Cam recommendation for EFI
 

There's a million threads on cam recommendations, but after searching I didn't see any that specifically address this question. If anyone can suggest a previous thread, I'd be happy to read it.

I have a 0.030 over 455 that was built about 8 years ago. It was a rebuild of an early 2000's street/combination. The specs:

- rotating assembly from Butler. Forged rods and pistons, cast crank.
- Ported 87 cc Edelbrock round ports from the early 2000's. I don't have flow numbers. On the earlier engine they made 580 HP.
- Torker 2 intake
- long tube headers
- 3" exhaust
- FAST EZ - EFI 1.0 multiport.
- Comp Cams XR288HR. Specs for those like me that don't have every cam memorized: adv duration: 288/294, duration @ .050: 236/242, lift: .520/.540, LSA: 110

This engine is in 1969 Firebird with T-56 transmission and 3.55 gears. I initially struggled with some tuning issues (most self inflicted) but now it runs well.

The car has about 5,000 miles since the engine was installed. It runs really well, especially over about 3000 RPM. Throttle response is great. It will idle at 850 RPM and has about 13" of vacuum.

I wish it ran a little better at lower RPMs.* At idle it has the stinky exhaust smell and will buck in first gear under about 2000 RPM on a residential street or in a parking lot. To me these are the symptoms of too much cam.

The issue could be the*EFI. It's an old system without many tuning options. The 110 LSA cam doesn't help. At some point it will probably switched out for something better, like a Holley Terminator.*

Currently, the rear main seal is leaking and the throw out bearing is making noise. I figure with the engine out it might be time to change the*cam for something better.

I was considering the Stump Puller with 114 LSA, but around here, that cam mostly seems to be recommended for iron heads, automatic transmissions, and iron exhaust manifolds. Old Faithful is a more popular recommendation for a combination like mine. Looking at the specs, Old Faithful seems very close to the Comp Cams XR288HR, other than the 110 LSA of the XR288HR. I know there is more to a cam than the duration @ 0.050 and LSA, but I'm not that sophisticated on the differences, even after reading all the previous threads on this forum.

Would Old Faithful with 114 LSA give me the street manners I'm looking for, or should I go with the Stump Puller? Do you have another recommendation?

I don't want to give up any more power than I have to, but I'd rather lose some at the top (which realistically can't be used on the street anyway) to not have bucking at low speeds and smelly*exhaust. This car spends its time driving around town and 100 mile highway trips with the A/C on. It's never been to the track.

The full throttle runs are fun, and there's nothing like feeling the rear get loose at 30-40 miles an hour, but the chances to do that on the street don't come around that much.

You should switch to the Performer rpm Intake and I bet the higher average torque values across the most useful rpm range of your motor will fully cover up the 5 peak hp loss that you MIGHT see.

Also right now I see your compression at no more then 9.9 to 1 tops!

And there no reason with Aluminum heads and fuel injection to not mill the heads to get to a 10.8 to one compression.

Aluminum heads need a 1/2 point more compression to match a iron head below 3K rpm.
This will up torque across the motors full rpm band and also provide you with more idle vacuum.

Can the FAST EZ unit allow you to change injector firing angle? I run a MUCH bigger solid roller camshaft than that and my motor runs pretty awesome and doesn't really smell much other than when cold because I really advance the injector firing angle but retard the injector angle as it heats up. Just because the fuel doesn't atomise as well when cold.

Bucking a low speeds with a manual trans can be tuned out but is a compromise. Usually airflow and timing will fix that but there's a few aspects to it and it's very much trial and error.

If the engine had a carb I'd try a dual plane. I'm using the Torker 2 because it has injector bosses. I don't believe those are available on any dual plane manifolds. Someone can correct me if that's wrong. I've also heard a lot of people say dual planes don't work well with multiport EFI.

I have heard people talk about higher compression with aluminum heads and the benefits you describe. It's an option.

