Holley Carb Baselining/Tuning

It's been a while since I've been asked a carburetor-related question, but this one came up this week so I figured I'd do a little writeup. This is how I baseline a Holley 4150 Double Pumper carburetor. I'm not going to go into great detail, there are many sites and books do that, but by following these steps, you should get the car running fairly well with a double pumper Holley and then you can take it from there.

Before you get started, I recommend that you buy a new set of spark plugs (or two) a Holley Jet Assortment kit, a set of reusable bowl gaskets (so you don't have to replace gaskets every time you change jets) and once it's baselined, an accelerator pump cam assortment and a few power valves in various sizes will come in handy! That stuff will set you back about $100, but once your carb is dialed in, replace the two sets of jets you used, along with the pump cam and power valve, and you can resell the rest as complete kits!

Road & Track Supercar Shootout

This month's Road & Track has an awesome 0-200 supercar shootout and they were kind enough to post the article on their site. Sweet!

Here's a video of the overall shootout, and here's an in-car view as driver Steve Millen pilots the Hennessey Twin Turbo Viper down the 15,500 foot runway. It looks like a hairy ride!

SBFTech.com

Hey gang, sorry for the week off, I got shipped to Oklahoma for work unexpectedly.

Here's a site I love to lurk on when I get the chance: http://sbftech.com/. There are a bunch of no-nonsense blue oval freaks on there that really know their stuff! Want to know if a 5.4" rod is better for your 347" stroker than a 5.315" rod? This is the site for you!

When I was blueprinting the bottom end of the 347 for my 79 Pace car, I had some very specific questions, and there were guys there that knew the answers right away.

Jay Allen from Camshaft Innovations is their resident cam expert and will custom grind you a cam based on the entire combination of your car and what you expect to get out of it, not just look at one or two aspects of your motor and give you a generic cam. I didn't realize it until I'd been lurking on the board for a while, but Jay is the guy that designed a cam for me a few years ago. I had never spoken with him directly, but he and Kelly Cansler (my cylinder head guy) spend a lot of time talking on the phone with one another discussing camshafts and head flow and port design and all that good stuff. At the time, I had a Honda S2000, and I wanted to build a 5-liter Ford derivative that would have the similar rev characteristics and horsepower per liter! (Roughly 125hp/liter or well over 600hp in a naturally aspirated 5.0 that would rev to 8500rpms!) To me, that sounded like a tall order, but Jay didn't bat an eye and a few weeks later we had the part in-hand that would do it. (With the right supporting cast, of course.)

Unfortunately, the car that engine was slated for came back to me from the body shop in a bunch of boxes. The outfit that was painting it for me fell on some hard times and got evicted from their shop. Many small parts were lost in their move, and the box containing every nut and bolt needed to reassemble the car got rained in and all of the hardware was completely ruined! So anyway, that turned it into a little more of a project than I had time to tackle, so it got put on indefinite hold. :-/ Once my kiddos get a little older, I'll pick it up again. It'll be a fun jigsaw puzzle to solve, and you still don't see too many 600+ hp naturally aspirated 5-liter cars, so it'll still be cool (to me anyway!) :D

Missing at High RPMs

I was reading a tech post on Austin Area Stangs where a guy had just installed a 6psi blower kit on 95 Mustang GT, and it was pulling hard until 5000 rpms, but then it fell on its face and acted like it was missing. I had a very similar issue on the 1990 Eagle Talon Tsi AWD I had back in the day. If I would run around at the stock 8psi of boost, it ran great, but if I would turn it up even a pound or two, it would fall on its face around 4500rpms.

I nearly pulled my hair out over that one! I was checking sensor voltages, looking for codes, checking boost and fuel pressures, reading plugs etc. and everything I checked was coming up fine. I spent hours scouring the web and reading through the archives of the old Talon Digest mailing list. (an incredibly invaluable resource for DSM owners that went the way of the dinosaur about six or seven years ago.) I was looking into high-dollar boost controllers and fuel-cut defencers, etc. I had just about exhausted every high-tech diagnostic trick I could think of, and then I remembered a piece of advice my friend/automotive mentor Dan Finn gave me when I was 17 or so. He said, "Scotty, it's gotta have air, fuel and spark. It's as simple as that." Now I know that sounds basic and obvious, but breaking it down to those basics made the reason for my elusive miss become suddenly apparent. I had air, I had fuel, must be spark... A $60 set of Magnacore wires and some NGK plugs, and I was pulling 14psi all day long! I spent DAYS hunting that down and it just needed a tune up!

I guess where I'm going with this is before you mod any vehicle, take care of the basics first. Give it a good complete tune up, brake job, check your tires, change your fluids, etc. before you go adding a bunch of speed parts (especially nitrous or boost!) Also, when you get stumped trying to track down a problem, go back to the basics... Does it have fuel? Does it have air? Does it have spark? Answer those basic questions first before you start tearing it apart!

Inspirational Video

If I ever need inspiration to drag myself out to the garage, or ever feel myself get stuck in a rut, I just crank up the speakers, fire up this video, and feel the blues just melt away!



