I have a problem I can't figure out
06-21-2008, 08:50 PM
#1
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I have a problem I can't figure out
First this is all new set-up. new engine etc.
It turns the rpm....goes through the top end 7400 but will only run 112 or so mph. I though it was the trans first, replced that, then thought iwas a converter so I got a ATI 8" 5500. Still does the exact same thing....
It turns the rpm but is slow as crap.......a dead duck. nothing
It a 14:1 LT1, ported heads, ported/matched single plane intake. Accel DFI, the air fuel is good all the way through. Plugs look good. th350 trans, ATI converter, 9" rear with 4.56 and 28" tire ET drag
I really feel its not a trans issuie anymore...the fluid is like new, no smell or anything. Could possibly the cam be wrong or off? Its 27x/28x @ .050 640/640 on a 106. The cam was used before in another car with the exact motor (just beeter parts, I have some eagle stuff) and went 135 mph. I said this thing should go at least 125 on a bad day....but it wont even get close.
I also used a converter that was known to be good......we pulled it directly out of a car that went 140 mph and tried it...same thing.
Dead out of the hole, dead everywhere. Maybe I have shifted it too low I thought? I shifted at 6500....but on the top end its still slow on mph. So if the cam was not in correctly would it make it that slow but still turn alot of RPM?
I am lost at this point and thousands of dollars later I'm also broke.....
It turns the rpm....goes through the top end 7400 but will only run 112 or so mph. I though it was the trans first, replced that, then thought iwas a converter so I got a ATI 8" 5500. Still does the exact same thing....
It turns the rpm but is slow as crap.......a dead duck. nothing
It a 14:1 LT1, ported heads, ported/matched single plane intake. Accel DFI, the air fuel is good all the way through. Plugs look good. th350 trans, ATI converter, 9" rear with 4.56 and 28" tire ET drag
I really feel its not a trans issuie anymore...the fluid is like new, no smell or anything. Could possibly the cam be wrong or off? Its 27x/28x @ .050 640/640 on a 106. The cam was used before in another car with the exact motor (just beeter parts, I have some eagle stuff) and went 135 mph. I said this thing should go at least 125 on a bad day....but it wont even get close.
I also used a converter that was known to be good......we pulled it directly out of a car that went 140 mph and tried it...same thing.
Dead out of the hole, dead everywhere. Maybe I have shifted it too low I thought? I shifted at 6500....but on the top end its still slow on mph. So if the cam was not in correctly would it make it that slow but still turn alot of RPM?
I am lost at this point and thousands of dollars later I'm also broke.....
06-21-2008, 09:47 PM
#2
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Location: Bay Area, CA
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Roll it across the dyno so that you can post a graph - that will greatly help.
Some common things could be plugged exhaust, bad ring seal, low pressure valve springs, ignition issues(very common)...
Some common things could be plugged exhaust, bad ring seal, low pressure valve springs, ignition issues(very common)...
06-21-2008, 09:52 PM
#3
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Springs are all still 200#+ on the seat.....my checker wont do higher but they are 260# when we did them
Ignition could be.....would I lose 10mph though? exaust is just headers and 3" pipes with bullets
06-21-2008, 10:20 PM
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LT1 guys I know usually don't run that much cam. Maybe the cam isn't a good match for the heads and the rest of the combination.
Joe Urban
06-21-2008, 10:28 PM
#5
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I think its kind of small myself.....LTx or not its a race engine.
06-21-2008, 10:44 PM
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Obviously it's your engine and your choice. I see 130 mph full weight LT cars with single planes and lots less cam. I was just curious as to who designed the cam and valvetrain. I'm always trying to learn.
No offense if you don't want to reveal the cam designer. I understand that.
Joe Urban
06-21-2008, 11:04 PM
#7
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Is this the 7400 rpm engine that broke the ARP rocker arm stud?
Obviously it's your engine and your choice. I see 130 mph full weight LT cars with single planes and lots less cam. I was just curious as to who designed the cam and valvetrain. I'm always trying to learn.
No offense if you don't want to reveal the cam designer. I understand that.
Joe Urban
Obviously it's your engine and your choice. I see 130 mph full weight LT cars with single planes and lots less cam. I was just curious as to who designed the cam and valvetrain. I'm always trying to learn.
No offense if you don't want to reveal the cam designer. I understand that.
Joe Urban
I have seen plenty of full weight cars run faster too...**** this car ran 119 with stocks heads and bottom end 7 years ago
I want to know why this one isn't running like it should. Its not the cam design Joe. as I said...this cam has been used before and done the job.
06-21-2008, 11:12 PM
#8
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Whats I don't understand is if its turning the rpm......not matter if it is making power or not it should still have some mph correct? Which would lead me back to thinking trans or converter again.....
06-22-2008, 12:12 AM
#10
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Give us a rundown on one of the passes. May give a clue to where your problems are.
How does the car feel down the track I know you said dead everywhere. But can you give us a little more info on how it feels, is any one part of the run crappier than the other? Does it launch half ok and fall on its face, or does it run hard then lay down on the big end?
Depending on how its doing down the track. It could be a whole laundry list of things. I'll say more when I see a complete timeslip rundown.
How does the car feel down the track I know you said dead everywhere. But can you give us a little more info on how it feels, is any one part of the run crappier than the other? Does it launch half ok and fall on its face, or does it run hard then lay down on the big end?
Depending on how its doing down the track. It could be a whole laundry list of things. I'll say more when I see a complete timeslip rundown.
06-22-2008, 01:29 AM
#11
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If everything is the same in the motor with proper assembly, then I suspect an ignition breakdown problem. You need to put an ignition scope on the car and watch it under load, we always run this testing while on the dyno and it can easily cost you 40+HP, with the car feeling like its running fine.
Edit: Are you saying that at the end of the track you are getting up to the same rpm that you were before?
Edit: Are you saying that at the end of the track you are getting up to the same rpm that you were before?
06-22-2008, 07:06 AM
#13
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Punch your #'s in HERE once to see if convertor is to blame.
The car pulls all the way through but is really lacking power bad. It has power but it just does not feel right, its too slow and it is turning up good.
I will try and get it on a dyno this week and get a graph. Its possible it could be in the tune also or be too rich. Possibly too much gear? but it should still run better in the 1/8
I'm going to get a few slips together and get an averag of the passes.
Most are like this
12.0-12.1 @ 112.4
1/8 it has been all over but runs about a 7.40 t 90mph.....way off.
60' have been anywhere from high 1.6's to 1.52....
