For valve clearance, they will be fine.  If the compression is 10-10.5:1, you'll probably need to get that lower to run on pump gas.  Ask John what he recommends for the 270 cam and mill the domes or get larger chamber heads to reach that ratio.



Lawrenceville, GA

Charlie, 

FYI I am running the Y-284-S cam from Mummert and even with a stick it does not like to idle below 1000 rpm. Also I am running 10 to 1 compression on my stock G heads (dome Mummert / Probe pistons) and I am able to run on the 91 octane that is sold around here. 

I love the smell of burning rubber in the morning!

On the cam selection:  Mummert's site says the 270-S is o.k. with a Fordomatic, It's a 108 LSA cam, & he suggests headers. However, pre made in chassis headers for those Fords are not readily available.  So, for a daily driver with exhaust manifolds, he says the 265-S works well with the Fordomatic. It has a 110 LSA, so will likely idle a bit better. Either cam should not need the valve guides to be trimmed.  It's your choice..
Note; Mummert's chart shows the 265S cam right below the stock early ( & later than 1957 cam), which from a performance point is is a bit misleading. However, as he notes down below, he does not handle the stock 1957 cam, which had more duration and lift than the listed regular cam. I presume this is because the Clay Smith company does not make that grind. The only place that does that I know of is Oregon Cams of Vancouver Washington.  


Paul

Rob, You can usually get away with more static compression with a bigger cam because the dynamic compression tends to be lower, everything else the same.  Your same ratio with a smaller cam might be too much.



Lawrenceville, GA

I'll second CHR on the 284, it's what's in the F code motor in my roadster.

I did a cam change last spring, and here's an articles members here sent me . Further in it gets to load centers and valve sizes.

http://www.hotrod.com/how-to/engine/0607phr-camshaft-basics

Here's a dynamic calculator. I think it's different from what Ted uses, but the results where close.

https://www.uempistons.com/index.php?main_page=calculators&type=comp2&zenid=8e9027fc60bbc5227c417444b739f709


miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

Check out Bullet Cams in Mississippi. They list hundreds of grinds. They be grinding the new roller cam for my GMC 6 Howard 12 port head engine. Good luck..

56 Vic, B'Ville 200 MPH Club Member, So Cal.

Miker:  INTERESTING link to the July '06  PHR article by David Vizard and Johnny Hunkins.  A VERY comprehensive article regarding camshaft selection and related valve train components.  I was surprised that dynamic compression ratio was not dealt with in greater depth.  Maybe I need to read the article again. 

The link to United Engine & Machine's 'Effective Compression Pressure Ratio Calculator' is interesting, too.  It's different from what I've seen referenced in other threads here on the Forum.  Below is the link to the Wallace Racing calculator.

http://www.wallaceracing.com/dynamic-cr.php

THANKS for the links, Miker!


NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York

It's interesting in the hotrod article where the rockers are discussed that the exhaust can benefit from .1:1 less lift than the inlet?
Has anyone experienced this or have any thoughts regarding? Being we have that variation with our std rockers 1.43:1 and 1.54:1.

And I like the lobe separation chart too, cubes to overlap.
It brings my 296 to an ideal 108-109 LSA

So this is how I understand compression. Compression dictates the operating speed of the engine amongst other things, and the faster the engine operates the less each individual cycle may induce making it a smaller combustion event, yet more frequently occurring. And this creates a higher HP (HP=the amount of work done in time). And alternatively the slower the engine operates a greater volume can be induced (yet less frequent) requiring a larger combustion chamber( lower compression) to achieve a correct combustion event.

CK.  Backing up just a little bit to the chart Vizard suggests for tie-ing the relationship of camshaft LCA to engine displacement...

I was also taken with Vizard's information pertaining to the relationship of valve size to engine displacement in considering the valve timing overlap interval for a given displacement.

The more I THINK I 'understand', the more complicated selecting a camshaft seems to become.  And even IF the engine build for your purpose (intended use) IS correct, you've got to have the gearing (transmission and rear end) coupled with tire size to complement the vehicle's weight.

FUN!    


NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York

those are 57 G heads the casting number tells all.73G built1957 march 6.