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Author
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Topic: I slowed down!
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Rustang
Journeyman Posts: 75
From:
Registered: Nov 2000
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posted 08-19-2001 08:54 PM
  
Well, my new cam seemed to slow me down! I went from a best of 10.93 to an 11.16. I expected this cam to pick the car up. I noticed on the shifts it seemed to take forever to "pull the gear". It would seem to take forever to pull from 4500 to 5500 and then seemed okay. I think this is a case of too big a cam for my converter(about 4500 stall). I think my motor is now making max torque at around 5600. The old cam was around 5400 (it was doggy too, but not as bad). I do have one cam that should put max torque about 4800rpm and only loose about 20hp on top. But before I switch cams again, how can I rule out if this is a fuel problem? I'm currently running 3/8" line and a holley blue pump.------------------
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perk
Gearhead Posts: 302
From: Staley,nc
Registered: Sep 2000
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posted 08-19-2001 10:13 PM
I know how you feel about the new cam and
slowing down.We lost 2.5 tenths when we had our cleveland.Alex had me advance the cam
4 degrees and then it jumped back up and over previous ETs with the old smaller cam.
Not enough gear and stall when running it
straight up.perk
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jkilroy
Gearhead Posts: 1205
From: Austin, TX
Registered: Dec 99
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posted 08-20-2001 08:49 AM
I think you have a pretty good line on what you need to do however, do you have a fuel pressure guage that can be observed during a run? A Holley 'blue' pump is rated at 110 GPH free flow, but only 70 gph at 9 psi. Thats good till about 400 to 450 hp tops IMO. If you have your regulator set down lower than 9 psi you are getting even less flow, and we know that factory figures are always a little optimistic. In any case I am guessing you are using every bit of capacity that pump has got.I think a good plan would be to put in a new 1/2 line for your feed and use the current 3/8's for a return line. Then either stick another Holley blue pump, or a larger single pump, and a new regulator to use the return line. If possible use an indivudual line from the tank, or cell, to each pump and make them large, like -10 or -12. Use a fairly loose (> 40 micron) filter in between the tank and pumps, and then a fine (<= 10 micron) filter on the pressure side on the 1/2 line. In any case return type fuel systems are superior in many ways to dead head pressure regulators. Other things to check... Is the filter clean? And is it capable of supporting the required flow? (Obvious I know but you never know who is reading the board) Make sure you have good voltage to the pump with the engine running. All of the factory ratings are probably at 13+ volts, and anything less is just less fuel. Use a relay for each pump and good hefty guage wire. Try to stay away from sharp bends and 90 degree (or more) fittings in your lines if possible. As you might be able to tell, the fuel system is one area I *do not* like to worry about, and I tend to over engineer them. But when going to the track, the less you have to worry about the better. ------------------
Jay Kilroy
68' Fastback GT 390
"No such thing as a cam thats too big"
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TomP
Moderator Posts: 2566
From: Delta BC Canada
Registered: Dec 99
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posted 08-20-2001 01:41 PM
...or stick another carb on it.... with dual carbs and 4 float bowls fuel pressure is not a problem in my car,once i get to half track the fuel bowls hold enough for the rest of the run... if i had 4 Holley 4V's i wouldn't even need a tank and pump! i do run a BG280 and big regulator now after having problems with a Holley blue and a Mallory 140, but only 4 lbs of fuel pressure so the needles and seats are never overloaded.
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n2oMike
Gearhead Posts: 204
From: Spencer, WV
Registered: Jan 2001
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posted 08-20-2001 02:34 PM
A good rule of thumb...If you are ever torn between two cams, pick the smaller one! 99% of the time, it's the right thing to do.  My car boogies that 302 up to 6800 rpm just fine with a solid lifer 236/248 110 lobe seperation unit. It pulls just fine down low, and REALLY starts to come on strong around 4k-4.5k. Automatics generally need smaller cams than stick shifts to launch. Either that, or stick an extremely loose converter in it. 302's just don't have the torque of a 400 small block chevy... which can be a GOOD thing, especially in a street race with limited traction. Ask me how I know...  Up until around 10 years ago, everyone ran those damned Holley blue pumps. I'm no fan, but know guys who have run 10's with em'. It's definitely best to over-engineer the fuel system. If you can fab up a fuel pressure gauge to watch, you can see what your carb is getting down track. It's really the only good way to test what you've got. Good Luck! ------------------
Mike Burch
66 mustang real street
302 4-speed 289 heads
10.63 @ 129.3
http://www.geocities.com/motorcitymustang/cmml/cmml_mburch.html
http://www.fortunecity.com/silverstone/healey/367
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clevelandstyle
Journeyman Posts: 25
From: Connersville, IN
Registered: Jul 2001
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posted 08-20-2001 06:29 PM
After you get your fuel figured out, I would try advancing the cam. If it picks the car up then you will know that it probably want's a smaller cam. If you don't want to back up to a smaller cam, then you will probably need more converter.
I have picked up three tenths by advancing the cam 4*. That usually means you got the wrong cam for the combination.
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Rustang1
Journeyman Posts: 64
From:
Registered: Nov 2000
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posted 08-21-2001 12:17 PM
Update: I pulled the front cover off and decided to check cam timing before switching cams and boy was I suprised!! The cam was 9 degrees retarded! And this was with my new Cloyes timing chain/gears set at 4 degrees advanced! When I degreed the cam the first time, it was with my old gearset. (I set it at 4 degrees advanced). I never ran the motor with this chain set. So my new chain set must be off! I ended up setting the crank sprocket straight up, and ran the cam sprocket 1 full tooth ahead to bring the cam to 4 degrees advanced!------------------
1968 Mustang,Clevor,C4
1969 Torino 351C 4spd
1978 F150 460 C6
1978 F150 351W C6
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