4800 rpm then nothing
#1
Junior Member
Thread Starter
Join Date: Mar 2014
Location: Aurora, CO
Posts: 98
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1992 camaro
Engine: 5.7L single turbo GT45
Transmission: 700r4
Axle/Gears: 3.73
4800 rpm then nothing
Hey guys so i cant turn anymore than 4800 rpm shes all out of steam. Is this normal or am i asking for too much? I have a 60 over 350 at 9.5 to 1 with HSR Vortec intake, chevy vortec bowtie 185 runners, gt45 single turbo 5lbs of boost, 3 inch exhaust into a single chamber with a turn down, 3 inch intercooler piping, comp cams 08-305-8 camshaft. I am not expecting anything crazy for rpms but the car almost lunges forward letting the rpm go any higher. I'm wondering if my cam is the cause or my valves are floating or maybe my stock throttle body is being restrictive? Maybe timing and or spark is weak? No MSD and before the turbo was installed it did the same exact thing... Any ideas would be great help.
Thank you,
Matt
Thank you,
Matt
#2
Supreme Member
Re: 4800 rpm then nothing
Need more description on the lunges forward. Normally I'd suspect valve springs, but lunging is often a fuel supply problem.
#3
Supreme Member
iTrader: (1)
Join Date: Apr 2008
Location: Utah
Posts: 10,401
Likes: 0
Received 2 Likes
on
2 Posts
Car: 89 RS 89 iroc 87 firebird
Engine: 3.1 Turbo/ 355 twin turbo
Transmission: a4 w/ 4500 stall/ a4 / t5
Axle/Gears: strange s60 /w 3:42's
Re: 4800 rpm then nothing
for starters get rid of the crap chambered muffler , flowmasters and all there chambered knockoffs are the worst thing u can use on a turbo car.
does it pop and bang or does the motor stay smooth , willing to bet on valve springs/fueling issue or the rev limiter is set way to low
does it pop and bang or does the motor stay smooth , willing to bet on valve springs/fueling issue or the rev limiter is set way to low
#4
Junior Member
Thread Starter
Join Date: Mar 2014
Location: Aurora, CO
Posts: 98
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1992 camaro
Engine: 5.7L single turbo GT45
Transmission: 700r4
Axle/Gears: 3.73
Re: 4800 rpm then nothing
So when making a pull it sounds good and strong then right around 4500 to 4800 you can her the tone change and if i stay in it the rpm just sorta hang at 4800. The car is making a ton of power at 4500 then just nothing not a slow tapper off like what i thought a normal power band felt like leaving. Sound alone makes you want to shift engine screaming with no/ very slow movement of the tach. No lean back fires fuel pressure is up at 45psi afr is at 12 or so. I ran the car a while with just down pipe till my neighbors called got pissy after a late night run same deal but i will for sure get rid of the chambered muffler. Checked the rev it maxed on the EBL iv put some thought into the timing just because 4800 is when the table changes to the extended SA. Tried many different sa changes in the area with no change in performance. But by no means have i mastered tuning yet... my thought is springs but i have had stock vortec heads run the same as these bowties just sorta exact. What is typical for valve float for a stock small block vortec?
#5
Supreme Member
iTrader: (1)
Join Date: Apr 2008
Location: Utah
Posts: 10,401
Likes: 0
Received 2 Likes
on
2 Posts
Car: 89 RS 89 iroc 87 firebird
Engine: 3.1 Turbo/ 355 twin turbo
Transmission: a4 w/ 4500 stall/ a4 / t5
Axle/Gears: strange s60 /w 3:42's
Re: 4800 rpm then nothing
So when making a pull it sounds good and strong then right around 4500 to 4800 you can her the tone change and if i stay in it the rpm just sorta hang at 4800. The car is making a ton of power at 4500 then just nothing not a slow tapper off like what i thought a normal power band felt like leaving. Sound alone makes you want to shift engine screaming with no/ very slow movement of the tach. No lean back fires fuel pressure is up at 45psi afr is at 12 or so. I ran the car a while with just down pipe till my neighbors called got pissy after a late night run same deal but i will for sure get rid of the chambered muffler. Checked the rev it maxed on the EBL iv put some thought into the timing just because 4800 is when the table changes to the extended SA. Tried many different sa changes in the area with no change in performance. But by no means have i mastered tuning yet... my thought is springs but i have had stock vortec heads run the same as these bowties just sorta exact. What is typical for valve float for a stock small block vortec?