It's Jimmy White from Circle City Hot Rods in his Hemi Coupe. In my book, Jimmy is one of the most talented builders out there today! When this video first hit the net a couple of years ago, Jimmy was building a wicked, low 27 pickup (Some pics and story of the build from the HAMB's 'Bass' here). Every piece on it is a work of art! It instantly became my favorite hot rod and gave me lots of good ideas for the Hemi roadster pickup I've been collecting parts for for years.

Anyway, a few months ago, I was cruising through the LoneStar Roundup and this beautiful Model A caught my eye... perfect mirror-like black paint, loads of chrome, vintage blue vented Plexiglas windows, etc. It was perfect! I looped around the front of the car and looked up and that's when I saw the Circle City banner flying above it. I wasn't the least bit surprised. Jimmy and crew had done it again! It was called the Murrell Coupe and it just may have passed up his 27 as my favorite! :D Here's a video of it pulling into the show. Awesome!

I can't wait to see what they bring next year!

Cooler thermostats

Pretty much every hop-up guide for every car out there lists switching to a cooler thermostat as one of the first mods you should do to increase performance. The reasoning behind it is that engine will run cooler, and the cooler the engine the more power it will make. This is true to a certain extent, but it's not as simple as that. In modern cars I think it's a bad idea to run a cooler thermostat without doing a little homework first.

First of all, most new cars have a much more sophisticated method for regulating heat than they did back in the day when engine temperature was solely controlled by the thermostat and and engine-turned fan. Most modern cars are cooled by electric fans regulated by a thermostatically controlled switch, or by the engine's management computer (or quite often both.) In a switched system, the fans will only come on when the coolant reaches a certain preset temperature, so even if you open the thermostat earlier, there will be no fan-driven airflow to cool the hot coolant in the radiator until it gets hot enough to trigger the fan (well over 200 degrees usually.) So in effect, your cooler t-stat is doing nothing unless you add an adjustable switch to bring the engagement point down. In computer controlled system, there is a "fan on" and "fan off" setting, where the "fan on" setting may be 210 degrees, meaning that the computer will turn the fan on when it sees 210 degrees and then turn it off again when it sees it drop back below say, 190. In this type of system, you would have to have to reprogram your vehicle's computer to lower that range or again, it would have no effect. Auto manufacturers spend a lot of time getting the balance just right on that, so you will have to as well. If you set it too low (too close to the t-stat opening point) your fan will be on constantly, which can be annoying and it takes away some margin of control(more on that later.)

Secondly, modern engines are designed to run optimally at a pre-set temperature. Most cars will have basically a "warm-up" mode where it runs a certain tune until it reaches a pre-determined operating temperature, and then it switches to another tune (fuel tables) or will switch from "open-loop" mode (running on a pre-defined set of parameters) to a "closed loop" mode (taking real-time feedback from o2 sensors, etc. and using that info to adjust the tune). (Here's a great article by Mike Wesley that goes into more detail on this specifically on the EEC-IV Ford computer.) If you do not allow the engine to reach the temperature required to make that switch, you will never leave that "warm-up" mode and your car will not run efficiently. One of the nice things about modern EFI setups is their adaptability. You can make all sorts of mods, and they will adapt (to a certain extent) to keep the desired A/F ratio even though you have increased the airflow into your engine. If your car never reaches the closed-loop (adaptive) mode and relies on the pre-programmed fuel tables, your A/F could be way off and you nullify your gains unless you've reprogrammed your ECU. Additionally, without the engine running optimally, you will get worse fuel economy. The engine's emission systems are designed to operate at those pre-set temps, so your car will potentially put out a lot more emissions at lower temps, which will make it much harder to pass a smog test. Some folks don't care too much about emissions (yet) but for them, this problem will manifest itself by giving the car that "fat" or "rich" smell that stings the eyes a little bit. That's no good either. I had a 454SS pickup that I was told had a 160 degree t-stat when I bought it. It was sluggish, the exhaust smell was terrible and the truck got around 8MPG. Luckily, a month or two later, the thermostat stuck on me and the truck started to overheat. I swapped in a stock t-stat (195, IIRC) and it ran like a different truck! It smelled better, ran more smoothly and got almost 10MPG! (I know that still sucks, but that's almost a 25% gain!)

Earlier I mentioned control. The thermostat, fans and radiator work in conjunction to keep your coolant in a certain temperature range. If you lower your thermostat (so it's basically always open at normal running temps) and always have your fan on, the only thing controlling your temperature is the efficiency of your radiator. If it's a hot day, or you're climbing a lot of hills with the A/C on in summertime, additional demands are placed on your cooling system. The open t-stat might start letting the water flow through the system so fast that the radiator does not get a chance to cool it down below 160 degrees and so "hot" coolant starts getting re-introduced into the engine where more heat is added. This creates a heat-soak situation and the system will lose its ability to control the temperature. A stock higher-rated t-stat combined with a longer-range window of fan operation (computer controlled) will hold the coolant in the radiator longer and cool more efficiently. I had this happen on my 83 Mustang GT, and later again on a 95 Mustang GTS that came with a 160 degree t-stat. Both times the problem was solved by switching to a warmer t-stat.

So will a cooler thermostat make more power? Maybe. If done correctly and tweaked to match your combo, sure, but it's not a simple "plug-and-play" operation anymore!