Cam timing for boost - Boost Forum

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Cam timing for boost
Friday, June 24, 2011 12:22 PM
Ok I have been doing as much reading as I can find around here and am curious what everyone else has experimented with.

My setup last year was stock '01 ld9 with secret cams(installed straight up), this year I am porting the head and and putting in my HO cams.

By my math each tooth on the cam gear is 9.47 degrees, I know thats a big increment, but depending on valve events may help with spooling and power if adjusted accordingly. I know you can offset drill the dowel in the gear also for whatever amount you want. I dont have any specs on the HOs to compare to stock or base adjustments from.

So if anyone has any experience with advancing/ retarding cam timing on a quad or ld9 lets hear it.

Not saying that putting them in normally isnt good but advancing the exhaust a bit or retarding the intake could show beneficial for boost. I may just have to bust out the degree wheel and take some measurements for myself when i start putting it back together.

Re: Cam timing for boost
Friday, June 24, 2011 12:34 PM
good deal on wanting to do this man... the HO cams were designed for an N/A engine so adjusting them out a bit for boost is definitely going to help some.

i do know that at 9 degrees (like you said, one tooth basically) advanced it basically kills an N/A LD9. dont know if it would on boost though...

from what i and others have found, the HO cams centerlines are near or at 108* INTAKE and 110* exhaust. if you could take some of the overlap out i think it would be beneficial for boost.

i hope mcmoney chimes in because he has actually dyno tested his adjustable gears and found gains with HO cams on his motor. i believe he found 7whp...

Edited 1 time(s). Last edited Friday, June 24, 2011 12:37 PM

Re: Cam timing for boost
Friday, June 24, 2011 12:46 PM
Essentially with a turbo application you will want to dial out as much overlap as you can which is a huge help to building boost. Overlap allows the cylinder pressure to bleed out which hurts boost. I am running my new setup ay +3 exhaust and -3 Intake. To effectively move my powerband down I can do +2 -4 and to raise my powerband up I can do +4 -2 so effectively changing the cams in equal degrees after primary timing is met you can adjust and manipulate you powerband.

Here is a GREAT read that oldskool and I did to go after my issue with cam timing

Cam Timing

LE61T PTE6262 Powered

Re: Cam timing for boost
Friday, June 24, 2011 2:27 PM
Just read through that and it helped reinforce my thought. My plan was depending on how far I can go and how much is needed, to at least advance the exhaust cam a tooth. If it can work out I may retard the intake cam a tooth. I have a few spare sets of gears so I may just offset drill a set for whatever degree I want also.

I am gonna start working on a design for a removable top half for the timing cover to change things easier. I know mcmoney makes one but thats too much cash for me right now. I gotta finish putting together the motor for my 98 z before I start back on the turbo car though.

The 98 is getting flat tops, secret cams, ported head, and LO intake. I may change cam timing on it to shift the powerband too.

Re: Cam timing for boost
Friday, June 24, 2011 8:57 PM
In the ld9 cams list post I found that Zs Z noted the HOs have an overlap of 31* according to desktop dyno. Can anybody confirm this and whats an acceptable amount of overlap to keep the motor from being a complete dog out of boost?

It looks like one tooth on each cam may be a possibility as long as it doesnt kill my low rpm. +9.47* exhaust and - 9.47* intake= 18.94 overlap decrease leaving 12.06 overlap.

Re: Cam timing for boost
Friday, June 24, 2011 9:43 PM
3...not 31. HO cams respond very well to boost at stock timings.

I have no signiture
Re: Cam timing for boost
Friday, June 24, 2011 10:20 PM
Sorry, I just looked at the thread, and he measured it @.005" lift. It's generally more meaningful to measure @.050" though. I'm not sure where brad got that chart, but according to that, HO's have -8 overlap @.050" at stock timing...which I'm not too terribly confident is correct. I could have sworn the LSA was smaller for the HO's.

I have no signiture
Re: Cam timing for boost
Friday, June 24, 2011 10:51 PM
courtesy of brandon blaga...

Re: Cam timing for boost
Sunday, June 26, 2011 7:40 PM
This is why I was wondering if anyone has actually measured the overlap because there is limited info anyway and its all conflicting.

I know they like boost at stock settings but I am just looking for the optimum spot for them, if stock is it then so be it.... I just want some *proven numbers.

Re: Cam timing for boost
Tuesday, June 28, 2011 5:30 AM
ok then check out mcmonie's thread... he has dyno proven results on HIS engine with an adjusted ho combo...

Re: Cam timing for boost
Thursday, June 30, 2011 8:27 PM
I just looked at his thread and his adjustment that gained 7 whp was 2.5* retarded on the exhaust. Thats going the opposite direction of the general idea for boosted engines. That would be adding overlap, which is still under 0 degrees anyway but its still confusing.

Re: Cam timing for boost
Monday, August 31, 2015 6:35 AM
Bringing back an old thread to possibly revisit this idea. I kinda dropped the ball on this because I popped a piston in my turbo motor. I haven't messed with anything in a few years and now I'm getting things going again. I was curious if anybody has come up with anymore info on the subject or proven setups with secrets or ho cams.

Re: Cam timing for boost
Thursday, September 03, 2015 5:46 PM
I think Chris Walters made 432whp on secret cams. We know over 500whp has been made on HO's.

FU Tuning

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