Proper jet/power valve sizes
- Thread starter Skrause118
- Start date
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There is no 'use this power valve, this size jets' answer, too many variables.
First, is this stick shift or auto?
Is the carb new?
Why a carb on an 88?
What ignition type?
First, is this stick shift or auto?
Is the carb new?
Why a carb on an 88?
What ignition type?
CAMTWO1070
Active Member
You need to unblock the powervalve passage and put a powervallve unless your car is intended for just racing..........
Like mentioned the perfect starter is a 6.5 because thats what Holley puts stock in carbs with powervalves installed...
Depending on how much inches of mercury your engine pulls determines the direction in which to make changes...Some carbs require drilling the PVCR to get a better emulsion so having a vacuum gauge helps alot.....
For your jetting and finetuning questions the best way to get the carb into the ballpark for your setup is contact the manufacturers technicians who manufactured the carburetor as they've done dyno tuning and have mathematical programs so its best to know where you sit as far engine specs like vaccuum at idle,, trans type ,,converter type if automatic and internal trans gear ratios if manual also your rear gearing and where you sit at sea level and current temps too as these and other variables like ignition type,,headder type ,,pipe size also how the exhaust exits all matter..
Heres the instruction manual in pdf that also offers basic starter tuning tips....
If you followed the math about cuin's to rpm's and bought the right size carb the carb should already be in the ballpark out of the box so alls youll need too do is set lambda with an air/fuel gauge and test it out and see how it responds to everyday driving but seeings you revealed the powervalve being blocked off Id put the powervalve back and if you didnt change the jetting when you blocked off the powervalve you'll be ok as when removing the PV the jetting must be increased in the secondaries too...
If carb came w/o a PV then get the recommended 6.5 and get jets that are 5-8 jetsizes smaller or like I stated eaerlier get all the cars info and call Holley..
For the street Im more partial to these types of carbs as they help with gas mileage but still offer performance......
I believe this one is Holleys Avenger Series I got on an engine in a parts truck..The 351w had 302 heads and a performer camshaft w/.493/.509" lift camshaft and adjustable valvetrain and OBX stainless shorty headders with a stock cast iron manifold I bought for a core for my 408w engine project..
I definately got a good deal for the $400.00 I paid for the whole truck as this is what that junk looking 351w looked like on the inside plus it had some pretty nice power and a shame to disassemble it til I pulled the heads and found ridges at the cylinder tops telling me the engine was refurbed by an ultra backyard mechanic as it shows because whoever did it didnt go the extra mile and change the rings and bearings or hone the cylinders but pulled the heads.......LOL
Good Luck
Like mentioned the perfect starter is a 6.5 because thats what Holley puts stock in carbs with powervalves installed...
Depending on how much inches of mercury your engine pulls determines the direction in which to make changes...Some carbs require drilling the PVCR to get a better emulsion so having a vacuum gauge helps alot.....
For your jetting and finetuning questions the best way to get the carb into the ballpark for your setup is contact the manufacturers technicians who manufactured the carburetor as they've done dyno tuning and have mathematical programs so its best to know where you sit as far engine specs like vaccuum at idle,, trans type ,,converter type if automatic and internal trans gear ratios if manual also your rear gearing and where you sit at sea level and current temps too as these and other variables like ignition type,,headder type ,,pipe size also how the exhaust exits all matter..
Heres the instruction manual in pdf that also offers basic starter tuning tips....
If you followed the math about cuin's to rpm's and bought the right size carb the carb should already be in the ballpark out of the box so alls youll need too do is set lambda with an air/fuel gauge and test it out and see how it responds to everyday driving but seeings you revealed the powervalve being blocked off Id put the powervalve back and if you didnt change the jetting when you blocked off the powervalve you'll be ok as when removing the PV the jetting must be increased in the secondaries too...
If carb came w/o a PV then get the recommended 6.5 and get jets that are 5-8 jetsizes smaller or like I stated eaerlier get all the cars info and call Holley..
For the street Im more partial to these types of carbs as they help with gas mileage but still offer performance......
I believe this one is Holleys Avenger Series I got on an engine in a parts truck..The 351w had 302 heads and a performer camshaft w/.493/.509" lift camshaft and adjustable valvetrain and OBX stainless shorty headders with a stock cast iron manifold I bought for a core for my 408w engine project..
I definately got a good deal for the $400.00 I paid for the whole truck as this is what that junk looking 351w looked like on the inside plus it had some pretty nice power and a shame to disassemble it til I pulled the heads and found ridges at the cylinder tops telling me the engine was refurbed by an ultra backyard mechanic as it shows because whoever did it didnt go the extra mile and change the rings and bearings or hone the cylinders but pulled the heads.......LOL
Good Luck
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