timing on 11.5.1 6.0
07-07-2014, 10:08 AM
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timing on 11.5.1 6.0 I was wondering how many degrees of timing are yall running i got mine set on 26 degrees and i has a spark knock around 5000 rpm it has 243 heads on it they are unmilled
07-07-2014, 11:46 AM
#6
I was actually shocked when I saw how much timing the other carbed guys said thier cars liked. So, I contemplated the topic a fair amount. I think it is a combo of combustion chamber design, static compression and volumetric efficiency. My car has more compression than the typical LQ4, LY6 or L92 and I have a camshaft that closes the intake valve at 41 degrees @.050" giving me a dynamic compression near 8.5. I am thinking that these cylinder pressures are a lot of it.
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07-07-2014, 05:22 PM
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If I checked everything right you are running LQ9 4.0" bore (typically .005" out the bore) with a 62cc chamber, and intake adv. duration 275 @ 110+3 cam?
07-07-2014, 09:34 PM
#11
My engines math looks like this:
The camshaft is a 226/234 .598"/.612" EPS/LXL 110 LSA in at 107.5 ICL. Advertised is 275/286.
Valve Events:
IVO is 5.5 ° BTDC ( - indicates ATDC)
IVC is 40.5 ° ABDC
EVO is 49.5 ° ATDC ( - indicates BTDC)
EVC is 4.5 ° BBDC
Overlap is 10 °
Bore: 4.00
Stroke: 3.622
Head Chamber (cc's): 64
Valve Relief / Dome (cc's): 1.8
Gasket Thickness: .051
Gasket Bore Diameter: 4.080
Deck Height: -.006
Static compression ratio of 10.88:1
IVC is 65.0 ° ABDC at .006" duration
Dynamic compression ratio is 8.64:1.
Dynamic cranking pressure is 175.60 PSI
Car runs great on pump. I have put in racing gas and increased the timing, It does not go any faster. It will even run good on 89 octane, but it has a tendency to run-on when I shut it off with the cheap gas. I have even hit it countless times on a 150 and 175 shot of nitrous on pump gas.
Last edited by speedtigger; 07-07-2014 at 09:42 PM.
07-08-2014, 02:23 PM
#13
I have swapped carb setup on EFI engines and needed way more timing.
And the fastest guys have less timing because of boost, compression, nitrous and all the other given attributes that make a car really fast, so no **** the have less timing.
And the fastest guys have less timing because of boost, compression, nitrous and all the other given attributes that make a car really fast, so no **** the have less timing.
Last edited by speedtigger; 07-10-2014 at 03:19 PM. Reason: Thread Cleanup -remove drama
07-08-2014, 05:21 PM
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When a rule change on fuel was put in place with the 6 cylinder dirt track class down here, we made considerably more power with less compression (10.2:1) running pump gas, all in optimizing the head/cam timing/carb combination over previous higher comp (11.3:1) setup running on avgas.
I only use the dirt track example as these engines endure way more punishment than a quarter horse ever will.
07-09-2014, 07:33 AM
#15
Consider why a lot of these combinations don't meet typical LS criteria. Most (not all) of these combos are not "designed" from the ground up. A lot of the guys in here are just putting together budget combos. Many budget guys have junkyard truck shortblocks with large combustion chamber heads and/or dished pistons that typically have lower compression ratios than their Camaro, Corvette, GTO counterparts.
The next thing that a lot of carb guys have to deal with is a short runner intake that has considerable different volumetric efficiency curves than the typical long runner, plastic EFI intakes than most are used to. The low RPM and midrange volumetric efficiency is much lower. So, now you have an engine with lower than optimal compression and a short runner intake that does a poor job of cylinder filling at lower and midrange RPM compounding the problem.
So, not only are you putting less in the cylinder at low and midrange RPMs, you are also squeezing that smaller volume less due to the lower compression. This is why they need more timing. In an ideal world, one would raise the compression to increase the cylinder pressures. But, that is not always in the cards for budgetary reasons.
Now with all that being said, that does not mean the combo cannot make power. There are guys who still managed to make power and go fast. They do this with a few key adjustments.