I've read about people changing the injector timing so that the injectors aren't spraying the exhaust valve. The EZ-EFI 1.0 is an old system without much adjustment. About the only options are adjusting the acceleration pump shot and AFR.

It is possible to change the Idle Air Control valve position on larger cammed engines to improve throttle response.

It is possible it's still a tuning issue on my part. I struggled quite a bit to get it running good in the first place. I just don't know of anything left to check.

This is similar to a 351W I had in a Superformance Cobra. The engine builder built the motor for maximum HP on the Dyno. He used a big cam and a single plane intake. The motor ran great in the upper RPM range but was really fussy at idle and lower RPM. He used a single plane intake to get max dyno numbers. I switched to a dual plane intake and all the low and mid RPM fussiness went away. I'm sure I lost a bit at the top end, but not enough to notice driving.

Also, I have the same cam as you but on a 112 LSA. Milder combo overall with D port heads. I have a factory iron intake and the street manors are very good. Yet it will toast the tires at will. I have to run sticky tires to make it reasonable.

OCMDGTO (Chris) is running that same cam in a similar engine combo, Torker 2 but with a carb. He should be able to comment on low end drivability.

I love this cam! Great performer as you can see in my signature. I also ran it in an iron headed 400 with 9.5-1 compression. No low RPM issues whatsoever. We are apples to oranges in comparison since you have efi, round ports, headers, and a manual trans. I have 10-1 compression, 3800 stall, and don't worry about vacuum since I have manual brakes. 455 Pontiac on here has a very similar setup as you and his car runs flawless.

Early systems like the FAST EZ EFI are somewhat limited in their tuning ability and you're probably dealing with the effects of reversion and overlap on fueling calculations.

Here's the short of what might be going on. Your cam has a calculated overlap of 71 degrees. During this overlap cycle, depending on your injector timing, you may be pushing raw fuel out of the exhaust ports. Your oxygen sensors read this as a rich condition. This will effect your short term fuel trims and often creates an oscillation between lean and rich as the system tries to compensate for what its sensors are telling it.

This can make the engine unhappy and create low rpm manner issues. Your manual transmission makes you feel all of that since there's not a torque converter in front of it soaking up any ill behavior.

Here's how I'd try and address it.

Richen up your AFR at idle and at lower rpm cruise. I'd target around 13.5:1 at idle and between 13.8 to 14.1 at cruise. You may also need to add in a bit more timing. With the old style edelbrock heads, you may want 25-30 degrees of timing at idle and you may want to add more at cruise rpm.

I was dealing with similar surging when my torque converter was in lockup. The cam in my engine is slightly larger than yours and didn't like to cruise around under about 1800 rpm. For me, richening the mixture in this range was the most helpful.

I don't know that I'd be in for a cam swap until I tried to tune around this first. In fact, before I did a cam swap on this, I'd be spending those funds on an updated efi system, probably a Holley Terminator. That type of system will provide the tuning adjustibility needed for your engine.

I'm not too far off of your combo relative to cam and top end. Plenty of power past 4000 RPM and I run it out to 6500. I run solid rollers on my OF so it is a bit milder but is a little soft down low with the TKII, might need some more compression as the OF was a monster in my 455.

Game changer has been with the timing control as that really cleaned up my idle. Plugs show perfectly tan, pipes are clean and the car gets pretty decent fuel economy now. I really don't lug it below 1600 rpm and with the improved fuel economy from the timing control, I just drive in 4th gear more. I have a large runner P4B that I have been getting ready to try with the hope of more linear power delivery and less need to string things out to 6500.

Are you seeing 20mpg?

This explanation makes sense to me. No doubt a more sophisticated EFI platform would help. I guess my thought was more LSA and less duration would reduce the 71 degrees of overlap help with the symptoms that causes.

