[DeTomaso] Roller Cam

Daniel C Jones daniel.c.jones2 at gmail.com
Sun Mar 3 21:01:56 EST 2013


> I have roller rockers in Aussie 2V heads and am interested in upgrading
> to a roller cam. Do some require machining of the block and others not?

The ones that use reduced base circle cams and the Ford 5.0L style
spider and dog bones arrangement requires the block be drilled and
tapped to hold the spider in place.  The ones that use link bar lifters
do not require any machining if the correct link bar lifters are used.
Some link bar lifters may not work with standard base circle cams and
may require block clearancing with reduced base circle cams.

> Does the car need retuning after the conversion?

No more so than any other cam change.

> Will roller rockers change the specs for the cam or should I keep the
> same specs of what's in there now?

You can run what you have now but the ratio should be kept in mind when
the cam specs are chosen.  With most heads, we've seen gains by running
a shorter rocker ratio on the exhaust side but you can do the same thing
with a custom cam by selecting the right exhaust lobe.

> Is there anything else I should do at the same time?

Valve springs will need to change and most roller cam cores will need
a different distributor gear material.  If your timing chain is loose,
replace it with a good double roller timing chain (note there are many
bad chains on the market)

> I can send you my cam specs if you like.

A cam that works great in a 408 with different heads may not work the
same way in a 351C with Aussie 2V heads.  Cam specs need to be tailored
to the individual engine and application.

> I put Crane-style hydraulics (made by Gaterman and well-priced)

Gaterman makes a clone of the Crane link bar that costs about half as much.
There's also a Chinese made clone that looks identical to the Crane but
failed on the spring tester at around 400 lbs, just the sort of spring
pressure you need to control a hydraulic roller in a 351C.  Morel also makes
a less expensive street performance lifter and a more expensive limited travel
race hydraulic roller lifter.  Note the Morel's are sold under other brand's
labels.

> I did need a lot of improvement in the exhaust system (2 1/2" minimum
> path) to get it right though.

Exhaust system efficiency is one important parameter to keep in mind when
doing a custom cam for a Pantera.

> I'd start by calling as many name brand cam grinder Tech Lines as I
> could find.

I've had quite poor luck with the guys who answer the phones at most
cam companies.  You can call the same cam company several times and ask
a basic question and get completely different answers.

The main issues to understand when running a hydraulic roller cam in a 351C
are:

 cam material - selectively austempered ductile iron versus steel
 distributor gear material - needs to be compatible with the cam material
 distributor gear ID - needs to fit you distributor
 cam base circle diameter - needs to be compatible with lifter oil band
 location and block lifter bore chamfer
 lifter style - link bar versus dog bone and spider retention

Then you need to pick the right cam specs (lobe separation angle, duration,
lift), lobe design and valve springs for the specific application.  There
are some reasonable cost options now but there are also ones that look
identical that can ruin your engine.

Dan Jones



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