4age exhaust port diameter

**toddw** · 13-11-2009, 10:45 AM

Hi all

I am getting a set headers made for my 4age AE86 to go with the motor I am currently building for my track car. The guy making the needs to know certain engine specs which I have compiled but am unable to give him an exhaust port diameter as the head hasn't been ported yet. I am chasing about the 200 hp mark. I think the stock exhaust port size is 30mm? Can someone help with an approximate modified exhaust port size. I know it is hard to determine but he needs to know what primaries to use - 13/4" or 17/8". Thanks in advance.

Todd

**mattysshop** · 13-11-2009, 10:55 AM

i'd talk to your engine builder,

who are you getting to make them?

are they stepping them at all? 4-1's? Merge collector?

**TERRA Operative** · 13-11-2009, 12:27 PM

Stock exhaust port diameter (measured at the flange face) is indeed 30mm diameter.

**The Last Streetfighter** · 13-11-2009, 01:33 PM

Isn't there some slight variation from model to model? OP didn't specify which Generation of 4AGE he is using.

**TERRA Operative** · 13-11-2009, 01:37 PM

I'm pretty sure the exhaust is the same, the intake varies between generation.

**toddw** · 13-11-2009, 03:38 PM

They are merge colector style. we havent got to the head yet regarding porting but my current set up has a set of extractors thathave cracked up. I want to get the new headers and exhaust to suit my future engine rather than wasting money on a set that I won't use in a month or two. I am building the motor myself but was going to get the headwork done my some else(yet to research someone good). I will only need an approximate sizing at this stage. The fabricator has recomended 1 3/4" or 1 78" - the latter I think might be to big.

**fixeruperer** · 13-11-2009, 10:43 PM

cross reference the atlantic 4ag thats a 240hp 1.6 4ag, all their specs are all over the net.

a bigger exhaust port in n/a form doesnt always mean more power, sometimes you have to shrink them to get more flow, the 4ag exhaust ports do need cleaning up tho.

i cant give you a figure sorry.

**progkamol** · 17-11-2009, 07:33 PM

1.5" primaries & 2" tail pipe ... powerful, and loud

**oldeskewltoy** · 25-02-2010, 11:41 AM

16V ports are all 30-31mm, not sure about silvertop, blktop is larger, I've forgotten if they are 33mm, or 35mm. the exit out of the head isn't really a problem.... there is some work needed inside the port that will improve flow.

How accurate is your header flange???

What rpm levels are you running this engine?

For 150 - 170hp(under 9000rpm) - 1.5"(38mm) w/primaries of about 28"-30" in length. A step to a 42mm pipe can be done about 3"-4" after the header flange. collector can be 2", or 2 1/4"

Over 9000 - 1 5/8"(42mm) w/primaries of about 24"-26" step to 45mm can be built in. Collector of 2 1/4" to 2 1/2"