Oversized valves?
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Oversized valves?
I'm going to be rebuilding my 300 I6, (after my book gets here) and am wondering if anyone has tried putting oversized valves in one of these motors...
How much room is there? What would be a good size to go with? Any guesses as to how much it'd cost to have the machine work done?
How much room is there? What would be a good size to go with? Any guesses as to how much it'd cost to have the machine work done?
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Joined: Aug 2010
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I have the SI valves, their 1.94, 1.60 and they are a direct replacement unlike the sbc valves that people install which are longer and require some pushrod changes. I sent a brand new enginequest head to a guy, Mikes Porting Service, and he cut for the larger valves, deshrouded and polished the chambers, did all the port, bowl and short side radius work and shaved .060 off for $650. Im very happy with his work, my wot afr went from 13.5 to 16.5. Also running a cam and header, the ported head made a huge difference, I cant say how much of it was from the valves though.
Lead Driver
Joined: Mar 2008
Posts: 7,172
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From: Near Los Angeles
The wise thing to do is to get the cam kit, with springs, lifters, keepers, etc. Use all metal t. gears. Replace the oem push-in rocker studs with screw in. If you replace with ARP 3/8" to 7/16", then you can buy a used set of roller rocker on ebay for a bbc, and they will bolt right in, giving you more valve lift. With the bbc r.rockers, you go from 1.6 to 1.73 ratio. Comp Cams, Crane, and Harland Sharp make the 1.6 for your engine.
Use the EFI year pistons with the higher compression ratio.
Use ONLY S.I. valves.
Use the EFI year pistons with the higher compression ratio.
Use ONLY S.I. valves.
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Why only SI valves?
As for kits, I was looking at just getting the rebuild kit from clifford, comes with a cam and everything... looking around here though, that's probably a little overpriced.
So... more lift > bigger valves, or would both be best?
As for kits, I was looking at just getting the rebuild kit from clifford, comes with a cam and everything... looking around here though, that's probably a little overpriced.
So... more lift > bigger valves, or would both be best?
Lead Driver
Joined: Mar 2008
Posts: 7,172
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From: Near Los Angeles
SI valves is the name of a company. The over size valves they have for the 240/300 are made for the ford engine. Some guys, like me, put in the sbc valves, which are .095" longer, and so start a process of trying to compensate with p.rod, etc.
Do your research. Steer clear of Clifford. Search on this forum.
Do your research. Steer clear of Clifford. Search on this forum.
Elder User
Joined: Nov 2005
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SI valves is the name of a company. The over size valves they have for the 240/300 are made for the ford engine. Some guys, like me, put in the sbc valves, which are .095" longer, and so start a process of trying to compensate with p.rod, etc.
Do your research. Steer clear of Clifford. Search on this forum.
Do your research. Steer clear of Clifford. Search on this forum.
The longer valves are useful if you're going with a camshaft with enough lift that you'd run into coil bind, but I seriously doubt thats a problem for most.
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Lead Driver
Joined: Mar 2008
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From: Near Los Angeles
[quote=NavyMIDN08;9657667]If you go with the longer valves then you end up needing different valve springs, pushrods, etc.
That is not quite true. You don't need different springs. And by that I mean you are using the springs that came with the Cam Kit. Springs are installed, and the seat pressure measured. I still run my .095" longer valves. Also, if you are going to use the oem rockers, then you can still use your oem pushrods. The valve train geometry of the 300 is very forgiving. It is only when/if you switch to roller rockers that the p.rod length needs to be addressed. Having said all that, it is still far better to use the SI valves made for you engine.
Have your machinist do a 30 degree back cut on your intakes, port match your runners to the intake, clean and polish your bowls and chambers, and exhaust runners, run a header or EFI into duals, use a 4v vacuum carb, get the dizzy re-curved, with the GM 4 pin ignition with a TFI coil and MSM or Summit or DuraSpark 11 box. Do those things and you'll have a little monster. Side gap your plugs and you'll pick up another 'holy crap' boost. Gap plugs at .050 --.058.
Use the EFI years hypereutectic pistons with good rings, and have the block milled .020 and the head .020. That will put you in the low 9's with c.r., and you'll still be able to use the cheap gas.
Magnaflux head AND BLOCK. Some guys bore the block .060 over and install 360 pistons. If you do that, it raises the c.r. to high 9's and puts you on mid grade gas.
I found these rockers at a swap meet for $100.
