Correct Timing question and Low rpm problem.
Thread Starter
Intermediate
Joined: Feb 2009
Posts: 34
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From: Upper Darby Pennsylvania
Correct Timing question and Low rpm problem.
I have a 85 Vette Worked to the Bone, But I'm having a low throttle (Hiccup), Mid Range seems ok and High isn't quite there either. I'm thinking this is a Timing Problem. I don't drive this car much and i used to take it down the track all the time with the old motor. But since this new motor went in, I am having a problem getting it tuned right. I have replaced the MAF and TPS Sensor thinking these were the problems but no luck. I'm thinking Electrical over anything else. please help if you have any thoughts
Melting Slicks
Joined: May 2007
Posts: 2,171
Likes: 1
From: Warwick RI
I have a 85 Vette Worked to the Bone, But I'm having a low throttle (Hiccup), Mid Range seems ok and High isn't quite there either. I'm thinking this is a Timing Problem. I don't drive this car much and i used to take it down the track all the time with the old motor. But since this new motor went in, I am having a problem getting it tuned right. I have replaced the MAF and TPS Sensor thinking these were the problems but no luck. I'm thinking Electrical over anything else. please help if you have any thoughts
Thread Starter
Intermediate
Joined: Feb 2009
Posts: 34
Likes: 0
From: Upper Darby Pennsylvania
355 4 Bolt Main, Dart 202,160 Heads, 490 Lift Comp Cams with Roller Lifters and Rockers, Accel Lower Intake and Runners, Ported Upper Intake, 58mm BBK TB, Accel 24LB Fuel Injectors, Walbro 255 LPH Fuel Pump, Hypertech Coil Cap and Rotor, MSD 6al ignition and 8mm Wires with AC Delco Plugs gapped at .035, B&M Shift Kit, K&N Air Filter with Straight Inlet Tube (no accordion), MAF Screens removed , TB coolant bypass, AIR system removed and Bypass pulley installed, TCI Torque Converter (not sure on stall)
recently checked or replaced - Plugs,Injectors,Pump,TPS Sensor,MAF Sensor, Timing is set at 8 degrees BTDC. idle is at 700rpm park is at 1000rpm (not bad for cam lift).
recently checked or replaced - Plugs,Injectors,Pump,TPS Sensor,MAF Sensor, Timing is set at 8 degrees BTDC. idle is at 700rpm park is at 1000rpm (not bad for cam lift).
Thread Starter
Intermediate
Joined: Feb 2009
Posts: 34
Likes: 0
From: Upper Darby Pennsylvania
Timing is at 8 BTDC
TPS is at .055
FP ??? not sure yet , I will know by end of week i'm making a contraption to hook up to fuel rail to use my FP Guage.
last time i checked it which should be the same is when i replaced the injectors I set my AFPR at 40 PSI (guaged on my brothers Testing tools).
TPS is at .055
FP ??? not sure yet , I will know by end of week i'm making a contraption to hook up to fuel rail to use my FP Guage.
last time i checked it which should be the same is when i replaced the injectors I set my AFPR at 40 PSI (guaged on my brothers Testing tools).
Thread Starter
Intermediate
Joined: Feb 2009
Posts: 34
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From: Upper Darby Pennsylvania
and there is a bunch of codes on there... I have to re set the codes and go out driving to see what is really the problem. I will do that by weeks end also;( But any and all advice is very appreciated.
Le Mans Master
Joined: Mar 2004
Posts: 5,107
Likes: 171
From: Dublin CA
Standard TPS setting is .54 volts with key on (car not running) and 4.49 volts with accelerator peddle fully to the floor (WOT).
Ignition miss - there is an old saying amoung us old time mechanics....low speed miss is valves and high speed miss is ignition.
Now to address your modifications....looks like a good set of part combinations...but I don't see anything about revising your computer chip. Anytime you change the cam you should have your chip reprogramed. With all the changes you have made this should be a #1 priority!
Battery 14.2 volts is good.
Concerning your "bunch of codes". Disconnect the negative battery cable and leave it disconnected for at least 30 seconds then reconnect. Drive your car for awhile and record your codes. Use the paperclip method if you don't have a scanner. Let us know the codes.
Ignition miss - there is an old saying amoung us old time mechanics....low speed miss is valves and high speed miss is ignition.
Now to address your modifications....looks like a good set of part combinations...but I don't see anything about revising your computer chip. Anytime you change the cam you should have your chip reprogramed. With all the changes you have made this should be a #1 priority!
Battery 14.2 volts is good.
Concerning your "bunch of codes". Disconnect the negative battery cable and leave it disconnected for at least 30 seconds then reconnect. Drive your car for awhile and record your codes. Use the paperclip method if you don't have a scanner. Let us know the codes.
Last edited by John A. Marker; Feb 2, 2009 at 08:47 PM.
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Melting Slicks
Joined: May 2007
Posts: 2,171
Likes: 1
From: Warwick RI
Standard TPS setting is .54 volts with key on (car not running) and 4.49 volts with accelerator peddle fully to the floor (WOT).
Ignition miss - there is an old saying amoung us old time mechanics....low speed miss is valves and high speed miss is ignition.
Now to address your modifications....looks like a good set of part combinations...but I don't see anything about revising your computer chip. Anytime you change the cam you should have your chip reprogramed. With all the changes you have made this should be a #1 priority!
Battery 14.2 volts is good.
Concerning your "bunch of codes". Disconnect the negative battery cable and leave it disconnected for at least 30 seconds then reconnect. Drive your car for awhile and record your codes. Use the paperclip method if you don't have a scanner. Let us know the codes.
Ignition miss - there is an old saying amoung us old time mechanics....low speed miss is valves and high speed miss is ignition.
