383 bad vibes. Tuning transition?
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383 bad vibes. Tuning transition?
Has about 250mi on it
Chinese 4340 crank manley rods Probe forged
Nice balance job to start with
Hasnt been abused or tracked yet as I havent had time to get one of those kits and double ck the A/F.Its seen 65/6800 a handful of times for the most part its just warmed up cruised with the occasional WOT blast througha few gears.
Had AED put together an 850HO. Came with 79/89...I had put 81/91 in it
Recently moved about 400-500 ft elevation increase doesnt have the snap it did prior guessing it may need less jet. Any suggestions on that?
And...
Between 24,2500 to just under 3 Im getting some type of vibration (even with clutch pushed in I did have all that balanced) . Almost feels like its dropping a cyl or too much fuel its hard to say. Butter smooth everywhere else. Definitely some type of vibration there
It has an Isky solid roller makes about 8 inches at 1000 rpm has a 5.5 pv in it.
AIB seem to be in line.
Is the PV opening too soon and flooding or attempting to possibly?
Dont think I have any bent pushrods.
I havent measured vacuum at the problem rpm yet due to time.
And for arguements sake it does have a fluidampner
Chinese 4340 crank manley rods Probe forged
Nice balance job to start with
Hasnt been abused or tracked yet as I havent had time to get one of those kits and double ck the A/F.Its seen 65/6800 a handful of times for the most part its just warmed up cruised with the occasional WOT blast througha few gears.
Had AED put together an 850HO. Came with 79/89...I had put 81/91 in it
Recently moved about 400-500 ft elevation increase doesnt have the snap it did prior guessing it may need less jet. Any suggestions on that?
And...
Between 24,2500 to just under 3 Im getting some type of vibration (even with clutch pushed in I did have all that balanced) . Almost feels like its dropping a cyl or too much fuel its hard to say. Butter smooth everywhere else. Definitely some type of vibration there
It has an Isky solid roller makes about 8 inches at 1000 rpm has a 5.5 pv in it.
AIB seem to be in line.
Is the PV opening too soon and flooding or attempting to possibly?
Dont think I have any bent pushrods.
I havent measured vacuum at the problem rpm yet due to time.
And for arguements sake it does have a fluidampner
Re: 383 bad vibes. Tuning transition?
Anxious to see the answer to this. I have a very minor vibration that comes on in the same range. It was also there with my old engine in this particular car, so I've just chalked it up to some kind of exhaust harmonic and I've not been too worried about it.
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Re: 383 bad vibes. Tuning transition?
Well here is a quick check that as have always used to get good ball park on the jetting with a carb .
With the motor at temp and running out of gear, disable the accelerator pump and wing the primary throttle open, if the motor just barely stumbles and does not back fire on you it should do pretty good on the primary's full on acceleration under load!
From there the fine tuning and full throttle plug reading can take place!
Unless that motor will be used full time at the strip and launch at 4500 rpm then that Carb needs to have secondary power valve also
Also unless that 383 has heads flowing over 290 Intake cfm@28" and a manifold that will pass that 290 cfm,and will be called upon to make power max power over 7k rpm than that 850 is a tad too big if you do not have 4.56 gears.
Poor throttle response at low to mid rpm can be mistaken for a vibration at times.
Also 8 inches of Vac at idle will not be enough for power brake function unless you have a duel diaphragm unit, about 14 inches is the limit I have found!
With the motor at temp and running out of gear, disable the accelerator pump and wing the primary throttle open, if the motor just barely stumbles and does not back fire on you it should do pretty good on the primary's full on acceleration under load!
From there the fine tuning and full throttle plug reading can take place!
Unless that motor will be used full time at the strip and launch at 4500 rpm then that Carb needs to have secondary power valve also
Also unless that 383 has heads flowing over 290 Intake cfm@28" and a manifold that will pass that 290 cfm,and will be called upon to make power max power over 7k rpm than that 850 is a tad too big if you do not have 4.56 gears.
Poor throttle response at low to mid rpm can be mistaken for a vibration at times.
Also 8 inches of Vac at idle will not be enough for power brake function unless you have a duel diaphragm unit, about 14 inches is the limit I have found!
You can cut a man's tongue from his mouth, but that does not mean he’s a liar, it just shows that you fear the truth he might speak about you!
Re: 383 bad vibes. Tuning transition?
