Too big of a cylinder head...

General engine tech -- Drag Racing to Circle Track

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travis
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Too big of a cylinder head...

Post by travis » Mon Jan 29, 2018 6:02 pm

Hypothetical question...

If you use too “big” of a head on an application (planning for future growth for example), and want/need good part throttle low end and midrange response...how would you cam it? Smaller duration and tighter lsa? Small and wide?

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Re: Too big of a cylinder head...

Post by swampbuggy » Mon Jan 29, 2018 8:19 pm

Calling for Camking, waving i mean. :hello2:

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Re: Too big of a cylinder head...

Post by swampbuggy » Mon Jan 29, 2018 8:30 pm

Camking says---if your port is to big you tighten up the LSA---Lobe Separation Angle= The degrees between the centerline of the intake lobe and the centerline of the exhaust lobe for the same cylinder. Mark :)

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Re: Too big of a cylinder head...

Post by MadBill » Mon Jan 29, 2018 8:40 pm

Yes, we need Mike to weigh in here; when I noodle on it, I come up with needing a wider LSA for a bigger port. :? (ASSuming the valve size and thus low lift flow grows along with the port volume; i.e., a given valve size and seat geometry will flow pretty much the same at low lift whether the port volume is 180 cc. or 220.)
Felix, qui potuit rerum cognscere causas.

Happy is he who can discover the cause of things.

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Re: Too big of a cylinder head...

Post by modok » Mon Jan 29, 2018 8:57 pm

Yeah probably a bit wider lobe center, and don't be conservative with the compression ratio.
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Re: Too big of a cylinder head...

Post by MTENGINES » Mon Jan 29, 2018 9:14 pm

travis wrote:
Mon Jan 29, 2018 6:02 pm
Hypothetical question...

If you use too “big” of a head on an application (planning for future growth for example), and want/need good part throttle low end and midrange response...how would you cam it? Smaller duration and tighter lsa? Small and wide?
With a stall converter. :D

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Re: Too big of a cylinder head...

Post by travis » Mon Jan 29, 2018 9:28 pm

swampbuggy wrote:
Mon Jan 29, 2018 8:30 pm
Camking says---if your port is to big you tighten up the LSA---Lobe Separation Angle= The degrees between the centerline of the intake lobe and the centerline of the exhaust lobe for the same cylinder. Mark :)
I read that in another post...it’s what got me thinking about it because I believe the reference was at WOT in a racing application. I was thinking wider also...but small and tight means more cylinder pressure, so if I think about it long enough it could be either :?

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Re: Too big of a cylinder head...

Post by travis » Mon Jan 29, 2018 9:29 pm

MTENGINES wrote:
Mon Jan 29, 2018 9:14 pm
travis wrote:
Mon Jan 29, 2018 6:02 pm
Hypothetical question...

If you use too “big” of a head on an application (planning for future growth for example), and want/need good part throttle low end and midrange response...how would you cam it? Smaller duration and tighter lsa? Small and wide?
With a stall converter. :D
Well, that is one way I suppose LOL

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Re: Too big of a cylinder head...

Post by turbo2256b » Mon Jan 29, 2018 9:45 pm

restrictive intake essentially what a old 70 boss 302 did

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Re: Too big of a cylinder head...

Post by swampbuggy » Mon Jan 29, 2018 10:38 pm

Yeah, now there is a great example of the O.P. question. So what did Ford give that engine for camshaft spec.'s ?????? Mark :-k

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Re: Too big of a cylinder head...

Post by travis » Mon Jan 29, 2018 11:43 pm

I believe all the performance OEM engines back in the day used wide lsa’s...whether they needed them or not. Off the top of my head, the only things that ever came with a tight lsa was the low-po engines...302’s, 305’s, and 351w’s (even the 290hp 351’s used a tiny 195@.050 cam on a 107.5 lsa)...all with very short durations.

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Re: Too big of a cylinder head...

Post by modok » Tue Jan 30, 2018 2:40 am

Maybe the ports are is too big, but they still made the intake the right size. :P
Sometimes I see that, different parts are designed by different departments or teams ect, and they don't always make full use of teamwork. :lol:
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Re: Too big of a cylinder head...

Post by Orr89rocz » Tue Jan 30, 2018 7:52 am

My thoughts are big port is low air speed. Low air speed is poor cylinder feel at low rpm. Tighter lsa is suppose to bring that up so i would go with a more aggressive valve motion and tighter lsa.

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Re: Too big of a cylinder head...

Post by turbo2256b » Tue Jan 30, 2018 8:56 am

betting fords cam specks for production were based on a lot of dyno time possibly Crane was involved back when Harvey still owned the company

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Re: Too big of a cylinder head...

Post by turbo2256b » Tue Jan 30, 2018 9:00 am

turbo2256b wrote:
Tue Jan 30, 2018 8:56 am
betting fords cam specks for production were based on a lot of dyno time possibly Crane was involved back when Harvey still owned the company
Back in those days from time to time i selected lobe profiles from the computicam section of their catalog starting with proper lifter dia. Still have that old catalog but that section is missing as well as the cover

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