408 stroker issues
#31
02-26-2013, 10:42 PM
#34
03-02-2013, 08:44 AM
Legend
After reading the thread, I agree it's being choked off by a too small TB and a tight exhaust system.
Headers need to be a minimum of 1 3/4" primaries for a 408 and a minimum of 3" cat back, IMHO. Factory y pipe is a massive restriction if you aren't running true duals. Look to that first.
If the TB was enlarged but the exhaust wasn't, you didn't really "diagnose" anything. You could have twin 100mm TB plates and it wouldn't matter if you can't get the exhaust out.
The other problem is the 94 PCM. really hard to tune those, only B&G Chrysler really had the tools to do that, but it was sketchy at best. They've recently partnered with Arrington performance, so hopefully it's improved some.
Barring their solution, matching of complimentary parts is critical. Basically, you need to upsize the injectors, TB, cam, and exhaust proportionally so it appears to the pcm that everything is within stock specs for the fueling and timing needs. Not an easy task.
Excessively lean can really cause damage, but too fat will cost you power as well. Maybe a pull or two on a dyno with a tall pipe sniffer would be worthwhile investment.
Headers need to be a minimum of 1 3/4" primaries for a 408 and a minimum of 3" cat back, IMHO. Factory y pipe is a massive restriction if you aren't running true duals. Look to that first.
If the TB was enlarged but the exhaust wasn't, you didn't really "diagnose" anything. You could have twin 100mm TB plates and it wouldn't matter if you can't get the exhaust out.
The other problem is the 94 PCM. really hard to tune those, only B&G Chrysler really had the tools to do that, but it was sketchy at best. They've recently partnered with Arrington performance, so hopefully it's improved some.
Barring their solution, matching of complimentary parts is critical. Basically, you need to upsize the injectors, TB, cam, and exhaust proportionally so it appears to the pcm that everything is within stock specs for the fueling and timing needs. Not an easy task.
Excessively lean can really cause damage, but too fat will cost you power as well. Maybe a pull or two on a dyno with a tall pipe sniffer would be worthwhile investment.
Last edited by aim4squirrels; 03-02-2013 at 08:50 AM.
#35
03-02-2013, 10:36 AM
After reading the thread, I agree it's being choked off by a too small TB and a tight exhaust system.
Headers need to be a minimum of 1 3/4" primaries for a 408 and a minimum of 3" cat back, IMHO. Factory y pipe is a massive restriction if you aren't running true duals. Look to that first.
If the TB was enlarged but the exhaust wasn't, you didn't really "diagnose" anything. You could have twin 100mm TB plates and it wouldn't matter if you can't get the exhaust out.
The other problem is the 94 PCM. really hard to tune those, only B&G Chrysler really had the tools to do that, but it was sketchy at best. They've recently partnered with Arrington performance, so hopefully it's improved some.
Barring their solution, matching of complimentary parts is critical. Basically, you need to upsize the injectors, TB, cam, and exhaust proportionally so it appears to the pcm that everything is within stock specs for the fueling and timing needs. Not an easy task.
Excessively lean can really cause damage, but too fat will cost you power as well. Maybe a pull or two on a dyno with a tall pipe sniffer would be worthwhile investment.
Headers need to be a minimum of 1 3/4" primaries for a 408 and a minimum of 3" cat back, IMHO. Factory y pipe is a massive restriction if you aren't running true duals. Look to that first.
If the TB was enlarged but the exhaust wasn't, you didn't really "diagnose" anything. You could have twin 100mm TB plates and it wouldn't matter if you can't get the exhaust out.
The other problem is the 94 PCM. really hard to tune those, only B&G Chrysler really had the tools to do that, but it was sketchy at best. They've recently partnered with Arrington performance, so hopefully it's improved some.
Barring their solution, matching of complimentary parts is critical. Basically, you need to upsize the injectors, TB, cam, and exhaust proportionally so it appears to the pcm that everything is within stock specs for the fueling and timing needs. Not an easy task.
Excessively lean can really cause damage, but too fat will cost you power as well. Maybe a pull or two on a dyno with a tall pipe sniffer would be worthwhile investment.
#36
03-03-2013, 03:21 AM
Legend
My bad, nor sure where i gleaned 94' from.
check the coolant temp sensor information, it'll pull timing if reading hot. I recall there being some debate about the accuracy of the coolant readings with the air gap manifold. The deck where the coolant sensor goes into the water jacket was so thick, barely any of the probe was sticking into the coolant stream.
check the coolant temp sensor information, it'll pull timing if reading hot. I recall there being some debate about the accuracy of the coolant readings with the air gap manifold. The deck where the coolant sensor goes into the water jacket was so thick, barely any of the probe was sticking into the coolant stream.
#38
03-03-2013, 11:42 AM