Now to address your modifications....looks like a good set of part combinations...but I don't see anything about revising your computer chip. Anytime you change the cam you should have your chip reprogramed. With all the changes you have made this should be a #1 priority!
Battery 14.2 volts is good.
Concerning your "bunch of codes". Disconnect the negative battery cable and leave it disconnected for at least 30 seconds then reconnect. Drive your car for awhile and record your codes. Use the paperclip method if you don't have a scanner. Let us know the codes.
Last edited by Iroc57; Feb 2, 2009 at 09:04 PM.
Le Mans Master
Joined: Mar 2004
Posts: 5,107
Likes: 171
From: Dublin CA
Yes the 58mm TB is big for what he is running, but this is just an air inlet. Fuel is dispensed by the injectors, and controlled by sensors (TPS, oxgen sensor just to mention a couple) that feed this data to the computer and the computer adjusts fuel to the engine based on this input. Since the cam and other items (including the TB) that have in impact on air/fuel flow have changed, the original settings in the computer are no longer valid. This could/would have an impact on the low end.
Last edited by John A. Marker; Feb 2, 2009 at 09:22 PM.
Melting Slicks
Joined: May 2007
Posts: 2,171
Likes: 1
From: Warwick RI
Yes the 58mm TB is big for what he is running, but this is just an air inlet. Fuel is dispensed by the injectors, and controlled by sensors (TPS, oxgen sensor just to mention a couple) that feed this data to the computer and the computer adjusts fuel to the engine based on this input. Since the cam and other items (including the TB) that have in impact on air/fuel flow have changed, the original settings in the computer are no longer valid. This could/would have an impact on the low end.
I have a basic understanding but thought that a TB that is too large would instantly cause a lean off idle.
To the OP - Do you know what the advertised range of the cam is?
Thread Starter
Intermediate
Joined: Feb 2009
Posts: 34
Likes: 0
From: Upper Darby Pennsylvania
274/286 duration 487/490 lift, and I understand about desperatly needing a chip programmed but thought i could get it running at least par before worrying about power but I guess why would I be doing all of this to begin with
any suggestions on chips and or programmers?
any suggestions on chips and or programmers?
Thread Starter
Intermediate
Joined: Feb 2009
Posts: 34
Likes: 0
From: Upper Darby Pennsylvania
and thats what i meant with the TPS .55 (close enough) I didn't actually think about a 58mm TB being to big but i think that is a 1000 cfm TB which is probably best suited for a 454 BB, not a 355 ;(
Thread Starter
Intermediate
Joined: Feb 2009
Posts: 34
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From: Upper Darby Pennsylvania
and when i say bunch of codes i mean all the codes stored since i put the new engine in the car, little problem here little problem there and fixed most of them and never cleared the codes. But I know that is my number one priority. It's hard to run this thing anytime short of nine o clock in the morning and five at night. The flomasters make it sould like old chevelle BB with straight exhaust
Le Mans Master
Joined: Mar 2004
Posts: 5,107
Likes: 171
From: Dublin CA
You had and extra 0 in your TPS setting which threw me off. .55 IS CLOSE ENOUGH.
The 58 MM TB is large; but I think once you get a tune, it will not be a factor.
What ratio of RR are you running?
The 58 MM TB is large; but I think once you get a tune, it will not be a factor.
What ratio of RR are you running?
Melting Slicks
Joined: May 2007
Posts: 2,171
Likes: 1
From: Warwick RI
Thread Starter
Intermediate
Joined: Feb 2009
Posts: 34
Likes: 0
From: Upper Darby Pennsylvania
1.6 RR its weird... starts up fine rough idle till closed loop then all seems fine. rough idle after that but expected for cam. then you start on the gas and the engine is like surging under constant normal throttle, then you goose it to kick into a higher gear and it seems to go away, ....then if you try to floor it there is just nothing there . And this is coming from a car that peeled for 100ft on take off, chirped in second and chirped in third (automatic).
I have tried different settings with Timing and plug gaps etc etc and I have mostly seen this problem go away buy messing with parameters but every time I get it to go away , i found another problem in the fuel curve or (constant throttle) somewhere in the RPM's a hiccup would show up telling me that i'm heading in the wrong direction.
I have tried different settings with Timing and plug gaps etc etc and I have mostly seen this problem go away buy messing with parameters but every time I get it to go away , i found another problem in the fuel curve or (constant throttle) somewhere in the RPM's a hiccup would show up telling me that i'm heading in the wrong direction.
Le Mans Master
Joined: Oct 2007
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From: Akron Ohio
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274/286 duration 487/490 lift, and I understand about desperatly needing a chip programmed but thought i could get it running at least par before worrying about power but I guess why would I be doing all of this to begin with any suggestions on chips and or programmers?
any suggestions on chips and or programmers?
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 8
From: Tampa Florida
1.6 RR its weird... starts up fine rough idle till closed loop then all seems fine. rough idle after that but expected for cam. then you start on the gas and the engine is like surging under constant normal throttle, then you goose it to kick into a higher gear and it seems to go away, ....then if you try to floor it there is just nothing there . And this is coming from a car that peeled for 100ft on take off, chirped in second and chirped in third (automatic).
I have tried different settings with Timing and plug gaps etc etc and I have mostly seen this problem go away buy messing with parameters but every time I get it to go away , i found another problem in the fuel curve or (constant throttle) somewhere in the RPM's a hiccup would show up telling me that i'm heading in the wrong direction.
I have tried different settings with Timing and plug gaps etc etc and I have mostly seen this problem go away buy messing with parameters but every time I get it to go away , i found another problem in the fuel curve or (constant throttle) somewhere in the RPM's a hiccup would show up telling me that i'm heading in the wrong direction.