[DeTomaso] 408C on the dyno

[Daniel C Jones]

Spent Sunday on Dave McClain's dyno with Glen Hartog's 408 cube
Cleveland.  Spec's on the engine are:

 4.030" bore
 SCAT 4" cast crank
 6" SCAT rods with SBC pin dimensions
 dished forged pistons
 4V closed chamber heads milled/drilled for screw in studs and guideplates
 approximately 10:1 compression
 Mid-Lift 1.73:1 roller rockers
 Ford over-the-counter aluminum dual plane (Boss 351C with Holley carb
 pattern)
 Boss 351 cast aluminum valve covers with screw-in Ford rubber grommets
 and push-in K&N breather
 140 lbs seat pressure 320 open (approx)
 Hooker Competition headers, 1 3/4" diameter by 27" long primaries,
 3" diameter by 8" long collector (probably part number HOK-6920HKR)
 12 inch long collector extensions and 3" inlet/outler Magnaflow mufflers
 Mallory Unilite distributor with mechanical advance only
 Boss 351C valve covers
 Dave's dyno carb (Competition Carburetion 950HP carburetor, 4 corner
 idle, no PCV port, did not use the dyno bellmouth)
 Crane Cams grind number (custom):  HR-232/352-2S-8
 Intake  232 deg duration @ 0.050" tappet lift
         294 deg duration @ 0.004" tappet lift.
         0.609" lift with 1.73:1 rocker ratio
 Exhaust 236 deg duration @ 0.050" tappet lift
         298 deg duration @ 0.004" tappet lift.
         0.621" lift with 1.73:1 rocker ratio
 108 degrees lobe separation, intake centerline 103 ATDC
 degreed in at 102.25 intake centerline with new chain
 (should lose about .5 to 1 degree once timing chain loosens up)
 Crane steel distributor gear (0.531 inch ID to match Mallory distributor)
 OEM Ford 5.0L hydraulic roller lifters and spider arrangement

The engine is destined for Glen's Pantera and he wanted to stick with
the Ford dual plane intake so he could retain the stock engine screen.
Dave worked on the Ford aluminum intake to bring the poorer flowing
runners closer to the better ones.  Surprisingly, the worst runners were
not the lower plane runners but the upper runners which "look" better.
The divider was cut down and the plenum entry blended back to help the
worst runners.  Two 4 hole spacers and one open spacer was tried.
Spacer height was limited to 1" since that's all that will fit under
the stock Pantera engine screen with Ford intake.  The open spacer
worked best but all peaked right around 5500 RPM.

Running through the mufflers, on Mobil 93 octane premium, the best pulls
came with 28 degrees timing, the reworked Ford aluminum intake with a 1
inch open spacer. Corrected numbers are 468 horsepower at 5500rpm and
486lbs/ft at 4500.  It was a cool day and the air density ratio was very
good, 98.17% for a 1.0238 correction factor.  Air temp was 56 Degrees F,
humidity 36% and abs baro 29.26 in Hg.  Very good conditions for the
1100ft altitude.  Dave was an EMC contestant and said his dyno is known
to be about 4% conservative when compared to other setups. Our dyno pulls
were from 3000 to 6000 RPM and the engine makes 440 or more lbs/ft from
3100 to about 5600rpm.  After that, the engine drops off.  At this point
we're not sure what the limiting factor is but the two top suspects are
the low rise dual plane intake and the OEM Ford hydraulic roller lifters.
Plans are to try the FRPP/Crane link bar lifters and a Holley Strip
Dominator to see if wee can pull another 500 RPM or so.  Hoping to make
500 HP through the mufflers.  Once we've satisfied our curiosity, we'll
try a 750DP and GTS Pantera headers and mufflers.  Kirk Evans did some
header testing a while back and found the GTS headers were pretty decent
(compared to the other Pantera headers tested) but the mufflers were
pretty bad.  We'll run the tests with and without mufflers.  Also, Dave
thinks we'll lose about 10 HP with the DP versus the dyno carb.
Interestingly, he didn't bother to jet the dyno carb on the dyno,
claiming his previous experience with that carb was that jetting only
made a slight difference in power.

We also tested a Blue Thunder high rise intake but it actually made less
power than the modified Ford intake.  The Blue Thunder made 437 horsepower
and 463 ft-lbs torque, at 5500 and 3900rpm respectively.  Adding a 1" open
spacer to the Blue Thunder helped the torque about 6 HP but horsepower
stayed the same.  It would be interesting to see what Dave could do with
the Blue Thunder but we're going to try a Holley Strip Dominator single
plane, instead.  The heads alone flow 322 CFM at 0.600" lift but when you
add the ported dual plane intake, spacer, and carb body the flow drops
into 270 to 280 CFM range.  Dave used a neat trick for the manifold testing.
He used hardware store weather stripping instead of RTV or cork gaskets.
Cheap, easy and lasts long enough for the dyno pulls.

Earlier I had taken some A/B measurements on several intakes:

                                           A         B
 Holley Strip Dominator                  4 5/16    5 3/8
 Blue Thunder                            4 7/16    5 3/8
 Ford aluminum dual plane                3 1/4     4 3/8
 Weiand Xcelerator 2V                    4 3/16    5 1/8

I know for a fact the Weiand Xcelerator 2V will clear the stock Pantera
screen with a 2 1/4" tall  14" diameter K&N element but there isn't a lot
of room beyond that.  A slightly smaller diameter air cleaner (13") should
clear the decklid and allow a bit more space.  At worst, Glen will have to
either mill the spacer or the intake 1/4" or try a different style air
cleaner.  If he's so inclined, a taller engine screen (or spacers under
the stock screen) can be installed.

