I see you limit the maximum advance at full load to 33°, is that where you get the most power or are you worried about knocking beyond that?
Thanks for pointing that out. It should probably be 36 degrees. What are you running?
I use what we call in France the Super 98 which has a ROM of 98 and a MOM of 87 or ROM + MOM /2 = 92.5
I don't know what that corresponds to for you
Iron heads typically like 36° total and aluminum heads 32-33°.
There isn't a lot of difference in results though. Drag cars get faster trap speeds by backing off the total ignition advance.
These days you can compensate to an extent for detonation by modifying the "dynamic compression" with camshaft timing. What it does is blows compression out of the exhausts by leaving the exhaust valves open longer.
That usually means more overlap of the intake and exhaust being open at the same time. Milder cams will tend to "detonate" while more radical cams reduce or eliminate that.
I can't tell you what those numbers are. You need to use the "dynamic compression" calculator on your camshaft timing events to determine that.
I have a static ratio of 10.6/1 and an effective ratio of 7.7/1.
I thought that the reduction in the risk of knocking with a more radical camshaft came from the fact that the intake valve closes later, the compression starts later and the pressure at the end of compression and therefore the gas temperature are lower.
@rene4406 posted:I have a static ratio of 10.6/1 and an effective ratio of 7.7/1.
I thought that the reduction in the risk of knocking with a more radical camshaft came from the fact that the intake valve closes later, the compression starts later and the pressure at the end of compression and therefore the gas temperature are lower.
I am not the cam design expert.
I do know that what has to happen is that the cylinder pressure under compression needs to be lowered to below the point at which fuel will explode by just being compressed.
In my old school thinking, this is by bleeding off the pressure by leaving the exhaust valve open longer?
If that can be done in other ways, that's fine. If you open the intake later or leave the exhaust open longer that is just the method of achieving the desired effect by the designer.
That is all just done in a computer program these days.
As far as I can determine, the two cams that you are using, the old GP design and the slightly modified new one, are doing that.
The cam grinder should be able to tell you what ignition advance you can use and what fuel octane you need to run on.
In some cases the actual angle of the valves at .500 lift effect the calculation in that the angle it is canted too un-shrouds the valve from the cylinder wall. That is partially why aftermarket heads make more power then their original counterparts did. They change the angle and center to center location of the valve guides in the inline designs but not as much as the canted valve Cleveland head does.
This is why canted valve Cleveland heads make 30 to 40 more horsepower then the original inline "Windsor" type heads do but the cam needs to have a minimal lift for them to work.
Clevelands start to make ungodly type power with cam lifts around .600" or more. Under .500" lifts, they are just like any other "grocery store" engines.
And if I believe what George says, open chamber cylinder heads give more valve clearance at low lifts. My maximum lift is 0.62''
@rene4406 posted:And if I believe what George says, open chamber cylinder heads give more valve clearance at low lifts. My maximum lift is 0.62''
Yes, I believe that is correct. The open chambers unshroud the valves sooner, or at lower lift. So you get them to work (flow) sooner.
In that sense, they are better then the closed chamber heads.
You actually need to measure the maximum lift since it varies from the published lifts. Hydraulic lifters don't give 100% lift and solids, you need to deduct the valve lash clearances from the advertised lift.
The efficiency of the hydraulic lifter can vary from manufacturer to manufacturer although they will tell you it doesn't.
The old "anti-pump up" hydraulic lifters were the most efficient. I had a set of those that sounded like solid lifters. They were loud.
Also the oil pressure varies the lift with hydraulic lifters as well.
.620" is nice but it probably will measure out at something like .605 or .610? It is right in the zone where you want it.
@buttondoor posted:Be forewarned, I am no EFI expert. I had a similar build done a couple years ago (636 bhp). Dennis Quella had recommended we go with the Sniper 2 Terminator X. But by that point, those were backlogged, and my builder got a FAST EZ instead. Ultimately, we couldn't get it to work well for any length of time once we installed it in the car, it kept fouling O2 sensor and plugs, and the EZ is not laptop adjustable. I know at least one P-car owner using a better FAST model that has worked well, but with more adjustability. I know the Sniper 2 has a generally good reputation now. I also know a member on here who had one installed/tuned by a performance shop, who has had many of the same troubles my system had.
I decided to swap out to a Holley DP chokeless (I'm in NC so that can work) carb custom set up and tuned by Chuck Nuytten out of Rockwall, TX. He is well known for this, he will have you furnish all relevant engine specs and your performance/driving style needs and build accordingly. I have nothing but positive things to say about this carb so far. In my (generously long) phone conversation with Chuck on the front end, as I recall he said my issues were common and that the extremely limited O2 sensor placement option in Panteras can inherently create challenges. My point is, if you were going to spend the money to "upgrade" to a Sniper 2, Chuck is another option, for less cost, easier installation, easier parts availability in a pinch, etc. The only possible drawbacks I see would be some sacrifice of fuel economy, a little attention to the throttle on cold start, and a good mechanic friend of mine says Holley carbs can get sticky with periods of sitting unused.
