GN1 Alum heads, port or not port when stroking motor

[troyk]

My car has been down for 6yrs, This was my build:
ATR headers/exhaust
BGC alum intake
212 hydr cam/stock rockers
GN1 alum heads stock/header port matched.
63mm 1st gen GT precision turbo

I'm going to:
ATR headers/exhaust
BGC alum intake
212 roller cam/T&D rockers
GN1 alum heads stock/header port matched.
Alky injection
63mm 1st gen GT precision turbo(to be upgraded to ball bearing after the build is done & the tweaks are made to see where we are at on HP)

So the question is, the motor will be pulling 8.3% more air with the stroker kit. If I leave the heads alone I would imaging I would have more bottom end tq, because the air is moving faster for the same size runners & less efficient at WOT. Should I not have the heads ported to have 8.3% more flow to maintain the same efficiency map in my FAST system? I know I have had 2 people look at my FAST maps in the past & said my VEs look 5-7% low at WOT.

A side note, is a 212 cam a little small for a street driven car on the latest turbos out today? I've tried a 218 hyd\stock rockers on my non GT63 turbo in the past & thought it was too doggy on low end & swapped out for the smaller cam.

 

[bison]

The turbo is almost always the limitation on these engines. It's true you will have 8.3% more airflow but not necessarily the same increase in mass flow and sometimes no more mass flow. Once the turbo is all in it's pretty much not going to matter what the displacement is. At that point you either go with more turbo or alter the mechanics of the engine to get every last bit of power out of it. If it's out of compressor maybe you'd look at the gearing and try to increase it a little to keep the engine in a spot where it's happier. If hitting backpressure maybe increase the CR and adjust the open close events of the valves. Especially the ex open and close to help with the intake opening and minimize reversion since you are limited by rules and can't increase turbine size. Don't get caught up in people telling you your ve table is too low. I've seen 50-60whp gains while dropping boost pressure and not adding any fuel. This is with just swapping turbos and adjusting the tune. If the engine operates more efficiently the ve numbers will be lower for a given hp

 

[Ttype6]

My car has been down for 6yrs, This was my build:
ATR headers/exhaust
BGC alum intake
212 hydr cam/stock rockers
GN1 alum heads stock/header port matched.
63mm 1st gen GT precision turbo

I'm going to:
ATR headers/exhaust
BGC alum intake
212 roller cam/T&D rockers
GN1 alum heads stock/header port matched.
Alky injection
63mm 1st gen GT precision turbo(to be upgraded to ball bearing after the build is done & the tweaks are made to see where we are at on HP)

So the question is, the motor will be pulling 8.3% more air with the stroker kit. If I leave the heads alone I would imaging I would have more bottom end tq, because the air is moving faster for the same size runners & less efficient at WOT. Should I not have the heads ported to have 8.3% more flow to maintain the same efficiency map in my FAST system? I know I have had 2 people look at my FAST maps in the past & said my VEs look 5-7% low at WOT.

A side note, is a 212 cam a little small for a street driven car on the latest turbos out today? I've tried a 218 hyd\stock rockers on my non GT63 turbo in the past & thought it was too doggy on low end & swapped out for the smaller cam.

Unported heads can get you into very low 9s.

 

[SloGN]

I do think porting will help on the mass flow depending on turbo and backpressure..

Posted from the TurboBuick.Com mobile app

 

[bison]

I do think porting will help on the mass flow depending on turbo and backpressure..

Posted from the TurboBuick.Com mobile app

^^^this. It will help when you run low boost/backpressure but won't do much if anything if the turbo is all in.


Sent from my iPhone using Tapatalk