silver86

I'm gettin' tired of this cam. Don't get me wrong, I love the choppy idle sound, but the vacuum signature sucks, and I have to run a higher idle setting than what I'd normally like (about 1,000 in gear).

So, I'm considering swapping to a hydraulic roller with shorter duration and larger lift numbers. Just wanted some input from the gurus...

My application:

Stock 86E shortblock
Vortech blower with 10 psi max @ 5,700 rpm (overspeeds above that rpm)
AFR 195 65cc's with 1.6 rr's
2,500 9.5" stall converter
9.42:1 static CR
appropriate intake mods (but still TPI), injectors, Long-tube headers, yada yada...

Here's the cam I'm currently running:

Hydraulic flat tappet SUM-1105
282 int./292 exh. advertised duration
224 int./234 exh. @ .050
.465 int./.488 exh. lift (.496 int./.520 exh. w/1.6 rr)
Lobe Sep. 114
operating range 2,500-5,700

Again, sounds great, but tough to live with...

Here's the one I'm looking at:

Hydraulic roller tappet Lunati 50155
268 int./276 exh. advertised duration
215 int./218 exh. @ .050
0.489 int./0.503 exh. lift (.522 int./.536 exh. w/1.6 rr)
Lobe Sep. 115
operating range 1,500-5,500
Cam card:
http://static.summitracing.com/globa.../lun-50155.pdf

What do you guys think?

bjankuski

My initial thought is that you should be able to get the cam you already have to idle at 750 RPM in gear with good vacuum. It is not that big and maybe you have a tuning issue that is causing your idle problems. The cam you have picked should idle smoother but I would shoot for more exhaust duration with a blower.

Master__Shake_

The cam will be smoother, but the blower will not make as much power in the top-end with that cam. I have a bigger cam than you(234/244 dur @.050) and it idles rough, but nicely, at 700 in gear. The LSA looks good, but maybe it's a bad tune. I run a carb so that's a different story altogether.

From what the EFI guys say, roller is better than flat for that application, so if you do go with a roller I'd suggest 218-222 intake duration and 226-230 exhaust for the blower. Even though the numbers are closer to the original cam, rollers are known to open sooner to get a better low-end and that will keep the RPM band lower than a flat tappet with similar durations.

And, of course, if you love the rough idle, I can suggest Thumpr CompCams camshaft to keep the sound we all love. Their durations are a perfect for a mild blower setup.

silver86

Interesting comments about the tune. I'm certainly not happy with mine, and some issues have come to light concerning it.

Perhaps that's the issue here.

383vett

I agree with the others. The cam duration and lobe center numbers are actually quite mild and you should be able to tune it to idle in the 7-800 range. Also, a roller cam will make more hp with the same duration numbers because the valves can open and close so much quicker (not to mention not having to worry about cam wear with today's oils).

USAsOnlyWay

You by no means have a monster cam. You should be able to get it to idle nicely.

cv67

Id go for more lift.

GREGGPENN

Considering the 195's real advantage is their extra flow in the .500"-.600" range, that recommendation is hard to argue with!

I'm wondering if you can go with less exhaust duration too. If you didn't have a supercharger, I'd say you definitely need more intake than exhaust duration (because of your intake). Since the SC helps force down your tight TPI, it may not be as necessary. Maybe this is a better question for the FI forum?

Ask comp for their recommendation... maybe a 224/218 XFI cam? If they can make one, ask about a 218/214 cam. You'll probably have MORE valve opening time (than your current cam) w/o all the overlap.

Don't underestimate how much area is "under the curve" of an XFI lobe.

silver86

Thanks for the replys guys. My main issue here is a hard starting situation when cold. I increased the idle settings in order to get her to idle normally when cold. This probably lends to my decrease in vacuum signature when the engine warms and the idle rpm drive upwards.

