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Discussion Starter #1
Looking for some input from the engine builders on here.

I rebuit a 360 Magnum motor in a Durango RT Clone, it’s a SLP+.

Botton end is stock.

I used the following components

New EQ 318 Heads:
2.02 stainless intake
1.625 stainless exhaust
.042 mopar head gasket
New stock head bolts
New stock lifters
M1 2bb intake
Fast Man 52 mm throttle body
8mm wires
Pioneer Spring 810102 installed at 1.66 height.
KN air filter
Comp Cams XR264HR with 212/218 and .480/.480 installed straight up / which is ground with 4 degrees advance.
Comp Cams 1.6 Roller Rockers with Comp guide plates.
Edelbrock hardened 6.93
1.5 inch shorty header thru. Custom 2 inch into 3 inch flow master in and out. High flow new cats
SCT tuner /tuned by Hemifever
Edge 2600 stall billet cover
MSaine valve body.


Computer Engine Dyno shows this combo making 351bhp at 5000rpm and 402 ft lbs at 4000 at the crank when I use ultra conservative inputs. Thats 100 hp over stock and what i was shooting for with heads, cam, intake and headers.


Here is my dilemma: I am missing 60 BHP and TQ at the wheels. Even if computer dyno is over estimating I should make 275 rwhp 320 rwtq with this combo.

The comp roller kit came with 6.8 pushrods, which looked good in the valve train set up as far as geometry goes. But I'm not a valve train expert.

The motor ran well but pulled a disappointing 222 rwhp and 273 rwtq. Valve train was loud.

When resetting the lash to 3/4 turn past zero lash I noticed several were below zero lash? I re-measured and the stock pushrods looked better on the roller tip. (Again I'm no expert). 6.8 seemed small. I ordered stock size but hardened for the guide plate compatibility. So 6.93 are in there.

This woke the motor up some and eliminated some of the sewing machine ticking noise. Still there at idle, could be there at higher rpm just can't hear it if it is.

My second pull was 243rwhp and 293 rwtq.

Here is my issue my peaks are way to low. At 5000 this thing is done. Dyno guy shuts it down, graph drops and line goes erratic. I can post graph is anyone can read these things. Peak HP is around 4500 rpm. Torque is highest at 3000 when the converter catches, and nose dives at 4000 rpm.

Cylinder pressure was good before the build but I will check again.

There are no misses or stumbles anywhere. Plugs good but I will check and re gap anyway. Fuel pressure is good and the motor gets fat when it dies off a little so there is fuel there. No valve damage from short push rods. Bind is at 5.44, not close to that.


valve float? But I have 125 and 310 for pressures. Comp says it is good for the cam. They recommend at least 115 / 300. Pull a spring and have tested? Did I get wrong items shipped?

Pushrods still undersized? The XR is a small base circle cam did I measure wrong twice? Use 7.05 or more and check for clearance rotating by hand, set lash and do a pull.

The motor works really well. Pulls nice and smooth and will toast the 275/60 17.

I just cant figure out why its running out of steam early?

Any thoughts would be greatly appreciated. Thanks all.
 

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Turbo Dakota Junkie
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1,912 Posts
Fuel sync needs adjusting. With an aftermarket cam - you will need to experiment some to get it to the "sweet spot". Only rotate the distributor about 1/8" at a time.
 

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Turbo Dakota Junkie
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1,912 Posts
It sounds like the injectors are firing early - so I would retard the distributor slightly by turning it clockwise.
 

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As far as the pushrods, get a measuring pushrod and check for proper length. With my re-ground cam and Edelbrock heads, I ended up using a 6.93 Edelbrock hardened pushrod. Actual measurement came out at 6.95 for my combo. Every combo is going to be different.
 

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ROFLcopter
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16,692 Posts
When it comes to fuel sync as duner mention. Mark the cap/rotor with a marker where it is at stock, so you can always set it back to a reference point. You can also find a shop with a modus or snap on or drbiii scanner and you can visually see on the scanner where the sync is at # wise, and the # will change as you rotate the dist, making it easier for you. By all means try it manually, but at least mark it so you can find a reference!!
 

