70 Z28 exhaust

[Johnny Horsepower]

Hi all, for anyone who has good 2nd gen knowledge or exhaust knowledge. I just started to enjoy my 70 Z28. It is an original/restored 4spd with its original motor and i think gardner exhaust. I will know today when i get it up on a lift.
Here is my question, I get a lot of back cracks when i deaccelerate in this car. If i hold a gear and acceelerate and than back of I get some solid exhaust pops.
Is this normal for the LT1? Is something not adjusted correctly?
I am running on 100 oct. race gas, (unleaded I think)

Thanks

[MosportGreen66]

If the car has the a.i.r. system in it... sounds like the pump and the diverter valve need to be restored. My old '69 Z popped and crackled. Once we sent the smog unit out to Jerry MacNeish, 95% of the popping, crackling went away.

[COPO427]

You should also ad yourself to this BB http://www.nastyz28.com/forum/index.php

No the crackle is not normal. Set your total advance @ 38* at 3000 rpm with the vacuum disconnected at the dist, If it pings at WOT then back off to 36* etc until the ping goes away. I gather your 780 carb is set up, floats, mixture screws, sec throttle stop screw setting, correct power valve, accel pump cam position, accel pump .015 setting at WOT. Jets should be 70 for prim and 76 in the rear. Solids set at 24I/30E.

[Johnny Horsepower]

Thanks for the help. I am active on Nasty. Just sold my 80Z on ebay and put it there after giving this bb first shot. I will have my mechanic check on this stuff.
JOHN

[DarrenX33]

John post pics. Congrats!

[Johnny Horsepower]

Thanks, I actually bought it in Dec. from Tom Brown here on the site. He was wonderful to work with and the car did not go on the market, he offered it to me during one of my pleas for a 70 4spd z. As luck would have it, it was in one of my top color choices, the brochure color of citrus green.
The car has been seen here it is the ex Jack Seymour (Jack was helpful too!) car. I am enjoying it quite a bit, as i like to drive my pieces, but i want them correct and with their born with drive trains. While this one is not perfect, it is a nice fit for me. I have to thank this website and Tom for passing it on to another good home.
If i can't post I will send them to bruce.


JOHN

[Xplantdad]

Send them to me if you want John...plus, you owe me a members ride...LOL

[Xplantdad]

Here are Johns pics!

I like the key fob!

[47Hammer]

Johnny, Congratulations on what I think is one of the most beautiful Los Angeles built, completely restored '70 Z 28's around and with great documentation. I restored the engine compartment my '70 Z 28 with pictures of this car that Tom had sent me. Great car, good luck.

[DarrenX33]

Sweet!