Re: Pormance on my 408
[Re: Wedgeman]
#2108002
07/11/16 05:03 PM
07/11/16 05:03 PM
|
Joined: Jan 2003
Posts: 5,487 SoCal
Brian Hafliger
master
|
master
Joined: Jan 2003
Posts: 5,487
SoCal
|
I was hoping you jump in Brian...
The plugs are a bit dark and the wideband says rich a bit....
But I should really be faster than just a jet change ?
Dan If you are starving it for fuel (either by jetting or fuel supply) you can lose 1-200 HP! You basically kill the engine. I'm not saying this is your problem, but typical 750 carbs with no PV's are jetted around 78-80's...and you have 2 carbs so think about it...it's an easy test. If nothing gets worse or better, it might be fuel supply. Make sure you check everything else out too...I still say dyno testing is the best way to start with a new combo to get you close on tune up, and also easy way to make sure engine is healthy and happy...i.e. valve train issues is one that comes to mind. Brian
Brian Hafliger
|
|
|
Re: Pormance on my 408
[Re: Wedgeman]
#2108162
07/11/16 09:10 PM
07/11/16 09:10 PM
|
Joined: Jan 2003
Posts: 5,487 SoCal
Brian Hafliger
master
|
master
Joined: Jan 2003
Posts: 5,487
SoCal
|
I was thinking the converter might be in fault......... This is where MPH data would help tremendously but also lack of fuel or fuel supply will show low MPH too....
Brian Hafliger
|
|
|
Re: Pormance on my 408
[Re: Wedgeman]
#2108164
07/11/16 09:11 PM
07/11/16 09:11 PM
|
Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
Master
|
Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
|
I was thinking the converter might be in fault......... I dont think its a conv issue.. its got a strong 60'... what are your rpms at the line.. if its slipping hard up top the rpm will tell you... I think its all a fuel issue.. either jetting or supply EDIT You might want to change the needle and seats to .120s... but normally with 2 carbs the .110s work fine.. but something to think of
Last edited by MR_P_BODY; 07/11/16 09:22 PM.
|
|
|
Re: Pormance on my 408
[Re: Wedgeman]
#2108196
07/11/16 10:05 PM
07/11/16 10:05 PM
|
Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
Master
|
Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
|
I recall last year going richer without success........the reason why I got myself a wideband
That's why I'm not sure going this direction will help, but I will keep an open eye on that this week-end....
Dan You need the MPH... if you jet up 4 sizes and if nothing changes or if it doesnt slow down (MPH) then you have a supply issue... could be a needle and seat being to small also... do you have a fuel gauge you can see during the run... and dont use a oil filled gauge... if its under the hood and filled it will show a lower pressure.. thats the oil heating up and pressing back on the gauge
|
|
|
Re: Pormance on my 408
[Re: Wedgeman]
#2108417
07/12/16 01:01 AM
07/12/16 01:01 AM
|
Joined: Jan 2003
Posts: 5,487 SoCal
Brian Hafliger
master
|
master
Joined: Jan 2003
Posts: 5,487
SoCal
|
What can happen on tunnel ram setups is they can pull a ton of fuel at high rpm causing performance loss in excess of 100HP and even pull enough fuel to sometimes cause the engine to rpm limit!
Hard to see when your trying to drive the car, shift, and all. Might be why the plugs are black?
Brian Hafliger
|
|
|
|
|