[DeTomaso] Overheating problem
Daniel C Jones
daniel.c.jones2 at gmail.com
Mon Jul 15 17:32:01 EDT 2024
> SVO heads are far more efficient and probably need no more than 28-32
degrees total advance (not including vacuum advance)
As cast, the SVO high port family (A3, B351, C3/C302/C302B) have exactly
the same combustion chamber shape as closed chamber iron 4V heads. They
are aluminum so can tolerate a bit more advance but may not benefit from
it. The bigger effect I see is with stroker engines. An iron 4V headed
351C may make best power on 34 to 36 degrees total timing. At 408 cubic
inches, with the same heads, that may drop to 28 to 30 degrees. Smaller
port heads with the latest combustion chamber shapes don't seem to be as
strongly affected by displacement. The 351C dyno mule made the best power
with iron 4V heads at 36 degrees. With the TFS 195cc 2V heads, it made
best power at 28 degrees. On a 408C, the TFS were best at 26 degrees.
With stock displacement, iron open chamber 4V heads need a bunch more
timing (40+ degrees) and respond well to multi-strike ignitions. I've
never tested them on a 408C stroker but I'd expect them to need less
timing. With iron 4V heads, I think it's a case of overly large ports and
valves that become more efficient with more displacement.
Dan Jones
On Mon, Jul 15, 2024 at 3:33 PM Mike Drew via DeTomaso <
detomaso at server.detomasolist.com> wrote:
> Larry,
>
> SVO heads are far more efficient and probably need no more than 28-32
> degrees total advance (not including vacuum advance).
>
> At least that’s what I’ve been told by people who actually know this
> stuff. I don’t pretend to myself, I just remember what I’ve been taught.
>
> And admit I could be wrong…but I don’t think I am!
>
> Mike
>
> Sent from my iPhone
>
> > On Jul 15, 2024, at 14:41, Larry Stock <larrys at panteraparts.com> wrote:
> >
> > You should have 36 degrees overall at over 3000 RPM, you should have 20
> degrees centrifugal advance, 16 degrees initial, with an additional 10
> degrees Vacuum advance at cruise. The MSD units need a tach amplifier
> adaptor for more accurate tach readings.
> > Larry Stock
> >
> > On 7/15/24, 11:38 AM, "DeTomaso on behalf of George Sekula" <
> detomaso-bounces at server.detomasolist.com <mailto:
> detomaso-bounces at server.detomasolist.com> on behalf of
> georgesekula at outlook.com <mailto:georgesekula at outlook.com>> wrote:
> >
> >
> > I was worried about the timing curve. I replaced the entire ignition
> > system over last winter. I installed the new MSD Ultra 6AL Plus and
> > pinned the weights in the crab cap distributor. I knew I would never
> > change springs and weights and I am spoiled by how easy it is to tune
> > my kid's Hondas. I tried to match the old distributor setup to start.
> > But I am not sure how close I am to having the correct timing curve for
> > a Cleveland with SVO heads. I have 14 at idle, 19 at 2000 rpm, and 22
> > at 2400 rpm (these are the rpm's at highway speed), and very little
> > vacuum advance. I am not happy about having to remove the head, but at
> > least I now understand the problem.
> > __________________________________________________________________
> >
> >
> > From: John Neal <jrnealjr at aol.com <mailto:jrnealjr at aol.com>>
> > Sent: Monday, July 15, 2024 1:47 PM
> > To: georgesekula at outlook.com <mailto:georgesekula at outlook.com> <
> georgesekula at outlook.com <mailto:georgesekula at outlook.com>>;
> > mikeldrew at aol.com <mailto:mikeldrew at aol.com> <mikeldrew at aol.com <mailto:
> mikeldrew at aol.com>>
> > Cc: detomaso at server.detomasolist.com <mailto:
> detomaso at server.detomasolist.com> <detomaso at server.detomasolist.com
> <mailto:detomaso at server.detomasolist.com>>
> > Subject: Re: [DeTomaso] Overheating problem
> >
> >
> > Retarded Timing can cause overheating and dieseling when the engine is
> > turned off.
> >
> >
> >
> >
> >
> >
> > I adjusted mine so the engine is hard to turn over when hot and then
> > backed the timing off until the engine cranks freely when hot.
> >
> >
> >
> >
> >
> >
> > Way less work then pulling the seats and bulkhead to connect a timing
> > light.
> >
> >
> > In a message dated 7/15/2024 11:57:44 AM Central Standard Time,
> > georgesekula at outlook.com <mailto:georgesekula at outlook.com> writes:
> >
> >
> >
> >
> >
> >
> > Thank you all for your help. Dozens of attempts, three times I could
> > idle for 30 minutes without an excursion, then 10 minutes on the
> > highway and the temperature climbs. Drained oil and found no
> > contamination. No smoke out the tailpipe. No little air bubble,
> > just
> > volcano like eruptions. Did a combustion-gas-in-coolant test four
> > times with no combustion gas detected. When I did a cylinder leak
> > down
> > test on cylinder 3, pointer was in the red and coolant was
> > overflowing
> > the pressure tank. I have some work to do, hoping it is just the
> > head
> > gasket.
