Edelbrock How To

[chedda_j]

Im trying to track down every little piece of information needed to do the Edelbrock to stock or street ported 12a and this is what ive come up with so far. At the bottom of the page is compiled information and part numbers for nessesary parts. First off you will need an Edelbrock Carb, obviously. The best choice, noted by many rx7 owners, is the 500 cfm Performer Series. I myself chose the 600 cfm Performer which probably wasnt the best choice. Sanspistions noted this about the 600 cfm : I have been sucessfully running an Edelbrock 600cfm (manual choke #1405) on my street ported 85 12A on the street and autocross for over a year now and am highly impressed with this combination. At the moment I'm getting 20mpg in town and about 25 on the highway with excellent response and drivibility. The carb is mounted on a RacingBeat manifold with a Carter fuel pump. There HAVE been a few quirks with this comb, however... I have been experiencing the top-end over-rich problem that peejay talked about. My (eventual) cure was to drop the secondary jets to .077 -the smallest Edelbrock makes. I HAD thought about connecting the secondaries as he suggested but at the moment I'm using a four-hole 2 inch spacer to bring the powerband down a bit. I'm going to try that on my old 1 incher and see if it helps. Good suggestion, peejay, thanks! I'm just running the stock needles and seats instead of the "off-road" spring loaded versions at the moment; the only cut-out it makes is in sharp, slow corners under light thottle. Also it tends to stall under heavy braking if you don't double clutch down the gears; sudden clutch-in stops can be heartstoppers if you need power suddenly! It also tends to spit if you back off the thottle partially at high rpm; air-valves fluttering? Going to try the seats soon... I was originally looking for a 500cfm Edel. to mount on my stock-with-exhaust 12A but I blew up the motor and decided to go with a 600 and street-porting. Besides, 600's are much cheaper and easily found and Edelbrock says that the only difference between the two is the size of the secondary airflow. 48mm Webers have about 600cfm (I've heard) and I figured the individual runner RB manifold would allow the on-demand secondaries of the Edel. to work well in this application. I'm glad to say that it works just fine. The secondary air-valves are counter-weighted for the air flow of a 5 liter engine so they don't open on the 2.3 liter 12A until about 6000rpm. Not only flat midrange but sudden power from 6 to 8000. Not conductive to smoothness OR blowing off that pesky Honda in the next lane... When inquired Edelbrock sent me instructions on how to drill the counterweights to allow quicker opening. I haven't gotten around to that yet so I came up with a VoTech solution; I simply tied the air-valves off so that they could only move from about 3/4 open to full! Works great, now has massive midrange at 4000 and SCREAMS from 5000 to 8000. The engine is now taking the full 600cfm from about 2500rpm (in the lower gears). Only at WOT in the upper gears and below 2500 does it protest (o.k.; it KILLS!). Is it a rig? Yes. Does it work? YES! I'll get around to drilling those weights someday; maybe it'll fill in the 4-to-5 gap.... So if you can't stand Holleys or afford a Weber think about the Edelbrock; it's working just fine for me. As the above information states, there is a few things that are needed to be worked out, including the drilling of the weights for proper acceleration in the midrage, i have not found an online guide on how to, but if Sanspistons could please post on how to do so, it would be much appritiated. As for other information that wasnt posted by S.P, i found several links on the Edelbrock website that lead you to PDF's on information needed to rejetting the carb, a nessesity to anyone who wants their Edelbrock Carb to run PROPERLY on a rotary. There is no PRE-tuned Edelbrock so anyone who is willing to give it a shot, will have to learn how to change mettering rods and jets. These two links are very helpfull and should, nvm that, MUST be read to ensure that the tuner can tune the carb properly. The links below are very useful, i printed off a copy of both as handbooks when im tuning my carb. http://www.edelbrock.com/automotive_.../1000/1477.pdf http://www.edelbrock.com/automotive_...403_manual.pdf The only intake manifold available to us Edelbrock users is the Racing Beat intake that can be ordered online at Racingbeat.com. Part number 16464. http://www.racingbeat.com/FRmazda1.htm As for brackets for the throttle cable, i had to make my own. Edelbrock sells brackets that bolt onto the manifold, although i dont know and havent experimented with any of the ones offered