NO, total timing MUST be checked W/O vacuum advance. Read again Lars papers.
Rev the engine until timing mark goes no further. You should reach this maximum before more or less 2800 RPM. ( Play with centrifugal springs if necessary ).
At this RPM, you should have about 32-36° total timing, WITHOUT VACUUM ADVANCE. If you have less, you are too conservative, even with your new heads. I don't say check it at 2500, 3000, or 3500 RPM. I say check it at a RPM you know the timing WILL NOT go any further. With vacuum advance hooked up, you should have about 12-16° more, which is OK with moderate accelerations ( part throttle & cruise ). If the car jerks, remove some initial by turning slightly the distributor clockwise, or buy an adjustable vacuum advance can, like Crane's, and limit it. Timing must be set correctly for WOT, where detonation can be really destructive because your engine delivers its full potential, and at WOT you have almost NO intake VACUUM. This is why total timing must be set without vacuum advance : it is the timing your engine will see in the hardest conditions : full power.
With vacuum advance hooked up, the timing advance can reach 52-54° with stock heads : 36°-38° total timing + 16° vacuum advance = 52-54°.
Vacuum advance is only for economy at part throttle, and some engines sometimes run more smoothly at idle with it ( long duration camshafts ). However, most race engines don't use it.
So vacuum advance has nothing to do with your engine max power. But total timing does make a huge difference. Its purpose is to reach the maximum cylinder pressure near 20° ATDC, whatever RPM and throttle position are.
The optimal timing depends on the combustion speed in the chamber, AFR and many other parameters... But you will always get maximum power and torque if the peak pressure is reached near 20° ATDC.
As combustion process and pressure build-up takes some time, the mixture must be generally ignited way before TDC. The higher the RPM, the sooner.

 

You need to recheck and reset your timing. You should be able to run 32 degrees timing with your heads no problem.

 

Well, took her out for a good run today. She must be on steroids, like one of those east german swimmers. Man, the components seem to be settling together. She runs GREAT! Exhaust is barely noticeable at idle, but you can feel the bumpiness with your hand. louder at throttle. Checked the timing at 2500 rpm, 32° all in, from 12° at idle, perfect. I highly recommend this upgrade. roller rockers also rule, well worth the 265 bucks, these Lunati rockers are really nice.

http://www.summitracing.com/parts/LU...t=LUN-85300LUN


2 new shots.....

 

Very nice...how long until the headers go in?

 

Gotta watch my little cash stores for a while... Couple of weeks? The power now has got me pretty happy. wonder what it's making?

 

L-48 is a 350, right? BTW, that is sweet!

 

Yes. Base 350, 2 bolt main. fine for street power. Thanks

 

Nice, RunningMan !
Should be even better with the new headers, and maybe a few more HP
Lunati rockers seem to be very similar to the Comp Cams aluminum rockers I have.



Do you know when the new heads have to be retorqued ? Is it a matter of time or a matter of miles ?
And how do you know if 32° total timing is optimum ?

 

Not to sure on the retorque,, don't want to do it....Edel says immediately retorque on cool down, but their just being cautious. head gasket manu says no retorque needed. I will retorque them tomorrow if i need to i guess, do you think it's needed? I believe Lars recommended 28-32°, all in at 2500rpm, that's where it sits anyway, out the box.

Have to remove the manifolds to retorque

I'll retoruqe them tomorrow..

 

i never retorque heads. its a good way to break the seal on the stud sealer. if you follow the original torque pattern and do it in 2 steps. 35 ftlbs followed by 60 for alloy heads(65 iron) and you should never touch them again.
looks good running man ! im glad your very happy.

 

Thank you GBM! i don't want to retorque them. please tell me again i don't have too , So, it's ok not to retorque aluminum heads? good. i'm a little bit obsessive about the 'Vette stuff, so if i think i need to retorque them........., When i installed them, i torques them in steps- 15, 25, 35, 55, 65. then checked every bolt on both heads at 65 with brand new Craftsman torque wrench. So I'll be ok.

btw, the roller rockers are made in Australia..

 

no problems running man, i wouldnt touch them again cause stud sealer is like loc-tite .once they are tight thats it !!! haha your 5 steps to torque them down sounds excessive , 2 steps would have been fine but i like your attention to detail.

 

Great, thanks. made my day,, or night over here. Great, I'm on vacation now too, so i can go do something else and just enjoy the 'Vette. Thanks for your concern Streetrace, but i'm glad to be done.

 

I wish you a wonderful summer and enjoy the vacation with your Vette.

I have to work three more weeks.

 

Put on the divorced electric choke as a finishing touch, and having a slight case of OCD, i had to check the head torque on at least a couple of bolts. since the spec was 65, i set the wrench to 63 and went down the upper and lower lines, under the valve cover, not one moved, all just clicked in nice. GB was right, and i can drive with confidence!

 

Have the headers been installed?

Any difference to sound/performance?

Were they easy to fit??

 

I'm trying to make the same engine... Edel e-street heads, lunati cam&rollers + 383 stroke kit... It is hard to do in Russia....wait for parts 2 months )

 

I'mean about to do the same thing are you happy with this compo

 

I doubt you will get an answer. This thread was over 5 years ago.