Thinking about buying percy's adjustajets.

Does anyone have any experience with these? Thoughts, concerns, opinions?

All welcome.

http://www.summitracing.com/parts/PHP-15001/

Just trying to see why these arent more popular. It seems like an excellent idea.

 

I had heard of these and was wondering the same thing myself. Other than why isn't this more popular, or more heard of, do they still use the main jets you already have in your carb, or that you may have spares of in the garage? I just bought a series of jets and would like to make sure that I would still be able to use these before dumping the money on this and finding out otherwise.

 

No the whole point of the percy's adjust a jets is to eliminate your factory jets all together.


After a bit of research it doesnt seem like a very good product. Biggest reason is LEAKS. Its made out of porous materials unlike the zinc that the carb is made out of. Also aluminum expands and contracts way too much and gives leaks.

Also if youre trying to get any type of repeatability from your engine, these are pretty well useless, since you cannot gauge in any way what adjustment youre actually at.

For example, if you put in a 71 jet and its too rich, you know you need to go to a 73. If you then gain 0.1 second on your ET, you know it slowed you down, so you can kinda gauge what to do next from your baseline of 71. With the adjustajet its just a crap shoot.

 

Hmm...well thanks for that info! Glad I hadn't given it much more thought than that, lol. I bought the jets last night so I'm still waiting for them to show up anyways. I just wanted to be sure that I went the right direction after reading your post. I'm still unhappy though that I had to buy $75 worth of small parts just to get a decent tune on my Holley. The thing that really irks me is that I will only use one set of jets out of the 8 that I had to buy according to the Holley Tuning sticky above. Bought those 8 and one power valve, hoping that I got the power valve right, or at least closer than what it is right now. Never did buy the secondary springs either. I'm not looking for OMG HP right now or even holy **** MPG, just looking to stop the bogging and stop pouring gas down the intake manifold.

 

You wont regret the jet purchase.

Thats the same way i thought when i bought them for $80 way back when. But since then, between a freind and myself, weve been through 5 carbs in 3 years) on a couple different engines, and they always come in handy.

 

Well in that case let me ask you this... what size power valves are you running? I bought my 80670 brand new so I haven't changed anything on it yet. I bought jets 58-64,66-67 and the power valve 10.5inhg, think that will get me in the ballpark of where the motor will like to run?

 

I have no idea. Those jets seem really big, but then again, ive only tuned 750+ cfm carbs.

Ive always had the 4150 DP models, and demons. My last 355 like the 750DP with 71/80 jets and had 4.5/4.5 power valves. It seemed to work well with that, but i was thinking of changing them out to 8.5 and 6.5 but ended up selling the car.

I would highly suggest investing in a vacuum gauge. If you dont wanna spend $40 on one, you can always do what i did and just get one for air fittings at a hardware store. It was about 2-3% off in accuracy compared to my autometer one, but its pretty cheap.

helps a TON for tuning.

 

I have a vacuum gauge that i use, I just wish that I had one inside the car so I could see what it is pulling while driving.

 

Thats what i had initially as well, then i bought a second smaller one for $4.00 , put a T-fitting on it, and ran a long vacuum hose inside the car, and mounted it on the dash. I kept the smaller one in the engine bay, and the bigger one in the car.

Make sure you run the fitting off of the proper port on your intake, or you might lean out one cylinder. (thats what i did, and my rings in #8 were shot).

Put the brake booster to the port thats on the #8 runner, and run any vacuum, or PCV fittings off of the main port at the back of the carb, or drill a hole right under the carb mounting pad on the intake and tap in there.

Reason being, PCV/Vacuum gauge or any other vacuum dependant device is pulling air contantly while the car is running, so if you run it off 1 cyl, it leans out just that cylinder. If you run it at the convergence point at the carb, you are giving the same fuel to every cylinder.

The brake booster is only pulling air for a couple seconds at a time, and wont harm anything if ran off that port on the #8 cyl.

Ignore the arrow, see the $4.00 vac gauge under the hood next to the wiper motor.


And here is the one in the car, below the fuel gauge.

 

If you decide to buy an "Adjust-A-Jet" let me know. I have one I can sell you. Changed set-up on my car and is not needed.