by Edelbrock. They can be found on the site. Edelbrock Main A picture of one custom fabbed one is in the link below, found originally on this site. Custom Bracket As for the choke and the OMP, i am not sure as what to do as of right now, I am working on the choke and the omp i have already elimated with the gas mixture formula. A throttle return spring was installed on my bracket to ensure that proper return was achieved. Luckily enough i used the old one off the NIKI carb, it was just big enough. Another thing to note is that the "throw" or length of cable that rests outside of the tensioning cover for the stock throttle cable is 6" approx. This means that the distance from the bottom part of the throttle/butterfly levers on the carb to the bracket cable holder should be no more than 6". A carb spacer is manditory for the Edelbrock carb to clear a few parts near the engine, Transadapt sells an open bore 3/8" , 1" and 2" spacer. I chose the 1" spacer and used a brass fitting to plug the vaccum port for now until i install a A/F gauge. Sorry no part number for this. Uprades will need to be done to the fuel delivery system. Starting with the pump, i changed mine out to a holley redline 7psi pump. They are cheap and very reliable. Due to the high psi, i baught a 4.5-11 psi fuel pressure regulator from holley aswell. Another cheap but very effective product, they are prety self explanitory for instalation and only basic hand tools are needed. Sorry no part numbers here either. The fuel pressure regulator, depending on make, will either have a localized gauge or without. I baught the one without and mounted a mechanical Autometer gauge (0-15) psi, from the extra holley port on the fuel pressure regulator (remember that holley fuel pressure regulators have two outlets, one for each bowl, i just made use of the second one) I mounted both on the fire wall so that easy tuning could be achieved. Edelbrock says that only 6.5 psi should be used on the 500 and 600 cfm carbs, any more will cause flooding. So a fuel pressure regulator is manditory. Many companies supply carbhats including Transadapt, Edelbrock, and youl even find some cheapies ones from CDN tire and so on and so forth. The correct one is determined by how much hood clearance you have after the carb is installed. You will need a shallow hat no matter what and most of all, you will probably need a drop hat to lower it below the hoodline. Its mainly trial and error due to the fact that some of our carbs will have different spacers. These carbs, like the nikkis will have a port for the power brakes, ports for the vaccum advance, and a inlet and outlet for fuel travel. The proper fittings are determined by the carb, so make sure to bring the carb in while matching the fittings. btw, 5/16 is the stock size for hose. I will note that most users will probably want to put in all new lines that are 3/8" to ensure adequate flow, so far i have not had a problem and im using 5/16. All clamps should be EFI clamps to ensure no dangerous fuel leaks. EFI clamps are smooth bands, unlike rachet style clamps, where a bolt and a ratcheting mechanism are used, these bolts and serated edges can cut the hose. Simple spring clamps should not be used, you just doubled the pressure on these lines and its time to beef up. This is all the info i have came up with so far, please note that i have not perfected anything but its getting close. Thanks. btw, its very late, mind the grammer. NO destructive critisism please. Metering Jets: Orifice Size Part # (Metering Jets Orificed in Pairs) .077” (0,196 cm) #1420 .080” (0,203 cm) #1421 .083” (0,211 cm) #1422 .086” (0,218 cm) #1423 .089” (0,226 cm) #1424 .092” (0,234 cm) #1425 .095” (0,241 cm) #1426 .098” (0,249 cm) #1427 .100” (0,254 cm) #1428 .101” (0,257 cm) #1429 .104” (0,264 cm) #1430 .107” (0,272 cm) #1431 .110” (0,279 cm) #1432 .113” (0,287 cm) #1433 .116” (0,295 cm) #1434 .119” (0,302 cm) #1435 Cruise Power Part # (Metering Rods Orificed in Pairs) .062” (0,157 cm) .052” (0,132 cm) #1441 .063” (0,160 cm) .037” (0,094 cm) #1442 .063” (0,160 cm) .047” (0,119 cm) #1443 .065” (0,165 cm) .037” (0,094 cm) #1444 .065” (0,165 cm) .047” (0,119 cm) #1445 .068” (0,173 cm) .042” (0,107 cm) #1446 .068” (0,173 cm) .047” (0,119 cm) #1447 .068” (0,173 cm) .052” (0,132 cm) #1448 .070” (0,178 cm) .037” (0,094 cm) #1449 .070” (0,178 cm) .042” (0,107 cm) #1450 .070” (0,178 cm) .047” (0,119 cm) #1451 .070” (0,178 cm) .052” (0,132 cm) #1452 .071” (0,180 cm) .047” (0,119 cm) #1453 .073” (0,185 cm) .037” (0,094 cm) #1454 .073” (0,185 cm) .042” (0,107 cm) #1455 .073” (0,185 cm) .047” (0,119 cm) #1456 .073” (0,185 cm) .052” (0,132 cm) #1457 .075” (0,191 cm) .037” (0,094 cm) #1458 .075” (0,191 cm) .047” (0,119 cm) #1459

