97 z28 back firing

 

Had a speed shop build the motor finally got the motor back in and Frist time I Tried to crank it backfired 2 times. Did not try it no more that day. The next day I tried it again and never tried to crank. All it did was shoot fire out the passenger side about 1 1/2 feet and the driver side a little smoke came out of it. I have not tried it today can someone tell me where to look for problem. Thanks

 

Check plug wire routing. Next would be opti indexing.

 

Did the shop test run the engine before delivering it? Incorrect timing chain install, valves too tight, etc., but they should have caught that. Start with Shoebox's recommendations.

Is the engine basically “stockish”, or has the camshaft, heads, injectors, etc. been upgraded? If so has the tune been modified?

 

Everything on the motor is new. The heads were done by Lloyd Elliott I had the LE2 370 to 410 rwhp and TB 58mm. Got my TB from Arizona Speed Marine. Had it bored 30 over 1.6 roller rockers comp cam long tube pacesetter headers. I have checked the plug wires 4 or five time they are right. The motor was never crank there I got it and had to put intake on it. Ever thing on this car is new even gas tank fuel pump relay and fuel pump. How would i check the opti indexing.Thanks for the feed back.

 

Sorry I forgot the Injectors are 36LB Trick Flow Computer was done by Moe at MoreHorsePower.

 

You use the term “crank”. Not everyone uses that term the same way. Appears the starter cranks the engine just fine, and you have spark. If the plug wires are correct, the Opti may not be indexed correctly. Who installed the Opti? If the cam dowel pin was a bit too short, it can end up in the wrong hole. Or the shop wasn’t careful installing the Opti.

http://shbox.com/1/opti_back.jpg

http://shbox.com/1/opti.jpg

Then there's the timing chain install:

4th Gen LT1 F-body Cam Install

http://shbox.com/ci/sprockets.jpg

Valve adjustment:

4th Gen LT1 F-body Tech Articles

And the flames are shooting out of the fully installed exhaust? Takes a lot of excess gasoline.

Are there any signs of “backfiring” into the intake manifold?

And you told Moe the injectors are 36#?

 

The backfire is coming from the exhaust, correct? That’s a bit of good news. Backfiring through the intake manifold rarely results in anything remotely good. I think you’re pulling the opti, as mentioned, to start off with and then testing the injectors to see if one is stuck open. When the opti is off, pull the timing cover and check to see that the sprockets are indexed correctly. If the cam gear is a couple of teeth off it can cause exactly what you’re describing.

 

Sounds like a fun build! I would to hear what the fix was... Im about to rebuild the engine in my 97 z.. good luck

 

Sorry so long to reply been sick. No, the speed shop never crank the engine. I had to put the intake on it myself. I also sent Moe Bailey a spec sheet all that was done to the engine. I have the open Pacesetters headers on it. I was going to put the y-pipe on it that came with the headers but it want work i got them from Jed's back in June 2020 and the other day find out they are closed. Where could I find a y-pipe that will fit the Pacesetters and mount to the bracket on the 6-speed trans. And yes, I told him about the 36lb trick flows. The engine will spin over just find but never tries to crank just backfires every now and then. I have had a friend of mine help run the plug wires 6 or 7 times i think we have them right. Thanks Again Merry Xmas

 

Who installed the Opti? What brand? New or used?

Not sure what you mean by saying you thought the headers were “open” but you found out they were “closed”???

If it does start, when the PCM goes into closed loop, the O2 sensors in the collectors will not read correctly without a Y-pipe.

Given the limited info, you have to start working your way through the possible causes three of us listed above.

 

I meant no y-pipe on them sorry. I got the Opti from Petris Enterprises it was New. The Speed Shop put it in. Thanks

 

This has been resolved:

https://www.camaroz28.com/forums/lt1...gauges-890197/

Opti was installed incorrectly.