L98 missing and backfiring into intake
Le Mans Master
Joined: May 2007
Posts: 8,448
Likes: 27
From: Valparaiso
Might give them a try, sometimes i have refused to do this
but ...wow ..new parts fail too !
I don't think they are the fault, but its a possibility !
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
There is usually only two things that will cause backfire into the intake,
1. spark going to the plug at the wrong time, (firing order) or
2. The intake valve is not closed when the cylinder fires.
A flat cam would not just show up after repairs so it sounds like you need to concentrate on the areas you worked on.
Cylinders 5 & 7 are two that are real easy to cross, as is 8 & 4.
1. spark going to the plug at the wrong time, (firing order) or
2. The intake valve is not closed when the cylinder fires.
A flat cam would not just show up after repairs so it sounds like you need to concentrate on the areas you worked on.
Cylinders 5 & 7 are two that are real easy to cross, as is 8 & 4.
Melting Slicks
Joined: Dec 2008
Posts: 2,772
Likes: 64
From: Mystic CT
There is usually only two things that will cause backfire into the intake,
1. spark going to the plug at the wrong time, (firing order) or
2. The intake valve is not closed when the cylinder fires.
A flat cam would not just show up after repairs so it sounds like you need to concentrate on the areas you worked on.
Cylinders 5 & 7 are two that are real easy to cross, as is 8 & 4.
1. spark going to the plug at the wrong time, (firing order) or
2. The intake valve is not closed when the cylinder fires.
A flat cam would not just show up after repairs so it sounds like you need to concentrate on the areas you worked on.
Cylinders 5 & 7 are two that are real easy to cross, as is 8 & 4.
It is usually the last thing touched before it ran bad. Rarely is it 3 other diffferent things that just popped up. If the cam was ok and did not backfire before why would it now.
Thread Starter
Racer
Joined: Aug 2009
Posts: 496
Likes: 4
From: Cordova TN
I have to agree but the wires are correct. 18436572.
I have checked the wires and pulled them all off to start from scratch. They are correct.
I also realize it has to be something i did. Figuring it out will let me sleep better.
I have checked the wires and pulled them all off to start from scratch. They are correct.
I also realize it has to be something i did. Figuring it out will let me sleep better.
Melting Slicks
Joined: Aug 2008
Posts: 2,082
Likes: 50
From: Palmdale CA
CW or CCW starting at #1.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 8
From: Tampa Florida
Your popping into the intake with too much preload on the rocker stud nuts. Back'em all way off again then spin (with the starter...pull the fuel injector fuses or the fuel pump fuse) the engine a couple revolutions with the ingition key...then go back to finding "0" lash. Easy/best/mistake free way to find "0" is just slide the push rod up and down until there is virtually no movement then apply your preload. Adjust each only once then move on to the next until your done with all 16 - do not back track. When your done don't worry if some feel loose than others...thats normal until the oil pressure is applied to/trough the lifter(s).
Thread Starter
Racer
Joined: Aug 2009
Posts: 496
Likes: 4
From: Cordova TN
I just backed them off to only a 1/4. Also rechecked the wires once again and checked all connections to the distributor.
Gonna crank in a few minutes. Hope it runs.
Before I went into check out the head it had been running fairly well on only 7 cylinders. Running out of ideas.
Gonna crank in a few minutes. Hope it runs.
Before I went into check out the head it had been running fairly well on only 7 cylinders. Running out of ideas.
Thread Starter
Racer
Joined: Aug 2009
Posts: 496
Likes: 4
From: Cordova TN
Cranked it and it died as it has been. I put the fuel pressure checker back on for kicks and it sits at 43 for 10 minutes. I have the #1 wire plugged in where the rotor is when the engine is at 1tdc. I may just have it towed to the shop and let them either figure it out or get a Jasper engine put in it. It has 146k on it and I was only hoping to get a few more Ks out of it by fixing the dead cylinder. Just killsme that the dead cylinder is now showing 145 on the compression check but the thing won't crank.
It cranked and ran good on only 7 cylinders. Geez.
It cranked and ran good on only 7 cylinders. Geez.
Thread Starter
Racer
Joined: Aug 2009
Posts: 496
Likes: 4
From: Cordova TN
This entire ordeal reminds me why working on my cars is only a hobby. If it gets much worse I may move to golf and I really hate that game.
I have checked everything 5 times. Bent over with a flashlight making sure everything is hooked up right. Chasing spark plug wires and removing distributor cap. I'm about out of ideas but I have to thank everyone for trying to help.
If I tow it to the shop and it ends up being something simple I will scream. lol
I have checked everything 5 times. Bent over with a flashlight making sure everything is hooked up right. Chasing spark plug wires and removing distributor cap. I'm about out of ideas but I have to thank everyone for trying to help.
If I tow it to the shop and it ends up being something simple I will scream. lol
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
I went back and re-read this whole thread, I do believe it is something very simple. Try one last thing even though you have went through this process before. Pull the distributor up away from the cam gear and turn it 180 degrees and drop it back in. If you did it right the distributor will drop all the way down again. It is soooo easy to be mistaken on this step, I have done it many times. Do just this and try it, don't change anything else.
Thread Starter
Racer
Joined: Aug 2009
Posts: 496
Likes: 4
From: Cordova TN
Coming back to let everyone know the problem. One of the runner gaskets had a massive vacuum leak, I finally found it when I had a friend over and I had him crank the car while I sprayed carb cleaner. So if you run into the same problem check for vacuum leaks.
Good news is it now runs about as good as a 22 year old engine with 148k miles can.
Good news is it now runs about as good as a 22 year old engine with 148k miles can.
