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304 ignition timing advance.

tim_pato

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I'm in the process of slapping together a 304, standard deck height, Hypatec flat tops, 284 cam. Will be running 95 and knock sensor. Just wondering where to set my ignition timing?
 

someguy360

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To set the base timing on an EFI engine you need to bridge the diagnostic plug pins under the dash with a paperclip (pins 5&6 if memory serves correct)

Start the enigne and the engine light will flash on the dash to let you know its in diagnostic mode.

Then you set your base timing to 10 degrees BTDC (Some do it to 11-12 on higher octane fuels but I just stick at 10)

The ECU controls the advance curve in the tune etc so all you have to do is set the base timing and your set.


What you do need however is to take the car to a tuner, you can't run a 284 on the stock tune, just won't happen (if it does run it will run like ass, won't idle and probably do some nasty things to your engine), a decent dyno tune will set you back around $500 if you shop around, but anything more than a 268 and you need a tune.
 

tim_pato

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Thanks mate, I've got a tune from "The1" engine is not complete yet I'm waiting on a new timing set, I was just wondering where to start off from with the dizzy.
 

mr j-man

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a plug in tune?? yikes!! I bought one when I had my vs ss thinking sh!t yeah this will be great...wrong! the car ran like arse and all I had done was pipes, CAI and a bigger TB....but It could've been a one off.

Pump 95 is the worst of all fuel selections, I watched a fuel testing episode on some Australian performance show a few years back and they did back to back fuel testing on one car on a chassis dyno. Each time a different fuel was used they retuned the AFR's so they were all the same ratio
95 made the least mileage and power in comparison to E10 P91 P98 and E85...just use 98, how much comp have you got low tens? you could use a thinner cometic mls head gasket to get a little bit more...flat tops are a good start.

im not sure how the ecu's control the timing but a cam with a bit of overlap will generate higher exhaust temps if the initial timing is too retarded which inturn creates a hotter engine but you could be ok with a 284 stick...mind you ive never really looked at its specs
 

tim_pato

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I know a mail order tune is far from ideal, it's the only option I've got atm. I should think comp would be early 9's? No head or block shaving. Im on a very limited budget. Here is the cam spec sheet. Thanks for the tip on 95. Guess I'll have to use 98.
 

someguy360

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Unless the tune has been done to suit that cam you are still no better off than the stock tune.

A generic mail order tune isn't going to help you at all with a cam.

The only way you can get a mail order tune done for a cam is if that tuner has tuned that cam before and has most of the data available still to throw something together or can remotely tune the car via a laptop connected to your ECU running tuning software over the internet (I have seen live tuning like this done before)

When it comes to a cam I always get a dyno tune done, there is just too many variables for a mail order tune to be spot on without a lot of piss farting around.


Also a 284 really needs at least a decent amount of compression, if you are leaving the heads alone I would only be going maybe a 268 or 274 at an absolute max....anything above a 268 and I would be doing the valve springs too.
 

tim_pato

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I sent all the info and mods to the1 will just have to pray. I know the comp is going to be a touch low for the cam but the cam was only $140 new in the box, it was that or standard. I have replaced the valve springs with lt1's.
 

delcowizzid

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cam will be fine its a baby we run bigger on stock pistons with a small skim off the heads .power from idle to around 5600
 
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