hobby28

I have a 95 z28 with the lt4 heads cam and intake kit with a bbk 52mm throttle body with a newly in stalled walbro fuel pump. The car also have slp headers and flowmaster exhaust. I also have a hypertech power programmer. Car has a new cap and rotor with stock replacement spark plug wires. Here is the problem at idle if you open the throttle wide open you can hear it pop back throug the intake. And when you make a full throttle pass when it gets to about 5500 it starts shuttering and you can hear it backfire through the exhaust. Pulls really good 1st and 2nd. Do you think a custom tune is in order or do i have another issue. I installed a new fuel pump b/c fuel pressure was only 35 and would drop under load, now 42 and climbs when you gas it. By the way this issue started after LT4 swap.

96capricemgr

The LT4 package was a poor choice without then trying to "tune" it with a hypercrap another BAD choice.

You are probably shocked to hear the LT4 package was a poor choice, it was an OK choice a decade ago but a lot has changed since. The Hypercrap was always a BAD choice. Putting them together was a really bad choice.

Try proper programming and then you still might have a mechanical issue but we can't tell till it is tuned right.

hobby28

Who do you suggest to tune it? Mailorder or do i need to take the car? I'm in mid missouri.

mad95z

search mail order tune

jclark311

MAD Z28 does a good tune. Are you sure you adjusted your valves right, and they are to tight?

hobby28

What are the valves suppose to be set at?

GreasyB

I sugest staying away from mail order tunes. I personaly havent had the best luck with them. They are good enough to make the car run though untill you can get a good tune on the car.

Injuneer

Courtesy of Shoebox:

http://shbox.com/1/4th_gen_tech2.html#adjust_valves

dr97z

If you can travel, there's Dynosport in Lincoln, NE.

shoebox

...or Ed Wright in Tulsa...