37 replies to this topic

[LXCHEV]

Looking to try something different with my 383 stroker (SBC) in the LX after many years of 'rich' motoring.....

 

Keen to hear advice from any carb / engine combo gurus as to what would be the perfect 'street focused' carb for my setup (looking at the traditional 4 barrel square bore Holley style range). Looking for both size suggestions (CFM) as well as secondary style (vac versus mechanical)...

 

Without revealing what my current carb is, I am trying to address a few issues:

 

I have no performance complaints with the current setup, but the car has always been a 'rich' runner (despite professional dyno tuning) - it generally smells a little fuellie, the spark plugs always come out filthy rich and black, and quite often it blows a bit of black smoke out the rear when you really stomp on it and give it a hard time. The current carb also does not have any vac port for either PCV or brake booster connections. And one other 'whinge' - it's never felt like a super 'snappy/responsive' carb (i.e. feels a little doughy) - unless you go straight for WOT.

 

We all too often get caught up in the quest for max power and 'racing performance' - but these days for me - to be brutally honest, my car spends 90% of it's life just cruising around at low and mid revs - with the odd blast here and there. After a bit of research, I have a new carb in mind - but once again, I won't comment until I hear a few other opinions first. And no, I don't wish to pursue EFI at this point in time.....

 

I want to get the most finely tuned carb with the absolute best street manners possible (yet still be able to attend a drag day once a year if I want to without completely compromising it's performance).

 

So clean slate - here's the key info for the current setup:

 

381 SBC

10.5:1 comp

Comp Cams hydraulic roller (XR288HR) - 236/242 @ 0.050" | 110LSA | .555/.576 valve lift

Iron 'Pro Lightning' heads (200cc intake runners) - flow numbers aren't exciting:

   LIFT 0.200 0.300 0.400 0.500 0.600 0.700
   IN 131 178 214 233 241 246
   EX 98 133 158 178 191 193

RPM Air-Gap dual plane intake

Tri-Y pipes (1.75" -> 2" -> 2.5") with twin 2.5" exhaust

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TH350 with 3,200 stall

3.7 rear gears

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Max revs - I reckon somewhere between 6,200 and 6,500 RPM (from memory peak power is 6,200).

To cruise on the freeway @ 100KMH, it's pulling a solid 3,000, maybe 3,200 RPM.

Car weights in around 1,680kg with driver

On the chassis dyno - makes 230 rwkW (by my maths, that's about 440 flywheel HP).

 

Open to any and all feedback!

 

 

[myss427]

Get an O2 gauge for it, you will find out if its too big with the jets cruising around, and is great for setting idle mixtures which give you the bad fuel smell. Set your car to run in the high 12"s or low 13's mixture wise and you will have no issues, you can adjust nearly any carbie to run clean, its all about size to power your after.

[dattoman]

I love dirty old carbs... rather than injection

But some of the injection systems out now are much better than they used to be

Have you looked at any of those ?

I know you say you don't want to pursue that atm... but worth a look

 

My choice on my 383 is 750 BG Demon ... electric choke .. vac sec

[axistr]

G'day Brett, My hatch is running a SBC 383ci 10.6-1 compression, 234@,050 cam, AFR 195 heads, 1"7/8 primary into tri-y 2"1/2 twin system. TKO Tremic 5 speed, I originally had a Edelbrock duel plane performer RPM inlet manifold with Holley 780 cfm Vac secondary. I could never tune the carby to my satisfaction. It was auto choke but was still a bitch on cold start ups. It was very easy to foul a plug if I didn't warm it up just right. I also have A/C and I had to be careful not to stall at the lights on a hot day when the compressor cut it. I was never happy with the performance over 4,000 RPM when it come off the torque band. I had an electronic Mallory distributor with electronic adjustable advance curve.

