Powerjection 3, Webers, or Vac secondary Holley?

[TNcoupe]

Been working a lot of OT and was thinking about some upgrades for the Coupe. Gonna do a cam change most likely, been out driving a couple of times and the AFM N51HR is a little too high strung for my liking. Its lurching real bad at 2000 rpms, I gotta keep it revved over 3k just to get around my neighborhood. With the cam change I was gonna change from the 650 Holley DP to something with a little better idle quality. I've tuned on this thing every direction and im just not happy with it. Spend my money wisely.

Its a 331 with Trick Flow 190cc heads 60cc chambers
1.6 rockers
Weiand Stealth dual plane
T5Z with 3.73 rear

[Bob Cowan]

Keep the cam and compression, switch to direct port EFI. You'll get excellent low speed drivability, improved gas mileage, and yet still retain all the high rpm power you want from that giant cam. Yes, you can have it all.

[TNcoupe]

So basically stack injection is where I need to be looking?

Will stack injection be happy with a 110 LSA on the current cam?

[Hankl]

My pick would be the PowerInjection III. You can use the same manifold that you currently have, it's a 4 wire hook-up, vs the wiring harness with the other system, and less tuning problems. Plus you can get it from Mike Forte, very good after the sales support.

Hank :cool:

[riptide motorsport]

Hankls got a point.

[TNcoupe]

What cam to go with it??? hydraulic roller

[Hankl]

TN,

A good mild roller would be good, you can go with one of the Ford "Performance" cams, or one of the Comp EFI rollers (XE270HR) that provides good torque.

Hank :cool:

[Stengun]

Howdy TN,

Your engine combo should run fine below 3,000rpms.

I would look for some reason why you do not have better low rpm drivability. Your cam, heads and intake aren't the most balanced combo but you should have better low rpm drivability in a 2400lb car w/ 3.73 gears.

Paul

[turbodon]

The surging you explain can be felt in a Fuel injected motor as well. Engine is too lean.

I would suspect that you have the idle circuit to lean.

As a test fatten up the idle circuit with your idle screws. Back them out 1/8 turn and drive. Back them out another 1/8 turn and drive again. You may have to reset your idle throttle screw.

These high performance motors do not like lean driving around town. The idling around at 2000 rpm should improve but the unburned fuel smell will not.

[Bob Cowan]

So basically stack injection is where I need to be looking?

Will stack injection be happy with a 110 LSA on the current cam?

Not necessarily a stack EFI. But an EFI with 8 injectors placed close to the heads. The direct port injections are more accurate, and are less dependant on intake manifold design.

Something like a powerjection is an easy and relativly inexpensive swap. But, it's still a wet manifold, and subject to some of the limitations of a carb set up. They're better than a carb, but not as good as direct port. Life's full of trade offs. Dodge, Ford, and Chevy all used the central throttle body for a few years. Nobody uses them any more for some very good reasons.

If you do decide to use an 8 stack system, it will run on a cam with 110* LSA. But, it will run a lot better with 115* LSA. The smaller the LSA is, the more reversion you get.

[TNcoupe]

The surging you explain can be felt in a Fuel injected motor as well. Engine is too lean.

I would suspect that you have the idle circuit to lean.

As a test fatten up the idle circuit with your idle screws. Back them out 1/8 turn and drive. Back them out another 1/8 turn and drive again. You may have to reset your idle throttle screw.

These high performance motors do not like lean driving around town. The idling around at 2000 rpm should improve but the unburned fuel smell will not.

Its not a lean carb condition, its like rolling up to a red light in 1st and never pushing the clutch in. The cams adv. Duration is right at 296 & 304, so its a little large for tooling around town. Its was recommended for my combo by AFM, I thought it was a little large but I figured they knew what they were talking about.

[TNcoupe]

Think I've about decided on Powerjection III and a Comp 270 or a Trick flow Stage 2 cam. Took it out for a drive today and it runs great as long as you drive it like you're racing everywhere you go. It wont idle or ease around worth a flip though.

[bobzdar]

What you just described is lean surge. I would wager on the carb being the problem, holleys are a poor choice for a street car and suck fuel like no tomorrow. I have a 650dp hanging on my wall for that very reason. I got it to try on the track and it was no faster than my quadrajet but was horrible in around town driving. Quadrajet is vastly better at low rpm and can lug the engine with it, also doesn't make my eyes water at idle. Only benefit to the holley was throttle response due to the mech secondaries but not worth the tradeoff even for track use.