For example:

If I set the idle rpm for a cold start level of 800 rpm, there's a point, whatever is going on, that the idle then increases to around 1,100-1,200 rpm, or around 1,000 rpm in gear. This is most likely the cause of my decreased vacuum issues correlating to the higher blower rpm (or maybe not, but makes since to me). If I set warm idle rpm to 700 in gear, she won't run cold, and I've got to keep my foot on the pedal for probably 45 seconds to over a minute.

This doesn't appear to be an IAC issue, but I need to pull it to ensure it's functioning correctly. My only other thought, going back to the tune, is that the open loop fuel tables are incredibly lean. Evidence for this is my A/F ratio guage hovers completely in the lean category (complete light up of all lean LED's as oposed to sweeping motion when in warm operation) while the hard running condition is present. However, the exhaust smells incredibly rich.

AKS Racing

You definitely will want a cam with more (8-10°) more exhaust duration at 0.050" in a healthy SC'ed application. The cam you are currently running is very mild and should easily idle at (or around) 800RPMm without a tremendous amount of "chop". There seems to be some issues with the tune.
Aaron

95BlueBomber

I like the idea of more lift... With your setup I think more lift would bring your numbers up, the 115 LSA is going to help with the boost. I personally like the new cam over the old one.

Do you by chance have flow charts on the heads? Most the time you can tell where you want your lift by these.

Timing was never mentioned in your post and neither was method of tuning. Your problem probably lies in the tuning with the cam you have now. Do you by chance have a wideband? Are you working off fuel pressure?

383vett

Interesting that your car smells rich even though your A/F ratio gauge reads lean. Does your gauge read from one bank of cylinders? Could your ecm 02 sensor be reading from one bank (which may be rich) and be trying to pull fuel out while your gauge is reading the other bank which may be lean due to a faulty injector or vacuum leak or whatever?

silver86

I had the car dynotuned back in March or April. After prelim numbers and performance at the track, the general consensus, mine and from input here, was that the tune wasn't done correctly. The tuner concentrated on A/F ratios, and pretty much excluded all other factors. For example, for the street tune, he limited max timing advance to 22.6*, but ran the car at that setting in addition to having the BTM set at 1.5*/psi. So at 10psi, total advance was in the neighborhood of 8* for the dynopulls.

He also burned a track chip, which I'm not sure of the parameters. I'm currently running this chip, but only for the last few months or so, and just for normal street driving, but will shortly be switching back to note any idle characteristic variances.

My initial advance is set at 8*.

95BlueBomber

You should be able to unplug the ECM and set your base idle timing. That should help a bit with the startup issue. Wow 8* on the dyno with 9.42 compression. You probably have some power left on the table. Have you thought of calling pcmforless and talking to Alvin? He could probably help you out a lot in this situation, and he is a really easy guy to work with.

tequilaboy

I agree with what others have already stated. You have timing and mixture issues with the tune, if you're having idle and low vacuum issues.

IIRC you have 42 lb. injectors. It should be noted that specific injectors will require specific tuning to the low pulse width and voltage offsets. I've seen 2 sets of Lucas 42s that required completely different settings.

If these offsets don't fit the actual injectors, you likely wind up with significantly more fuel than desired, especially at low rpm or lower voltage.

One way to tell that the injector offsets are incorrect is if you have a large discrepancy between the displayed fuel economy and actual fuel economy, assuming that both the injector #/hr constants and display gallon/hr constants are properly set for the injector size.

The lean indication may be due to a misfiring cylinder.

silver86

Yes, I do run the FMS 42#, and I'm not sure if the tuner took that into consideration (I don't remember him asking). I am quite rich on moderate tip-in at low rpm around town (the cars behind me get a good look at unburnt fuel). The tune I drove to the dyno with was 42# specific, but I'm not sure if he used any of that base tuning.

I contacted Alvin late last year, and he suggested I tune on a dyno given the FI, which is why I had it done in the first place.

Thanks for all the comments/input so far!