[Daniel Jones]

>I did have a question on the cam you recommended. Maybe I am reading the
>specs wrong (or maybe reading the wrong specs), but it looks like the H-290
>actually has less duration at .050 than what I am currently running, 216 vs
>220, although it does have more lift, .524 vs .505. So, is it really that
>much more aggressive of a cam? In addition to the lift increase, I was
>thinking I would need duration figures in the low 230's.

With 4V quench heads and flat top pistons (10.5:1 compression will run fine
on 92-93 octane), I'd want at least 230 degrees duration, 0.550" lift,
108 lobe centers. Tim Tullio had a well sorted, very streetable combo in
his Pantera. His engine consisted of an Erson hydraulic flat tappet cam
(232 deg duration @ 0.050", 108 LSA, 0.545" lift), Rhoads lifters, 4V quench
heads, flat tops pistons, 735 Holley, coatings, C&A rings, MSD ignition,
wrapped headers, and MPG Stinger exaust port plates. He tested a bunch of
4V intake manifolds, including an Edelbrock Torker, Weiand Xcelerator 4V,
Offy Port-o-Sonic 4V, Holley Strip Dominator, along with a couple dual planes.
Tim spent a lot of time optimizing the carb for each intake. In the end, the
Holley was 4 tenths quicker in the 1/4 mile than the Torker and had, by far,
the best driveability (smooth with no flat spots) of all of the single planes.
He said it rivaled the dual planes down low, as far as driveability was
concerned, and by 3000 RPM was pulling away. He could never get the Torker
to smooth out at lower RPM, despite a lot of tuning time. He never got to
try a Blue Thunder high rise dual plane which is generally regarded as the
best dual plane for 351C's.

>While I'm asking about cams, do roller cams really generate 30-40 additional
>HP over non-roller cams?

Not warranted in this case. You might want to consier a solid lifter flat
tappet cam though.

>If you want an engine with low end torque and moderate HP at the top end,
>4V heads probably arent the best choice.

True. Aussie 2V heads would be the choice in that case. To make big
horsepower they will need porting work though.

>If you are willing to sacrifice a little torque down low in exchange for
>some more HP up top, you can do it with the 4V heads, but you really need
>more compression and cam to make best use of them.

Absolutely. 4V heads like lift (2V's peak early but 4V's keep climbing)
and compression. The best streetable 4V combos are built around flat top
pistons and closed chamber heads.

>But as others have shown, you can more than likely reach your target of
>350 with a cam swap and some tuning.

Yup, 2V heads are fine to 400 HP with a little attention. A good all
around 2V build is one I spec'd out for a club member's Pantera. Charlie
had a Pantera with a basically stock open chamber 2V engine with Holley
Street Dominator intake and Pantera GTS headers and he was not happy with
its performance. He wanted something that would pull from 2000 to 6000 RPM
with some idle lope. I talked him into:

ported Aussie 2V heads
Weiand Xcelerator 2V intake
Holley 700DP
1.73:1 roller rockers
flat top pistons
Comp 282S solid lifter flat tappet cam (part # 32-238-4)
236/236 @ 0.050" lift, 0.570"/0.570" lift (minus 0.022 lash), LSA 110
windage tray
MSD 6AL ignition

He absolutely loves the new engine. With proper tuning, it should be
over 400 HP and still be street friendly.

>I think youll be giving up a noticeable amount of torque with the huge
>headers though. So my opinion would be to try installing the exhaust
>port plates,

One of the guys in the Pantera club did quite a bit of testing of exhaust
port plates. The only ones he found that worked were the MPG Stingers
exhaust plates (the 1/4" thick brass ones, not the stainless steel ones).
As a rule, the Mustang drag racers don't care for exhaust port plates
because the headers have to make a tight turn down at the exhaust port
to clear the shock towers. With those sort of headers, the 4V dropping
port floor helps the flow make the tight turn and blocking it off with
a port plate just introduces a constriction. Pantera headers may respond
better to exhaust port plates because the header goes straight out from
the port. I'd expect your Cobra headers are similar so the Stingers would
be worth a test.

