LoTu5

They mention on the LT5 build video that it is possible to be 360 degrees out of time how is this possible if the cam pin holes and crank locator line up?

RatRacer

Yes, it's possible. In fact, someone that will remain nameless timed one bank of cams 360 out when doing a little work on my car. The reason that it is possible is because a 4 stroke engine's crank turns 720 degrees to complete the valve events.

It was not Corey, BTW.

LoTu5

Ime confused by this,how is it possible if the pins are in and the crank locator is in ,ime aware that the crank turns 1 rev to the cams two,is there a way of checking?,thanks

ZR-the one

Easy , It take 2 (360)degrees to make a full cycle on a four stroke engine

The four strokes of the cycle are intake (Down), compression(up), power(Down), and exhaust(up). Each corresponds to one full stroke of the piston, therefore the complete cycle requires two revolutions of the crankshaft to complete.

make sure you check which valve open intake or exhaust to find position.
Joseph

LoTu5

Thanks.

RatRacer

Actually the crank turns 2 rev to the cams 1.

You really don't have anything to worry about because when you time all four cams simultaneously with the crank pinned, you can't screw this up. It's only if you pulled the crank pin, move the crank and decided to pull the cams on one side that you would potentially have a problem with the phasing of the cams.

As long as the crank is pinned and all the timing holes on the cams line up, you are fine.

LoTu5

Yep thanks for correcting me on the cam/crank revs,so with the Crank locator all the way home and the 4 cam pins home she should be timed right,and in reality it is only possible to time one bank 360 degrees out?
Thanks for your patience.

RatRacer

As long as the crank is pinned and all the timing holes on the cams line up, you are fine.

LoTu5

Fantastic,i was double checking as the quote in the video has been at the back of my mind.

LoTu5

Does this mean the spark is only delivered every other crank revolution?

RatRacer

I may be wrong but I recall reading that spark is provided to each plug at every revolution of the crank.

JordiZR1

spark is provided every revolution of the crank, this is why the sytem is called "waste spark", because you have spark in the cyl. in the exhaust stroke too, this is due to the system design of double tower coils, each time a coil is triggered it sends 2 sparks, one going to a cyl. in the compression stroke and the other going to a cyl. in the exhaust stroke in the opposite bank (waste spark).
Cliff, if you have the crank locator full in it could be either the compression or the exhaust stroke depending on the cam positions, is really when you position the cams and pin them when you are is determining that it will be the compression stroke.

I don't know if I have explained it correctly... plain and easy: pin everything down and it is OK.

LoTu5

I wasnt sure if i had fitted the cams on which revolution ,but i can see that once all 5 holes(4 cam pins and crank locator) are lined up then the groove on the left exhaust cam tells the ECU via the cam sensor where the cams are and determines the stroke on the crank ,motor timed.
I can see the problem on one bank being 360 degrees out,this is when you remove one side of cams after aligning the 2 cam holes and also with crank locator in,then for some reason taking out crank locator and only turning the motor 360 degrees ,then installing the 2 cams,you would effectively put this pair of cams 360 degrees out with the other cams and crank ,the basic thing to remember is to rotate the engine 720 degrees for a complete turn ,is this true.

LoTu5

Then there's a crank sensor to consider

VetteMed

Wow, was it really necessary to resurrect a 5 year old thread, to add one word to it?

VetteMed

Thanks for pointing out the obvious need for cam timing -- I still don't see what you added to the thread by adding the word "exactly" to it. Just sayin...

Dynomite

For you ......nothing
For some like yourself ........everything might be obvious

"Exactly" was referring to specific technical points made by RatRacer and JordiZR1


I should have just "Bumped" it