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Degree the cam. If you just install it "straight up" without checking the tolerances with a degree wheel, you have no idea where you're at.

I found that my last timing chain set was off by around 12 degrees when I checked it.
 

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Degree the cam. If you just install it "straight up" without checking the tolerances with a degree wheel, you have no idea where you're at.

I found that my last timing chain set was off by around 12 degrees when I checked it.
You beat me to it, just gotta degree the cam in.
Straight up is crap shoot.
 

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Looking for some input from the engine builders on here.

I rebuit a 360 Magnum motor in a Durango RT Clone, it’s a SLP+.

Botton end is stock.

I used the following components

New EQ 318 Heads:
2.02 stainless intake
1.625 stainless exhaust
.042 mopar head gasket
New stock head bolts
New stock lifters
M1 2bb intake
Fast Man 52 mm throttle body
8mm wires
Pioneer Spring 810102 installed at 1.66 height.
KN air filter
Comp Cams XR264HR with 212/218 and .480/.480 installed straight up / which is ground with 4 degrees advance.
Comp Cams 1.6 Roller Rockers with Comp guide plates.
Edelbrock hardened 6.93
1.5 inch shorty header thru. Custom 2 inch into 3 inch flow master in and out. High flow new cats
SCT tuner /tuned by Hemifever
Edge 2600 stall billet cover
MSaine valve body.


Computer Engine Dyno shows this combo making 351bhp at 5000rpm and 402 ft lbs at 4000 at the crank when I use ultra conservative inputs. Thats 100 hp over stock and what i was shooting for with heads, cam, intake and headers.


Here is my dilemma: I am missing 60 BHP and TQ at the wheels. Even if computer dyno is over estimating I should make 275 rwhp 320 rwtq with this combo.

The comp roller kit came with 6.8 pushrods, which looked good in the valve train set up as far as geometry goes. But I'm not a valve train expert.

The motor ran well but pulled a disappointing 222 rwhp and 273 rwtq. Valve train was loud.

When resetting the lash to 3/4 turn past zero lash I noticed several were below zero lash? I re-measured and the stock pushrods looked better on the roller tip. (Again I'm no expert). 6.8 seemed small. I ordered stock size but hardened for the guide plate compatibility. So 6.93 are in there.

This woke the motor up some and eliminated some of the sewing machine ticking noise. Still there at idle, could be there at higher rpm just can't hear it if it is.

My second pull was 243rwhp and 293 rwtq.

Here is my issue my peaks are way to low. At 5000 this thing is done. Dyno guy shuts it down, graph drops and line goes erratic. I can post graph is anyone can read these things. Peak HP is around 4500 rpm. Torque is highest at 3000 when the converter catches, and nose dives at 4000 rpm.

Cylinder pressure was good before the build but I will check again.

There are no misses or stumbles anywhere. Plugs good but I will check and re gap anyway. Fuel pressure is good and the motor gets fat when it dies off a little so there is fuel there. No valve damage from short push rods. Bind is at 5.44, not close to that.


valve float? But I have 125 and 310 for pressures. Comp says it is good for the cam. They recommend at least 115 / 300. Pull a spring and have tested? Did I get wrong items shipped?

Pushrods still undersized? The XR is a small base circle cam did I measure wrong twice? Use 7.05 or more and check for clearance rotating by hand, set lash and do a pull.

The motor works really well. Pulls nice and smooth and will toast the 275/60 17.

I just cant figure out why its running out of steam early?

Any thoughts would be greatly appreciated. Thanks all.
I'm not a pro builder by any means, but I'd take the computer program results and toss em in the trash, and the only thing a Dyno is REALLY good for is tuning...Or giving you a base to work off of, and then it's only good if the DA is exactly same everytime you dyno.

I only Dyno at 315 RWHP, and that's corrected RWHP, up here it's probably 50RWHP...But I can run 12's all day.

Degree the cam, check your valve train geometry and stay away from the Dyno.
 

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As said, degree cam and check fuel sync.

