I have a SuperRam and LT1 cam now. Should I retard the cam 4 degrees now that I have a timing chain with keyways? I thought I could exchange a little low-end torque for some high-end hp. Maybe this will match better with the new intake and cam, right? Help!

 

don't think i would retard it. straight up ought to be 4* advanced

 

Only way to know, is to try it.

Dyno it before, and then dyno it after. Don't rely on the "butt dyno". It lies.

Don't try to use track times, unless conditions are identical between the 2 runs; same DA, same air temp, same 60'.

Don't expect miracles.

Be prepared to tear it down, change it, dyno it, decide whether it's better or not; tear it down, either change it back and leave it alone; or change it the other way, dyno it again, and decide if it's really better or not; and tear it down and put it back if it's not.

I think you'll find that it's an enormous amount of maze to run, in exchange for - maybe - a tiny crumb of cheese if you're lucky.

 

Well, testing is the best way but was thinking about theoretically or maybe someone that has done this before.

 

Back in the mid=late '60s (1967 according to some, 1966 if you listen to others) , the factory powertrain guys decided it would be a good idea to change the valve timing to adjust the power output for the changing fleet of vehicles. Cars were getting heavier and emissions requirements were beginning to appear. More and more vehicles were getting automatic transmissions and would tolerate a slight loss of lower RPM power. With engine displacements growing, and emissions requirements looming, it was viewed as a sound decision.

Although the basic lobe profiles didn't change for a given engine, the valve timing was retarded an average of 4° to promote more torque at higher RPM (which sacrifices torque at lower RPM). Since the location of the dowel hole in the cam was changed, even newly designed cams took on the 4° retard as a basic philosophy of design.

Most aftermarket cams have the dowel drilled at the original (1955) location to effectively restore the "original" valve timing. Many aftermarket timing sets allow for ±4° adjustment in the installed location.

GM did a lot of testing on both designs. Aftermarket cam grinders have done and continue to do a lot of testing. The presumption is that most vehicles that get an aftermarket cam are likely to have headers or a modified exhaust, which lends itself better to effective scavenging. This allows for a bit more valve timing overlap, and a bit more advanced valve timing. Thus, most cams you'd buy from an aftermarket source are likely to have a slightly advanced basic valve timing designed right in.

 

See? ede got it covered in one sentence. I took three paragraphs to fumble around and try to make it clear.

I GOTTA learn to be more terse...

 

So, I shouldn't do it then? Just how accurate is DD2000? When I simulate the engine I can see a considerable increase in power by retarding the cam by 4 degrees. I can't simulate the SuperRam so I'm using the TPI manifold in the simulation. I don't have the flow #s of the heads (083 iron units with mild porting) so I'm using the 113 aluminum heads. The hp seems a little low for the mods also...I think. Please help...

The mods are as follow

1. Accel/Lingenfelter SuperRam Intake
2. hooker super-comp long tubes
3. Dynomax 3" exhaust w/ Flowmaster 80series
4. Shift Kit Stage 2
5. SLP CAI
6. !CAT
7. AFPR
8. Throttle Body Air Foil
9. high volume fuel pump
10. MSD-6AL
11. 8.8mm Accel wires
12. Accel BilleTech Distributor
13. MSD Blaster II Coil
14. March Alum.Pulley set
15. 24# injectors
16. aluminum driveshaft(JG1)(actually an option, not a mod)
17. LT1 pistons and connecting rods
18. Compucam 2032 (214/220, .452/.456, LSA 112deg , centerline 107deg)
19. Fully balanced rotating assembly
20. Mild porting of cylinder heads
21. !AIR pump
22. 160 stat
23. Double Roller Timing Chain
24. 52mm Throttle Body

This are the results with the cam at 0deg:
RPM HP TQ

2000 172 451
2500 207 435
3000 246 431
3500 280 420
4000 301 395
4500 301 352
5000 283 298
5500 249 238
6000 203 178

At -4deg:
RPM HP TQ HP gain TQ gain

2000 172 451 0 0
2500 210 440 +3 +5
3000 249 436 +3 +5
3500 284 426 +4 +6
4000 311 408 +10 +13
4500 315 368 +14 +16
5000 301 316 +8 +18
5500 275 262 +26 +24
6000 233 204 +30 +26

 

Don't use tpi in the simulation, use a single plane intake or tunnel ram which that intake pretty much is.

 

regardless of the intake I use the gain is always there. Can I trust this