 

The car had to be driven by drivers with good driving skills with performance engines. In the end I bit the bullet and purchased a Holley multipoint EFI system which included a single plane air gap manifold and 1,050 CFM throttle body. I also fitted a MSD small cap HEI distributor. I installed the system  myself which was easier than expected. After answering and entering five simple questions into the setup screen it started first pop and hasn't missed a beat in the past five years. It self tuned during an initial 30 min drive and I only adjusted the ignition a couple of degrees in one spot. It has provision for a knock sensor but I haven't needed to hook it up. I can now lean in through the window turn the key and starts first pop every time hot or cold, never stalls, better millage, no more over fueling smells or dirty exhaust or plugs. I would never go back to a carby again and both my toranas are EFI. I probably don't have any more torque over the carby but top end is much better. My wife can drive it now because it has so much more drivability. I can also change the tune quickly for when my son takes it out and he cant rev it over 5,500 RPM. I can control fans, relays and many other external devices. It can also limit or control lights due to low or high engine parameters. No looking back to the dark ages. Done my apprentiship on this old stuff but defintley seen the light over the past twenty years. EFI systems have gone a long way in tech and durability on  both factory OE vehicles and aftermarket systems, why not take advantage of it

 

Cheers lenny.       

 

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[yel327]

I’m with Datto on the modern EFI. Holley Sniper is what I went for on a near identical 377 to you with same gearbox. I bought the Quadrajet version but the square bore is cheaper.

[LXCHEV]

Many thanks for all the replies so far - excellent reading. And Lenny, really appreciate that detailed feedback. They are the type of stories I was hoping for.

 

I personally love the idea of EFI - it's more the cost factor that holds be back there...

 

Selling my current carb would pay a significant portion of a new carb - then it's just a tune and I'm done. Not a big outlay.

 

With EFI - to all those who have done the conversion - what's an actual/realistic cost to complete the full setup end-to-end then (including the hidden costs)? Can it be done for 1k, 2k, 5k, 10k? Hit me with some numbers. I like quality kit and I'm a big believer in "you get what you pay for"...

 

I'd be interested to hear which current EFI system in the market would be best suited for my setup. There are so many to choose from, it's quite overwhelming to be honest. I note one vote for Holley Sniper above.

I suspect the costs will be up there, but keen to see just how much I'd be looking at.

 

In parallel - still keen to chat carbs too.

 

Datto - I do like the Demon carbs. At one point in the past I ran a Mighty Demon (noting it was too big for my combo at 825CFM, and also a double pumper). Engine builder at the time commented they were notorious for having extremely rich fuel curves - and I'd say he was right. Very keen to hear how you get along with your 750 vac sec version.

 

Just quickly on the O2 idea - it's something I've often contemplated. What's the best kit on offer these days in that space?

[yel327]

I'd bank on $5k for a Sniper EFI done properly. This is what I have bought, but I've substituted the spreadbore setup:

 

Kit, available in black, silver or gold: https://www.ebay.com...&frcectupt=true

 

You can run it with a HEI or even a MSD. If you go to the Holley website it has all installation manuals and how to wire it all up. I bought these three though as the Sniper ECU controls the whole lot:

 

https://www.ebay.com...bkAAOSwA8tfKVUD

https://www.ebay.com...HwAAOSw5-1e2u6o

https://www.ebay.com...hAAAOSwQ2ZfUsBu

 

You might find you can get it all a lot cheaper buying from Jegs or Summit or others. Just do the maths.

 

Then you have the pump. You can go cheap and nasty, and use an external pump and a return line. Holley also sell the Sniper with an external pump as a kit, or buy a Holley in tank pump. I bought a weld in ring from EFIHardware to run a VZ returnless MRA. Depending upon how deep your tank is you may use a Ford one or a VE one. Get the weld in ring added to the tank. Worth doing a POR15 or KBS tank clean, etch and epoxy after its done. It cost me $300 to get my HK tank done with the top lowered and the ring welded in.