As far as pushrod length, due to tolerance stack up, different part combinations, ideal pr length will vary. Just make sure the preload is the same each time you measure for pr length and that you are in the same spot on the base circle of the cam also. I, personally, would bottom out the lifter pluger, check for length, then subtract from the length to get correct preload on a hyd lifter.

Another thing I noticed is the smallish 1.5" primary shorty headers. I'd like to see, at least 1 5/8" primaries. Not sure I understood the rest of your exhaust setup.

Need to make sure ignition is in excellent working order and get your tune(a/f ratio and ignition advance curve) dialed in but an LM2 would help with acquiring data to see what's going on.

I think 1.7 rockers would help a fair amount also. The flow curve on those heads keeps going until .600, then flow starts to drop.
 

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As said, degree cam and check fuel sync.

As far as pushrod length, due to tolerance stack up, different part combinations, ideal pr length will vary. Just make sure the preload is the same each time you measure for pr length and that you are in the same spot on the base circle of the cam also. I, personally, would bottom out the lifter pluger, check for length, then subtract from the length to get correct preload on a hyd lifter.

Another thing I noticed is the smallish 1.5" primary shorty headers. I'd like to see, at least 1 5/8" primaries. Not sure I understood the rest of your exhaust setup.

Need to make sure ignition is in excellent working order and get your tune(a/f ratio and ignition advance curve) dialed in but an LM2 would help with acquiring data to see what's going on.

I think 1.7 rockers would help a fair amount also. The flow curve on those heads keeps going until .600, then flow starts to drop.
To measure push rod length, you use an adj push rod, mark the top of the valve stem, set the valve lash as normal, hand torn the motor over a few times, pull off the rocker and look at the tip of the valve stem. Centered = good. If not centered, change the pushrod length and repeat till it is centered.
 

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To measure push rod length, you use an adj push rod, mark the top of the valve stem, set the valve lash as normal, hand torn the motor over a few times, pull off the rocker and look at the tip of the valve stem. Centered = good. If not centered, change the pushrod length and repeat till it is centered.
Lol, you're makin' it too easy for him. Correct! Hopefully he already knew that.:D
 

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Hydraulic lifters should be set at .020 preload on these engines. If you have adjustable rockers, it's easy. If not, then you need custom pushrods if they don't fit the specs.
 

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Discussion Starter #15
Thanks for the positive replies. I really appreciate the info. I will get the sync set asap.

The 1425 comp roller rocker conversion has 5/16 studs that convert the top part of the stud to 3/8. If I'm not mistaken the 1.6 roller rocker in the kit is a Chevy rocker?

Does anyone know if i can use 1.7 Chevy adjustable rollers rockers with this. That will bring my lift to 5.12?

If not anyone know what 1.7 will work with the kit?

Thanks again.
 

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Get it running right as it sits first, then change things afterward.

After reading the initial post again, it seems like your cam timing is advanced too far. You may need to retard it to raise the powerband up some.

Check it out with a degree wheel. Your cam card should tell you where they recommend installing it.
 

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I hate you people.
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I noticed that besides the SS valves and hardened pushrods, you haven't lightened anything else up in the drive train. Ever consider titanium retainers and/or locks as well as lighter springs? Or are those components not available for the Magnum engines?
 

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Hydraulic lifters should be set at .020 preload on these engines. If you have adjustable rockers, it's easy. If not, then you need custom pushrods if they don't fit the specs.
Then he could just find the total travel of the plunger then subtract the difference. Ex. .100 travel-.020 preload= .080, the number to subtract from pushrod length when correct pattern is present on stem with plunger bottomed out while measuring.
 

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Computer Engine Dyno shows this combo making 351bhp at 5000rpm and 402 ft lbs at 4000 at the crank when I use ultra conservative inputs. .

Theres your problem. While I agree with most that you probably should have degreed in the cam there is probably some tuning that needs to be done on the dyno to get the full potential..with that being said the program you used to simulate the engine should really only be used for fun. I have yet to see any of them that were close to being accurate
 
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