I want to convert my lt1 into a carbed setup should I go with a new cam? The old cam was a custom comp cam 534,576 230, 244 on a 112. Will this cam not work well with a carburater? Should I put in an earlier generation cam? Is there a big difference between a fuel injection cam versus a carbed one?
Thanks

 

I've heard that single patterns work better on carbed cars, when compared to a single on an FI car, but I dont know the truth in this. This is not to say that single is best on a carbed car either.

Why are you going carbed? I HATE working with carbs, especially since I have a manual choke.

Lets see, hates cold weather (hard starting, has to sit for 2-4 minutes to back the choke off at all), still having to run the choke until it gets fully warmed up, nowhere NEAR the fine tuning of FI, a good carb wether for full race or progressive carb with some ability to get decent street MPG + power, is going to set you back big moola, so why? Why would anyone go carb? Is this something imposed by rules in your organization?

I'm working with Webers, which for early carbs are some of THE most flexible to work with, but they still are in some ways more confusing, and troublesome to work with than FI especially since you have everything right in front of you as of now with ability to fine tune your AF curve at your whim.

 

I have had nothing but probl;ems with FI. Car would never run right with anyones tune. Had ED Wright ,PCM for less and a local dyno tune. Can't stand shipping out computer for upgrades and having the thing run great one day and like crap next day. I've always had carbed race cars before lt1 and had no problems and I have lots of parts for carbed motors lying around to use. Not to mention I'm buildind the bottom end up on the lt1 and throwing in a nice solid cam I think now. Love the sound of a healthy carbed motor with a big old cam. For me it's alot easy to work on than relying on a computer to tune my car.

 

i rember reading someting about having a certian lobe center on efi i guess its to tome the pulses correctly.

 

typically, injected engines run cams with greater LSA's to be more ecm friendly (gives you a bigger difference between extremes in vacuume signal allowing the ECM to get a better impression of what is actualy going on). Typically cams used with carbs are just the opposite, tighter LSA's which fatten midrange and give it the cool sound...

If it's in an f-body I suspect that you'll have problems clearing the cowel...

 

Too much fuel going out the tail pipe.. requires a short duration cam to allow closed loop.

 

Mail order is a TOTAL crap shoot, I thought that I would use mail order for a baseline tune and it wasn't even useable as that, I did much better with one I got off the net for my baseline, almost made no timing changes, just AF.

If someone can't tune it on a dyno though, thats pretty bad, and doesn't sound like that leaves you many options.

This is why I do things myself, if you want it done right, you know what they say... and you save money that way, and you can make compromises or not make them when and where you feel its needed instead of someone else being conservative with the tune and you missing power.

With the cam your talking about that should be absolutely tuneable by anyone with modest experience, how it could not be dyno tuned I dont understand, although I have seen a dyno tune on here with AF so haywire that I shudder to think of the other cars they turn out, and I wonder how many of them blow up. If you feel like getting into this yourself myself or plenty of others can help you with the tune, there are plenty out there who have the ability to do this themselves. In fact the cam I ran was similar to yours, and like I said I used the timing tables almost exclusively from another tune of someone elses, and it worked great with only minor changes.

Best of luck

 

That makes sense, as well as what was said above. A cam like a 230/240 on a 108º LSA will not be the most fun to tune at idle when in closed loop.

Generally this is why 'big' cam people will run an open loop idle, fatten it up a little extra on purpose, and past 1200 RPM (LT1 anyway) go back to closed loop operation. You can fix this in your PE vs RPM table (dont know what LT1 Edit calls it).

 

If no one can seem to tune your combo, or it runs right one day and bad the next, it sounds like you have more going on then just bad PCM tuning. I would look to loose grounds and bad sensors before condemning the FI. I would agree that the cam you mentioned should be easily tuneable unless you have a electrical or mechanical problem. My suggestion: get back to the basics and check all connections and sensors as well as ground wires. After that, do your mechanical checks like compression and leak down to make sure there is no problem there.

 

In my honest opinion going carb will cause more harm than good, UNLESS YOU KNOW CARBS like the back of your hand.

IMO they are more complex to work with than an FI system that is already in place, there are 5-7 parts inside the carb you will have to modify for best results, especially if you want driveability other than WOT. Midrange almost ALWAYS suffers when you jet the carb for top end, and dont change emulsifiers and yada yada, because you ruin the balance and progressiveness of the carb. This is why generally speaking FI will make more power across the curve, AND be more driveable, AND be more fuel efficient.

I think your seriously looking at going back to the stoneage, unless this is a race only car in conjunction with you already being a genius with the carb of your choice.

Plus, unless you run a nice $700 or so MSD box with programable ignition, your going to give up your programable timing MAP. There are cheaper boxes which allow several curves to be programmed, but not full MAPs, pretty close to as good, but still, I see nothing but stepping back, very far back.

JMO from my own experience with carbs and FI, when you dont have FI it can be expensive to get started especially if you go with an aftermarket setup, if you have FI in place and are FORTUNATE enough to be able to readily obtain programming software for it like we are, then FI is the cats pajamas.

Tunercat or LT1 edit, grab a tune off the net for a similar car (make sure stroke is the same or similar, timing is different for strokers), and LEARN to do it yourself with the help of the people on this great site. Again the cam you mention is totally common, everyone, thier brother and thier grandma have it in thier car, its well known how to set up that kind of cam to run well, so there is lots of help here for you.

 

Just as another opinion on the subject, there are tons of LT1's running around with bigger cams and reprogrammed ECM's that run fine. If you've been unable to tune it I woud strongly suspect something besides a tuning problem.

 

yeah another vote against carb, heck I'll tune your car send me your tune I'll see whats wrong, & tell me what it does that you don't like.

 

A big cam and Stock PCM on FI dont mix, because they dont have the MAP tables that go in to the higher and lower regions that a low vacuum cam or high boost motor may need.

Need DFi on a FI racecar Id talk to Joe Overton about it.

I know of a guy with 106 or so LSAs on FI cars