to posting and read your post about the oil contamination. Definitely something to keep in mind. The more I hear from different folks about the Opti, the more it sounds like that is probably the issue. Espeically since my water pump went just recenly and the weep hole pretty much shoots onto the opti.

Going to try this, and see what happens. Getting sick of draining coolant and pulling the crank pulley!

[N20LT4Bird]

Originally posted by Torque
I just bought a scanner. No codes are being thrown, have not tried to read on the fly, I will read the manual and see if it can do this. It is a actron from Autozone. Probably a piece of crap but just wanted to pull some codes as quickly as possible. Any suggestions on better scanners?

You look like you have built a pretty solid motor. Did you degree your cam? I put a seperate post on this. Wondering if its related....

thanks for the info...

As far as the scanner goes, you really need something thats going to give you live data stream info (O2 readings, spark advance, rpm, MAF, throttle position etc..) Diagnosing a problem like yours may depend on it if all other mechanical test (fuel pressure, compression etc.) turn up without leads.

Some are better than others, but are going to be a bit more pricey than the auto zone scanner. I use an OTC genysis scanner ($2500) and also have access to a ferret palmscan (which is not bad for the money - 500 bucks), but I teach at a school and use their equipment. Some of the other guys could give you better advice on a good inexpensive scanner for the do it yourselfer.

Degreeing the cam - I have done it, but not on an LT1, sorry. The hotcam is installed straight up. Seems to run real nice, so I am assuming it is pretty accurate. I would like to degree it someday though to make sure, so if you get some info on that optispark issue, let me know. Injuneer or Joe1320 may be good guys to check out on it.