[DeTomaso] Roller Cam

Daniel C Jones daniel.c.jones2 at gmail.com
Sun Mar 3 21:04:28 EST 2013


Also the pushrods will need to be shorter to compensate for the taller lifters.

Dan

On Sun, Mar 3, 2013 at 8:01 PM, Daniel C Jones
<daniel.c.jones2 at gmail.com> wrote:
>> 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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