Firing order for 302

[Robin Little]

May sound like an obvious question but I have some confusion on the firing order of the 302.

Most literature says 1,5,4,2,6,3,7,8

But a sticker on the rocker covers stated a different order.

could this be just rocker covers from a different engine? eg 351?

the engine was originally a new marine engine.

Thanks

 

[Steve26]

Hi Robin,
there are two firing orders possible on a 302 depending on the cam you choose. It can be a 351 firing order if that is the cam you are using, my engine uses the 351 firing order. Do you know what cam is installed? Also, some marine engines rotate backwards! If you have one of these you will need to change the cam. Hope this helps.

Steve

 

[Robin Little]

Fitted a new performer cam into the engine during build as it had a marine cam fitted. but no literature with the cam but I presume it will be the first option. is there any other differences with the reverse rotation engine? as I presume the pulley bolt etc etc would be lefthanded??

 

[Cliff Beer]

Water pump rotation.....? I know the WP on my Mercruiser marine 5.7ltr engine is handed with vanes that are designed for a certain rotation direction. The stock cam is a standard automotive cam.

Main differences between the marine and non-marine are just the WP impeller (bronze in the marine), flame arrestor in the carb filter, hard lines for fuel downstream of the fuel pump, valve cover venting back into the carb inlet....and the rotation can be different too, but not always as boat props are both LH and RH.

 

[Steve26]

Robin,
The cam should have come with the specs including the firing order. If you don't have them you can call the manufacture and give him the part number and he will have the specs on file. Do not guess or presume what the firing order is, find out and set it up right. There might be a difference in the dizzy drive between a standard and reverse rotation cam, not sure on this. Your options on the warter pump will be determined by your belt configuration and front housing, it could be either clockwise or counter clockwise, your choice.

Steve

 

[Jason Lycett]

It can also be a 302 cam , but one used for the HO series engines. Most of which built beyond around the early 90's are High Output "HO" engines.

 

[Mark R]

Its pretty easy to figure out. Both the 302 and the HO/351 firing order start off firing on #1.

Just turn the motor to see which cyl is on the compression stroke next. compression on cyl #5 or cyl #3.

Several methods to check this as well....
Pressure on the spark plug hole, lack of tension on both pushrods and rockers also lets you know you are on the compression stroke.

Its either going to be 15426378, or 13726548. 1xx26xx8 are always the same.

 

[Robin Little]

Thanks for the help guys.

The water pump has been removed as I am running an electric pump now and the dizzy has been replaced with just a drive to the oil pump as running Megajolt electronic with coil packs.
And as for the carb has changed for a 650 holley vacuum secondaries so hopefully removed all of the marine items. only noticeable things are the brass core plugs i think.

will speak to cam provider and confirm with valve opening order.

Thanks again