efi or carb

[84merc951]

I just set the new 306 in the 84 gm and am needing some advice from the pros that have been there and done that. the 302 is bored 40 over and has flat top pistons with 2 valve reliefs and a stock camshaft. i still have all the cfi wiring not hooked up but ready to go but i also can switch to a 2 barrel motorcraft swap. i have all the parts need for the swap like carb, bypass reg, hei dist. what should i do? put the cfi that funcuntions just fine or try the swap. im not looking for performance just a DD engine with good milage that i can thro a easily 200,000 miles on. what will be better in the long run? thanks

[Mercracer]

Just keep the CFI. Don't mess with your daily driver...

[Brown_Muscle]

Based on others experiences a basic 2-barrel would be more reliable in the long run...easier to diagnose and fix as well. However if you are confident the CFI stuff is all in great shape theres no harm in throwing that back on until it starts to malfunction...then do the 2 barrel swap.

[84merc951]

thats what ive been thinking but all of my car buddys tell me to get rid of the crappyy cfi but is done my family well. the original 302 cfi we put 240k on it and the only thing that went wrong were the rings. she started pooring oil into the air cleaner. you guys think the computer for the cfi will do fine with the new engine having flat top pistons.

[marquisman]

im a carb guy but, if you got a CFI car and want to upgrade, SEFI sounds like the better choice.

[84merc951]

i thought about doing a sefi swap cause i also have 1986 colony park with it and i love it .but during this engine build my savings have sort of depleted and the only reason i thought of doin the 2 barrel swap is because the parts where given to me. I just would like to keep my car reliable as it was before the engine swap.

[johnunit]

I see you're in cali. I doubt highly that a carb is emissions legal. That goes for visual and sniffer.

I'd in sefi personally. Unless you want pure performance on a real tight budget. That's where a 4barrel carb wins. I'm not sure I see a big advantage for any carb over cfi in a non-performance build.

[84merc951]

i fly under the radar for emmissions test here in cali. i havent smogged my cars in 15 years sence iv moved to a rual area here in blythe ca out in the hot desert. here you smog your car just one time and thats it. sounds weird but its true loop polls are still in the system. yeah im not looking for performance as it has to be reliable as all hell living out where the temp can easily surpass 120 and i drive 50 miles aday. i think thats why my cfi has lasted out here as the weather is so dry.

[gadget73]

If its running properly, leave it alone. CFI isn't bad if you replace the vacuum lines and the problematic timing chain. With a fresh motor, I'm wagering you have a fresh chain already and the vacuum lines are easy enough to deal with.

[84merc951]

yes the timing chain is now a double roller. hey gadget you think the computer will be okay with a little higher compression with the flat top pistons. the heads are just the d8s. so the only upgrades are the timing chain and gears, the pistons, a oil pan with dipstick provision, and the block being a 74-77(witch really isnt a upgrade i guess).

[84merc951]

should i disconnect the coolant hose going to the egr valve or leave it. i have all the cfi stuffed hooked up. i hope the cfi will be able to handle the little boost in compression. thanks matt

[Mercracer]

A Coolant hose going to any EGR should be left in place as its purpose is to cool the plate. Exhaust gasses are far more hot than coolant is.

[84merc951]

okay thanks for the reply on the egr hose. i still havent heard if you guys think the computer will be okay with the bump in compression. i guess we shall find out soon enough. what is the procedure on the first start up for 302s. i put 10W 30 with a bottle of zinc additive.

[gadget73]

probably OK. if its not pinging and carrying on, its not a problem.


I like to prime the oil system ahead of time. I've got a distributor with the gear removed just for that purpose. Stab that in, run it on the drill for a couple minutes, or until smoke comes out of the drill, then go for it. Check for obvious oil, fuel, and coolant leaks, then go for a drive. Try to vary the speed, a couple of accelerations followed by coasting and that should take care of seating the rings. Change the oil for the first time around 500 miles, and run with it.