Changed carb and lost power...HELP!

[eastcoastcivil]

I have a 67 SWB 1/2 ton Chev with an engine built at a race shop. 350 four bolt bored .30 over, Energizer cam, hydraulic valves, edelbrock intake, Edelbrock 600 carb, headders, flowmaster 40 series with 2.5 inch pipe, 3.73 in the rear and a 400 turbo with a 2400 stall and a shift kit.

The truck has lots of bottom end and takes off real fast...heres my new problem.

I put a 750 Edelbrock carb with non stock metoring rods on and found that it didn't have the same power at all (Take off). It was off a high compression chevelle 350.

I took it off and put the 600 back on but installed a 1" spacer... I thought that it would take off the same as before all this but it wont. I have all kinds of top end though.

I want to have my bottom end back...I want to be able to run 1/4 mile on the streets like I used to. What should I do? (Which combination)

Thanks

[shortbed70]

The 750 was too much for your motor first off and what to do...Take the spacer off and run the original setup.

[Wild83C10]

like shortbed70 said go back to the original setup.

[85_prairieboy]

Originally Posted by eastcoastcivil

I want to be able to run 1/4 mile on the streets like I used to

Might also want to take your racing to the track. Its a lot more fun and safe and you can compare times when trying new parts

[eastcoastcivil]

I didn't mean literal 1/4 mile on the streets . . . I just meant that sometimes its nice to step on the gas and go. My bad.

[Bad70sbchevy]

I agree, bigger carbs make power but its at higher rpms with sacrifice to the bottom end. Also the spacer will also shifts peak power to a higher rpm if memory serves me right. The original setup is probably your best bet.

[Truckracer]

Throw all of that Edlebrock in the for sale section of craigslist.

Buy a Holley 3310, get a secondary spring kit for it. Tune to fit your driving. You don't need the spacer.

Here's my 3310 with proform main body running on my altered. leaving the line at idle (950) rpm.

http://www.youtube.com/watch?v=Cqb0bBOmal0

[Marv D]

I'm betting there is yet something else going on. The difference between the 600 and 750 should not be this big 'seat of the pants' difference your describing. Timing the same? Vacuum advance hooked to the same port? no vacuum leaks? Same tires, traction and air pressure? I think I'd look closer before condemning any carb or spacer.

But then I'm always skeptical when someone tells me their ride 'feels' quicker or 'slower'. Typically (and I mean no disrespect to anyone here) I find the 'feel' o-meter is 100% relative to how much lighter their wallet is because of this particular change. Go to the track, get a time slip with both combinations (on the same night preferably) and THEN we have real data to compare. I have a good buddy that I build his engines and we race together all the time. He will come back from a pass and tell me how the car 'feels' real happy. Or it's really running strong tonight. I load his data in my weatherstation and see,,, he's running 0.03 to 0.05 seconds faster or slower than the last race and MPH is .2MPH from 'right' for the air. You can NOT feel 0.03 and you typically can not 'feel' small changes. If you do, you corrected or made worse some other problem.

Any of us that race a lot will agree, we have been out on a first or second pass of the night and thought,, wow, this thing is on a hell of a pass... only to get to the timeshack and find it's nothing spectacular like we thought we 'felt' . All I'm getting at is the butt-o-meter will lie to you,,, especially on the street with varying air/conditions. Go get some real time slips at the track so you can see if 60' time and MPH are effected by the changes.

[djracer]

I agree with Marv the timeslips will help to maximize your potential.

[prostreetC-10]

Something else to consider is that we might be assuming we had a perfectly good 600 and a perfectly good 750 to start with. With non stock rods, who knows how that 750 was set up.

Now as far as this spacer goes. It's a rule of thumb that if you use a good 4 HOLE spacer, you will pick up a little low end. Something you DO NOT want to do is put an open spacer on a dual plane intake. It really messes up the signal to the boosters. You can run a 4 hole on both open and dual plenums but don't put an open on anything but any open intake. That might be your problem with not being able to get back to where you were.

As far as the 3310, it's just too big for your application. You need an 1850 or 80457 600 vac Holley. I'm running a 3310 and love it but it's on a warmed up 454. I built a 600 for a local guy and decided to throw it on my rig for an initial tune. Was amazed at how good it worked on the 454. Only lost a little up top but she launched hard off the get go and had a nice snappy throttle due to the smaller venturies.

[eastcoastcivil]

Well I have a dual plane intake and an open spacer....so I will start by changing that. The only vacuum leak I could think of might be the connection from the brake booster. I will check this stuff out and let you guys know on the weekend how it worked. I appreciate all the info you guys are giving me. This site is my main source.

As for the track...the nearest track is 1.5 hours away but I spoke with a guy and I am gonna try to get there before end of season.

[Super73]

I'm with Marv.. Funny thing too, I don't "feel" a difference between my motor NA and the 100 hit of N20. However, I do hear a different tone of the exhuast and RPM seems to increase faster, oh, and the 1/8 mile clock shows better ET and MPH, but I don't "feel" any of it. Really, my but-o-meter has never worked well.

[Shon]

Originally Posted by Super73

I'm with Marv.. Funny thing too, I don't "feel" a difference between my motor NA and the 100 hit of N20. However, I do hear a different tone of the exhuast and RPM seems to increase faster, oh, and the 1/8 mile clock shows better ET and MPH, but I don't "feel" any of it. Really, my but-o-meter has never worked well.

Funny how that works, In my 94Z28 i did not think the hose was working but time slip showed otherwise and in the 71 I could not really feel it either but knew it was rolling b/c the 'race car' beside me was not walking off....