post up a data log u will prolly have to zip the file up first
#6
TGO Supporter/Moderator
iTrader: (12)
Join Date: Jul 1999
Location: SALEM, NH
Posts: 11,720
Likes: 0
Received 89 Likes
on
75 Posts
Car: '88 Formula, '94 Corvette, '95 Bird
Engine: LC9, 355" LT1, LT1
Transmission: T5, Zf6, 4L60E
Axle/Gears: 3.42, Dana44 3.45, 3.23
Re: 4800 rpm then nothing
So when making a pull it sounds good and strong then right around 4500 to 4800 you can her the tone change and if i stay in it the rpm just sorta hang at 4800. The car is making a ton of power at 4500 then just nothing not a slow tapper off like what i thought a normal power band felt like leaving. Sound alone makes you want to shift engine screaming with no/ very slow movement of the tach. No lean back fires fuel pressure is up at 45psi afr is at 12 or so. I ran the car a while with just down pipe till my neighbors called got pissy after a late night run same deal but i will for sure get rid of the chambered muffler. Checked the rev it maxed on the EBL iv put some thought into the timing just because 4800 is when the table changes to the extended SA. Tried many different sa changes in the area with no change in performance. But by no means have i mastered tuning yet... my thought is springs but i have had stock vortec heads run the same as these bowties just sorta exact. What is typical for valve float for a stock small block vortec?
Valve float will feel like you hit a brick wall.
What's the air cleaner situation like? I've sucked intake tubes closed before.
The combo should spin to 6000 rpm.
Springs should be at lest 120lbs closed, 360 open. What did you use?
Like he said, post a log. MAP will go nuts if you have valve float, we will see it right away. It's probably the tune.
-- Joe
#7
Junior Member
Thread Starter
Join Date: Mar 2014
Location: Aurora, CO
Posts: 98
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1992 camaro
Engine: 5.7L single turbo GT45
Transmission: 700r4
Axle/Gears: 3.73
Re: 4800 rpm then nothing
This is not on a dyno and the air cleaner is a filter on the turbo. It has also been ran with no filter to check this issue with same problem. the spring pressure is at " installed height IS 101# @ 1.78" with 332# the average rate of pounds per inch" Low spring pressure causing valve float? I will try and get the log loaded after work tonight.
Trending Topics
#8
Junior Member
Thread Starter
Join Date: Mar 2014
Location: Aurora, CO
Posts: 98
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1992 camaro
Engine: 5.7L single turbo GT45
Transmission: 700r4
Axle/Gears: 3.73
Re: 4800 rpm then nothing
Sorry i posted the incorrect cam part number... It is a comp cams 12-268-4
#9
Supreme Member
iTrader: (1)
Join Date: Apr 2008
Location: Utah
Posts: 10,401
Likes: 0
Received 2 Likes
on
2 Posts
Car: 89 RS 89 iroc 87 firebird
Engine: 3.1 Turbo/ 355 twin turbo
Transmission: a4 w/ 4500 stall/ a4 / t5
Axle/Gears: strange s60 /w 3:42's
Re: 4800 rpm then nothing
im really thinking valve float as this point , it has all the symptoms of it.
should be real easy to spot in the data log
should be real easy to spot in the data log
#10
Junior Member
Thread Starter
Join Date: Mar 2014
Location: Aurora, CO
Posts: 98
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1992 camaro
Engine: 5.7L single turbo GT45
Transmission: 700r4
Axle/Gears: 3.73
Re: 4800 rpm then nothing
From what ive found out about the springs they are stock LT4 spring and the come in the zz4 engine... specs show a larger lift cam than my running and making power about 1000 more than me. But valve float is what it feels like to me to. be off in a few hour ill try and load a log.
#11
TGO Supporter/Moderator
iTrader: (12)
Join Date: Jul 1999
Location: SALEM, NH
Posts: 11,720
Likes: 0
Received 89 Likes
on
75 Posts
Car: '88 Formula, '94 Corvette, '95 Bird
Engine: LC9, 355" LT1, LT1
Transmission: T5, Zf6, 4L60E
Axle/Gears: 3.42, Dana44 3.45, 3.23
Re: 4800 rpm then nothing
This is not on a dyno and the air cleaner is a filter on the turbo. It has also been ran with no filter to check this issue with same problem. the spring pressure is at " installed height IS 101# @ 1.78" with 332# the average rate of pounds per inch" Low spring pressure causing valve float? I will try and get the log loaded after work tonight.
-- Joe
#12
Junior Member
Thread Starter
Join Date: Mar 2014
Location: Aurora, CO
Posts: 98
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1992 camaro
Engine: 5.7L single turbo GT45
Transmission: 700r4
Axle/Gears: 3.73
Re: 4800 rpm then nothing
ya just a bit of a difference between flat tappet and roller lol sorry about that. Im going to have to wait till this weekend to get a full pull on a log too much traffic in Colorado these days..
#14
Member
Join Date: Oct 2004
Location: Lapeer, MI
Posts: 491
Likes: 0
Received 1 Like
on
1 Post
Car: 86 IROC, 89 GTA
Engine: 350 blocks, both of em
Transmission: 700r4s
Axle/Gears: 10 bolt and 9 bolt, 3.73, 3.23
Re: 4800 rpm then nothing
I had an issue similar to that. It ended up being a junk msd ignition module.
