Visit The Dirt Forum for More Information

Author Topic:   How do i check for an intake leak?
CrazyT
Member
posted April 12, 2004 10:42 AM
I am running a flat top 355 with double hump heads. When i put the intake on the holes just did line up. I ran the car in test and tune and it did fine. But we kept playing with jets in my 2G rochester, that has had extensive port and polish work, and went from a 81 to an 86 and it ran better, but the plugs still looked really good. So just to see what would happen i drilled some jets out to a 98 and the car wouldn't wrap up very good so i figured the plugs would be black, but they still looked fine. My jets were drilled out with 81 thounsandths and 86 thousandths drill bits i am assuming that is how everyone gets there numbers.


KPLugnut
Member
posted April 12, 2004 10:58 AM
Holley jet numbers do NOT correspond to drill sizes. An 86 Holley gas jet actually has a .101" orifice size.
A jet that was hand-drilled to .086" actually corresponds to a 77 Holley jet.
And that's ONLY if it is reamed out to exact size. Using drill bits and a power drill will always yield a hole larger by a couple thousandths (at least) than what you intend it to be or think it'll be.
That is why we do not recommend anyone drill their own jets. It's not accurate at all, or consistant.
So if you tried to drill your jets out to .098", and assuming you got it very close to that size, you're close to a Holley 84 jet.

Now, if we're talking in terms of OEM Rochester jets, then THEY do use a numbering system that corresponds directly to the orifice size in thousandths of inches...i.e., an 86 equals a hole that is .086".

Hope that helps...
If you need custom sized jets, just hollar.
KP


CrazyT
Member
posted April 12, 2004 11:39 AM
Thanks a lot i have been getting worried when i read that everyone is using mid seventies jets, now it makes a lot more sense. I think i have been getting worried for no reason.


racer17j
Member
posted April 14, 2004 06:35 PM
to answer your question tho if you ever think you might have a leak just start the car up and spray some wd40 anywhere you might get a leak if the car revs a little that where your leak is


gonfast
Member
posted April 15, 2004 09:22 PM
KP...Have you ever heard of designing a leak between the carb and intake to fool the engine into thinking it has a bigger carb?If so how would it work as far as fuel atomization?


19J
Member
posted April 16, 2004 02:41 PM
We have to use a stock 2bbl is why I asked.It's pretty much a restrictor in itself.


juliaferrell
Member
posted April 18, 2004 09:14 PM
drill the hole, tap it and install a check valve. Heck drill two or three of them? HEHE


KPLugnut
Member
posted April 19, 2004 07:57 AM
To answer racerman's question, yes, we've heard of it..... (wink)....but there are far more efficient ways to meter air/fuel properly and gain power.
Intentional air leaks like that make it nearly impossible to tune a carb properly and we don't recommend it for the faint of heart...OR for a class with rules against it. :-)

KP


Back to the Archives