Willhave to try that test sometime
Heads are 230cc flow 294/230@ 600
I use a vac reservoir its just enough for the power brakes to work good
I noticed when trying to time it as I increased rpm and went through that range it was almost likea slight shuddering feeling. Couldnt hear it just feel it. Gotten slightly worse
So it does it stationary and at steady cruise/part throttle. Full throttle I cant tell goes through the rpm band so fast
Not to add "to" but theres a 50cc pump and a 40 squirterin the rear. Maybe for drag racing it would be ideal but seems to lag a little on the street. Smaller pump and squirter?
Built the car mainly for the track and limp it around on the street for fun. Other than the shuddering feeling in that one range the cars really driveable. 750 ran about the same til about 6kish I plan on running it til around 7 or just above when it poops out.
Ported single plane
4.11 rear gear went to a 26" M/T rather than the 27.5street tire in lieu of regearing
May not be "ideal"but pretty close.
Could a bad crank cause something like this or one thats say got a crack and getting worse?
Its also done a jumping around thing when I time it(the mark) as I increase rpm butunderstand I need an MSD timing light dont know if that tells you guys anything. Cam enplay was set around .007-008. When it was a 350 (same everything except rotating assy and cam did something similar just not as bad.
Heads are 230cc flow 294/230@ 600
I use a vac reservoir its just enough for the power brakes to work good
I noticed when trying to time it as I increased rpm and went through that range it was almost likea slight shuddering feeling. Couldnt hear it just feel it. Gotten slightly worse
So it does it stationary and at steady cruise/part throttle. Full throttle I cant tell goes through the rpm band so fast
Not to add "to" but theres a 50cc pump and a 40 squirterin the rear. Maybe for drag racing it would be ideal but seems to lag a little on the street. Smaller pump and squirter?
Built the car mainly for the track and limp it around on the street for fun. Other than the shuddering feeling in that one range the cars really driveable. 750 ran about the same til about 6kish I plan on running it til around 7 or just above when it poops out.
Ported single plane
4.11 rear gear went to a 26" M/T rather than the 27.5street tire in lieu of regearing
May not be "ideal"but pretty close.
Could a bad crank cause something like this or one thats say got a crack and getting worse?
Its also done a jumping around thing when I time it(the mark) as I increase rpm butunderstand I need an MSD timing light dont know if that tells you guys anything. Cam enplay was set around .007-008. When it was a 350 (same everything except rotating assy and cam did something similar just not as bad.
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Re: 383 bad vibes. Tuning transition?
Is your timing slapping around between 2000 and 3000, and or does a timing light all on its own show any unsteadiness between those rpm points when you rev the motor both fast or slow?
Is the oil pressure bounce around at all in that range?
Is the oil pressure bounce around at all in that range?
You can cut a man's tongue from his mouth, but that does not mean he’s a liar, it just shows that you fear the truth he might speak about you!
Re: 383 bad vibes. Tuning transition?
Timing light seems to "bounce" some. I was using a Craftsman dial back light at the time
Was told I need an MSD light to stop it. Did the same when it was a 350. Same timing set same melling pump(I only had 60 mi on the 350 when I tore it down). Had some wanna be manley (imposter) pushrods, first time I hit 5k they either bent or broke. Wonder if this MSD is the issue? Runs clean or sounds like it anyway
I dont have another light to compare with right now;no access to another carb or say an HEI to try and compare
Oil pressure seems to be steady. Maybe I can try a mech at the motor. Melling pump....shaft seems to wander off to one side when I pull the dist other than being annoying I understand thats common. Are you thinking this could be a cracked pump? Its from that era...
Fwiw I never flowed the intake. Probably considerably better than stock (team g) but who knows what its doing now. Next time its off I will. I worked it quite a bit from plenum to head entry
Gotta be something Im missing really dont want to pull the motor right now
Shoulda had Big Joe do this one and sort it out on the dyno
Was told I need an MSD light to stop it. Did the same when it was a 350. Same timing set same melling pump(I only had 60 mi on the 350 when I tore it down). Had some wanna be manley (imposter) pushrods, first time I hit 5k they either bent or broke. Wonder if this MSD is the issue? Runs clean or sounds like it anyway
I dont have another light to compare with right now;no access to another carb or say an HEI to try and compare
Oil pressure seems to be steady. Maybe I can try a mech at the motor. Melling pump....shaft seems to wander off to one side when I pull the dist other than being annoying I understand thats common. Are you thinking this could be a cracked pump? Its from that era...
