Jvette73

As my sig shows I am using the entry level Holley600cfm Vac sec list1850. Since buying this carb new I replaced the vac sec housing with the quick change type housing. It took no time to realize that this moter ran better with the use of the lighest spring in the kit. Today I did some other mods including re jetting and converting this 4160 carb to the 4150 type with the use of the kit available from Holley. Hers a rundown of what I did today:

Original setup: #66 primary main jets, 6.5 power valve, #9 secondary metering plate equvilant to #67 jets.

Mods: Installed #68 primary main jets and 7.5 power valve. Installed 4160 to 4150 conversion kit using #72 main jets in secondary block.

The jet sizes were selected based on average jet sizes that would come in the 600 double pumper model carbs.

On test drive it seems as this moter is accepting these jet increases well. Its a difference I can feel in the seat of my pants. It also seems to idle smoother too. As smooth as an XE268 could be anyway. Having said that, we will see if the E.T's improve as I plan to run it at test and tune this Fri. Gates open @ 6pm and ill be there. Anyone else in this area game? Ive gotten great information in the past from forum members and I thank you all again. Some have recomended that I scrap the 600 and go to a 750 vac. sec. You guys are probably correct in that it would make an overall improvement in performance, however at this time funds are getting tighter. The 750 would set me back more than I can handle right now. These latest mods to this 600 carb cost a bit over $65. It will be interesting to see what improvement I can get from my current carb. The air should be cool and crisp. As long as I can launch it good, im optimistic. After Fri. night, hopefully I'll have a good reason to edit my sig. :chevy

lars

Jvette -
Good job on the tuning and tweaking you're doing! I get all pumped up when I see guys like you diving in and doing a little fine-adjustment of your setups. The mods you've done, with the car responding positively, do indicate that your carb may be a touch on the small side and that you could gain some performance by stepping up to a 750 vac secondary eventually. Does Santa come to your house...?

Jvette73

Thanks lars, it seems to have more grunt thats for sure. I bet the 750 would help me on the top end with some sacrifice of bottom end, compared to the 600. Santa is going broke....Santa needs to cut up his credit card...He will be stopping by though. I doubt he will have much for me though :crazy:

clem zahrobsky

# 9 metering plate is equal to a #64 jet :chevy

Jvette73

Thanks for the info clem. Its interesring that you mention that. The Holley spec sheet that came with the conversion kit indicated that #9 metering plate was = to #67 jet. Of coarse im aware that mis-prints are not that rare. This spec sheet does not list any match to a #64. The closest it comes is #63, which they say is = to #'s 5,13,18,30,33 metering plates.

In any event the car seems to have more power now. Its most evident when I launch from a stop. Before the jet change, the car would not spin wheels all that much. Now it will spin through 1st and into second before finally catching up and hooking. There should be good cool air at the track tonight. Its a matter of being able to hook off the line good. One other thing I will try tonight which I have not yet done is remove the air breather. All my previous runs were made with breather and filter intact. Some have said I could improve E.T. with the breather removed. Tonight I will make a couple of passes with the breather on, then pull it off for the test. I never run on the street without the filter installed. I've always run through the mufflers on the track as well.

clem zahrobsky

i am listing what both my holley parts catalogs list. give it a go with with the jets you have in there and take a look at the plugs at the end of the strip using a clean cut off of the engine. a #9 plate has a .067 dia hole.

Jvette73

Results from test and tune are in. Overall a good night. The only drawback of the night was poor brakes. My pedal got spongey and I couldnt hold the car on the line good enough. I was unable to load really good before a launch. As a result I could not improve on my previous best 60' time of 1.93. Nevertheless, I still beat my best trap speed on every run. It took 7 runs before I finally set new lowest E.T. and trap mph on the same ticket.

Heres the rundown in order.

1. 13.67@101.73 60' 2.01

2. 13.78@102.00 60' 2.16

3. 14.00@101.19 60' 2.35

4. 13.80@101.12 60' 2.08

5. 13.68@101.70 60' 2.02

6. 13.69@101.69 60' 2.06

7. 13.57@102.14 60' 1.98 lucky #7 I guess.

In other unrelated news. My brother ran his best ever with his '87 V6 Turbo Regal. He was grinin ear to ear with a 11.67@117.