LSx Motors: why switch to a carb intake?

[shudog]

I see it all over this board and ls1tech which I frequent. Why spend the time & hundreds of $$$ if not more for a carb intake? A standard LS1/LS6 intake can provide 450+ rwhp with the right head/cam setup, is a carb setup really that much better?

[andrewb70]

I see it all over this board and ls1tech which I frequent. Why spend the time & hundreds of $$$ if not more for a carb intake? A standard LS1/LS6 intake can provide 450+ rwhp with the right head/cam setup, is a carb setup really that much better?

A carb setup is not better, but some feel it is easier. When converting an older car to EFI there are things that you have to change. Mainly the fuel system. By converting to a carb most of the stock fuel system can be left in place.

Andrew

[parsonsj]

is a carb setup really that much better?Don't assume that a carb intake means one is using a carburetor.

You can use a carb intake with an aftermarket throttle body and ECM and go with a speed density setup. That's an easy way to get unhooked from the OEM PCM.

jp

[shudog]

I see. Thanks for the quick response. I sold my '00 Z28 this fall and I've got the bug for another project and this pro-touring scene has definitely captured my attention. I'm just wondering also how you "tune out" the mass air flow sensor, throttle position sensor, and other items that tie into the computer controlled spark & ignition. I'm sure it can all be done, just depends which way a person wants to go. I know some people think the carb setup just looks cooler....

[WS6]

MSD makes a setup to run the ignition if you decide to go carbed. The carb style or what I like to call spider intakes make more power because they deliver the air to all cylinders in a more even manner. Just look at where all the cylinders are in relation to the stock manifold or spider manifold and it should be obvious. However, that it not to say the stock manifolds do not work. You just have to decide what direction you want to go.

Go browse around John's site on his Chevy II called II Much. You should find pictures of a spider manifold running EFI. I'd like to go that route next time since the car will be an older previously carbed motor. Just looks motor fitting and potentially more deceptive if the person doesn't look closely.

[parsonsj]

The carb style or what I like to call spider intakes make more power because they deliver the air to all cylinders in a more even manner.Wegner Automotive Research has done a lot of dyno tuning using LSx motors. The GMPP carb-style intake manifold makes more power than the factory front engine TB styles. I've seen the dyno graphs. The factory plastic manifolds are needed to allow the plumbing for a MAF and to keep the hood low for better body airflow and fuel economy.

And, just to mention, the LSx engines run great with a carb and an aftermarket ignition controller (like the MSD). No EFI needed, and you have a great all aluminum small block.

jp

[shudog]

Very interesting responses guys. I guess I'm continually blown away by people searching for "more power" on this board. Like 400+ rwhp is really usable anywhere but the track.

[Mike Norris]

A lot of folks go to the carb style manifold and use EFI and still have the carb style air cleaner look. As mentioned, the carb manifold used with EFI will work better then the front inlet standard LSx intakes due to better distribution. Personally I would stick with EFI no matter what style intake is used.

Have fun with the new project.

Mike Norris

[DB Z28]

Here mine
https://static1.pt-content.com/images/noimg.gifhttps://static1.pt-content.com/images/noimg.gif

[WS6]

Looks nice DB.

[shudog]

That's really cool, a fuel rail setup with a carb style intake... plus keeping the coil packs but relocating them. Very unique combo of vintage & modern.

[TitoJones]

We did one because the owner only had one requirement for the engine- It must be carb'd. So we found an LS6 and put a carb on it so he can tune it himself should the need/desire arise.

https://static1.pt-content.com/images/pt/2007/12/6nte3v5-1.jpg

https://static1.pt-content.com/images/pt/2007/12/80l61ck-1.jpg

Tyler

[trapin]

Another reason to do a carb, and John and Andrew can probably speak to this, is that you may not have any efficient way of putting the air breather somewhere where it can draw cool air. LS1 composite intakes don't like to get too hot, if they do they rob you of power. So you might opt for a carb instead so you can put the air inlet on top of the engine as opposed to out in front. This would enable you to use an air cleaner with cowl induction hood thus solving your cool air problems.

[parsonsj]

Tony, good point. My top mounted throttle body results in my air cleaner being in the air stream from my cowl induction hood. I was gonna take it a step farther and get real cowl induction working, but never got around to it. I can say that my IAT (inlet air temperature) is right at ambient when the car is moving.

jp

[DCx]

Why spend the time & hundreds of $$$ if not more for a carb intake?

i snagged a complete ls1 engine with no accessories, and no wiring. the carb setup saved me money over the cost of EFI.

