Engine Knock
 

Hey guys, Ive got a temper mental 318 on my hands and i was wondering if you guys could help solve my problems. Some times when i start it up, mostly cold starts, it will produce a very distinctive knock for about 30 seconds or so. It goes away after the engine has had a chance to be lubed by the oil, but it concerns me because I am about to put a 4 bbl intake and carb on it and i just want to be sure the engine is sound befor putting that extra strain on it.

Thanks.

CB71 -

What oil are you using? You might need A. something with more ZDDP (zinc and phosphate in it), B. something with a lighter component or both. Sounds like the oil isn't getting where it needs to be fast enough.

The old trick of adding a little Marvel Mystery oil couldn't hurt.

Yes, it could be a failing oil pump or clogged passage, but first things, first.

Also, before you throw on a bigger carb, make sure it's not too big for the cam and exhaust.

Archer

thanks archer, ill try changing the oil and see what happens.
Also, will a stock '71 318 cam handle an edelbrock 600 cfm carb?

it will but a 525 cfm would be a bit better,

my dads 03 dodge ram is having the same problem. It has 250,000 miles on it (dodge for ya) and when he does coldstart in the morning I can hear this knock sound coming from the bottom end. After a min. or so it goes away. Truck runs great otherwise.

Would it cause problems with a 600? Because I already have the intake and carb.

CB -

"Having problems" is relative, you might experience some bogging or poor response at low end. You might be able to tweak it, if you know how to re-jet, but the air flow is still high for a stock 318. Never know, you might get away with it.

The thing a lot of people forget is that with bolt-on parts, the cam is what determines the size of the carb/manifold and exhaust.

Archer

Im experiencing some low end bogging with my stock carb as it is, so with any luck it wont get any worse.. it sucks because i already have the carb and intake. I wonder if summit would take it back and send me a 550?

CB -

Summit is pretty customer friendly. Call them and tell them what you have both the carb/manifold and engine (they should ask about the year, etc) and see what they suggest. If you haven't "played" with the carb, they might do a swap, doesn't hurt to ask.

OR, you could use it and plan on a new cam and headers/exhaust in the future. You wouldn't be the first person going that route.

Archer

i think ill plan for new cam/headers... I already have an aftermarket exhaust.

CB -

Yup, that's what I'd do ;). Just do your research on what cam specs will work with a 600 cfm and figure what size primaries will work best with the cam and intake.

An engine that's matched will make more usable HP than one that's just thrown together.

Good luck!

Archer

i get what your saying, but it more than cam, comp ratio has to be there for the cam to actually work properly, and rear gears, and many other factors, i see your point. but 600 cfm will work with low end loss, also is that a vacuum or mechanical carb?

vacuum carb. How much low end loss we talkin' about here?

not alot to really notice on the street in normal driving conditions, the only time you will really notice is when you stomp the pedel to the floor

thats what i do at red lights =D. Is there any way to tune it down some?

id 1st do the swap then see how it acts for you, you may be happy with what you have,

Im gonna do the swap anyway. Im just planning on a new cam/headers and all the other things for a well built motor. Im pulling the engine this winter or next summer for a full rebuild.

zddp
 

Sounds like a lack of zddp in the oil. Check out www.camoils.com Collector Automobile Motor Oil. Specially formulated for flat bottom lifter engines. Their site is not pretty but has lots of information on different oils.