QuestionI have a 85 gmc 1/2 ton 4x4 with a 79 350 engine automatic. recently rebuilt, having problems with backfiring when underload. dosent backfire at idle and doesnt backfire in park and reved up. What could the problem be. and also what is the correct timing for this engine. thanks very much.
AnswerFor the 79 350 timing is:
1. Distributor vacuum line disconnected and pluged at the hose, NOT on the vacuum advance unti.
2. With a Rochester 4bbl carb.
3. 6 to 7 degrees BTDC. (Before Top Dead Center).
4.engine speed at 500 to 650 in DRIVE.
As to the backfire make sure you have the istributor vacuum connected to the correct vacuum port as some require it to be connected to manifold vacuum and some require it to be connected to a port on the carb.
PLEASE keep your questions on the ALLEXPERTS BOARD because without it, Us volunteers would NOT be needed.
I do not have a staff of people helping me answer your questions, I do it all by myself, except some typing help from my wife or son as the old fingers just don't flex as well as they used to. Therefore, Due to being retired and an OLD computer, That is so old it does not even have SPELL CHECKER on it and being on a dial-up connection, Please excuse the TYPO'S.
I do my best to respond to questions within 4 to 5 hours, But due to the volume of questions I receive on a daily basis I answer them ASAP. If you require a faster response you can e-mail me directly at the below e-mail address as I check it more frequently.:
meperganfortis@msn.com
When you are asked to RATE THIS EXPERT the site it only allows for about 10 (TEN) words. Therefore, I never get to read your full response. You can e-mail me directly at the above said personal e-mail site. But make sure that you RATE ME before e-mailing me directly if you so desire to do so.
Sometimes when you have to replace a part, I will ask you if I can have the old part, As my son and I rebuild them and sell them for extra income. I will pay the shipping costs as long as it does not exceed $10.00.
There are also times that you have some written information that you just don't understand or need help with it, You can e-mail it to me at the above siad e-mail address or you can fax it to me, But contact me FIRST at the e-mail address and I will give you my fax #. However, Again due to my OLD computer I have to log off from the dial up service in order to receive any faxes on my seperate fax machine.
I am alway in need of Car, Truck and SUV service manuals as well as MOTORS MANUALS and if you would like to donate any that you have, I will be more than happy to pay REASONABLE shipping to get them. I do not want any Chilton or Hayes manuals as I personally do not like them as the information contained in them is very mis-leading in my opinion.
Retired in New Mexico and teaching my son to learn the trade.
autohelp