While I think we would all agree that higher compression makes more power, there are other elements and strategies that can be manipulated to increase power. I could easily take the position that the way I make my power is the only way to do it, but I need not look too far to find other successful combos who have made just as much or more power than me and they are doing it with less compression and more timing. Typically they have more camshaft duration and overlap and are spinning it harder, but they are getting it done with what they had. To me that is what hotrodding is all about.
The next thing that a lot of carb guys have to deal with is a short runner intake that has considerable different volumetric efficiency curves than the typical long runner, plastic EFI intakes than most are used to. The low RPM and midrange volumetric efficiency is much lower. So, now you have an engine with lower than optimal compression and a short runner intake that does a poor job of cylinder filling at lower and midrange RPM compounding the problem.
So, not only are you putting less in the cylinder at low and midrange RPMs, you are also squeezing that smaller volume less due to the lower compression. This is why they need more timing. In an ideal world, one would raise the compression to increase the cylinder pressures. But, that is not always in the cards for budgetary reasons.
Now with all that being said, that does not mean the combo cannot make power. There are guys who still managed to make power and go fast. They do this with a few key adjustments.
- Increase midrange efficiency by using increased valve timing overlap to improve cylinder filling. ~ This is done by opening the intake valve sooner and closing the exhaust valve later. These particular valve events are a very important distinction because it is limited by piston-to-valve clearance. This is another reason why the budget guys are limited in the amount they can mill their heads because it will exacerbate their valve clearance issues.
- Raise the RPM range to where the intake manifold is efficient~ High stall converters or stick shifts with high numerical gears. But again, piston to valve is a problem for the budget guys because the larger cams that are needed are limited by valve clearance.
- Advance the ignition timing to increase the combustion efficiency ~ As said above, the lesser low and midrange RPM cylinder charge needs more advance to burn more efficiently.
While I think we would all agree that higher compression makes more power, there are other elements and strategies that can be manipulated to increase power. I could easily take the position that the way I make my power is the only way to do it, but I need not look too far to find other successful combos who have made just as much or more power than me and they are doing it with less compression and more timing. Typically they have more camshaft duration and overlap and are spinning it harder, but they are getting it done with what they had. To me that is what hotrodding is all about.
Last edited by speedtigger; 07-10-2014 at 02:35 PM. Reason: Thread Cleanup -remove drama
07-09-2014, 08:36 AM
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Speedtigger is on the money, it all comes down to a compromise with budget racing.
But not only that, all engine combinations have some sort of compromise. And regardless of whether it is low budget or high budget, when you are talking street engines running on pump gas that will always mean having considerable compromise for it to work effectively.
That's why I mentioned the dirt track motor. Going from avgas to pump gas, meant combustion chamber cooling became very compromised, and in drag racing - engines don't spend enough time at WOT to realize these sorts of flaws in such a short duration.
But not only that, all engine combinations have some sort of compromise. And regardless of whether it is low budget or high budget, when you are talking street engines running on pump gas that will always mean having considerable compromise for it to work effectively.
That's why I mentioned the dirt track motor. Going from avgas to pump gas, meant combustion chamber cooling became very compromised, and in drag racing - engines don't spend enough time at WOT to realize these sorts of flaws in such a short duration.
07-10-2014, 01:20 PM
#19
370" 11.2:1 SCR here. haven't ever taken the time to calculate DCR. 242/250 on a 108, .615/.615. 93 octane, 36* timing locked out, no MAP. no signs of detonation on plugs or on piston tops last time i had it apart.
for whatever that's worth.
car runs good too. been 10.4x's @ 132 at 3260lbs.
for whatever that's worth.
car runs good too. been 10.4x's @ 132 at 3260lbs.
07-16-2014, 08:59 PM
#20
370" 11.2:1 SCR here. haven't ever taken the time to calculate DCR. 242/250 on a 108, .615/.615. 93 octane, 36* timing locked out, no MAP. no signs of detonation on plugs or on piston tops last time i had it apart.
for whatever that's worth.
car runs good too. been 10.4x's @ 132 at 3260lbs.
for whatever that's worth.
car runs good too. been 10.4x's @ 132 at 3260lbs.