Fwiw I never flowed the intake. Probably considerably better than stock (team g) but who knows what its doing now. Next time its off I will. I worked it quite a bit from plenum to head entry
Gotta be something Im missing really dont want to pull the motor right now
Shoulda had Big Joe do this one and sort it out on the dyno
Last edited by cv67 on Sat Sep 13, 2014 10:59 pm, edited 1 time in total.
Re: 383 bad vibes. Tuning transition?
Know Im jumping around a bit and guessing thus the thread
Want to run the car this fall when it cools off and dont want to hurt it
Rebuild is NOT in the cards right now just want to cover all bases
Stumped...never ran into this before
Want to run the car this fall when it cools off and dont want to hurt it
Rebuild is NOT in the cards right now just want to cover all bases
Stumped...never ran into this before
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Re: 383 bad vibes. Tuning transition?
sometimes engines run OK with ignition timing that jumps around more than 2 degrees at a constant rpm. At some point the timing variation WILL cause a noticeable problem. I would expect and rely on a timing light in decent working condition to make spark scatter from mechanikcal OR electronic sources obvious.
Re: 383 bad vibes. Tuning transition?
Makes sense...got to be the ign....it was a Summit system supposedly msd
Found someone willing to loan me an HEI to try out when I get some time hopefully that tells me something. Guess I need to get an MSD timing light to tell exactly where the timing is? No other light will work?
Found someone willing to loan me an HEI to try out when I get some time hopefully that tells me something. Guess I need to get an MSD timing light to tell exactly where the timing is? No other light will work?
Re: 383 bad vibes. Tuning transition?
If you rule out the timing light I would consider a crank trigger ignition system could be after the fact you try several distributors and a timing chain it may be more economical to just get a MSD crank trigger setup
Re: 383 bad vibes. Tuning transition?
Dont think I could afford a crank trigger good point though
After more thought thinking the balancer could be more suspect
I cant afford an ATI but want something SFI rated thats reliable any suggestions>
I will also ck the dist to see if theres up/down play and tear the intake off and ck endplay on cam.
Spoke with a Summit tech at length on the msd keep steering towards the balancer. its been on both motors.
Sounds like those fluidampners do their job on accel but steady speed they dont do anything Who knows.
It was recommended the longer stroke I have to put the larger balancer on it and use one with an actual 2 pc deal to absorb more.
Anyone?
After more thought thinking the balancer could be more suspect
I cant afford an ATI but want something SFI rated thats reliable any suggestions>
I will also ck the dist to see if theres up/down play and tear the intake off and ck endplay on cam.
Spoke with a Summit tech at length on the msd keep steering towards the balancer. its been on both motors.
Sounds like those fluidampners do their job on accel but steady speed they dont do anything Who knows.
It was recommended the longer stroke I have to put the larger balancer on it and use one with an actual 2 pc deal to absorb more.
Anyone?
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Re: 383 bad vibes. Tuning transition?
the end play on the dist should be no more than .010 with a aluminum housing and .005 with cast iron housing to prevent spark scatter caused by the oil pump gears. changing from a wet sump to a dry sump I could not believe how much the timing became more steadycuisinartvette wrote:Dont think I could afford a crank trigger good point though
After more thought thinking the balancer could be more suspect
I cant afford an ATI but want something SFI rated thats reliable any suggestions>
I will also ck the dist to see if theres up/down play and tear the intake off and ck endplay on cam.
Spoke with a Summit tech at length on the msd keep steering towards the balancer. its been on both motors.
Sounds like those fluidampners do their job on accel but steady speed they dont do anything Who knows.
It was recommended the longer stroke I have to put the larger balancer on it and use one with an actual 2 pc deal to absorb more.
Anyone?
Re: 383 bad vibes. Tuning transition?
I have a thick aluminum cover but will double ck endplay anyway
I have one of those melling hv pumps from that era of bad ones. pressure is good and steady..do I even go there not in engine pulling mode just yet
I have one of those melling hv pumps from that era of bad ones. pressure is good and steady..do I even go there not in engine pulling mode just yet
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Re: 383 bad vibes. Tuning transition?
Sounds like a carb issue. Maybe try and borrow someone else's to verify, or reduce the jetting back to stock. Sounds like it's going rich between 2500 and 3000 rpm's and loading up. Double check your ignition too. If the spark plug wires are old, replace them. Also consider going to a hotter plug.
Joe Facciano