I started my car for the first time yesterday since a recent rebuild. I replaced the pistons and rings, honed the cylinders, and decked the head. Yesterday it was running, though not idling, and revving crappy below 2500rpm, above that and when cruising it was fine. So I assumed it was just that the rings needed to seat. Today I went to start it and it would crank and crank and it I gave it any gas it would backfire extremely loudly. any ideas on where to start with this?

mods are 95 block, weisco pistons, eagle rods, arp hardware, 99 head, ms pnp, gt2871 turbo, 550cc injectors.

 

Check timing. Take off valve cover and take pictures of your cam gears when they are in line.

 

ok I will do that tomorrow evening when I get off work.

 

After running several tests I have concluded that the timing is good, compression is 170 across the board, both coils are good, the cas is good, and all 4 injectors are working. Is it possible that this is a problem with the megasquirt or the tune?

 

it's getting too much fuel....why? what did you change?

 

I don't think I changed anything that would cause it to get too much fuel.

 

and you're certain of your cam timing?

 

Here are some pictures...

Intake cam lobes with cyl one at tdc


Exhaust cam lobes with cyl one at tdc


intake cam gear


exhaust cam gear


crank pully


There are 19 teeth on the timing belt between the notch on the intake cam and the notch on the exhaust cam.

As you might notice the crank pully isnt reading that it is at tdc, which confused me because I used the screwdriver in the spark plug hole method to find tdc, so it's perfectly at tdc if I'm not mistaken.

 

Does anyone have any ideas on what I can try or test to get this thing going again?

 

Also I just remembered that I replaced the plugs with ones that were 2 stages colder. From a bkr5e to a bkr7e. I wasn't sure of this could be a problem. But im grasping for ideas

 

Could your valve timing be out?

If you've skimmed the head then you might need to use verniers to correct the timing.

 

Thanks everyone one for the ideas. The cam timing was a little off, but it still was able to run with it like that. The problem was that my tune went bad on ms, I reflashed the firmware and reburned the tune and it fired right up. Then I just had to change the timing a little bit and now it runs like a champ!