I have been using a 240 head and a comp cam 252. A recent gear change from 3.25 to 3.70 (trutrac) made me wonder if the 268 cam would give me a higher comfortable rpm to spin those gears. Soooo...
I thought let’s freshen that 240 (valve guides and stuff)
And drive a fresh 300 head I’m working up with adjustable studs while the 240 head sits at the machine shop.
Questions:
Will the 300 head be better for the 268 anyway since
My local gas is 91-93 tops in octane?
Is it possible the 240 could work with detonation controlled by jetting and ignition curve changes?
Any input on experiences concerning the comp 268
Straight up versus the 4 degree advance slot?
(Holley 390 on Clifford with fuel injected exhaust manifolds, TOD 4 speed)
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Cam swap and head swap
Moderator: Mod Squad
Cam swap and head swap
Blessings,
Dr Jay
1978 F100 Shortie, Lowered front and rear, 300 .030 over, 300 carb head, Clifford, Holley 390
268 Comp Cam, Cloyes, Fuel Inj. exhaust manifolds, MSD 6A, TOD, 9"
Dr Jay
1978 F100 Shortie, Lowered front and rear, 300 .030 over, 300 carb head, Clifford, Holley 390
268 Comp Cam, Cloyes, Fuel Inj. exhaust manifolds, MSD 6A, TOD, 9"
Re: Cam swap and head swap
Happy New Year!!
You people are the best.
You people are the best.
Blessings,
Dr Jay
1978 F100 Shortie, Lowered front and rear, 300 .030 over, 300 carb head, Clifford, Holley 390
268 Comp Cam, Cloyes, Fuel Inj. exhaust manifolds, MSD 6A, TOD, 9"
Dr Jay
1978 F100 Shortie, Lowered front and rear, 300 .030 over, 300 carb head, Clifford, Holley 390
268 Comp Cam, Cloyes, Fuel Inj. exhaust manifolds, MSD 6A, TOD, 9"
Re: Cam swap and head swap
Happy New Year!
If the 240 head was working OK with the 252 cam it certainly will not have detonation problems with the 268 cam.
What is the compression ratio with the 240 head?
If the 240 head was working OK with the 252 cam it certainly will not have detonation problems with the 268 cam.
What is the compression ratio with the 240 head?
Re: Cam swap and head swap
Valid question, no answer...
Stock round depression 300 hypers with a parts house gasket. .030” overbore.
I really struggled with the 240 head concerning ignition curve. Runs great now.
I’m encouraged you think dynamic compression will drop with the swap.
As a side comment cores for 300 carb head not as common as they were and 240 heads, worse.
Thank you for your help.
Stock round depression 300 hypers with a parts house gasket. .030” overbore.
I really struggled with the 240 head concerning ignition curve. Runs great now.
I’m encouraged you think dynamic compression will drop with the swap.
As a side comment cores for 300 carb head not as common as they were and 240 heads, worse.
Thank you for your help.
Blessings,
Dr Jay
1978 F100 Shortie, Lowered front and rear, 300 .030 over, 300 carb head, Clifford, Holley 390
268 Comp Cam, Cloyes, Fuel Inj. exhaust manifolds, MSD 6A, TOD, 9"
Dr Jay
1978 F100 Shortie, Lowered front and rear, 300 .030 over, 300 carb head, Clifford, Holley 390
268 Comp Cam, Cloyes, Fuel Inj. exhaust manifolds, MSD 6A, TOD, 9"
Re: Cam swap and head swap
The 268 cam should slightly lower your dynamic compression ratio. So like pmuller9 said running the 240 head should be no problem. If it worked with the 252 they 268 will only make it better. 
These engines are getting old, so parts are getting slightly harder to find. There is a reason I've got a shelving unit with like 8 240 heads and 3 or 4 300 heads. When I find cheap 240's or 300's for sale I try to buy them.
These engines are getting old, so parts are getting slightly harder to find. There is a reason I've got a shelving unit with like 8 240 heads and 3 or 4 300 heads.
When I find cheap 240's or 300's for sale I try to buy them.Re: Cam swap and head swap
I was 2 deep in 300 carb heads. Dropped them off at Wheelers in Cullman Alabama. 1 week later they called.
Both cracked.
Back out we go... 3rd one good!!
Sooooo I’m getting ahead on freshened heads!!
Excited about cam upgrade.
Thanks guys!
Both cracked.
Back out we go... 3rd one good!!
Sooooo I’m getting ahead on freshened heads!!
Excited about cam upgrade.
Thanks guys!
Blessings,
Dr Jay
1978 F100 Shortie, Lowered front and rear, 300 .030 over, 300 carb head, Clifford, Holley 390
268 Comp Cam, Cloyes, Fuel Inj. exhaust manifolds, MSD 6A, TOD, 9"
Dr Jay
1978 F100 Shortie, Lowered front and rear, 300 .030 over, 300 carb head, Clifford, Holley 390
268 Comp Cam, Cloyes, Fuel Inj. exhaust manifolds, MSD 6A, TOD, 9"
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