4AG 256/256 What cam timing to use??

[irishtwincam]

The serach functiond oesnt allow these as search terms, so Im asking here.
Can someone please tell me what cam timing to use for 256/256 cams on a normall aspirated 4AGE.

stock 240 cams are max lift at 111/111
HKS 264 cams are max lift at 106/116 difference of -5/+5

Im guessing the 256 will be in the 109/113 area?
Maybe 108/114?

[amichie]

Do you have headers or a stock exhaust manifold??

[irishtwincam]

Have two cars that need them dialled in.

My mates trueno: Standard inlet system and completely standard exhaust system front to back.
Other is a levin: ITBs, 4-1 header, straight through JDM exhaust.

If you have various timings for various installs, please give me them all.

[oldeskewltoy]

Irishtwincam - you might want to include that you are looking for the specs on the earlier HKS 256 cams, those using 8.35 lift.

Btw, if/when you do find them... please post them up!

[The Real Roadrunner]

you will never find out the correct timing unless it goes on a dyno, that is the simple truth.

and also there is no 1 position that they work best, cam timing can either deliver a high HP number or a High midrange tourque figure. unless you have VVTi you will never get both with the same cam timing.

put it on a dyno, get the highest AVERAGE power figure out of it for street use or the highest PEAK power for dedicated track usage where you should be high in the rpm band the whole time.

unfortunately in this senario you can't have your cake and eat it to, sucks but that the way it is.

cheers
linden

[irishtwincam]

Im looking for the recommended timing, preferably by TRD.
Cams are actually 256/8.1mm in 256/8.1mm ex.
Came in an imported Japanese AE86s engine.

OldSkewlToy provided these cam sheets (many thanks).
intake - http://i79.photobucket.com/albums/j1...dHKSIntake.jpg
exhaust - http://i79.photobucket.com/albums/j1...HKSExhaust.jpg

None of the specs on the card above match the ones on Club4AG tech reference any bit.

272degree Ex. max lift set at 98° BTDC. In. max lift set at 100°
264degree Ex. max lift set at 116° BTDC. In max lift set at 106°
(^^ from Club4AG)

We used the TRD recommended cam timing on a 4ag with pistons, ITBs, EMS and an exhaust system, it made 131tq and 160hp. TRD recommended timing seemed BANG ON!
http://i250.photobucket.com/albums/g...QvsRPMBINS.jpg
http://i250.photobucket.com/albums/g...PvsRPMBINS.jpg


For the 256s if I pick the numbers that start to make sense from the list on the cam spec sheets its
256degree Ex. max lift set at 102° BTDC. In max lift set at 105°
At least with these numbers Id be dialling out some of the overlap.
Max lift on intake at 115 would increase overlap? the only other number for exhaust that seems to make any sense is 110, which is factory timing?

So
optional INTAKE timing values from the list are MAX LIFT AT
105 and 115 ATDC

optional EXHAUST timing values from the list are MAX LIFT AT
102 and 110 BTDC

Any one else want to weigh in on this?

[amichie]

I have similar spec cams on my 7m-ge which is a similar design although not nearly as popular due to too many issues to list. Anyway the cam timing I can use with and without headers is totally different. At present(with headers) I am running with both cams at 112 LCA. The cams came with timing cards with the exhaust at 114 and intake at 110. I was chasing a little more power up top and retarded both cams. I really haven't lost much down low but my idle quality is average. I must have tried 100 different settings between +/- 4 cam degrees on both cams.

Before I fitted the headers I couldn't get decent power anywhere except in the midrange no matter what cam timing I used. I think a four banger would be better in this respect but anyway I am sure you will get more out of it with headers.


Did the cams not come with timing cards?

[Starfire]

Unless the manufacturer has a reccomended cam timing for the items, your best bet is to dial them in to the standard timing, or that of a similar set of cams from another manufacturer.

Some dyno time will then tell you what direction to tune them in to. Adjustable cam wheels are highly recommended with aftermarket cams as they make adjustment easier, more precise and repeatable.

As always optimim cam timing will vary depending on the rest of your engine config and don't forget that each time you change the cam timing, you will need to reset your ignition timing back to what it was.

Cheers,
Terry

[irishtwincam]

An AE86 was imported here and the cams removed, owner was upgrading I suspect.
My mate had a set and this other guy with the levin had a set.
No cam cards.
As for cam gears, I wouldnt be asking about timing if we didnt have them already on both cars ;-D

When you say 112lca in / 112lca ex, what do you mean by LCA?
Is that the same as "Max lift at X degrees before/after TDC".

In this case youd have increased overlap on both cams 2 degrees from stock timing if I understand you correctly, for more top end.

Your cam spec sheet said max lift at 114in/110exhaust.
This in effect means adding more overlap by advancing the intake cam, and leaving exhaust cam at OEM timing.


So for now the 3 cam timing setups to try are
IN / EX
114/110 (based on Amichies useful input, or 115/110 if the HKS cam sheet numbers are taken with this in mind)
112/112 (Amichies final choice, was this with or without headers and exhaust?)
105/102 (Dialling out a litle overlap?)

Looking at the 264 cam timing Amichies sheet sounds right, intake advanced, exhaust left stock/advanced. But the cam timing on the 272s still does not correlate to other info or experience?

Anyway the 3 sets of timing above will serve as a bench mark.
For each, hopefully, well set base spark timing to 10 degrees and maybe try 2 degree advances to see what happens at the seat of the pants , if no dyno is affordable...

[amichie]

My 112 112 settings were with headers.

LCA stands for Lobe Centre Angle. If the cam is symmetric then this is the same as angle at peak lift. The most important event in cam timing is the inlet valve closing time. Early closing will favour low rpm. Late closing will favour high rpm. Retarding the intake cam will delay intake closing and reduce overlap.

Intake valve closing time and intake cam advance/retard will set the whole character of your cam shaft. SO get this approximately correct first.

Then you can tweak the exhaust cam. The more retard you can get on your exhaust cam and still retain an aceptable idle the better the overall performance you will get. Exhaust retard will increase overlap.

The other consideration is your static ignition timing. If your intake closing time is delayed(or retarded) then your car will tolerate and benefit from a little more static advance.

[Chrisso]

Subscribing as I know I'll want to read this again in a month.