Max compression with 268 cam

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deere114
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Max compression with 268 cam

Post #1 by deere114 » Wed Jan 17, 2018 7:15 am

With a 268 degree cam installed straight up, how much compression can be run while still having the head gasket be reliable assuming no detonation? Thinking of e85 as the fuel here. Arp studs and Felpro 1024. I know frenchtownflyer has has experience with high compression and head gasket leaks.

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Re: Max compression with 268 cam

Post #2 by pmuller9 » Wed Jan 17, 2018 9:58 am

The stock cam is also a 268 so any 268 cam including Comp's gets about the same consideration as the stock cam.
Why not use a longer advertised duration cam?

deere114
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Re: Max compression with 268 cam

Post #3 by deere114 » Wed Jan 17, 2018 12:16 pm

Not looking for high rpm power, looking for big torque low end-mid range while matching or coming close to the mpg of a 87 octane pump gas motor. Comp's 219 degrees at .050 is as big as I'm considering, but may end up with something closer to 210@.050. Not sure what e85 likes is far as lsa and overlap are concerned have to do some more research. I want to be conservative on things pertaining to peak cylinder pressure as this will be run on PUMP e85 which we know has varying ethanol content. At the moment I'm thinking something 268 advertised, 10-1 compression, lightly ported efi cylinder head with stock valve sizes.

deere114
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Re: Max compression with 268 cam

Post #4 by deere114 » Wed Jan 17, 2018 12:21 pm

I should add long tube headers and properly sized exhaust system for best scavenging while retaining mufflers will be used. Unsure on intake manifold/carb combo. Offy C seems big. I'm not sure how I really feel about the dp manifold. May mill the stock piece for a 2 barrel of some sorts.

pmuller9
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Re: Max compression with 268 cam

Post #5 by pmuller9 » Wed Jan 17, 2018 12:46 pm

If you want a lot of low end grunt with strong midrange and you are using headers, keep the LSA tight. A 108 LSA is recommended.
Something around a 210* .050" duration will work just fine.
Here is an old cam list.
viewtopic.php?f=2&t=69462&hilit=camshaft#p532392

The Howards 280026-08, .448”/.448”, 209/209, 263/263, 108 deg LSA, looks like a good candidate.

A 10:1 compression ratio should be good with plenty of margin fo pump E85

deere114
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Re: Max compression with 268 cam

Post #6 by deere114 » Wed Jan 17, 2018 2:01 pm

How much is plenty? Is there any room to go up to 10.5 or maybe even 11-1?

pmuller9
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Re: Max compression with 268 cam

Post #7 by pmuller9 » Wed Jan 17, 2018 6:06 pm

Limit the DCR for E85 in a 300 six to 9:1
That would allow up to a 10.5 static compression ratio with the Howard cam.

deere114
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Re: Max compression with 268 cam

Post #8 by deere114 » Thu Jan 18, 2018 11:22 am

Think the head gasket will remain reliable at this level? 100,000+ miles?

pmuller9
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Re: Max compression with 268 cam

Post #9 by pmuller9 » Fri Jan 19, 2018 7:11 pm

With studs it should be OK. The turbo group seems to be doing ok with the Felpro 1024.
There isn't any other choice unless you want to have a MLS gasket made for high dollar.

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Re: Max compression with 268 cam

Post #10 by Fordman75 » Fri Jan 19, 2018 9:05 pm

pmuller9 wrote:With studs it should be OK. The turbo group seems to be doing ok with the Felpro 1024.
There isn't any other choice unless you want to have a MLS gasket made for high dollar.


What about adding larger studs. That would help the 1024 survive better too, wouldn't it?
Ted

54 Ford F100/F150 4x4
300, NP435 4spd, NP205 transfercase

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THE FRENCHTOWN FLYER
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Re: Max compression with 268 cam

Post #11 by THE FRENCHTOWN FLYER » Fri Jan 19, 2018 9:12 pm

Fordman75 wrote:
pmuller9 wrote:With studs it should be OK. The turbo group seems to be doing ok with the Felpro 1024.
There isn't any other choice unless you want to have a MLS gasket made for high dollar.


What about adding larger studs. That would help the 1024 survive better too, wouldn't it?

Yes
Converting to 1/2 inch studs is a common trick. But I would hone the block with a block plate in conjunction with their use.
FORD 300 INLINE SIX - THE BEST KEPT SECRET IN DRAG RACING

deere114
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Re: Max compression with 268 cam

Post #12 by deere114 » Sat Jan 20, 2018 11:11 am

Starting to sound like this much compression is pushing it for a street motor.

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Re: Max compression with 268 cam

Post #13 by pmuller9 » Sat Jan 20, 2018 11:52 am

deere114 wrote:Starting to sound like this much compression is pushing it for a street motor.

No, not at all!

Like I said, you will have less cylinder pressure than the turbocharger group and they are not having head gasket problems with 7/16 head studs.
You will need to have the head and block deck surfaced to ensure a flat clamping surface for the head gasket.

A high compression E85 engine will give you a lot of low end torque along with a wide power band.
The Howards cam I recommended will give you a very strong mid range to work with along with low end torque.
You will like the whole combination!

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