Changing the AFR targets and adjusting the timing aren't too difficult. It's been awhile, but I think it's at 14-16 initial/36 all in. Wouldn't running that much initial timing make for hard hot starts/ a hotter running engine?

Are you running any type of timing control, or are you still utilizing a traditional distributor with weights and springs?

Typically, with an EFI setup, your cranking timing is whatever is set in the base timing table and the system then increases timing based on current load and run state parameters. This keeps the starter happy. It's much the same as having 14 degrees of initial advance in the distributor and the vacuum can adding another 10-12 degrees based on available vacuum.

as far as running hot is concerned, adding a couple degrees of timing likely isn't going to make any real difference there. You're also adding more fuel which has a cooling effect itself. The range you're adding this to is low rpm and low load, so it shouldn't be adding much in the way of heat.

If you're still running a traditional distributor, you might consider looking at the Progression Ignition distributor if you're intent on keeping your FAST EZ EFI. It will give you better and more control over spark events and may help.

I spent some time looking over the system you have and it being batch fire isn't helping. Your system fires all injectors bank to bank without regard to firing order. As a result you get fuel sitting on the backs of the valves until the intake valve opens. This causes fuel to pool in a liquid form and you're drawing it in and out of the chambers during your overlap window.

Moving to a system that is sequentially fired is going to be helpful here. As I mentioned the Holley Terminator would be a good choice, but I also think the Edelbrock ProFlow 4 would work for you as well.

If you didn't have an intake with injector bosses, I actually think a Sniper or a FiTech would actually be better than what you have as well. That would also allow you to get a dual plane manifold on the car that may help with it's low speed efficiency.

It's a traditional distributor. MSD pro billet. The smallest amount of centrifugal advance that it can do with the included bushings is 18 degrees. There are options to get larger bushings that would bring that down to 10 or 14 degrees. It seems it would need one of those if initial timing was set to 25.

I get what you're saying about a more capable EFI platform. Within even one platform, like the Terminator, there's a lot of choices to be made, like throttle body, timing system, etc. It would be nice to get it running a bit better while researching which way to go with an EFI upgrade.

I'll try advancing the timing and changing the AFR targets and see how much of a difference it makes.

You may not need to change the weights or the amount of advance in the traditional distributor. You may need to tune the vacuum canister to provide more vacuum advance in the area we are discussing. If you are not running a vacuum advance of any kind, that would be a big part of the problem.

With 14 degrees of initial advance, I would start at 10 degrees from the vacuum canister at whatever vacuum you are seeing when cruising. If the car is idling at 13", you probably see somewhere around 16" ad low load cruise. Set the vacuum advance to provide 10" additional in that range and see how the engine likes it. If it gets better, but not quite there, try 12" extra in that range. That of course assumes an advance can with an adjustable stop and the ability to tune the diaphragm. I believe the Crane Cams unit is often discussed as a good can for this type of tuning.

The vacuum advance is hooked up, but it's not adjustable. I'll look into one that fits.

I never ran vacuum advance on either engine with this cam

That may work in some cases, but you've got a turbo 400 with a 3.50 gear and probably some type of decent torque converter. That setup will soak up some of the ill behavior created at low rpm's with a good bit of overlap from the cam.

The OP has a 6 speed and is likely driving around at lower rpm's with a completely coupled drivetrain. He's going to feel more of what the engine is doing.

There's a reason vacuum advance canisters are on street cars.

Of course, the easiest fix for this, since the OP does have a 6 speed is to drive around 1 gear lower where the engine is going to be in a happier spot.

On the highway, that would be plausible. Overall, not sure. I have no data other than with a my carb and standard distributor, the same combination would use 1/4 tank of fuel between warm up and driving around (usually to a local cruise night or cars and coffee). I would refill to about half a tank. I can do that twice on a 1/4 of a tank pretty easily now. As my Tanks Inc tank has slightly more capacity and a different sending unit, I am certainly not saying fuel economy had "doubled" but it is noticeably better.