Finally got the 85 IROC running GOOD. In the end, I believe it was a combination of ALOT of things. A functioning EGR system will help fight spark knock Sometimes modified motors and bigger cams like more spark advance, and imagine that, they even run ALOT cooler operating temps......

Anyway, tune is good. Fuel pump / pressure seems fine, although I do get a almost INSTANT pressure drop when the key is turned off after fuel pump primes, but it drops from the initial reading ( vacuum line disconnected on AFPR ) of @45-46psi to @ 28-30 psi, and it holds ROCK STEADY at that...so I'm assuming it's NOT leaky injectors.

A FULL can of Seafoam in the gas tank cleared up a nasty miss I couldn't get rid of, and replacing the no name module in the new distributor with the GM unit from the car originally seems to have cleared up a hesitation.....but I digress........


Car runs GREAT right now. The stock manifolds are REALLY holding this engine back I feel, and I'm picking up some used headers this weekend.

The ONLY bitch I have at this point is the slight "hunt" at idle and the slight "rich" smell / feeling I get.

Mileage was @ 13mpg on the last tank, 3.23 rear, 700 tranny, but granted there was ALOT of heavy throttle blasts in there when I was road-testing the car chasing down some problems I inherited when I bought the car.

I ran some Seafoam thru the TB via a vacuum hose today, and while I did get the obligitory smoke show, I didn't get near as much as I have on other engines, so I think that's a good thing. What I DID notice ( Thanks again Seafoam ) is a decent exhaust leak at a weld on the y-pipe leaving the manifolds.

Could this cause a false lean condition to be reported to the ECM by the O2 sensor? Or is this far enough from the sensor it wouldn't matter?

Also, at this point, the car has ONLY improved with more intial timing each time......1st from 6 BTDC to 8 BTDC......now it's at 10 BTDC and it runs STRONG, and the temps have even dropped on the engine when running......idle still creeps up around 220, but any part throttle or full throttle runs keep it at 180 or so.....nice.

I'm thinking that I need to back off the fuel pressure, maybe even lower than stock to help the stock '870 ECM and 305 PROM compensate for the fatter injectors that replaced the 19 pounders when the 305 still lived under the hood.

Also I need to redo my WINALDL cable to get some readings before I go off half cocked, but I'm going to try giving it more timing. Since I don't know the full history on the engine, I know it's not stock, ( I've seen the heads, intake, etc, and it doesn't have valve seal smoke......show me a STOCK SBC that doesn't have valve seal smoke )

The car acts like it has a bigger cam than stock. And maybe it was installed retarded, or another reason could be the balancer has slipped, causing the timing marks I see to be retarded from what the timing actually is......

Guess we'll see. For now it's STRONG. Got beside a C4 Vette today on the interstate......he pulled up beside me ( I was in the left lane doing 70 in a 60 ) and slowed......then dropped it down a gear. I just hammered it, it shifted down to 3rd, and a second or two later I passed the Vette, and looked down to see my speedo needle bouncing off the limit.....darn 85 mph speedo's...

He looked a bit shocked to say the least

I'm planning on hitting the local test and tune Friday night.....so we'll see how it's really running, not just the unreliable SOTP dyno I've tested it with so far......


Thanks
Chris
85 IROC

 

Seafoam seems to be *** sent. going to try that this weekend myself.

 

As for Seafoam......buy 2 cans......they are about $5 each at NAPA, CArQuest etc. Autozone, Advance etc DO NOT stock it.

If you think you're fuel system is dirty, you might do what I did, and add a FULL 16oz can to a full tank of gas.......that cleared up a miss I was having and smoothed the idle out ALOT.

As for cleaning the top end..

Warm the car up, have someone hold the RPM'S up a bit, maybe 1500 or so, just so it won't die out.

Open the can, pull the vacuum hose off the brake booster. With the car running, put your thumb over the can to regulate how much Seafoam gets sucked into the engine......keep it going in slow and steady, trying to keep the engine from stalling....when you get about a 1/3 of the can in, tell the person in the car to let it just idle. Then give it more Seafoam until it dies.

Let it sit for 5-10 minutes......

While you're waiting , dump the rest of the can in the oil......just plan on changing the oil soon.....you won't believe the CRAP that it will clear out of your engine......

Now start it up, and go for a drive.......prepare for EVERYONE to stare as you give them a HUGE smoke show......the dirtier the engine, the more the smoke.

The IROC smoked for about 15 minutes then stopped.......

BTW, it could be coincidence, but the IROC has been running 10-20 degrees cooler in temp, with no other changes, since I did this a few days ago.

HTH
Chris
85 IROC
Test and tune on Friday, time slips to come......

 

thanks for the info

 

I be Damed......... It works. Well so far, Did the
vacume line run and darn if it did not smoke up the office park hehehehe. Look like a fleet of foggers. Pis*ed alot of the lunch crowd off. Put 1/3 in my oil and 1/3 in the fuel. Drove it a few minutes till the smoke cleared and it does have a better idle.

 

seafoam huh? from what you guys have said about it, looks like ill have to invest in a few cans. sounds like good stuff

 

Old thread, I know. But rather than starting my own...
I just did a round of seafoam to check for exhaust leaks and sure enough, a pretty substantial one spewed out smoke from the 8th cylinder. I have headers, came with the car. The leak is on the passenger side. My o2 sensor is on the driver's side, on the collector, a foot or two before the Y. Could air from this leak be throwing off my o2 sensor? It reads lean constantly, even though you can smell rich exhaust a hundred yards away. Warmed up and idling, it will drop steadily until it reaches 4 and stay there. Brand new sensor, just put it in today to replace what I thought was a faulty one doing the same thing (changed to a 3 wire though). Is this my culprit? I didn't see any leaks whatsoever on the driver's side.

 

I Used Seafoam once a few years ago on my 82 Trans AM 305 Crossfire that I sold for parts, since it was a rust bucket. After putting this in the gas and air intake, I was running it for about five minutes, when a cop showed up and at the front door and I didn't know it. I had the garage door almost closed since it was winter, with hose from the exhaust under the door. So the cop called the Fire Department and an Ambulance (I live in town). Luckily I did not have to pay anything for this cop kind of going overboard. At least if my house was on fire, I know they will show up in about 5 minutes.

On my 88 GTA I have now I had put a new Magnflow cat on and then I noticed an exhaust leak. It turned out it was from someone using cheap exhaust manifold gaskets and the back one was not covering the entire hole. But you could not hear it with the stock cat. I bought a one piece aluminum header gasket and slid it in from the front. Bolted it back in and got rid of the leak. It made a big difference in the power. I still have cold hesitation and misfire in one or two cylinders (runs rough) and I am not sure why. I change the plugs wires to Accel 8mm Race wire, burned a chip to bypass the cold start injector, new MAF, and new IAC, but it still does it. It might be the injectors, but I am not sure at this point. It might be time to bring it to a mechanic, to diagnose it.