retarding exhaust cam for better spool

[dsmfreak555]

I was wondering what experience people on this forum had with retarding the exhaust came a few degrees(like 2.5 to 3.5) using cam gears to increase lobe seperation to improve spool up? is it worth it? or will cause a larger turbo like a 60-1 to surge? a friend of mine has this turbo and i was considering doing this but, 1 its not my car 2 i only used cam gears to dial in cams before, and 3 ITS NOT MY CAR! . any advice would help

 

[kspharris]

I would ask Andy he has dealt with some of that stuff. I have no experience with retarding.

 

[brute]

ADVANCING
Begins Intake Event Sooner
Open Intake Valve Sooner
Builds More Low-End Torque
Decrease Piston-Intake Valve Clearance
Increase Piston-Exhaust Valve Clearance

RETARDING
Delays Intake Event Closes Intake
Keeps Intake Valve Open Later
Builds More High-End Power
Increase Piston-Intake Valve Clearance
Decrease Piston-Exhaust Valve Clearance

If you don't know what you're doing, you can actually degree one or both cams too much and have the valves contact the pistons. I am a believer that it's way too much work for the tiny amount of payoff you'd get from it, not to mention the risk.

Here is a pretty good article.

 

[andymoraitis]

Nice post Derek although I do disagree about it not being worth it. The gains on my setup were huge.

I would treat it this way. On stock cams, don't advance or retard them. On aftermarket cams, it's beneficial to degree them properly in case they're off. Once you zero them out, the most common practice for increase spool and lowering the torque peak (i.e. for a stroker that won't see revs past 7200 RPM) it's 3 degrees advance on the intake and one retard on the exhaust. Checking different settings on a load holding dyno would be the best way to find out which adjustments make max power in the desired range.

I would strongly follow Derek's advice however and not try large adjustments on both cams since it can easily create piston to valve contact, especially on a motor with a decked head.

Hope that helps,

Andy

 

[dsmfreak555]

thanks andy, i didn't know about doing it like that with the intake and exhaust gears(i only heard about retarding exhause or advancing the intake) thats a great suggestion! as i will be building a stroker in the near future, you think eagle rods are enough(personally i was going to just shell out the money for manley ibeams or crowers cause of the rod angles)
and i think on tooth of is like 5 dgrees? or am i mistakin? and yeah the hole decked head thing makes alot of sense.

 

[andymoraitis]

Eagles are fine up to around 600 WHP as are the Manley's. I chose the Manley's due to personal preference but most built motors run Eagles. I really don't think it matters.

Also, one tooth of advance is closer to 7 degrees, but since my intake cam was around -2 on a straight up install, a full tooth is closer to +5 advance. It's a bit too aggressive but it'll do until I can add a set of adjustables and dial both cams in correctly. I should mention that although the intake cam is advanced, the exhaust cam has been left alone.

 

[StockSpyder]

Hi there everyone, saw that this thread had a broken link and wanted to share the new one.

http://my.prostreetonline.com/2013/08/16/how-to-tune-your-4g63-cam-gears/

Thanks

 

[DogWhistle]

Thanks for fixing the link. I learned a lot in a short, concise article.

Never go full retard.