The heads are iron 4V closed chamber Clevelands with some short side
radius work, a good valve job and stainless valves, and 30 degree back
cuts on intake valves only.  Dave said the shortside radius was
everything on the 4V heads.  He also opined the 2V short side was worse
and would likely respond to similar modifications.

Dave mentioned the SCAT cast crank had a Cleveland snout and did not
require the Ford Motorsport snout spacer.  If you call SCAT and ask,
they'll tell you the snout spacer is needed.  Note that the SCAT forged
cranks may still need the snout spacer.  My 4340 forged steel SCAT crank
did need it but that crank was made a year or so ago.  I don't know if
they have separate FMS and Cleveland crank part numbers now or not for
the forged cranks.  6" Scat I beam rod with SBC pin dimensions were used
and the rods and pistons were light enough quite a bit of material had
to be removed from the counterweights on the SCAT 4 inch stroke cranks
to use the 28.2oz balance factor.  It would take some heavy metal to
make it internally balanced.  Everything ends up pretty light:

 Piston 390 grams(with ring support)
 Locks 4 grams
 Rings 41 grams
 Pin 117 grams
 Rod Big End 437
 Rod Small End 173
 Bearing 37
 Oil 3
 Total: 1676 gram bob weight for a 50% balance factor.

On the initial fire up, we heard some noise.  I suspected a roller
rocker was hitting the Boss valve cover baffle since I've had that
happen before.  However, Dave said he had checked that and the baffle
had been clearanced.  When we removed the valve cover, there were no
marks on the rockers so that wasn't the source.  Also, the sound appeared
to be coming from multiple locations.  After wondering if it was just
start up slap from the cold forged pistons, Dave bumped the engine over
with the starter while I watched for valve train interference and
noticed that some of pushrods were just brushing the guide plates.
Dave made the guide plate slots deeper and that took care of the
noise.  Glen thought catching was worth the dyno cost.  It's one of
those things easy to catch on the dyno (and hard to verify during mock
since the lifters aren't pumped up) but would be a pain to catch and
fix in the car. Required intake and exhaust pushrods are different
lengths, BTW.  That's likely due to the different intake and exhaust
lobes.

I was surprised the Hooker Competition headers were only 1 3/4" primaries.
4V headers tend to be 1 7/8" since that covers the exhaust port better.
The Hooker Super Comps are 2" but that's too large for this engine.
Some 351C headers make a sharp down turn right at the flange to clear
the narrow Mustang shock towers but the Hookers came out a few inches
before turning down.  Pantera headers come straight out but the primaries
are very short and the collectors very short and small in diameter (2 1/4"
outlet).  Glen is buying a set of GTS Pantera headers which have 2"
primaries feeding into a tri-y type collector of 2 1/4" diamter outlet.
It will be interesting to see how big a hit we take on those relative to
the Hooker headers.

A friend has run both the OEM Ford lifters and the Ford Motorsport
M-6500-S58 retro-fit hydraulic roller lifters (made by Crane and
sold by them under part number 36532-16 but the FMS part number is
$30 cheaper through Summit Racing) and verified the lifters are
dimensionally identical.  The pushrod cup is in the same location and
the plunger travel is the same so we can use the same pushrods.  Marc
mentioned they set the pre-load a full turn, rather than the 1/2 turn
we were using.  The full turn includes the setting of the locks (from
zero lash to locked in place).  Marc also mentioned that is what Crane
recommends.

Since Glen is going to use the left-over stock parts to build a back-up
engine, he's going to buy a set of the Ford/Crane link bar lifters and
we can swap the OEM lifters to the back-up engine.  With the Strip
Dominator and the Crane lifters, we should see if the stock lifters
are a limiting factor.

I have to travel out of the country on business but I'm hoping they'll
wait until I return to resume testing.

I've got all the flow data for the heads and intake so I'll run this
through Dynomation when I can spare the time and see how well it predicts
the trends.

Another builder built a similar 4V headed (no porting or bowl work) 408C
with flat top pistons and open chamber heads.  He used the Crane lifters
and a cam of 240 duration, 0.620" lift and 112 LSA.  It made over 500 HP
and 500 ft-lbs.  Idles at 800 RPM (15 psi vacuum) and pulls strong to 6000
RPM but then drops like a rock.  He's wondering if the lifter bores are
bleeding off oil pressure.  He was running a 2" spacer and made the best
power with a 850HP.  He tried an 950HP and even a worked over 750HP and
saw no more than 435HP.  He said his combo did not like the smaller carbs
at all.  The 850 he used had downleg (not annular) boosters, 82 square
jets with two power valves running 0.059" PVCRs.  Airbleeds were at 0.033"
HS.  He noted he had never seen any motor more sensitive to intake manifolds
and carbs than the Cleveland.  His guess is the intake is the restriction.
Ty said at 5900RPM the graph is running an aggressive slope as if its going
to 6500RPM and then at 5950RPM it drops South like a rock.  He had all eight
tubes instrumented and said all cylinders were running 12.2:1 A/F plus or
minus 0.01 so fuel distribution was clean and organized.  Total timing was
34 and it wouldn't take anymore without killing torque which is sort of
odd for an open chamber head.  Static compression ratio was at approximately
10.6:1.

Dan Jones