Victor Intake - $285
MDS 6LS - $312
Mighty Demon carb - free

i reused my demon carb from my small block. when adding up the cost of swap specific parts such as autokraft oil pan, hooker coated swap headers, and ats t56 parts, i could not justify the cost of a new programmed EMC and speartech harness. the speartech harness alone is $150 more than my intake and msd. so i sold the throttle body and LS6 intake from my engine made $400 on that sale so all in all i have a means of timing and running my LS1 for $200 when all is said and done.

plus the MSD box runs MSD pro data software that allows you to set timing limits. i wasnt about to buy EFI live, or LS1 edit.

and for my fuel system, im adding a sump to my fuel tank and i got an edelbrock 120gph fuel pump rated at 6.5psi plumbed to the stock 3/8 fuel line. ill post pics of the timing software for the LS1 ignition. lots of people (especially LS1 tech dont understand that feature).

[DCx]

Why spend the time...
what time? the MSD box only has 3 wires. 12v, ground, and tach lead. other connections to make are plugging in the coils, cam, and crank sensor. a map sensor lead is provided if you want to use it as a vacuum advance.

the MSD box comes with 6 preset timing curves and look like the little rpm pills that all 6 series ignitions take. here are the 6 pre set curves.

https://static1.pt-content.com/images/pt/2007/12/timingcurves-1.jpg

if those dont work for you then all you need is a screw driver for the carb and a lap top with a serial to usb connector. here are some screen shots of the MSD software.

this is a shot of a generic timing curve i made. you are allowed to plot up to 6 points.

https://static1.pt-content.com/images/pt/2007/12/timingexamplesmall-1.jpg

and here is the digital dash board that displays rpm, timing, and map advance

https://static1.pt-content.com/images/pt/2007/12/gaugessmall-1.jpg

and for piece of mind here are my engine. sorry tony and andrew, im sure you are tired of seeing this pic!

https://static1.pt-content.com/images/pt/2007/11/victorintake-1.jpg

[trapin]

Yeah really...get us some newer pictures ya slacker! :slap:

[DCx]

i wish i could progress forward! i keep finding little things wrong with my swap. the new headache is the alternator is touching the frame. whats up with my wacked out frame and motor mounts?

[trapin]

That's weird. I had actually worried about my alternator to frame clearance because I heard others had needed to make modifications. The S&P plates leave about a half an inch of room from the alternator to the frame. It's perfect.

[Mike Norris]

Looking at the MSD spark curves posted by DCx has me worried. All of them have 36* on top and every LSx I have tuned makes the most power at 28-30* timing from 5200 and up. Some take even less depending on compression. Through the 4000 range most want 25-27* timing and the lowest out of the MSD presets is 29 for three of them and the others are more. Not what I would call LSx friendly base curves.

Some will take 36* timing on top if they have larger cams with no spark knock, but also pick up no power or even drop power when going from 30* to 36*. The same can be said for the 4000 RPM range in that some with larger cams that bleed off compression will take 29* through this area.

But it was also mentioned that if you have the software you can make changes which is cool. Just odd they do not have a little better base setup for the LSx engines. I can see someone just plugging in the box and driving her without checking things and over time you have a burnt piston. Basically, be aware of what you are doing and getting into.

Mike Norris

[DCx]

can you give me some tips on making a good curve? how much timing is typically needed, when should all the timing be in by?

im running a texas speed magic stick 3 cam and a 6 speed.

[Mike Norris]

For a very large cam like the MS3 (237/242 113 LSA), you can just about run 28* timing from 2800 RPM and up. This is assuming that you still have stock compression and that big cam will bleed off a lot. Down below 2800 it should taper down to about 12* at idle. There are some variables for sure. A cam like that would really benefit from a compression ratio of at least 11.8 to 1 and help the low end torque. Usually the cams with an intake duration of 23x* will be kind of dead below 3500 RPM.

If you want, you can send me a copy of the MSD software and I can build you a program that should work. My e-mail is [email protected] Just let me knowand I hope this helps.

Mike Norris

[DCx]

you can get the latest version from their web site. the cd that came with my ignition was actually outdated.

pro data V 3.17
http://www.msdignition.com/1softdownload.htm

when installed choose ignition 6010

im running a stock 01 short block with texas speed stage one ls6 (243) heads and a factory graphite head gaskets.

my e mail is [email protected]

Thanks! let me know what you come up with. also, im not running a map sensor.