Top End Needed

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Ozcuda

Ozcuda

gotta love a MOPAR
Joined
Feb 24, 2006
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Hi Guy's,

Ok went out for the 2nd time last nite. we are running pretty consistant 1.6sec 60ft times & going well till we get to about 5500 RPM in top gear then it feels a little breathless. We are crossing the line at 6400 RPM doing consistant 11.4's at 116+ MPH

Motor is 360 stroker + 0.60 oversize, 11.5 comp, ported J heads, Comp Cam # 20-633-5, Edelbrock RPM air gap, 750 Holley vas sec, 4500 stall, 3:9 to 1 diff.

Is the RPM air gap restricting us ?

Now I am thinking of going to a Edelbrock Super Victor & 850 DP carb any thoughts

Cheers Oz
 
I would not run a super victor on that. The RPM can feed that OK. I'd look for a Victor340 if I was going to choose an alternative intake.

I'll say fuel delivery issues. The current carb can carry it fine. If you have another carb that is known to be good, swap it and see if the car still lays over. If it does I'd be looking at fuel pump/regulator/line sizing.
 
I'm hoping to borrow a mates 850 DP to try next week will hopefully tell us weather we are going in the right direction. If that works well I will look at getting another carb......if not back to the old drawing board as they say
 
850 or a 950hp wouldn't be a bad choice to me.

Minimum for fuel delivery, 120-140gph elec pump, 3/8" line including pickup and a good regulator.
 
Ozcuda said:
Hi Guy's,

Ok went out for the 2nd time last nite. we are running pretty consistant 1.6sec 60ft times & going well till we get to about 5500 RPM in top gear then it feels a little breathless. We are crossing the line at 6400 RPM doing consistant 11.4's at 116+ MPH

Motor is 360 stroker + 0.60 oversize, 11.5 comp, ported J heads, Comp Cam # 20-633-5, Edelbrock RPM air gap, 750 Holley vas sec, 4500 stall, 3:9 to 1 diff.

Is the RPM air gap restricting us ?

Now I am thinking of going to a Edelbrock Super Victor & 850 DP carb any thoughts

Cheers Oz
Click to expand...
If it revs well in low gears and only dies in high gear it sounds like a fuel related issue. Make sure you have a reasonable fuel system with no restrictions and you'd be happier with a 750 or 950 holley DP.
 
I missed the vac sec part. Run a DP on it!

If you have room and don't already have one, put a 1" open spacer on your RPM intake.
 
goldmember said:
If it revs well in low gears and only dies in high gear it sounds like a fuel related issue. Make sure you have a reasonable fuel system with no restrictions and you'd be happier with a 750 or 950 holley DP.
Click to expand...

It is reving well till the top end in top gear. I have had a car in the passed that had insufficiant fuel at high RPM but this feels different it isn't hitting a wall just takes it's time like it is out of oxygen
 
Ozcuda said:
It is reving well till the top end in top gear. I have had a car in the passed that had insufficiant fuel at high RPM but this feels different it isn't hitting a wall just takes it's time like it is out of oxygen
Click to expand...
The heads are a cork to making power above 6000rpm unless the porting was pretty magical. LOL If you can confirm the fuel system is capable of keeping up,I'd try a KNOWN good carb first. Another thought is to try reducing the total timing a few degrees and see if that helps. I assume your not trying to get by on low grade fuel.
 
If it is a 3310 750 carb it does not have secondary jets, it has a metering plate. I upgraded mine with a kit to add a metering block with replaceable jets. Gained 4 tenths and pulls hard on top end now.
 
Get a double pumper on it, the intake should be fine, but I would add at least a 1" open spacer. The real bottle neck are the heads (as you probably know), but a double pumper carb should help with the 60' times, which in turn will lower your ET's. If you're buying one, I would go with a 950dp.

For what its worth, I ran an Air-gap intake on my small block stroker for a few years with a small 750dp carb, less compression and a smaller cam....it ran 10.89 @ 122 mph. So I don't see the intake as being a restriction.
 
Also check your valve spring pressure. Could be floating the valves on top end. More noticable in high gear. Car just lays down. We got a bad set that crapped out on 3rd pass. From around 6000 thru 6400 the car was just flat.Company rep. told me they had a bad run of springs made good on the springs. Woke it right up and we turn 6900 now with no problems. Just a thought. Good luck!!!
 
Thanks for all the advice guy's I will source a bigger carb to try next week & see what happens before doing any other changes
 
Are you talking about the car in your pic?

Is your carb sealed to the scoop? How much clearance do you have above the carb vent tubes? I believe Holley calls for 1".

I've seen some sealed carb/hood scoop combos cause some weird issues. Airflow can do some strange things with some scoops on the outside as well as in the inside. A friend cleared up some issues when he cut some openings in his '65 Satellite/Hemi scoop seal!

Just a though that will only take a run to confirm.

OEM jetting on a 3310 is 72 front and the plate is equal to 75 or 76 in the rear. That might be lean for your engine.
 
RPAGAN said:
Also check your valve spring pressure. Could be floating the valves on top end. More noticable in high gear. Car just lays down. We got a bad set that crapped out on 3rd pass. From around 6000 thru 6400 the car was just flat.Company rep. told me they had a bad run of springs made good on the springs. Woke it right up and we turn 6900 now with no problems. Just a thought. Good luck!!!
Click to expand...


Plus 1 on bad valve springs. Especially if you changed nothing and this symptom just occurred.
 
Locomotion said:
Are you talking about the car in your pic?

Is your carb sealed to the scoop? How much clearance do you have above the carb vent tubes? I believe Holley calls for 1".

I've seen some sealed carb/hood scoop combos cause some weird issues. Airflow can do some strange things with some scoops on the outside as well as in the inside. A friend cleared up some issues when he cut some openings in his '65 Satellite/Hemi scoop seal!

Just a though that will only take a run to confirm.

OEM jetting on a 3310 is 72 front and the plate is equal to 75 or 76 in the rear. That might be lean for your engine.
Click to expand...

Yes the old Long roof racer the scoop is sealed I run a 6" filter under it plenty of room. The carb has a rear metering block with jets can't remember what size might have a look at that first
 
I'll take some under hood pic's on the weekend might help everybody to picture what is there.
 
Valve springs should be 135lbs(or more) seat and 325lbs(or more) open. I hope your not using comp 995's as they suggest. If so it's an easy fix.
 
What size header are you running? A cheap 1 5/8 header will kill that at top end also. You'll need at least 1 3/4 tube header.
 
I had the same issue.
Had a rpm air gap and was running 11.3's, changed to a mopar m1 and ran 11.0. felt much stronger up top.
I have a quickfuel 1050 and 1/2 inch fuel line with a magnafuel 500 pump
also have a 1 inch spacer
Cheers
Dave
 
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