>borrow a 600 or 650 cfm vacuum secondary carb and play with your timing.

His 700DP isn't overly large for a 351C, assuming it has been properly
tuned. Double Pumper carbs will be set up overly rich out of the box,
so they will need some tuning. I should be able to dig up the jets were
ran in Charlie's 700 DP.

I run a Holley 735 (off a 428CJ) and it works just fine and will even pull
down 20 MPG on the highway (Panteras don't have much aero drag). If you've
got the hood clearance, a Predator would be ideal for a big port 4V, due to
it's variable venturi area and CFM. A friend runs one on his 372 Cleveland
stroker and loves it. Says it doesn't lack for torque, even on the the big
port Holley Strip Dominator.

>Keith, I would like to give you some more input. The aussie 2V heads that
>Mike mentioned will help low end torque with increased port velocity but
>there not going to improve HP numbers.

Stock 4V heads will outflow a set of stock 2V's, Aussie or U.S., by a fairly
wide margin. To get realy good horsepower out of a set of 2V's, I recommend
bowl porting and installation of a somewhat larger intake valve (4V is too
large for 2V ports, 2.1" seems to be the best). Retain the 1.65" exhaust.
Use valves with neck-down stems, back cut the heads of the valves, and tear
drop the guides. Worked over Aussie 2V's will perform quite well. The
beauty of 4V heads is you can just bolt them on and make big power. A guy
I know just sent me his dyno sheets of a very simple 351C with 0.597" lift
Ultradyne solid lifter cam, Holley Strip Dominator, flat top pistons, and
bone stock quench heads... 500 HP at 6800 RPM.

>Also, if you consider the swap to closed chamber heads be aware that
>depending on your pistons and the chamber volume of both heads you could
>increase your compression as much as 2 points.

True. For pump gas, you want flat top pistons and closed chamber heads.

>You don't need torque in a 2500lb straight shift car you need horse power.

Agreed. My approach is to not worry about the amount of power that a
4V headed motor makes below say 3000 RPM. All that really matters is
that it is tractable down low and then let the RPM build power. In a
drag or road race, your RPM's will be up anyway.

>You asked about the exhaust port plates and would they help? I think they
>will because the exhuast port on a cleveland 2V or 4V is a bad design. The
>exhaust exits the chamber going up into the port and then has to turn down
>to exit the head.

2V exhausts don't need the port plates. They don't turn as far as the 4V
ports (actually they don't have the floor drop away like the 4V does).
2V heads flow nearly as much as 2V (at least at lower lifts) and have higher
average flow velocity (important for scavenging).

>The aftermarket world has figured this out and raised the exhaust ports
>dramaticly to improve exhaust flow.

Just like Ford did way back in the early '80's on the Motorsport high port
heads.

>Just for you information the exhaust ports on 2V & 4V heads are almost
>the same size at there smallest point were they turn 90 degrees in the head.
>The 4V head exhaust port is a little wider but is the sams hieght. (see
>atached photo).

A very good point most people don't realize. The big problem with the 4V
head is the exaggerated area change of the exhaust. The minimum areas of
the 2V and 4V exhaust ports are fairly similar but the 4V exit area is huge,
much of it wasted dead space. There are some tuning tricks that are important
with The narrow lobe center cams that work so well on 4V motors (helps keep
the intake velocity up). An important one is an efficient exhaust (free
flowing mufflers and pipes...otherwise you can have a reversion problem).
For the same reason, I've moved away from recommending dual pattern cams
with lots of extra lift and duration. Given the sort of cams a performance
Cleveland runs, the extra duration just causes reversion problems.

>As for carburetors, any custom carb shop will tell you vacuum secondaries
>are for automatics and mechanical secondaries are for straight shift
>transmissions.

True but if you have a vacuum seconadaries carb and a manual tranny, all
is not lost. Holley makes a quick cahnge spring kit which makes it easy
to tailor the opening point.

>Bottom line is don't be afraid of those 4V heads. They will make horse
>power and lots of it

Yup. If ther ever was a vehicle built for 4V heads, it would be a nice light weight Cobra.

Dan Jones