> > __________________________________________________________________
> > _______________________________________________
> >
> >
> >
> >
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>
>
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-------------- next part --------------
> SVO heads are far more efficient and probably need no more than 28-32
degrees total advance (not including vacuum advance)
As cast, the SVO high port family (A3, B351, C3/C302/C302B) have
exactly the same combustion chamber shape as closed chamber iron 4V
heads.A They are aluminum so can tolerate a bit more advance but may
not benefit from it.A The bigger effect I see is with stroker
engines.A An iron 4V headed 351C may make best power on 34 to 36
degrees total timing.A At 408 cubic inches, with the same heads, that
may drop to 28 to 30 degrees.A Smaller port heads with the latest
combustion chamber shapes don't seem to be as strongly affected by
displacement.A The 351C dyno mule made the best power with iron 4V
heads at 36 degrees.A With the TFS 195cc 2V heads, it made best power
at 28 degrees.A On a 408C, the TFS were best at 26 degrees.A With
stock displacement, iron open chamber 4V heads need a bunch more timing
(40+ degrees) and respond well to multi-strike ignitions.A I've never
tested them on a 408C stroker but I'd expect them to need less
timing.A With iron 4V heads, I think it's a case of overly large ports
and valves that become more efficient with more displacement.
Dan Jones
On Mon, Jul 15, 2024 at 3:33a-PM Mike Drew via DeTomaso
<[1]detomaso at server.detomasolist.com> wrote:
Larry,
SVO heads are far more efficient and probably need no more than
28-32 degrees total advance (not including vacuum advance).
At least thatas what Iave been told by people who actually know this
stuff. I donat pretend to myself, I just remember what Iave been
taught.
And admit I could be wronga|but I donat think I am!
Mike
Sent from my iPhone
> On Jul 15, 2024, at 14:41, Larry Stock
<[2]larrys at panteraparts.com> wrote:
>
> i>>?You should have 36 degrees overall at over 3000 RPM, you
should have 20 degrees centrifugal advance, 16 degrees initial, with
an additional 10 degrees Vacuum advance at cruise. The MSD units
need a tach amplifier adaptor for more accurate tach readings.
> Larry Stock
>
> i>>?On 7/15/24, 11:38 AM, "DeTomaso on behalf of George Sekula"
<[3]detomaso-bounces at server.detomasolist.com
<mailto:[4]detomaso-bounces at server.detomasolist.com> on behalf of
[5]georgesekula at outlook.com <mailto:[6]georgesekula at outlook.com>>
wrote:
>
>
> I was worried about the timing curve. I replaced the entire
ignition
> system over last winter. I installed the new MSD Ultra 6AL Plus
and
> pinned the weights in the crab cap distributor. I knew I would
never
> change springs and weights and I am spoiled by how easy it is to
tune
> my kid's Hondas. I tried to match the old distributor setup to
start.
> But I am not sure how close I am to having the correct timing
curve for
> a Cleveland with SVO heads. I have 14 at idle, 19 at 2000 rpm, and
22
> at 2400 rpm (these are the rpm's at highway speed), and very
little
> vacuum advance. I am not happy about having to remove the head,
but at
> least I now understand the problem.
> __________________________________________________________________
>
>
> From: John Neal <[7]jrnealjr at aol.com <mailto:[8]jrnealjr at aol.com>>
> Sent: Monday, July 15, 2024 1:47 PM
> To: [9]georgesekula at outlook.com
<mailto:[10]georgesekula at outlook.com> <[11]georgesekula at outlook.com
<mailto:[12]georgesekula at outlook.com>>;
> [13]mikeldrew at aol.com <mailto:[14]mikeldrew at aol.com>
<[15]mikeldrew at aol.com <mailto:[16]mikeldrew at aol.com>>
> Cc: [17]detomaso at server.detomasolist.com
<mailto:[18]detomaso at server.detomasolist.com>
<[19]detomaso at server.detomasolist.com
<mailto:[20]detomaso at server.detomasolist.com>>
> Subject: Re: [DeTomaso] Overheating problem
>
>
> Retarded Timing can cause overheating and dieseling when the
engine is
> turned off.
>
>
>
>
>
>
> I adjusted mine so the engine is hard to turn over when hot and
then
> backed the timing off until the engine cranks freely when hot.
>
>
>
>
>
>
> Way less work then pulling the seats and bulkhead to connect a
timing
> light.
>
>
> In a message dated 7/15/2024 11:57:44 AM Central Standard Time,
> [21]georgesekula at outlook.com <mailto:[22]georgesekula at outlook.com>
writes:
>
>
>
>
>
>
> Thank you all for your help. Dozens of attempts, three times I
could
> idle for 30 minutes without an excursion, then 10 minutes on the
> highway and the temperature climbs. Drained oil and found no
> contamination. No smoke out the tailpipe. No little air bubble,
> just
> volcano like eruptions. Did a combustion-gas-in-coolant test four
> times with no combustion gas detected. When I did a cylinder leak
> down
> test on cylinder 3, pointer was in the red and coolant was
> overflowing
> the pressure tank. I have some work to do, hoping it is just the
> head
> gasket.
> __________________________________________________________________
> _______________________________________________
>
>
>
>
> Detomaso Email List is not managed by POCA
> Posted emails must not exceed 1.5 Megabytes
> DeTomaso mailing list
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>
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> Members who post to this list grant license to the list to forward
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>
>
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