[JOE ALLAN]

Here's something funny: Changed from a 850 cfm Holly to a 1000 cfm Holly. Pluged the power valves jetted 88 square - Went to 1/8 th mile track - went 6.34 et at 107.00 mph - no inprovement over 850 ------ follow'n weekend went to 1/4 mile track....first run car just quite pull'n about 1000'......we went to 87's square ran 6.38 at 106.53 mph in the 1/8 then ran 1/4 at 10.14 at 131.52 mph......Jett'n was rich ran good 1/8 mile had to lean out for 1/4.... runs were made at a weather corrected elevation of 2750'--we're in high gear about the 330' mark.....Motor stays between 4200 and 6050 rpm......Anyone had a problem like this? Joe

[JOE ALLAN]

Here's something funny: Changed from a 850 cfm Holly to a 1000 cfm Holly. Pluged the power valves jetted 88 square - Went to 1/8 th mile track - went 6.34 et at 107.00 mph - no inprovement over 850 ------ follow'n weekend went to 1/4 mile track....first run car just quite pull'n about 1000'......we went to 87's square ran 6.38 at 106.53 mph in the 1/8 then ran 1/4 at 10.14 at 131.52 mph......Jett'n was rich ran good 1/8 mile had to lean out for 1/4.... runs were made at a weather corrected elevation of 2750'--we're in high gear about the 330' mark.....Motor stays between 4200 and 6050 rpm......Anyone had a problem like this? Joe

[tikiklubracing]

The weather has been all over the place this fall. I've seen as much as a 300' change in altitude in a 1/2 hour from day to night. The only way to tell differences in carb. change is, to make a couple base line passes then change carb. and hope the weather stays the same then, do a couple more passes.Jetting should be a little leaner I feel. Start leaner say 74 and 78 then work your way up till there is no improvement in speed, then back up to previous jetting. Try to keep a 4 jet spread between pri & sec. Change to a red cam front and orange cam sec. as the pink ones only give 1/2 a squirt off the line.

BIGGERISBETTER-78 Catalina, 3650#, 13.567@100.51, 400 .060 .260 domes, 6x8, RPM, 750cfm 4150. 15 yrs in NHRA tech ret.

[JOE ALLAN]

Thanks for the info - Question: Why a 4 jet size diff front to back and isn't 74-76 jet'n way to lean for a holly 1000 cfm - it came with 6.5 power valves and 84-84 jets......Also because of the change'n weather here in Texas we correct each run to a base which is equal to perfect weather for that tracks phyical elevation.....At Abilene the track elevation is 1750' so we corect back to this elevation with 60 degree Temp- 0 humidity and 29.92 Barometer.....I have an old Chrysler Pro-Stock Program from 1970 i use.....works great - i use it for Dial'n the car also. We changed jets 5 times that day and the 1/8 runs liked 88-88 and the 1/4 liked 87-87 both best runs corrected to 2750'.....I thought we have seen a couple of mph faster going from the 850 to the 1000.......Of course this was the first test-n with the 1000.......Joe ..Never had this happen with the 850.

[JOE ALLAN]

I guess i got of track, what i met to say was the best runs were made at 2750' and then were corrected to a base of 1750' and perfect weather.

[tikiklubracing]

You may not need to start at my jetting but you do need to go lean at sometime, then richen. Forget ET just watch speed when it stops increasing your there. I'll get you an answer on the jetting differences as soon as my, fuel answerman, opens up Mon. He explained it to me once. I'm probably the kind that needs to hear it twice before it totally sinks in. When I did the 4 spread thingy, the car was more consistent. The biggest pickup I got was 60' and changing those damn pink cams on my 4150 to red front orange back.. Went from a .98 60' to .91 60'. What is your cu. in.? What squirters? On a friends car, 455 with eheads, he uses 89 sec with 80 pri. any bigger and it looses ET.

BIGGERISBETTER-78 Catalina, 3650#, 13.567@100.51, 400 .060 .260 domes, 6x8, RPM, 750cfm 4150, 3.73 spool. 15 yrs in NHRA tech ret.

[77TA]

Why plug the powervalves ? I'm running 2 in my 950HP and 79/82 jets. He carb was used from a 540 BBC boat motor making about 650 hp it was jetted 79/88 with a plug in the rear power valve.

1977 TA SE y82 I think. T-tops Black on black

[JOE ALLAN]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by 77TA:
Why plug the powervalves ? I'm running 2 in my 950HP and 79/82 jets. He carb was used from a 540 BBC boat motor making about 650 hp it was jetted 79/88 with a plug in the rear power valve.

1977 TA SE y82 I think. T-tops Black on black <HR></BLOCKQUOTE> We use a trans-brake and a rev-limiter to stage and leave,throttles to the floor-motors at 3500 rpm-this just works better with the power valves blocked for us and on jett'n, its kind of scareeee to start out lean on a new motor, i'd rather back it down then to hurt in test'n.

[tikiklubracing]

Forget the cam thingy cause at 3500 your out of squirt.

BIGGERISBETTER-78 Catalina, 3650#, 13.567@100.51, 400 .060 .260 domes, 6x8, RPM, 750cfm 4150, 3.73 spool. 15 yrs in NHRA tech ret.

[Goathead]

http://www.dannys65gto.com

http://kurtspontiac.homestead.com/dannys65gto.html

[Goathead]

we went to 87's square

Why do some carb builders say square is bad?



http://www.dannys65gto.com

http://kurtspontiac.homestead.com/dannys65gto.html

[Goathead]

we went to 87's square



http://www.dannys65gto.com

http://kurtspontiac.homestead.com/dannys65gto.html

[rumair]

square might be bad if you have power valves, but for a racing application with no valves it's the way to go.

97 Trans Am WS6
12.13 @ 114.6
M6, stock heads, stock bottom end
74 Formula 455
11.78 @ 114.4
3800 lbs., d-ports, 9" slicks

[77TA]

why would it be bad to jet square with Front and rear Power vlaves power valves ???

1977 TA SE y82 I think. T-tops Black on black

[torqjunki]

If the power-valve malfunctions and stays closed or if the engine pulls enough vaccum at high rpm to close the valve, it will not allow fuel through the power circuit. Just a precaution and one less thing to worry about. Don't have to tune around the opening and closing of the power-valve either.