Valve Overlap and reindexed cams

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Valve Overlap and reindexed cams

Postby h-bot » Thu Jan 23, 2003 4:50 am

From: doctorduke_REMOVE_277359_THIS_@yahoo.com

Are you including a set of instructions with the redrilled sprockets?

If the distributor drive spocket is not correspondingly drilled the
initial spark timing will be retarded 8 degrees, so the engine must be
retimed.

Also, unless you make changes to the MAP sensor and ECU idle pot
settings, the engine will not run. In fact, it probably won't even
start to allow you to reset the timing!

I have published this information on this forum.

Duke




[This is message #10378 by user doctorduke on Yahoo! Group Cosworth Vegas: http://groups.yahoo.com/group/cosworthvegas ]
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Valve Overlap and reindexed cams

Postby h-bot » Thu Jan 23, 2003 5:08 am

From: markrock_REMOVE_957792_THIS_@yahoo.com

Duke:

Detailed installation instructions are provided.

Included is an instruction to verify the timing after installation.

Also included is the instruction to adjust the MAP sensor and the ECU
idle pot, with your recommendations provided as "ballparks".

Mark




[This is message #10379 by user markrock on Yahoo! Group Cosworth Vegas: http://groups.yahoo.com/group/cosworthvegas ]
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Valve Overlap and reindexed cams

Postby h-bot » Thu Jan 23, 2003 6:18 am

From: doctorduke_REMOVE_871157_THIS_@yahoo.com

--- In <a href="/group/cosworthvegas/post?protectID=219233066105193209050199029077192253163098100009128121188190230091025019053061151110147">cosworthvegas@yahoogroups.com</a>, longg01 <<a href="/group/cosworthvegas/post?protectID=091233212180056219138097203245129208071">no_reply@y...</a>> wrote:
> Duke, didn't you also mention in your TCT Portfolio that the vacum
> advance distributor will also help bring the revs down quicker?
> Will both the modifications work together?
> ~CHRIS

Yes, I highly recommend the Delco D-1356 vacuum advance also. I think
it's still available from Delco, and it's probably available from
other manufacturers, but I don't have a cross reference. This can
provides 10 degrees at 8", and was used on late seventies Corvette
L-82s and other applications. It can be installed without removing
the distibutor, but it will alter the initial timing, so the engine
must be retimed, and I recommend 15 degrees initial timing. Use the
PAIR diverter valve signal line, which is full manifold vacuum, either
directly if the PAIR is not installed or via a tee if the PAIR is
installed, however, I recommend removing the PAIR and only installing
it for emission testing.

Duke




[This is message #10386 by user doctorduke on Yahoo! Group Cosworth Vegas: http://groups.yahoo.com/group/cosworthvegas ]
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Valve Overlap and reindexed cams

Postby h-bot » Thu Jan 23, 2003 8:19 am

From: doctorduke_REMOVE_439568_THIS_@yahoo.com

--- In <a href="/group/cosworthvegas/post?protectID=219233066105193209050199029077192253163098100009128121188190230091025019053061151110147">cosworthvegas@yahoogroups.com</a>, "Mark A. Rock <<a href="/group/cosworthvegas/post?protectID=029166091163127190025067203043129208071">markrock@c...</a>>"
<<a href="/group/cosworthvegas/post?protectID=029166091163127190025067203043129208071">markrock@c...</a>> wrote:
> Duke:
>
> Detailed installation instructions are provided.
>
> Included is an instruction to verify the timing after installation.
>
> Also included is the instruction to adjust the MAP sensor and the
ECU
> idle pot, with your recommendations provided as "ballparks".
>
> Mark

Very good. Have you tested a set of your redrilled sprockets on a
car?

Duke




[This is message #10381 by user doctorduke on Yahoo! Group Cosworth Vegas: http://groups.yahoo.com/group/cosworthvegas ]
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Valve Overlap and reindexed cams

Postby h-bot » Thu Jan 23, 2003 9:19 am

From: longg01_REMOVE_903216_THIS_@yahoo.com

Duke, didn't you also mention in your TCT Portfolio that the vacum
advance distributor will also help bring the revs down quicker?
Will both the modifications work together?
~CHRIS




[This is message #10382 by user longg01 on Yahoo! Group Cosworth Vegas: http://groups.yahoo.com/group/cosworthvegas ]
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Valve Overlap and reindexed cams

Postby h-bot » Thu Jan 23, 2003 1:14 pm

From: markrock_REMOVE_228553_THIS_@yahoo.com

Duke:

No, I haven't tested a set personally. My Cosworths are "asleep" for
the winter. It is 4 degrees this morning, and we've had a thick
blanket of snow for some time now. Lots of salt on the roads too.
Not Cosworth weather at all.

Roy installed a set of the sprockets on his car and experienced an
improvement in idle quality and throttle response. His exact
quote, "I have 2393 running now with them, very good idle, good low
end response. Has been too long to remember how it ran 2 years ago
when I drove it last."

Hopefully I can avoid this problem by doing some baselining in the
spring and then installing the sprockets and re-testing. I will
measure engine vacuum and idle speed numbers. In addition, I have a
g-tech that will provide some hard performance data. But, as you have
repeatedly said, the performance numbers don't tell the whole story.
The big improvement is in just plain driveability. The engine simply
feels more peppy and responsive, especially at part throttle, without
sacrificing anything at the top end.

Mark




[This is message #10383 by user markrock on Yahoo! Group Cosworth Vegas: http://groups.yahoo.com/group/cosworthvegas ]
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