What kind of intake manifold are you using on your engine? An EFI throttle body system should work good on a Pantera . I know of a couple of Panteras here in Arizona that run very well with them. You are quite possibly pushing the limit of a throttle body system with the horsepower that you are making. I have been using the FAST XFI 2.05 sequential port fuel injection system for 12 years and haven't had any problems with it. I have a CHI 3V single plane air gap intake manifold and the engine is making about 550 horsepower at the flywheel. I have two O2 sensors that are on each exhaust pipes right next to the header collector. One O2 sensor is for the in dash O2 gauge and the other runs the EFI. Although this FAST system is quite old and has not been updated in at least ten years, it performs like a modern fuel injected vehicle. It does have a great deal more tunability than the throttle body systems that I have seen, which could be why I have not had any trouble with it. It also may have helped to have the engine tuned on a dyno by someone that was an expert in EFI systems. I am certainly not and know just enough about EFI to be dangerous!
@jffr posted:What kind of intake manifold are you using on your engine? An EFI throttle body system should work good on a Pantera . I know of a couple of Panteras here in Arizona that run very well with them. You are quite possibly pushing the limit of a throttle body system with the horsepower that you are making. I have been using the FAST XFI 2.05 sequential port fuel injection system for 12 years and haven't had any problems with it. I have a CHI 3V single plane air gap intake manifold and the engine is making about 550 horsepower at the flywheel. I have two O2 sensors that are on each exhaust pipes right next to the header collector. One O2 sensor is for the in dash O2 gauge and the other runs the EFI. Although this FAST system is quite old and has not been updated in at least ten years, it performs like a modern fuel injected vehicle. It does have a great deal more tunability than the throttle body systems that I have seen, which could be why I have not had any trouble with it. It also may have helped to have the engine tuned on a dyno by someone that was an expert in EFI systems. I am certainly not and know just enough about EFI to be dangerous!
@jffr, I'm using a Victor Jr. intake. My FAST EZ TBI had 4 injectors. 1 O2 sensor (as you know, there's basically only 1 spot per side to accomplish upward angle and easy access, so it was basically where yours are). 636 bhp was within the limit for the FAST EZ per its manual (we set the fuel pressure regulator accordingly by their manual). I also called FAST (Edelbrock) several times in the process and was given some interesting suggestions, some of which were contrary to the manual and the logical startup wizard and TPS reset procedure, etc., but nothing was really solving it, and it was out of warranty by the time we put it in the car, and I had already had "successful" Pantera FAST users (not EZ versions) spend considerable time with it, also unsuccessfully if for no other reason than fouled O2 sensor, so after a few more resets on new O2 and plugs, I bailed on it. Tuning was initially done on a dyno, but that was of course without my exhaust, etc., and that shop was over 5 hours from me at the time.
@jffr posted:What kind of intake manifold are you using on your engine? An EFI throttle body system should work good on a Pantera . I know of a couple of Panteras here in Arizona that run very well with them. You are quite possibly pushing the limit of a throttle body system with the horsepower that you are making. I have been using the FAST XFI 2.05 sequential port fuel injection system for 12 years and haven't had any problems with it. I have a CHI 3V single plane air gap intake manifold and the engine is making about 550 horsepower at the flywheel. I have two O2 sensors that are on each exhaust pipes right next to the header collector. One O2 sensor is for the in dash O2 gauge and the other runs the EFI. Although this FAST system is quite old and has not been updated in at least ten years, it performs like a modern fuel injected vehicle. It does have a great deal more tunability than the throttle body systems that I have seen, which could be why I have not had any trouble with it. It also may have helped to have the engine tuned on a dyno by someone that was an expert in EFI systems. I am certainly not and know just enough about EFI to be dangerous!
Excellent to hear since I am applying the same manifold CHI 3V single plane!
@buttondoor posted:@jffr, I'm using a Victor Jr. intake. My FAST EZ TBI had 4 injectors. 1 O2 sensor (as you know, there's basically only 1 spot per side to accomplish upward angle and easy access, so it was basically where yours are). 636 bhp was within the limit for the FAST EZ per its manual (we set the fuel pressure regulator accordingly by their manual). I also called FAST (Edelbrock) several times in the process and was given some interesting suggestions, some of which were contrary to the manual and the logical startup wizard and TPS reset procedure, etc., but nothing was really solving it, and it was out of warranty by the time we put it in the car, and I had already had "successful" Pantera FAST users (not EZ versions) spend considerable time with it, also unsuccessfully if for no other reason than fouled O2 sensor, so after a few more resets on new O2 and plugs, I bailed on it. Tuning was initially done on a dyno, but that was of course without my exhaust, etc., and that shop was over 5 hours from me at the time.
