Need cam ideas for my 318 Duster
I like your guesstimate on the cam numbers. Makes sense. Probably pretty accurate IMO. With RPM, the ramming effect, though low through a dual plane will help the dynamic ratio and I’d bet still use low octane.
Excellent mention on first gear / rear gear ratio for a good take off from a stop number mention.
You cannot use the 050 numbers.
You have to use the advertised numbers.
It says so right on the top line;
"seat to seat or advertised".
(Use seat to seat or advertised specs for Intake spec for best results)
Dynamic Compression Ratio Calculator :)1) ° (Feet)
As for this cam; Hughes fails to publish those numbers, so you have to guess, by looking at other older obsolete grinds.
History shows that Hughes cams are "hi-intensity." or at least higher than some others.
Here's my attempt at converting this to advertised?
238/242/108 ....... This might be;
284/292 gross advertised; it might be a lil less, and lashing might take a few degrees but there is no way for me to guess what it would be, so at this stage, I'm not looking for super-accuracy. I just want to estimate the point when the Intake valve actually closes.
From those numbers, I can guess the overlap to be ~72 degrees. Giving 36* to the intake side I get
180 less {(360+36) less 284} = Ica of ~68* This would be at about Split overlap.
To get 190psi with an Ica of 68*, in a 318+020 @500 ft elevation will require an Scr of 11.9,
If you advance that to in at 66*, as in the example I previously explored, then the Scr becomes 11.7
the swept of this engine is ~665.7cc
To get 11.7;
665.7 ( CD-1)= Combustion chamber so;
665.7/10.7=62.2cc; TOTAL chamber size.
Therefore, to get the head volume;
62.2 less (deck, eyebrows, and gasket)=
62.2- (zero +5 +8.6)= 48.6cc maximum
and yur hoping the 039 FelPro is gonna hold.
Now remember, I guessed at ALL the advertised numbers, so I might be out a bit. This does not change the fact, that it's a very long way from the delivered 63 to the required 48, equals a required loss of 15cc, and then you still have to machine the intake to fit, then portmatch.
>And that was the point I wanted to make.
>And, normally not a problem, is, that dropping the heads drops the headers; which sometimes requires some header "adjustments".
>Also, I guessed at your operating elevation. 500ft either way will change the numbers a little bit. I was not striving for accuracy, Rather, shooting for "awakening". and that has not changed.
Happy HotRodding
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Btw, I have a similar-sized cam, but a hydraulic flat tappet
230/237/110. The advertised is
276/286/110.
Mine has overlap of 61*
Giving 30 to the intake I get an Ica of 66*
My chambers are 63 +8.6 +5 -2.5pop-up= 74.1 Very close to what you will get. BUT, my swept is 752cc, and therefore my Scr is (752+74.1)/74.1= 11.15
If you have; 63 +5 +8.6 +zero deck= 76.6, then your Scr will be (665.7+76.6)/76.7= 9.69
At 9.69 Scr, your CCP might come in at 150psi,
and your bottom end performance is predicted to be less than the stock LA318
Whereas my bottom end is so strong, I have in the past, run it with a starter-gear (manual trans) as low as 8.59, and she would easily have run geared at 65=1600. But as I was sorting this out, I ended at
10.97 Starter and 65=2240, which gave a reasonable hiway economy with a killer take off. This car is a killer-fun street car.
I like your guesstimate on the cam numbers. Makes sense. Probably pretty accurate IMO. With RPM, the ramming effect, though low through a dual plane will help the dynamic ratio and I’d bet still use low octane.
Excellent mention on first gear / rear gear ratio for a good take off from a stop number mention.