new motor problems...

[stangjunkie]

ok so me and my dad just finished building the 306 for his car... it sounds like timing but let me explain....

stock 306 carbed holley 570
timing set at 14 btc
starts and runs fine however there is a constant popping sounds like small back fire's out of the carb... all stock except for e-cam....

were thinking that maybe were using the HO firing order and should be using standard... but it would run rough... any ideas??

this is in a kit car and we junkyarded all the parts so we really dont know much about the motor... how do i tell which firing order to use??

 

[bill302]

have you adjusted carb? and firing order is as simple as top dead center take #1 cyl to top dead center and slowly rotate 1/4 turn looking at valves if valve covers are off or place screw driver in #3 cylinder it should be top dead center piston all the way up on compression stroke(both valves closed)if top dead center order falls in order 1-3-7-2-6-5-4-8-its a 302ho, if top dead center order runs 1-5-4-2-6-3-7-8 its a non h.o. click on link for some good info.

http://www.totalengineairflow.com/tech/valvelash.php

 

[bdazzgt]

I am gonna take a stab at this and say it is a a carb problem. I blew the powervalve in my holley and it did the same thing it would sound like small backfires out of the carb, i put in a new powervalve and it ran great, i just switched to EFI though because carb sucks for daily driving well i think so.

 

[bill302]

I am gonna take a stab at this and say it is a a carb problem. I blew the powervalve in my holley and it did the same thing it would sound like small backfires out of the carb, i put in a new powervalve and it ran great, i just switched to EFI though because carb sucks for daily driving well i think so.

exactly my thoughts too, bdazzgt.

 

[retro50]

Take a compression test to verify engine integrity. If the compression is good then it is a timing issue or carb issue. If not then one or some of the valves could not be seating. With the E-cam the firing order used is the H.O. 1-3-7-2-6-5-4-8.

 

[stangjunkie]

ok thanks alot guys i thought we already checked the firing order... we got the motor from a junkyard but when we pulled it apart it had already been mostly rebuilt new pistons crank valve job... but we took it apart just to check other people's work... we checked the valve lift and duration (the guy said it had an e cam but we wanted to check) so when we pulled the cam and measured it it matched e cam specs also on the end it had an E stamped in it.... anyway so you guys thnik its the carb... that makes sense when we had everyone over to fire it up it ran fine and now is poping so that works out well good!! i work at a parts store thats an easy fix... it must have been a defective carb... so i get a new one free....

 

[Modular2v]

my friend had the same problem, turned out to be a colapsed lifter

 

[5.0Droptop]

The cam determines the firing order so an E cam uses 351 windsor firing order, If you have the valves adjusted to tight it could be slightly holding the valves open letting it pop thru intake also.