Super82

iTrader: (1)

Yeah, my stock port feels like it keeps pulling after 7k. It didn't before the exhaust mods but now it pulls hard well out of the tach, or atleast it feels that way. I'm no expert here but I've always heard that streetports can pull furthur than the motor would handle. If I remember right you said you had a fairly agressive port so perhaps you need to figure out whats wrong.

And Kentetsu, Holleys are very tuneable, moreso than Sterlings. Because holleys are made for a huge number of applications you can change just about anything. If your problem is in the carb you should be able to find it. Are your secondary jets big enough? I'd try advancing your timing a bit more.

ndmrpwr

Another thought here, since your in Colarado Springs. Your altitude is? I live in Idaho Falls Id. with an altitude of about 5000. I found that an extra 4 to 6 degrees of advance woke my 12b up quite a bit. HTH

RX-7 Chris

iTrader: (19)

I'm at about 6500+. So what are the actual timing numbers that everyone is running leading and trailing?

Sterling

Bullshit. A truly ignorant statement.

RX-7 Chris

iTrader: (19)

Please don't go here, I'm just looking for good info not a carb flame war.

Sterling

24 btc Leading, 16 btc Trailing.
These are recommended timing settings by Paul Yaw.
...Anyone wanna say Paul Yaw doesn't know his ****?

Sterling

-And I'm just keeping the info good, that's all.

RX-7 Chris

iTrader: (19)

That was what I was looking for, thanks.

those numbers are really different then what RB recommends.

Edit: another question- RB recommends hooking up the leading vacuum advance and leaving the trailing unhooked, it this the way I should do it be cause this is what I have?

RX-7 Chris

iTrader: (19)

I was looking at the Yaw site and it looks like he is doing his timing above 4k not at idle, is this true?

Sterling

Yes, that is advanced timing done at over 4K

ndmrpwr

I just noticed I called my motor a 12b :-(( oops. I was also looking for parts for my se at the same time. Just to clarify sterling the timing you stated at 4000 rpms is for near sea level correct? With the very high altitude the op is at it should be ok to add 4, 6, or even 8 more degrees to compensate for the lack of o2. As an example when I used to race my pisston firebird stock settings were fine at near sea level. But where I live 4 to 6 extra were needed then when I went to Bandamier (sp) near Denver I added another 4 degrees with no problems> This was a pontiac 400 ram air 4 with 10.75 comp ratio. HTH

80's old school

iTrader: (7)

Man this hit the nail on the head!! Bring that car down to sea level on a cool day with high atmospheric pressure and you are golden.

I used to have a wore out Toyota 4-runner that ran OK at sea level.. When I took it to Bigt Bear CA, 7000'.....holy crap...that car was suicidal!!! No power at all. Had to floor it just to pull out in traffic!!

bad 83

iTrader: (3)

If your running the Holley 465 cfm, the best I have found them to run is with a 50 main, and a 54 secondary. They come with secondary metering plates, so you will have to change that to the jet style plate. If you haven't changed anything from the RB specs, I suggest dropping the 30cc acc pump, and dropping in a 50cc. Running your timing a little higher will help. You should run a higher octane fuel also.

ndmrpwr

Why does he need high octane? He has way lower compression since he has no atmosphere! The lower octain the faster the burn. Also since he is at such a high altitude he needs to run leaner than you peeps at closer to sea level. More o2 = more fuel, less o2 = less fuel its a given.

bad 83

iTrader: (3)

Higher timing can create rotor knock with the lower octane..........

ndmrpwr

Not when you have no o2 to help compression. I also live at about 5000 feet and until I boosted my 12a the lower the octane the better it ran. I have a good friend that has a 1982 z28 that runs 12.5 to 1 compression and as long as he isn't running nos pump gas is fine. It is only with a 250 horse shot he needs the good stuff. :-)

Methanol+Boost

Hey now.....Holleys are extremely tuneable. Sometimes. Some Holleys, Unlike the RB holley's have exchangeable bleeds and jets for EVERYTHING. It makes them quite complex- and it doesnt change the fact that their idle system is a joke.

Above statement applies to quickfuels, proforms, demons, HP series ETC. NOT the RB POS

RX-7 Chris

iTrader: (19)

In colorado we run lower octane, regular gas is 85 octane instead of 87. We have 85, 87, 91. 91 is super.

At this alt. the 1/4 mile time are about 1 sec. slower. So if you are pulling a 15 at sea level then it is a 16 up here.

When I had my car tuned, we tried moving away from the 50 main jets and always went back because the 50 seemed like the sweat spot. Before I did the exhause it looked like I needed to change out the secondaries but now they look good if you look at my a/f on my dyno sheet.

Yesterday I changed out my AP discharge jet from a 28 to a 31 and I can feel better acceleration. This isn't going to give me any more whp but is will help my A/F and my 1/4 time (although I haven't taken it to the track yet).

one question I still had was RB recommends hooking up the leading vacuum advance and leaving the trailing unhooked, it this the way I should do it because this is what I have?

Methanol+Boost

I dunno, I've hooked up both vaccum lines before and never noticed a difference, ive also unhooked them with same result. I eventually left them both hooked up before i said hell with it, and tried digital ignition *Failure*

Kentetsu

No idea why they would recommend leaving the trailing vac advance disconnected... I can't see it making a damn bit of difference either way.

RX-7 Chris

iTrader: (19)

no idea why

I will try hooking it all back together before I check the timing. I have the added timing marks on my pully already per the Yaw explanation so it should be easy.

4portgsl

vacuum advance is not going to help high end power, it is strictly for idle quality. When the engine is under load especially at WOT, there is almost zero manifold vacuum.

RX-7 Chris

iTrader: (19)

So what is the advantage of doing the timing at 4k? What we used to do with old V8s is just disconnect the vacuum advance and block off. Then do our timing at idle.

RX-7 Chris

iTrader: (19)

I was just rereading the yaw site. I understand now why I need to do the timing at above 4k. It has to do with the centrifugal advance and not the vacuum advance.

Off of the Yaw site: "In case you were wondering, centrifugal advance, and mechanical advance are two different terms for the same mechanism. The centrifugal advance will advance the timing based on engine rpm. It consists of two weights held in place by springs which are attached to the distributor shaft. At low rpm, when the shaft is spinning slowly, the weights are held in place by the springs. As the rpm increases, the centrifugal force of the spinning weights overcomes the spring tension, and allows the weights to move outward. These weights are attached to the advance mechanism in such a manner that as they move outward, the timing of both leading and trailing will be advanced. This advance will begin at about 1,500 rpm, reacing maximum or "total" advance of approximately 20 degrees by 4,000 rpm, at which point no further advance will result from increasing rpm."

Edit: If the total advance is 20 degrees by 4,000 rpm, can't I just set the timing at idle to L 4 BTC, T 4 ATC and get the yaw numbers of L 24 BTC, T 16 BTC at total advance?

Sterling

I've always assumed it's because you can't trust that the springs will be perfect in the centrifical advance mechanism.