#15
Supreme Member
iTrader: (2)
Re: 4800 rpm then nothing
Could be lots of things, but I wouldn't have even tried those springs with that cam (either one, especially the hr you posted the first time, but even with the flat tappet xe cam) + boost + the restrictive downpipe/muffler.
like everyone has already said, a datalog will show valve float, but barring that ditching the muffler will make a big difference in power even if it isn't your problem (a bigger downpipe woudn't hurt but 3" should be enough to go well past 4800rpm). I'd be planning on replacing those springs even if they weren't your problem either. Unless timing is doing something really weird or you have a problem with the ignition hardware that shouldn't be it. If you really suspect it the fast way to check for an ignition issue is tightening up the plug gaps to something in the .024" range and see if that changes the RPM that it will pull to. Fueling could do it, but if you've been running out of fuel up there and hitting it repeatedly I would be surprised that you haven't blown it up yet.
like everyone has already said, a datalog will show valve float, but barring that ditching the muffler will make a big difference in power even if it isn't your problem (a bigger downpipe woudn't hurt but 3" should be enough to go well past 4800rpm). I'd be planning on replacing those springs even if they weren't your problem either. Unless timing is doing something really weird or you have a problem with the ignition hardware that shouldn't be it. If you really suspect it the fast way to check for an ignition issue is tightening up the plug gaps to something in the .024" range and see if that changes the RPM that it will pull to. Fueling could do it, but if you've been running out of fuel up there and hitting it repeatedly I would be surprised that you haven't blown it up yet.
#16
Supreme Member
iTrader: (1)
Join Date: Apr 2008
Location: Utah
Posts: 10,401
Likes: 0
Received 2 Likes
on
2 Posts
Car: 89 RS 89 iroc 87 firebird
Engine: 3.1 Turbo/ 355 twin turbo
Transmission: a4 w/ 4500 stall/ a4 / t5
Axle/Gears: strange s60 /w 3:42's
Re: 4800 rpm then nothing
good point i didnt even think of asking him what his plug gaps are, they should be in the .024-.026 range anyways.
though if that was the issue he would getting poping out the ex at higher rpm
though if that was the issue he would getting poping out the ex at higher rpm
#17
Junior Member
Thread Starter
Join Date: Mar 2014
Location: Aurora, CO
Posts: 98
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1992 camaro
Engine: 5.7L single turbo GT45
Transmission: 700r4
Axle/Gears: 3.73
Re: 4800 rpm then nothing
I cant for sure recall what the exact gap is set at but know they are set larger than .024- .026 range. My ignition system inst really upgraded at all just have a MSD billet dis, MSD coil, and MSD wires. Will check the gap ASAP
#18
Supreme Member
iTrader: (1)
Join Date: Jan 2002
Location: garage
Posts: 4,432
Likes: 0
Received 1 Like
on
1 Post
Engine: 3xx ci tubo
Transmission: 4L60E & 4L80E
Re: 4800 rpm then nothing
Are you 100% sure the spark limit and fuel limit is set right? It seems odd that it is being limited to the stock ecm 4800 rpm settings.
I don't see the mechanical parts limiting it to that low of an rpm.
If it was breaking up then I would think ignition problems if ecm isn't limiting it. A healthy stock ignition at 4800 rpm and 5 psi should have no problem igniting.
I don't see the mechanical parts limiting it to that low of an rpm.
If it was breaking up then I would think ignition problems if ecm isn't limiting it. A healthy stock ignition at 4800 rpm and 5 psi should have no problem igniting.
#19
Junior Member
Join Date: Jun 2013
Location: Upstate NY
Posts: 62
Likes: 0
Received 0 Likes
on
0 Posts
Engine: TPI 327 SBC Turbo MS2
Transmission: 200-4R CKP Stage 2
Axle/Gears: 3.73
Re: 4800 rpm then nothing
Are you 100% sure the spark limit and fuel limit is set right? It seems odd that it is being limited to the stock ecm 4800 rpm settings.
I don't see the mechanical parts limiting it to that low of an rpm.
If it was breaking up then I would think ignition problems if ecm isn't limiting it. A healthy stock ignition at 4800 rpm and 5 psi should have no problem igniting.
I don't see the mechanical parts limiting it to that low of an rpm.
If it was breaking up then I would think ignition problems if ecm isn't limiting it. A healthy stock ignition at 4800 rpm and 5 psi should have no problem igniting.
#20
Junior Member
Thread Starter
Join Date: Mar 2014
Location: Aurora, CO
Posts: 98
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1992 camaro
Engine: 5.7L single turbo GT45
Transmission: 700r4
Axle/Gears: 3.73
Re: 4800 rpm then nothing
Are you 100% sure the spark limit and fuel limit is set right? It seems odd that it is being limited to the stock ecm 4800 rpm settings.
