OK, so i have been reading about carburetors and i kinda like the sound of the Edelbrock 500cfm Thunder series carb, it seems some of you guys really seem to like it and i have not read anyting bad about it anywhere else. I want to use it on what is soon to be a hybrid s5 4 port n/a high compression engine. I may even do a half bridge or something. But I want this to be a weekend track car, the whole reason i am going with a carbed n/a set up (this is actually for a 2nd gen, but it seems most of the carb guys are here) is so i can simplify everything and just drive the crap out of the car, hopefully with less problems. I take no short cuts as far as cooling the engine tranny and diff go and i always keep fluids fresh, so that stuff shouldnt be a problem. The only thing i am worried about with any carb is possibly having fuel starve/spill over problems in the twisties. I am sure with suspension and good wheels and tires these cars can easily pull over 1G and i was wondering if the Thunder series carbs are up for this or if my car is going to run like crap out of the turns? I know most holleys have different vents, floats, fuel pick up tubes, and other things to help with this type of thing, will this edelbrock need anything like that, and if so do they make the stuff for it and how much?



I have also been reading that everyone says to use an open spacer between the mani and carb, but i was thinking, wouldnt the car be more streetable if you didnt do this? If the secondaries on the carb actually opened up the 3rd and 4th ports on the engine wouldnt low end torque (below 3000 or so) be a bit better with the air moving through only 2 ports at a higher velocity? I would like the car to still be very streetable, and at the track anything below 4000rpms isnt going to matter one way or the other.

My idea right now is to do a mild street port on the ports in the center housing and a bridge on the outer 2 ports. This way, the 2 center ports will be for cruising and when i get on it and the secondaries on the carb open then the big ports will be sucking air and fuel. I could be way off here, so someone tell me if this is doable.

 

The porting is called a Half-Bridge. It's a bridge on the secondaries, while leaving the primaries without a bridge. Been done a lot from what I understand.



As far as the carb goes, definately not my specialty. I've got a Holley 600 that's giving me trouble so ... heh

 

Im not that familiar with the edelbrock carbs. Not sure how the secondaries work. Maybe they will work better than the Holleys.



The open spacer under the carb doesnt affect streetability as much as it seems it would. When I started, I was all for keeping the IR (independent(isolated) runner). I even bought a N2o kit that kept the carb on the manifold. But it was just impossible to tune and operate the secondaries. In fact Racing Beat began selling at least the 6 port Holley kit with a mech. secondary carb. Which I dont agree with mech. secondary, but thats another story.



Now im running a N20 plate so the open spacer worked out anyway.

 

If your porting is the same across all four ports, then a spacer is a good idea. The whole concept of a half-bridge is based on having separated primary and secondary airflow, and an open spacer would allow the bridged ports to draw through the carb all the time. If you can borrow a 4-hole spacer, I would try it with and without it and see what runs best.

 

Yeah, i think i am going to shoot for seperate primary and secondary runners. Everyone has said the secondaries on the edelbrock are extremely easy to adjust, you just turn a screw that adjusts spring tension, so i think I can get it all to work the way i want.

 

Post your results, im interested to see how the edelbrock works.

 

I run an Edelbrock 650 thunder series carb on my S/C with great results. Very, very tuneable! As for the spacer, it is cheap and removeable, buy one and try it. The secondary actuation is sooo adjustable, primary jetting is a piece of cake with the metering rods. Out of the corners is better than a Holley since the jets are right at the bottom of the carb so fuel slosh is not a big issue.

 

Any updates on the spacer issue? I just relized that my edelbrock 500cfm has a slight clearecne issue when the secondaries try to open up. I'm thinking a spacer will do the trick but undecided if an open spacer is better than the ones with seperate runners????

 

Your running a camden as well right?? secondaries shouldn't hit, if they do just pull the spacer off and do some appropriate grinding. A 4 hole caused a power loss for me, the charger needs the plenum space. I has 1/4" milled off the camden spacer to help with hood clearance. Email me at gingles@shaw.ca to compare notes.

 

Update: I found the spacer to be a great help. The idle is smooth and the power is fabulous even at WOT. I love my Edelbrock!