318 running with low power - dyno

-
L

lucasdaytona

Member
Joined
Mar 3, 2010
Messages
12
Reaction score
0
Helly guys. I'm Lucas, a great fan of fabo.

I have a Brazilian Dodge Dart 1975, you guys could think in a 1969 USA Dart (basically the same car). Here are the engine specs:

Rebuilt (5k miles), bored 0.30 over.
Federal Mogul Dished Pistons (8.5 CR)
Original Heads, port porting (poor job), 1.88/1.6 Valves (Milodon)
Adjustable Rockers (273 engine)
Action Plus Weiand Intake 8007+
Edelbrock 750 cfm
1" carb spacer
stock headers
2.5" dual exhaust
camshaft comp K20-223-3
std crankshaft
mopar spring kit for new mopar performance distributor (32º degrees max advance)
flex-a-lite 17" fan
high volume oil pump
mopar performance orange ignition
3.15 rear axle ratio
and regular itens

The car runs fine, but have a very poop wheel hp (160 whp), see image below.

I'm running 10.6s in 1/8 mile.

I'm depressed about the power peak rpm (just 4600 rpm)
There's something wrong? Cam too big ?

Thank you guys!

Please help me.

See ya!
View attachment best_run.jpg
 
that carb seems a little on the large size to me. a 600 should be plenty.
the exhaust manifolds cant be helping much either.
what trans? stall convertor?
 
Two thing pop out right away...your compression ratio(8.5) and your rear gear ratio(3.15).Not knowing your rear tire size?A rear gear change or tire size change would help with better time slip in the 1/8th.
 
While it may depress you, your stats sound about right for the combo you're running.

Some thing that are contributing to your numbers are

Low compression
Tiny valved iron heads with poor porting done
Mediocre intake
Weak carb
Stock exhaust manifolds
Tiny cam
Not enough total timing
3:15 gears
 
roccodart440 said:
While it may depress you, your stats sound about right for the combo you're running.

Some thing that are contributing to your numbers are

Low compression
Tiny valved iron heads with poor porting done
Mediocre intake
Weak carb
Stock exhaust manifolds
Tiny cam
Not enough total timing
3:15 gears
Click to expand...
These are my thoughts.

Looking at it the biggest culprits look like the heads, manifolds, and possibly intake though the heads are probably the worst offenders if they're stock 318-2bbl/273 heads with the 318 manifolds a close second bottleneck. The tall axle gears won't be helping its times.
 
you will see the most ET at the track and seat of the pants improvement by stepping up to a min of 3:73 rear gears. if it were mine i would throw in a set of 3.91's.

Then a better torque converter with a stall speed of 3500+ rpm. This is the last place to skimp on quality. Id call dynamic, ptc, coan for there suggestions.

You could pull the heads and have .020 milled off and gain a little compression but it sounds to me like the heads were ported poorly so it might be better to leave it running and get a set of cores milled and rebuilt and either ported or get a template kit and do yourself. This much work almost warrants you buying a magnum head that is done already.

What is your timing curve like? initial timing? Total timing? at what RPM does it all come in by?
 
Was the camshaft properly degreed?
Add more max timing, but check for engine-pinging.

My bone-stock '73 318 made 145 RWHP on the dyno so there must be something wrong with your engine-tune.
 
when it was on the dyno did u try carb jetting/measure air/fuel ratio? did u try more ignition advance? if u think peak hp is at a low rpm, the cam is not too big, too low rpm is stuff is too small. and is it a standard or auto trans? auto trans loss on the chassis dyno is more than standard. valve springs strong enough for 5500 rpm=110# seat and 280# open minimum. 1.88"/1.60" is perfect for a 318
 
Have you done a compression test wet and dry?

That's where I would start.
 
I have personally ran 8:90s in the 1/8th mile with a 318, cheap stock rebuild of a 74 model engine, but with a iron 4 barrel intake with a thermoquad, and a racer brown, .430 lift cam. In a 70 duster street car with a 3:21 OPEN rear on street tires. So yeah, something is off in your combo
 
One thing that I don't care for is the intake and carb configuration.

You have a spread bore dual plane intake..

And a square bore carb...

With a 1" spacer....


What is the reason that you are using the spacer? Is it to shift the peak rpm or to adapt the mis-matched carb and intake?


I would either run a spread bore carb with that intake and a gasket with a center divider...

Or get the other Wiand intake that is spread bore.


You are using this one, which is rated from idle - 6000 RPM and spread bore, but have a square bore carb:

https://www.holley.com/products/intakes/dual_plane_manifolds/parts/8007

View attachment Wiand 8007 Action plus lg.jpg


I would use this one which is rated from idle - 6800 rpm and is square bore which will bolt directly to your carb.

https://www.holley.com/products/intakes/dual_plane_manifolds/parts/8022


View attachment Wiand 8022 Stealth lg.jpg


And to keep the strong dual plane intake signal all the way to the carb base, I would use a gasket with a split center similar to this one:

View attachment Carb Gask Holley 108-18 lg.jpg


Or an old Edelbrock LD340 would also work nice with your combo...
 
I am not in the know on the action plus intake. Is it the same as the performer, or are the runners enlarged to 360 size? Reason I ask is for one I am planning on using the same intake, but on magnum heads. If the original heads have the smaller intake ports that would make for a restriction between the intake and the heads. I may be wrong, but I would think that would be somewhat of a factor.

Also, would a thermoquad work better for his setup?
 