 

Here is the weld in ring kits:

 

https://www.efihardw...Conversion-Kits

 

MRA's. This is a VX style, if you read their website on the weld in ring pages they tell you what fuel tank height each one suits. VE suits 155-180mm, VT/VX suits 255-310mm, BA-BF suits 180-215mm. My HK tank was 325mm so they had to weld in a shelf to lower the top down to about 300mm, Torana probably won't need that. I bought an MRA modified for 255L/Hr.

 

https://www.efihardw...e-Series-II-LS1

 

Just have to decide whether to run it as a return system or returnless. I bought new GMH VZ fuel filter and hoses to go between the tank and the filter. You might want to upgrade your fuel line to 3/8" too.

[Heath]

You may want to consider 8 throttles. I hope my contribution has been helpful.

[myss427]

You may want to consider 8 throttles. I hope my contribution has been helpful.

 

Maybe not when he try's to tune it!

[76lxhatch]

Most third parties either don't care about your car, or simply don't want problems coming back to them - a rich tune is "safe" but far from ideal.

 

I'm firmly in the camp of doing as much as I can myself, which means the wideband oxygen sensor, plenty of research and testing. Then you'll know what you want to work with and can consider all the options provided above. The alternative is to spend some time hunting down that elusive professional who actually gives a toss what the result is, may not be cheap but generally worth it. If you find this person/business, you are a lot better off using whatever they prefer to work with with than providing your own - there are a lot of reasonably good tools but the tradesman who knows how to use them is much more important and them being familiar with the product saves time and money.

 

For example you can do a VN-VP Delco EFI conversion for around $1200 depending on what parts you can find second hand, and it is very flexible. BUT there will be a lot of your time in it and you need to be interested in getting your hands dirty, and its probably not a good choice if you want a professional to do the work for you.

 

A well-tuned carb might be complemented by one of these newer programmable ignition systems for excellent street manners - the ignition timing is the biggest gain for an EFI conversion, not the fuel side (personally I fail to see the point in those fuel-only kits).

 

I've always used the basic Innovate wideband setup, apparently the Spartan ones are good too. All you really need is an in-car gauge for tuning a carb, you'd be surprised how easy it is to pick which areas need tuning and make good improvements.

 

Everyone wants 8 throttles.

[gtrboyy]

Most of what you described sounds like it has no street tuning done to it at all...just tuned to idle & w.o.t on dyno.

 

Lots of tutorials/clips & kits out there to better what you have...decent air/fuel + vacuum gauge then start learning & having a go as street tuning/manners side most shops don't spend much time on at all.

 

Got 750dp demon on 355 stroker sle...behaved basically same when I got it & was slowly sorting it out for street driving untill rear main shat itself.

 

Must admit find it harder to understand & get into carb stuff again compared to efi conversions.

[LXCHEV]

I’d love 8 throttles.

Seriously tempted to purchase an Innovate LM2 - at least then I can make educated decisions based upon my actual data.

The point about ignition timing is a really good one too - went to a Wolf tech night recently and they were talking about the significant benefits for the old school carb folk.

PS. Would love 8 throttles.

[yel327]

That is why I bought the Hyperspark stuff to go with the Sniper. Full fuel and spark control. I have air and steer too plus will use aux outputs on the Sniper to control the electric fan and the TH350C converter lockup.

[rexy]

I used one of the innovate O2 sensors to sort out my Holley Street HO 750 dp on the 383 holden in the hatch. Now very happy with it. Doesn’t smell and doesn’t foul plugs. That carb series has a base plate with all the vacuum ports you need.

 

I bought an all aluminium Holley 750 vac secondary to run on the yellow LJ and after a little bit of fiddling I’m very pleased with how it drives. Certainly doesn’t feel like it’s giving up much power compared to the old DP I had on it.

 

Why not buy an O2 gauge and see how much progress you can make with your current carb?