The FAST XFI 2.05 system is port injected. I have an injector for each cylinder, which was made easy because the 3V CHI manifold already had the castings for the injectors. CHI is one of the few companies that offers an intake manifold for a 9.2 deck Fontana aluminum block. When I decided to go from batch fired injection to sequential it was quite easy because FAST offered a dual sync distributor which allows the ECU to control the timing. When I switched to sequential port injection the car ran even better than it had when it was in batch fired. The gas mileage also went up by about two mpg, not that I was doing it for economy. The big problem with FAST is that when they were bought out by Comp Cams, the upgrades to their systems stopped. I think the last time that their software for the XFI systems was upgraded was in 2014. Not sure about how their tech support works these days because I haven't called them in years. There is a man in California that has a website called Fast Man EFI. He is an expert on the FAST systems along with other aftermarket fuel injection products. I have quite a few miles on this car with the fuel injection system. When we had the POCA rally in Monterey California, I drove the Pantera straight through back to my home in Arizona. It was a 1100-mile drive through numerous altitude and temperature changes and the EFI system performed just like it does on a modern car.
@FWJ posted:Excellent to hear since I am applying the same manifold CHI 3V single plane!
If you already have the CHI 3V single plane air gap manifold, then it should have the castings in the manifold to install the injectors. If you go with a port injected system you won't have to worry about horsepower limits and the system will be fully tunable via a lap top computer. The newer Holley systems now allow you to run coil on plug or coil near plug ignition right through their ECU. In my opinion, these simple throttle body systems work good for engines around 500 horsepower or less.
Thanks for the info. I am not yet into port injection (also it’s quite expensive). I will keep that in mind in case things go south. The updated Sniper-2 (which is essentially the AMD Atomic-2) has been increase to 800cfm (versus 750) and holds now up to 650hp and has no limitation on camshaft sharpness any more. In my case the setting for street/strip is 8“ to 13“ vacuum in the manifold and my camshaft is ranking in the race area of below 7”. However, my manifold produces still 6” of vacuum, so just a bit on the “race” side 😎. I think and hope that everything will be fine with the Sniper2. In any event Holley provides besides the self-learning also direct laptop support for fine tuning.
@FWJ posted:Thanks for the info. I am not yet into port injection (also it’s quite expensive). I will keep that in mind in case things go south. The updated Sniper-2 (which is essentially the AMD Atomic-2) has been increase to 800cfm (versus 750) and holds now up to 650hp and has no limitation on camshaft sharpness any more. In my case the setting for street/strip is 8“ to 13“ vacuum in the manifold and my camshaft is ranking in the race area of below 7”. However, my manifold produces still 6” of vacuum, so just a bit on the “race” side 😎. I think and hope that everything will be fine with the Sniper2. In any event Holley provides besides the self-learning also direct laptop support for fine tuning.
That is the issue with the fouling. The MAP is beyond it's limitations in determining if the engine is under load or not with only 7".
I don't know how you compensate for that unless you find a current production vehicle that has a very low vacuum reading at idle and can wire it into your system?
First I hope that it’s still working with 7” vaccuum. If this fails my fallback is the same as with the Holley carby to increase idle speed to 1.250-1.500 rpm. Even if this is needed I strongly believe that with the EFI the need for an increased idle will be for sure on the lower side than with a carby.
I can see that already today with the atomic-1 and a smartly tuned 430hp engine (non stroker) under all weather, temperature and altitude conditions. And the effect of dynamic timing in combination with the EFI should not be underestimated as well. I am positive (until I am proven wrong) 😎
FWJ you should check out the MSD forums or contact MSD themselves. Atomic "1" supports 650hp with a good enough pump. I had one on my Pantera running 640hp and it was pretty good. Excellent starting, hot or cold, ~20mpg on a 1,500 mile trip including track time. I set the regulator to 55 psi, I think. I used a Bosch 044 pump and set non-pwm with regulator, idle at 900rpm with 17in vacuum at idle, no problem with power brakes. I moved the Atomic to a Mustang and works well there also. You will need to run with timing control to get the full advantage.
Here are a couple of old threads. https://forums.holley.com/foru...ndard-kit-to-high-hp
Is the big pump okay with less than 525 hp? - Holley Performance Products Forums
Bdud, keep in mind, Holley owns MSD, so it's unlikely that MSD's Atomic and Holley's equivalent have significantly different logic.
The Bosch 044 fuel pumps are the best value on the market. Great performance, super reliability, low noise and cheap price. Just be sure you are getting a real one. Counterfeits are everywhere, so be careful. Even Summit got burned. If you Google "Bosch 044 fuel pump" there are web pages that show you how to spot a phoney pump.
Using a smaller injector at higher pressure is a pro-tuner trick. It gives you better starting, better driveability and an idle you'd find difficult to achieve with a larger injector and lower pressure.
I am aware Holley now owns MSD, however when I purchased my MSD Atomic they were still owned by MSD and the old forums still exist. The techs and contributors were quite active in their day. I am running a Holley Terminator throttle body with a Dominator ecu for my latest build. I wanted to keep away from the all-in-one style and keep some sort of first glance originality by keeping the throttle body.
I also did not want to purchase a "black-leg" Bosch pump which is why I purchased mine from Pegasus Racing as they are certified genuine.