Head Question
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New User
Joined: Nov 2011
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From: Southern Maine
Head Question
There's a head for sale on e-bay that I'm considering that has been ported/polished oversize valves etc. It has also been milled 60 thousandths. Seller claims 11 1/4 Compression ratio. using flat top pistons.
So I'm looking for some opinions Right know I'm doing the clifford intake edelbrock 500 with efi manifolds swap. I was not planning on changing my cam or getting too deep into the engine at this time. I currently run 93 octane. What do you guys think about the driveability of a head like this on an otherwise internally stock motor? Am I going to have issues with stock pistons? Could I get a thicker head gasket to lessen the impact of the 60 thousandths mill? Or is it possible to just adjust my timing? Thanks
So I'm looking for some opinions Right know I'm doing the clifford intake edelbrock 500 with efi manifolds swap. I was not planning on changing my cam or getting too deep into the engine at this time. I currently run 93 octane. What do you guys think about the driveability of a head like this on an otherwise internally stock motor? Am I going to have issues with stock pistons? Could I get a thicker head gasket to lessen the impact of the 60 thousandths mill? Or is it possible to just adjust my timing? Thanks
Lead Driver
Joined: Dec 2000
Posts: 6,298
Likes: 47
From: South central, Minnesota
Why do you currently run 93 octane? Has your engine already been modified?
And what year engine do you have? Is it your 80 F100?
Was the head on ebay a 300 head ( carbed or efi? ) or a 240 head?
Unless your engine currently has flat top pistons I don't think you'll have an issue with the compression being too high for 93 octane. But the only way to know for sure is too cc the chambers and do all the calculations.
If you get the head you want to also check the valvetrain geometry. Because of the material removed from the head you may or may not need shorter push rods.
And what year engine do you have? Is it your 80 F100?
Was the head on ebay a 300 head ( carbed or efi? ) or a 240 head?
Unless your engine currently has flat top pistons I don't think you'll have an issue with the compression being too high for 93 octane. But the only way to know for sure is too cc the chambers and do all the calculations.
If you get the head you want to also check the valvetrain geometry. Because of the material removed from the head you may or may not need shorter push rods.
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New User
Joined: Nov 2011
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From: Southern Maine
Why do you currently run 93 octane? Has your engine already been modified? I've been running 93 just because the truck only gets used seasonally and my experience has been that 93 holds up better over the winter months. Engine is stock.
And what year engine do you have? Is it your 80 F100? The engine is the original 300
Was the head on ebay a 300 head ( carbed or efi? ) or a 240 head?
Its a carbed 300 head
Unless your engine currently has flat top pistons I don't think you'll have an issue with the compression being too high for 93 octane. But the only way to know for sure is too cc the chambers and do all the calculations.
If you get the head you want to also check the valvetrain geometry. Because of the material removed from the head you may or may not need shorter push rods.
And what year engine do you have? Is it your 80 F100? The engine is the original 300
Was the head on ebay a 300 head ( carbed or efi? ) or a 240 head?
Its a carbed 300 head
Unless your engine currently has flat top pistons I don't think you'll have an issue with the compression being too high for 93 octane. But the only way to know for sure is too cc the chambers and do all the calculations.
If you get the head you want to also check the valvetrain geometry. Because of the material removed from the head you may or may not need shorter push rods.
Postmaster
Joined: Mar 2005
Posts: 2,949
Likes: 6
From: Earth
Ja, the only way to know for sure is to measure the chambers on the head. There are a lot of variables that determine the cr - compression height and face on the piston, deck height, chamber size - so saying it yields 11.25:1 with flat top pistons is pretty meaningless.
That said, milling a 300 (76cc chamber) head 60/1000ths probably wouldn't make the chambers smaller than a 240 (68cc chamber) head. A 240 head on a 300 short block only increases compression ~.5 point, so you shouldn't have any problems.
That said, milling a 300 (76cc chamber) head 60/1000ths probably wouldn't make the chambers smaller than a 240 (68cc chamber) head. A 240 head on a 300 short block only increases compression ~.5 point, so you shouldn't have any problems.
Lead Driver
Joined: Mar 2008
Posts: 7,188
Likes: 384
From: Near Los Angeles
I agree with everything Fordman said.
I would add: Having gone the route of oversize valves, I would take it apart and check everything b/f running it. I want to know: did the guy use sbc valves or oem Ford length valves. The sbc valves are a bit longer than the ford ones. If he used sbc v's, did he use chevy or ford keepers and retainers? Did he install the needed screw in rocker studs? or does it still have the oem push in ones?
To avoid probs, I want oem length ford valves from SI valves.com, with all the keepers, retainers, screw in rockers, and the proper v.springs set at the proper installed height with the proper psi.
With that head it is designed to help the engine breathe. Your restriction would be the efi manifolds, but it should still run great.
Mine has .020 off the block and the same off the head. I am border line with the cheap gas. Also, with the higher compression you need the $50 head gasket, the hp one, from Felpro.
I would add: Having gone the route of oversize valves, I would take it apart and check everything b/f running it. I want to know: did the guy use sbc valves or oem Ford length valves. The sbc valves are a bit longer than the ford ones. If he used sbc v's, did he use chevy or ford keepers and retainers? Did he install the needed screw in rocker studs? or does it still have the oem push in ones?
To avoid probs, I want oem length ford valves from SI valves.com, with all the keepers, retainers, screw in rockers, and the proper v.springs set at the proper installed height with the proper psi.
With that head it is designed to help the engine breathe. Your restriction would be the efi manifolds, but it should still run great.
Mine has .020 off the block and the same off the head. I am border line with the cheap gas. Also, with the higher compression you need the $50 head gasket, the hp one, from Felpro.
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