This ad is not displayed to registered or logged-in members. Register your free account today and become a member on RX7Club.com!

[Latin270]

This is good info but I think you gave it too much thought. Its really as simple as starting w/ the right size carb, using a spacer, RB throttle bracket and Nikki linkage. I didnt have to rejet yet but I may after the 4port 13b is completed. Great work Chedda!

[84stock]

You absolutely must use a "thunder series" whether it's a 500 or 600. Been there, done that!

[Latin270]

Originally Posted by 84stock

You absolutely must use a "thunder series" whether it's a 500 or 600. Been there, done that!

I disagree as I'm using the "performer" series w/ no issues.

[chedda_j]

The one that S.P chose was the 600 cfm Performer. The only downfall is that the mechanical secondaries are not adjustable. Well they are but a little custom modifying would have to be done. Concidering that the only connection between the primarys and secondaries is a push rod about 1" in length, any one can make their own with some cheap rg60 welding rod. Instead of having little pins to hold it on, you could squeeze a set of tiny o-rings with a small washer to hold the linkage together. There is no outward pressure on the rod so o-rings would suffice. This way you could make your own rods with a couple simple hand tools like a pair of plyers and a ruller.

I believe that the primarys push nearly 280 cfm of the 600 cfm produced at WOT. With that thaught, the secondaries are sure to drown the engine because a stock 12a only needs around 450 maybe 480 at the most. Therefor the steps writen above are manditory to provide a perfect fuel mixture. If you read through the second manual it shows how you can change the cruise power, the idle a/f, and the power a/f for the entire carb.

[chedda_j]

ON second thaught i had a look at the carb and instead of messing with the length of the rod, you can install a restrictor so that the 4barrels wont open all the way. This would prevent any topend flooding due to the enormous size of the new carb. Because the secondaries are spring loaded on the performer series, a small adjustable blocking plate could be made tp prevent how far the 4 barrels open. You could even ghetto it with a piece of wire or something. Anyways

Ive got a few more part numbers for the archives that i left out above.

TransDapt 1" Spacer #2103 (includes spacer, two gaskets, and moutning hardware)
TransDapt Aircleaner Stud #2175 (for 3" aircleaner)
Autometer Pressure Gauge 0-15psi #2411
Autometer Stainless Braided Gauge Line #3228 (3') or #3229 (6')
Holley 4.5-9psi Fuel Pressure Regulator #12803
Holley Redline Fuel Pump (preset 7psi) #128011

Note that when installing the new intake, a set of o-rings and an intake gasket are nessesary from Racing Beat. These intake kits can be found on the Racing Beat site under intake parts. Also note that these intakes will eliminate the former coolant passages through the intake.

Intake Gasket #16730
Intake O-ring #16735 (two needed for new instal)

[trochoid]

One mistake so many seem to make is if size X carb is good, the next size bigger is better. This doesn't not work with carbs, air flow and intake velocity, it works against improving the performance.

I take it you got the RB intake, never heard back from you on whether you received it or not.

[chedda_j]

Originally Posted by trochoid

One mistake so many seem to make is if size X carb is good, the next size bigger is better. This doesn't not work with carbs, air flow and intake velocity, it works against improving the performance.

I take it you got the RB intake, never heard back from you on whether you received it or not.

yes that us often a huge mistake, although on the 500 and 600 series performer, stated before, is that the only difference is the size of the secondaries. SO infact aslong as you can limit the opening of the secondaires somehow you wont draw too much. Yes velosity is often a problem, with the added spacer it will help alot. ALthough it is slightly too large, there has been promising work with the 600. The best part is that if i go to a turbo setup which i plan on doing in the next two years with a street port, il just have to turbo prep because it wont be too large. Im also obliged to mention that this carb and setup probably wont show too much of its true power until you get rid of the restrictive exhaust and buy a header.

yes i did recieve your intake trochoid, but because there was no invoice in the box i was charged an extra 50 dollars to bring it accros the border, i guess i should have mentioned that. oh well.They basically had to guess the price of the object because they thaught it was bran new because it was in the that turbo box that you sent it in. Bloody assholes.

[Sanspistons]

Wow! -I've never been so extensively quoted before!!! That post is a few years old and I think I have solved most of the problems with this carb. Drilling and adding a little lead to the counterweights slowed the air valve opening and cured (most) of the drop throttle bog. No need for the airvalve tie-off's after all. See Thunder series for the real cure...

I'm amazed you had the same idea of o-rings for the secondary linkage!! -I kept losing the damn little clips, also. Disconnecting the linkage does seem to help in primary tuning, though.

As I have said before leaning the secondary jets to the smallest available was the key to my street port success. If you have a more stock motor dropping the fuel pressure could also help.

Most of my cornering bog is gone 'cept in long sweepers in AutoX; hey, it's mounted SIDEWAYS afterall!!!

I would LOVE to try the Thunder series carb... donations accepted...!

Hope you like your Edelbrock, love it myself! Good job, Chedda!!

Sanspistons, your Edelbrock pusher...

[Ozmodiar-X]

Has anyone figured out a way to hook up the choke?

[dat1kid]

good thread keep it up and alive