I ran 10.60's in the 1/8 with my 3/4 ton 5000 lbs dodge ram all stock 360. So yeah, you have a problem. Where is your timing set??? You may need to go up about 15 degrees with your distributor. Is your carb coming all the way open when you floor it?? You have a big problem that should be easy to find. I've done better than 10.60's with a stock 318 2bbl auto with 2.94 gears. I wouldn't spend money until you fix what ya got
 
If you order that intake for a set of magnum heads you'll need to have the heads drilled to take an LA pattern...unless Weiand started making one for magnum heads with the straight up bolts.

OP, follow the advice above...diagnose where you're at, what your actual cylinder pressure is, your timing (initial, total and curve), ensure your lash/preload is properly set, etc. You may need to get back in there and either advance the cam or possibly (I know this sounds backward, but) swap to a smaller cam or possibly swap to heads that haven't been messed with.

There's any number of reasons why you're low on power, but start with basics as mentioned by those like krazykuda, bigblockmopar, marcohotrod...

Compression
Cam timing
Ignition timing
Mixture (wideband tuning if available)
 
Dragonbat13 said:
I am not in the know on the action plus intake. Is it the same as the performer, or are the runners enlarged to 360 size? Reason I ask is for one I am planning on using the same intake, but on magnum heads. If the original heads have the smaller intake ports that would make for a restriction between the intake and the heads. I may be wrong, but I would think that would be somewhat of a factor.

Also, would a thermoquad work better for his setup?
Click to expand...

I would match the intake with what kind of carb that you are going to run.

You loose flow energy when you use adapters.

The Action Plus is made for a spreadbore carb, and has a power band from idle - 6000 RPM.

The Stealth is made for a square bore carb and has a power band from idle - 6800 RPM.

I like wiand dual planes over the performer. They have a wider RPM range and wiand makes a good casting. I've seen less core shift on wiand and offy intakes than I've seen on Edelbrock.

Also when you use a dual plane intake, use a split gasket to keep the stronger pulse all the way to the carburetor for stronger off line performance.
 
Lucas, Your heads are no good, compression/quench is no good, and that cam is way too big, to start. The power it is making is reasonable and there is no quick or easy fix in my opinion. Forget jetting-waste of time. Take a look at the ignition timing-there may be some easy power there but it is doubtful if it will be the magic bullet either.

The 318 can make very respectable power--This is how I would do it. http://www.forabodiesonly.com/mopar/showthread.php?t=304300

J.Rob
 
My relatively similar 318 ran 9.7s at a very high elevation (very important consideration). With a stock converter and stock distributor (with unknown timing since the balancer didn't have marks) it ran 10.8s. Also swapped to 3.91 gears from 2.73s.
 
I have a Weiand action plus right now on a stock 318, and I love it!! Bottom end out of this world.... you'd think it's a 360 :D
 
krazykuda said:
I would match the intake with what kind of carb that you are going to run.

You loose flow energy when you use adapters.

The Action Plus is made for a spreadbore carb, and has a power band from idle - 6000 RPM.

The Stealth is made for a square bore carb and has a power band from idle - 6800 RPM.

I like wiand dual planes over the performer. They have a wider RPM range and wiand makes a good casting. I've seen less core shift on wiand and offy intakes than I've seen on Edelbrock.

Also when you use a dual plane intake, use a split gasket to keep the stronger pulse all the way to the carburetor for stronger off line performance.
Click to expand...

I should have been clearer. I plan on using the EQ heads drilled for LA intakes with stock magnum valves.

I thought the OP had an action plus with an adapter for his squarebore. That was the reason for bringing up the thermoquad.

I take it that the action plus has 318 sized runners that can be ground to match to a 360 size.

In any case, I agree that timing needs to be looked at first.
 
Dragonbat13 said:
I should have been clearer. I plan on using the EQ heads drilled for LA intakes with stock magnum valves.

I thought the OP had an action plus with an adapter for his squarebore. That was the reason for bringing up the thermoquad.

I take it that the action plus has 318 sized runners that can be ground to match to a 360 size.

In any case, I agree that timing needs to be looked at first.
Click to expand...


If I'm not mistaken, the edelbrock performer has the smaller 318 ports, and the wiand intakes have the larger 340/360 ports. But either way, they will all work, you're just chasing the last few HP with matching the ports...
 
krazykuda said:
If I'm not mistaken, the edelbrock performer has the smaller 318 ports, and the wiand intakes have the larger 340/360 ports. But either way, they will all work, you're just chasing the last few HP with matching the ports...
Click to expand...
Correct. The Weiand Action Plus has 340/360 ports, thus why I like it better than the performer.
 
Port windows sheesh this never dies

IIRC
AP 1.96 x1.00
Performer 318 1.96 x.96

.04 of an inch on width. :)
 
Compression and Gears

Are the 'primary' culprits here.

Easiest change, is to get a little more Gear in that Rear.
 
What valve springs? You peak at 4600 rpm and lost almost 70hp by 5600 rpm!!!??? Valve float?
 
'Output'

RWHP ........ 160 HP @ 4800 RPM's
FWHP ........ 205 HP @ 4800 RPM's

A basic 1975 '318' only puts out about 175 to 180 HP at the Flywheel.

There are some 'basic' tweaks that can be done here, to get the
Horsepower up.

What 'Valve Springs' are on the Cylinder Heads ?

I see that you are running with a Comp-Cams XE-268H. That is a very
good Camshaft.

Lift ...................... .477" / .480"
Duration ............... 268* / 280*
Duration @ .050" ... 224* / 230*
Overlap ................ 54*
LSA ...................... 110*
Centerline ............. 106*

That Camshaft is designed for some better Compression, and works
well in the Middle and early-Upper RPM range.

And that is the 'area' where you are 'falling-off-the-cliff'.
 
You must log in or register to reply here.
-

Back
Top