| FAQ |
| Members List |
| Social Groups |
| Calendar |
| Search |
| Today's Posts |
|
#21
11-10-2021, 08:51 PM
|
||||
|
||||
Whether the cam is advanced on point or retarded. The intake valve is open before TDC. Check out a Comp Cams Master Lobe Catalog and it will tell you what the lifter raise is at TDC for a couple of different ICL for any give lobe.
Stan
__________________
Stan Weiss/World Wide Enterprises Offering Performance Software Since 1987 http://www.magneticlynx.com/carfor/carfor.htm David Vizard & Stan Weiss' IOP / Flow / Induction Optimization - Cam Selection Software http://www.magneticlynx.com/DV Download FREE 14 Trial IOP / Flow Software http://www.magneticlynx.com/DV/Flow_..._Day_Trial.php Pontiac Pump Gas List http://www.magneticlynx.com/carfor/pont_gas.htm Using PMD Block and Heads List http://www.magneticlynx.com/carfor/pont_pmd.htm |
|
#22
11-10-2021, 09:56 PM
|
||||
|
||||
|
Yes, but is it open more than the exhaust valve at TDC overlap? That's what we are trying to accomplish.
I'm not pushing the idea, just trying to explain it, but I do know I've tried it on several engines and have had excellent results. Paul and Jeff are a lot smarter than me so not only am I flattered when they share a tip or trick, I'm more than willing to try it. Since Paul has shared this with others on the forum in the past I don't think it's a secret anymore. It's worked on my 11:1 302 Chevy with iron heads that has logged 50k miles over the last 5 years, my 10.13:1 Pontiac with Iron heads that has logged nearly 25k miles now, my fathers 10.84:1 571 Pontiac with aluminum heads, and a couple other engines I've built including another Pontiac with 9.98:1 and iron heads. All of them are running the same crappy California 91 octane pump gas they sell here in Arizona, and doing it in the desert heat. I really like the results I've obtained and will continue to play with this more in the future. |
|
#23
11-10-2021, 10:31 PM
|
|||
|
|||
|
Engine is a 462 with iron 1972 7F6 iron roundports, milled to somewhere around 100 ccs. (can't find my notes). Cam is just a RAIV with Rhoads lifters. Distributor (second one installed chasing this problem) is a Davis Unified HEI. Roundport HO manifolds. Pings like crazy under load. In a 72 GTO.
|
|
#24
11-10-2021, 10:40 PM
|
|||
|
|||
|
Engine is a 462 with iron 1972 7F6 iron roundports, milled to somewhere around 95-100 ccs. (can't find my notes). Cam is just a Crane RAIV with Rhoads lifters. Distributor (second one installed chasing this problem) is a Davis Unified HEI. Roundport HO manifolds. Pings like crazy under load. In a 72 GTO.
|
|
#25
11-10-2021, 11:20 PM
|
||||
|
||||
|
Just a rough guess but a 455, with a flattop piston and 95-ish cc head is probably going to be around 9.5:1 compression at best. Even lower if your CC is more than 95.
That honestly shouldn't have a detonation issue with the RAIV camshaft. That cam, being what I'd consider the smallest choice I'd make in a 455, should still do a pretty good job at controlling cylinder pressure at that compression ratio. Even if other things at play aren't optimized like pistons at zero deck and where the cam is installed. |
|
#26
11-11-2021, 11:30 PM
|
|||
|
|||
|
@FormulaJones, that's what I was expecting too. So it's been a puzzle why it has such problems. The advanced cam timing is the what I'm left with at this point.
|
|
#27
11-12-2021, 12:45 AM
|
|||
|
|||
|
my understanding is RAIV likes to be at 110 ICL in a 455. do you know where it is currently?
__________________
1979 Firebird Trans Am 301/4spd (Now 428) 1977 Firebird Formula 400/Auto 2007 Grand Prix GXP 5.3L |
|
#28
11-12-2021, 11:33 AM
|
||||
|
||||
|
Like Grandville mentioned, the RAIV camshaft tends to run best around 109-110 ICL from the many who have tried them in 455's.
Personally I don't know where that puts the intake/exhaust relationship at TDC overlap because I haven't messed with a RAIV grind since I learned that trick from Paul C. But I bet someone like Stan could probably run his numbers and give us a pretty good idea where that might be. My guess, being that this cam is generally on a 113 LSA, you would have to go more than 109-110 ICL to get the intake valve open to at least .030" more than the exhaust valve at TDC overlap. The last wide LSA cam I played with on this scenario was an 068 on a 114 LSA and I moved it forward quite a bit and still only got the intake about .025" open further than the exhaust at TDC overlap, and I stopped there. The wider LSA cams are harder to accomplish this with. |
|
#29
11-12-2021, 03:43 PM
|
|||
|
|||
|
I don't remember and don't have any notes anymore on this. Maybe before I take the timing cover off I should do a compression check with all the plugs out....
|
|
#30
11-12-2021, 06:43 PM
|
||||
|
||||
|
Quote:
If it's around 170-180 psi it should run on 91 octane just fine. I find that when they start getting up around 200-210 they get really finicky on pump gas. |
|
#31
11-14-2021, 04:58 PM
|
||||
|
||||
|
Quote:
__________________
Jeff 
|
|
#32
11-14-2021, 06:06 PM
|
|||
|
|||
|
RETARDED!Sorry,Tom
|
| Reply |
|
|
The PY Online Forums is the largest online gathering of Pontiac enthusiasts anywhere in the world. Founded in 1991, it was also the first online forum for people to gather and talk about their Pontiacs. Since then, it has become the mecca of Pontiac technical data and knowledge that no other place can surpass.
Linear Mode