[axistr]

In my experence over the years with tuning and carby choice is, engines which have 14" of vacuum and above with cam duration below [email protected] & 383ci [email protected] the old Quadrojet is a good choice, and Holley vac secondarys comes in 2nd. With engines below 14" of vacuum and greater than 234@50 double pumpers Holley, BG or Demon are required. However trying to tune engines with low vacuum and long cam duration cams are always going to be a compromise. I don't care how good your tuning skills are you will never get the perfect AFR on a performance engine with a carby for good well manor street application.  EFI wins hand down in my opinion and you can get a perfect tune at every set point throughout the complete engine speed and load. I never really considered fuel consumption when going to EFI but its nice to know the extra few bucks in your pocket is better than in the oil company's pocket, and after many years of giving the enviroment a hard time its nice to know I am now doing a better job. My choice was for better drivability, easy startups and total control over external devices and engine warnings. My distributor only cost me $120 new. The multipoint Holley HP EFI system complete with manifold, injectors, regulator, ECM, electric pump and hoses cost me $3,600.00 all up installed and driving down the road $3.800.00

 

The cheaper Holley stealth system has the ECM inside the carby look alike throttle body assemble. If you can install a carby than fitting a Holley stealth EFI system would be just as easy. And for the price of a good Demon or BG carby there wouldn't be to much difference in outlay. I would think under $2,000.00 and you can control a electronic distributor. I think you can also control a electric fan relay. The next step up is the Holley Terminator or Holley HP systems which have external ECMs for greater control over just about anything you want to do. You can also upgrade from the Stealth system to multipoint at a later date with the same ECM. I can even go sequential injection with my HP EFI if desired just by clicking on an icon, or control a 4L60E transmissions. I haven't had much to do with other EFI system besides the Holley and Holden Delco systems. But talking with many people that have played around with other aftermarket systems the Holley EFI seems the easiest to install, tune and reliable. Bugger the carbys I just have no desire to bugger around with a compromised tune of old fuel design carbys.       

[LXCHEV]

Fantastic insights Lenny, thanks. My combo (low vacuum and larger duration) certainly doesn't suggest that I'm wasting my time with the current double pumper (which by the way is a Holley 750 Ultra HP). I've been real tempted to try a vac-sec carb, and even go down to something like a 670 cfm....

 

But the more I think about all of this, I'm getting keener on the idea of investing in some kit to monitor the air:fuel ratio and get my hands dirty - as per myss427 and rexy's little nudge.

 

It is beyond doubt that EFI is the ultimate end goal. For me right now though, the funds just aren't quite there. I think I'll persist a little more with the current carb...

 

This dual gauge has spiked my interest. Can you data-log from this too with optional accessories? I love the idea of having a permanent gauge mounted for constant live data readings....

 

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It's either that, or just stick with the LM2 workshop style (handheld unit) which is obviously more versatile and could then be used on other cars (my wife's EH with the VK injection seems to run rich too, despite the Bosch injection) - so that could be another little project to troubleshoot too....

 

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Does the group agree that these 2 options from Innovate are the pick of the bunch in the market? I'd be keen to monitor both banks, so the dual sensors is what I'd go with. But just out of curiosity is a single sensor still sufficient for tuning a V8? What did you do with yours rexy?

[76lxhatch]

A single sensor is sufficient, you can always weld a bung in both sides and swap it over to double-check. Having it well located in the collector (and making sure there are no leaks) will help with good readings, the tail pipe bolt-ins aren't great.

 

Datalogging is nice but not all that useful if you can't log other inputs. Its great with EFI when you can trace the speed, RPM, manifold pressure etc etc throughout the tune at the same time as the A/F ratio but if you're logging the wideband alone with no reference I'm not sure there's much point. As I mentioned above once you're familiar with the adjustments to tune the carb simply having a live readout is very helpful and you can pretty much tell exactly what you need to change straight away. The gauge doesn't have to be permanent, you probably will want to remove it once you have things running well; but make sure you can see it easily (and safely) while driving.

