RC51DRAG

who has purchased one of these kits from RB or Mazdatrix. what is the percentage hp gain with or without a full exhaust. I am mainly trying to find out if this is worth the purchase price. Also have you had any difficulty setting it up properly or is it truly a bolt on carb. finally any concerns running this in cold weather situations.

SilverRocket

Because the port size is really the limit on a stock motor once you get to this stage of modification, most good aftermarket carbs (Weber, Dellorto, Mikuni, Holley) will make similar power. That is, a stock 12A will make about 150 hp and a stock GSL-SE 13B will make about 180 hp. Some will make a little more or a little less. This assumes running in conjunction with a good aftermarket exhaust system.

For the money, I would say the RB Holley kit is probably not worth it, *if* you have the ability to buy and rebuild a used kit. There are lots of them out there for around $300.

For example, I bought a used RB Dellorto 48 DHLA kit in excellent shape for $300, including intake manifold, heat shield, all linkage, etc. Shipping cost me another $50 (from Oregon to Ottawa, Canada). I rebuilt it for almost free, since a friend of mine had a few gaskets I needed and I was able to make the rest of them myself. A few adjustments were tricky, but overall I got it done without much trouble.

For any carb, you'll need a good aftermarket fuel pump (ie. Carter 7psi), fuel pressure regulator and guage (although good luck finding one that works worth a **** lol). These cost me another $160 or so. Fuel line, fittings, hardware, dremel bits I used up, etc, probably cost another $75 or so, maybe less.

It took me about a week to get all of this done, from the time I received the carb to the time I had it tuned and running nicely.

So for around $600, I have an awesome setup and am, according to Racing Beat, making about 154hp. The downside to this approach is you need time to do some work, and need to be comfortable taking carbs apart and pulling everything off the top of your engine. If you buy the new one, it cost much more, but you get it all shiny in a box and you don't have to mess with it too much. It depends what you want...

Personally, I wouldn't worry too much about whether you get a Holley, Weber or Dell. According to what I've heard, the best carbs for power are probably the Weber 48IDA and the Dellorto 48DHLA. The Weber 45DCOE might have a little less potential, but is very popular. On a stock motor it wouldn't be much of a difference. There are other kits available, like dual Weber's, but I don't know anything about them. I'm not exactly sure where the Holley fits in. Thing is, again, on a stock motor the differences between these will probably be fairly minor. If you're talking about a bridgeport 13B, the choice of carb becomes more important.

The Holley is supposedly a little more driveable (since it has 4 barrels of course), but it also supposedly has a reputation for stumbling in corners. However, this might just be the experience of people who haven't tuned theirs properly. The Dell's have a reputation for stumbling, hesitating and being hard to find parts for and tune - but I and another friend I know had no problems getting ours to work very well. It's all in the tuning - you can't expect to slap a carb on and be running perfectly. It takes time, experimentation and fine adjustments to get it perfect.

I've never heard anything specifically good about that Holley kit, but then again I haven't heard much bad about it either. I'm sure they're very good if tuned well.

rxtasy3

iTrader: (2)

I have the RB holly kit on mine. I've also used the Mikuni kit with one piece wrap around intake and I prefer the holly. I can't tell any difference between the two at WOT, plus I think u get better fuel economy with the holly due to the fact that ur running on much smaller barrels during normal driving as to the much larger ones with the other carbs. True with the mikuni and other side draft carbs, u get the feel of greater responce with normal acceleration due to the large two barrels but if u rigged the holly so all 4 barrels would open simultaniously, it would have the same result. Only prob I have found with the holly is that the plastic cam that operates the fuel pump wears fairly quickly causing a stumble when u very gradually press the accelerator. The 13b that I building also has the holly but it's jetted for the street port engine.

SilverRocket

Good point - the Dellorto goes through fuel like a college dormitory goes through 24 packs. But the throttle response and instant availability of power is fantastic compared to the Nikki. Don't know about compared with the Holley, never driven one.

RC51DRAG

silver rocket are there any good shops in the Ottawa area. I'm just down the road and visit there every weekend.

RC51DRAG

so for the money i'm looking @ a carb setup, and a full exhaust for around 150sih rwhp. anyone running a street port with this application. if so what are the cost and hp levels and is it still driveable?

1st7heaven

I started with rotarys using the Holley and loved it! I fixed the vacume secondarys to mechanical and you get the same response as a Dellorto or Weber(which I also run). Also to solve the stumble in the corners, all you have to do is convert to a center pivot float bowl and connect the overflow vents with a piece of fuel line and cut a slit in the top for venting. I autocross and trust me this solves the stumble in the corners. I am now running a Weber. I also ran a Delorto on a stock SE motor with a header, 2-1/2", Dynomax.....worked GREAT!!!!

1st7heaven

Also, this Holley set up from RB, exhaust as I mentioned above, dynoed at 155hp at the rear wheel.....not too bad!

RixRotary7

Only problem with porting is that the engine will need to come out.

RixRotary7

What does everyone prefer: 2 or 4 barrell/ mechanical or vaccuum secondaries?????

FB II

4 barrel mechanical!