I don't see the mechanical parts limiting it to that low of an rpm.
If it was breaking up then I would think ignition problems if ecm isn't limiting it. A healthy stock ignition at 4800 rpm and 5 psi should have no problem igniting.
I don't see the mechanical parts limiting it to that low of an rpm.
If it was breaking up then I would think ignition problems if ecm isn't limiting it. A healthy stock ignition at 4800 rpm and 5 psi should have no problem igniting.
#21
Supreme Member
iTrader: (1)
Join Date: Apr 2008
Location: Utah
Posts: 10,401
Likes: 0
Received 2 Likes
on
2 Posts
Car: 89 RS 89 iroc 87 firebird
Engine: 3.1 Turbo/ 355 twin turbo
Transmission: a4 w/ 4500 stall/ a4 / t5
Axle/Gears: strange s60 /w 3:42's
Re: 4800 rpm then nothing
What do you guys consider safe plug gap for a properly functioning stock ignition with quality parts, basically, no MSD box or other ignition add ons? A recommendation at different boost levels would be greatly appreciated. I.e. at what point will .035", .030", etc. be an issue?
I triple checked all spark/ fuel cuts because I was thinking the same thing you are. I checked my plug gaps and they we huge .045... Installed some fresh plugs and gapped them at .025 will test this weekend when I can do a full pass and get the log loaded. Thanks guys
#22
Junior Member
Thread Starter
Join Date: Mar 2014
Location: Aurora, CO
Posts: 98
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1992 camaro
Engine: 5.7L single turbo GT45
Transmission: 700r4
Axle/Gears: 3.73
Re: 4800 rpm then nothing
new plugs gaped to .025 and a bit of tweaking on timing brought me up to 5500 rpm with no issues! thanks for the help now i can turn up the boost lol
#24
Supreme Member
iTrader: (1)
Join Date: Jan 2002
Location: garage
Posts: 4,432
Likes: 0
Received 1 Like
on
1 Post
Engine: 3xx ci tubo
Transmission: 4L60E & 4L80E
Re: 4800 rpm then nothing
Ah, just noticed you posted msd dizzy and coil. Got the specs on it? What is the L & R of the coil? Some aftermarket stuff is worse that stock 1990+ GM parts.
#25
TGO Supporter/Moderator
iTrader: (12)
Join Date: Jul 1999
Location: SALEM, NH
Posts: 11,720
Likes: 0
Received 89 Likes
on
75 Posts
Car: '88 Formula, '94 Corvette, '95 Bird
Engine: LC9, 355" LT1, LT1
Transmission: T5, Zf6, 4L60E
Axle/Gears: 3.42, Dana44 3.45, 3.23
Re: 4800 rpm then nothing
That is good news. Every time I have come across too big of a gap the engine would break up up top (pop/misfire). If that is a stock GM module, 1990+ TBI/TPI coil, good wires it should be capable of more PSI. If it is a large coil-in-cap setup, then it is already maxed out.
Ah, just noticed you posted msd dizzy and coil. Got the specs on it? What is the L & R of the coil? Some aftermarket stuff is worse that stock 1990+ GM parts.
Ah, just noticed you posted msd dizzy and coil. Got the specs on it? What is the L & R of the coil? Some aftermarket stuff is worse that stock 1990+ GM parts.
-- Joe
#26
Supreme Member
iTrader: (1)
Join Date: Jan 2002
Location: garage
Posts: 4,432
Likes: 0
Received 1 Like
on
1 Post
Engine: 3xx ci tubo
Transmission: 4L60E & 4L80E
Re: 4800 rpm then nothing
I was interested in DIS also. I had some time to mess with coils last year. I found the 1996+ vortec truck coil and module rivaled most aftermarket manufacturer coils and modules. The vortec setup was designed so that the module sits external to the dizzy and has a heat sink to dissipated all the extra heat it makes from being high power.
Any module that sits inside the dizzy can't produce the same power reliably. So even a great coil is limited by the module.
With a little voltage translator ckt, the stock dizzy coil fire (gnd) output can be converted to a 5v output to signal the vortec module/coil pair.
DIS is nice but the same ignition power up to about 6500 RPM can be had with the stock ECM and a $20 JY/ebay vortec pair.
Any module that sits inside the dizzy can't produce the same power reliably. So even a great coil is limited by the module.
With a little voltage translator ckt, the stock dizzy coil fire (gnd) output can be converted to a 5v output to signal the vortec module/coil pair.
DIS is nice but the same ignition power up to about 6500 RPM can be had with the stock ECM and a $20 JY/ebay vortec pair.
Thread
Thread Starter
Forum
Replies
Last Post
Damon
Tech / General Engine
8
09-26-2015 04:29 PM