I have a smallblock stroker motor I just built. Hair under 10.5:1 SCR, forged internals (steel crank), trickflow 175 heads and a modified TPI intake. I took a pair of SLP runners, lightly ported them throughout and ran through them with a flex-hone. I big siamesed and radiused them by completely removing around 4" of the upper divider wall and ported the plenum to match. Gave the same treatment to a superram base with the exception of siamesing. I repeat I did NOT siamese the base. Also running a superram/lingenfelter throttlebody and ported the plenum to match (with a 58mm nitrous plate sandwiched in between!).

The cam I had custom ground by CC is essentially a 272XFI with a few tweaks. 222/230 @ .050, .534 lift on the intake with 1.5 rockers, 110LSA and 106* ICL. During degreeing, I discovered the actual ICL to be 108.5*. With this cam already being on the far edge of my intake, this obviously raises a concern with the additional 2.5* retard that I do not need for my application. From my considerations, it seems I have 3 options:

Option #1 - Bush the cam gear. This would give me the convenience of not having to pull the gear off the crank and I would be able to get within half a degree of the intended 106* ICL.

Option #2 - Install a Comp Cams Ultimate adjustable timing set. This would correct my current issue and allow me to easily make any changes later down the road if needed. It would also compliment my two piece timing chain cover well and would not require that I remove the crank gear off my current double roller CC set assuming it is compatible with the ultimate timing set chain. I will call comp to verify (Current timing set is installed at the 0* keyway). Downside to this method will be the extra cost involved with buying that adjustable timing set.

Option #3 - Re-degree my current timing set with a 4* advance. The current timing set I'm using is a 3 key-way and will allow a 4* advance. This will correct the "missing" 2.5* and give me an additional 1.5* advance over the official cam specs. It had been suggested that this would probably actually end up benefitting me for my setup and application and I am not necessarily going to argue that point as I am partial to it myself. The downside of this method will be the extra effort involved in removing the crank gear (I do have a small concern that I will not be able to fit a 3 jaw puller between the gear and lower half of the two piece timing chain cover. Oil pan is already in place) with the upside being that it is FREE with no additional parts or modifications to existing parts necessary.

The vehicle is 90% street although for the times I do hit the track for fun or for testing I want it to scream. I am running 3.73 gears and a 9.5" 3000 stall street edge converter. Engine is still on a stand and I am really trying to get this thing dropped in soon. What are everyone's thoughts?

 

I would recommend #3:

Your timing set will "stretch" (actually, wear) a little bit immediately at startup, and more gradually over time. Odds are, within the first 10 minutes of operation you will lose a degree of that advance and in acoupla k miles the other half degree.

It's the simplest, most failsafe, least ambiguous of the 3. (although #1 is a close second on all of the above)

And of course, it's free, and you already have everything you need for it except possibly for a suitable puller, which definitely exists and can most likely be "rented" for free.

 

Good stuff. Thanks Sofa.

 

Yea w/o an engine dyno to sort it out and nail it at least 4* advance is the safe bet. Funny u mention u found the cam 2.5* off as my last time i timed a cam it was like 2.5* adv from the spec sheet. But they say 0.5* is slop in the setup though i measured more than twice. Hey it is what it is and i dont race NASCAR so the 0.5* is tolerable.

Good luck and let us know how it runs.

 

4* advance done. Damaged the original chain because I had to pull the gear with the chain still on it.

Got it off with a 2 jaw and the exact same chain being $24 shipped to replace I'm not even mad.

 

That's why I like the added investment of my Milodon fixed idler gear system. Once the cam timing is done, it will never change unless there's a catastrophic failure.

My camshaft is a custom grind but wasn't originally for my engine. The specs were what I wanted. The cam card said to install it 4* retarded but after playing with the grind in Desktop dyno, the power curve looked much better installed straight up so that's what I did.

Advance a cam for more bottom end power. Retard a cam for more top end power. Many street cams already have advance ground into them since they're designed for bottom end power on the street.

Depending on cam specs, piston shape etc, advancing or retarding the cam timing can have bad internal results. Since just about all cams are designed to be installed straight up, advancing or retarding it needs to have the piston to valve clearance checked.You don't want an intake valve to hit the piston before the piston starts moving down or the piston hitting an exhaust valve before it's fully closed.

Of course to properly degree your cam, wildly adjusting it with adjustable timing sets, offset bushings etc means nothing if you don't use a degree wheel/piston stop to see how close the timing is to the cam card specs. As mentioned above, chains stretch and wear out so your cam timing will never stay the same.

 

I concur just advance as you did in #3. That is a nice cam. Advance will help with the limited rpm of the tpi plus there is a chance of chain stretch as sofa says.

 

Intake valve clearance straight up was .177. With the 4* advance it spec'd at .158

The ONLY thing that is concerning me about this is the DCR. With a 4* advance the .006 seat timing of the intake valve is 61* ABDC which, with all other things factored in, puts the DCR on the high side at 8.64:1. Now that is on an unfired engine sitting on the stand to that number will probably drop to 8.5x:1 after breakin. Hopefully it will run without issues on 93 octane.

 

It will

 

You know, re-reading through this thread it's kind of hard to believe that a mere 7.5 years ago when I was working part time and scraped together what little savings I had to buy this car, I was barely able to change my own oxygen sensor