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Old 05-19-2009, 10:48 AM   #1
madmattmustangs
1971 Ford Mustang
 
Join Date: Jan 2009
Vehicle: 1971 ford mustang
Location: Arkansas
Posts: 30
Default Engine Rpm issues

Alright guys i have a slight problem with my Car.... again
Its a 351 small block V-8 bored and stroked to 408 with high revving cam, headers machanical advance distributor and an intake.
Im starting to think it could be my intake because in park i can get the rpms to 4 grand then it takes a bit to get them up to even 5 grand on the tac.
Then when its under load its slows down at 3 grand and just crawls up from there.
Could it be the intake?(edelbrock preformer dual plane 351c 2v) or do i have a bad tac?
I also have a 2600 stall converter in the car right now if that helps any.

Aprreciate any help i can get here.
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Old 05-19-2009, 11:27 AM   #2
urban_cowboy
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Vehicle: '69 Mustang Mach1
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It could be a bunch of things. Here are some questions I have.

1. What are the cam specs? Everyone has a different opinion on what a "high reving cam" is.

2. What heads are you running?

3. What intake are you running?

4. What carburetor are you running?

5. What size headers and exhaust do you have?

6. What AFR are you running under load?

7. What is your fuel pressure at the carb?

8. What size fuel line and fuel pump do you have?

9. What size air cleaner do you have?

10. What initial and total advance timing are you running?

11. What do your plugs look like (burnt or sooted up)?

12. What compression ratio is this motor?

13. Have you done a cylinder compression test?

14. Have you ever dyno tuned this motor?

You may can gather from my questions that it sounds like there is a restriction in your system somewhere. It is either not getting all the air it needs, not getting all the fuel it needs, or not able to get rid of its waste.

Something is definitely wrong. My 383W will go from idle to 7000 rpms in a second and a half or so in first gear even under load.
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Last edited by urban_cowboy; 05-19-2009 at 11:31 AM.
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Old 05-19-2009, 11:34 AM   #3
kalli
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Vehicle: 1964, Ford, Mustang
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when you are parking and floor the throttle every engine should over-rev and die a horrible death (unless you have a rpm limiter installed)
I never heard of an engine that just gives up at 4000 when revving in park
does it backfire or misbehave?
do you floor the pedal or fully open the throttle plate on carb? maybe your carpet doesn't allow you to fully open the throttle or something

what is idle timing set to and what is the timing at 3000rpm?
maybe you have a slipped balancer causing the timing marks to be off?

very odd alright though

edit: reading urbans post. disconnect the exhaust from the header and try again. could be well your exhaust is blocking
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Old 05-30-2009, 12:28 AM   #4
madmattmustangs
1971 Ford Mustang
 
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ok we nailed down some of the problems, one the secondaries were not opening, 2 the intake just flat out did not flow enough for the engine, 3 my distributor was way advanced at 3000 rpms which apparently hurt the climb on rpms. now im back to kicking the crap out of all these rednecks and there trucks thats for the imput guys.

oh yea cam runs from 2000 to 6500 rpms
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Old 05-30-2009, 12:58 AM   #5
Starfury
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Good to hear
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Old 05-30-2009, 01:03 AM   #6
67mustang302
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Strokers do really well with single plane intakes, or large dual planes if you care about mileage(with a stroker?)
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13.20's with 2.25-2.30 60's, 40+ year old suspension sucks!
Best trap 107.11mph, we'll see what the new intake/carb setup does.
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