 

All I use is the basic Innovate LC-1 (now replaced by LC-2). For EFI use it plugs in to the ECU for datalogging but for carb tuning I just have a bright LED readout that I cable tie to the ashtray.

Edited by 76lxhatch, 22 September 2020 - 01:45 PM.

[LXCHEV]

Awesome. Sounds like the dual sensor deal with permanent gauge is overkill! (not cheap either - and I'm all for keeping costs down). I might look at the single sensor option. Can I ask which type of LED readout you use with the LC-1?

 

As for the data-logging - I agree there's not much point unless you're capturing other data. For drag racing - I'd have thought as long as you capture the RPM - you could then get quite a good idea for what the car is doing during a full pass.

 

Would welding the bung into the exhaust system (not the extractor collector itself) be sufficient? My extractors are HPC coated and it'd also be a million times easier to simply drop the mid section out to add a bung. I'm talking an inch past the extractor collector. The Innovate website suggests having the sensor at least 24 inches downstream of the head ports (and being further away again wouldn't be detrimental, as long as it's before any H or X pipe).

[76lxhatch]

I have a Moates O-Meter:

http://www.moates.ne...eter-p-134.html

It was a cheap option and I got some other EFI tuning gear from the same place at the time. Really anything that gives you a number that is easily readable is fine.

 

You can get away with putting the bung a little further downstream, but you need to be extra careful about sealing joints from air leaks as upstream leaks cause a lot more error.

[rexy]

This is what I bought.

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I initially fitted the O2 sensor to the extractors in the port that was put there by the manufacturer. It was in one of the secondaries and the readings fluctuated a fair bit. Shifted it to about a foot past the flange on the collector in a nice convenient spot. Found it was worth properly sealing the head mounting flange. 
Bought myself a big box of jets and started to play. Very easy to read, even in daylight.

I doubt you need to bother logging with a basic solo gauge like this. A quiet road and a bit of time is all you need.

 

I do like fiddling and learning new things though!

 

No doubt ultimate driveability is had with EFI and that’s one of the reasons I love my LS powered LJ. Always starts, never pig roots and I’ve never had to take a plug out of it to see what’s going on!

 

 

 

[caterham2]

I have had one of the Inovate AFR setups for about 8 years . Works well, doubt if you really need the twin sensor setup unless you are trying to extract the last poofteenth out of a race engine.. Having said that Motec dyno v8 supecar  engines with 8 sensors and adjust injector flow and timing to each individual cylinder, but they are playing for sheep stations at this level.

[jd lj]

Having a data logging capability I find to be valuable. At WOT you don't want to take your eyes off the road and if you do the values shown will change rapidly with throttle position etc. If you have data logging for AFR then also logging rpms is a must otherwise ypu won't know which circuit needs a jet change.

I used to use lm-2 but all the cables were annoying and I had lots of problems with mine not working properly or consistently or sometimes at all.

I replaced it with the AEM failsafe AFR gauge. It does logging of AFR, rpms and vacuum. Ir can shut the ignition down if the AFR falls outside your desired levels. It's constantly recording on about a 2 hour loop.

[jd lj]

PLX Devices makes some good sounding stuff but unfortunately they don't have built in data logging, although this can be done with a separate unit from what I understand. You can also use your phone as the gauge.

[Heath]

ould welding the bung into the exhaust system (not the extractor collector itself) be sufficient? My extractors are HPC coated and it'd also be a million times easier to simply drop the mid section out to add a bung. I'm talking an inch past the extractor collector. The Innovate website suggests having the sensor at least 24 inches downstream of the head ports (and being further away again wouldn't be detrimental, as long as it's before any H or X pipe).

Just put it after your collector, it won't be a problem at all.

 

The one that really doesn't work well is having it at the tailpipe, particularly in a state of low air consumption, like idle.

[Peter UC]

Yes just as long as the collector to exhaust join doesn't leak.