<a href="http://s659.photobucket.com/albums/uu316/bobbyrogue/?action=view&current=P1010334.jpg" target="_blank"><img src="http://i659.photobucket.com/albums/uu316/bobbyrogue/P1010334.jpg" border="0" alt="Photobucket"></a>
The next photo below you can see the difference between the 300 and 360 pistons.
<a href="http://s659.photobucket.com/albums/uu316/bobbyrogue/?action=view&current=dishvsvrelief.jpg" target="_blank"><img src="http://i659.photobucket.com/albums/uu316/bobbyrogue/dishvsvrelief.jpg" border="0" alt="Photobucket"></a>
IMHO the pre 84 heads are easier to work on.
That is not quite true. You don't need different springs. And by that I mean you are using the springs that came with the Cam Kit. Springs are installed, and the seat pressure measured. I still run my .095" longer valves. Also, if you are going to use the oem rockers, then you can still use your oem pushrods. The valve train geometry of the 300 is very forgiving. It is only when/if you switch to roller rockers that the p.rod length needs to be addressed. Having said all that, it is still far better to use the SI valves made for you engine.
Have your machinist do a 30 degree back cut on your intakes, port match your runners to the intake, clean and polish your bowls and chambers, and exhaust runners, run a header or EFI into duals, use a 4v vacuum carb, get the dizzy re-curved, with the GM 4 pin ignition with a TFI coil and MSM or Summit or DuraSpark 11 box. Do those things and you'll have a little monster. Side gap your plugs and you'll pick up another 'holy crap' boost. Gap plugs at .050 --.058.
Use the EFI years hypereutectic pistons with good rings, and have the block milled .020 and the head .020. That will put you in the low 9's with c.r., and you'll still be able to use the cheap gas.
Magnaflux head AND BLOCK. Some guys bore the block .060 over and install 360 pistons. If you do that, it raises the c.r. to high 9's and puts you on mid grade gas.
I found these rockers at a swap meet for $100.
<a href="http://s659.photobucket.com/albums/uu316/bobbyrogue/?action=view&current=P1010334.jpg" target="_blank"><img src="http://i659.photobucket.com/albums/uu316/bobbyrogue/P1010334.jpg" border="0" alt="Photobucket"></a>
The next photo below you can see the difference between the 300 and 360 pistons.
<a href="http://s659.photobucket.com/albums/uu316/bobbyrogue/?action=view&current=dishvsvrelief.jpg" target="_blank"><img src="http://i659.photobucket.com/albums/uu316/bobbyrogue/dishvsvrelief.jpg" border="0" alt="Photobucket"></a>
IMHO the pre 84 heads are easier to work on.
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Wow... Thats a beautiful list... add to that a tranny and t-case rebuild, and dual sticks on the t-case and thats pretty much what I'm planning to do...
My one question about intake manifolds.... does the offy have provision for heating, is this something you have to rig up, or can it safely be ignored?
Also, what exactly is a 30 degree back cut on the intake?
My one question about intake manifolds.... does the offy have provision for heating, is this something you have to rig up, or can it safely be ignored?
Also, what exactly is a 30 degree back cut on the intake?
Lead Driver
Joined: Mar 2008
Posts: 7,172
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From: Near Los Angeles
<a href="http://s659.photobucket.com/albums/uu316/bobbyrogue/?action=view&current=P1010245.jpg" target="_blank"><img src="http://i659.photobucket.com/albums/uu316/bobbyrogue/P1010245.jpg" border="0" alt="long hose fittings to clear headers"></a>
If I were you, I'd weld all the joints to prevent leaks. Also, I wish I had make both pipes long. The length helps clear the exhaust, and makes it a lot easier to put on the hoses. Weld a bead around the end of each pipe too for the hoses.
If I were you, I'd weld all the joints to prevent leaks. Also, I wish I had make both pipes long. The length helps clear the exhaust, and makes it a lot easier to put on the hoses. Weld a bead around the end of each pipe too for the hoses.
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Ah, that looks like it'd work nicely.
Last question (for now)
Which bolts would you suggest using to pick one of these engines? head and manifold, or head and head? I've never pulled anything bigger than a 20r previously, and we just wrapped a come-along around that and strung it to a rafter.... dont think that method will work with a 300...
Last question (for now)
Which bolts would you suggest using to pick one of these engines? head and manifold, or head and head? I've never pulled anything bigger than a 20r previously, and we just wrapped a come-along around that and strung it to a rafter.... dont think that method will work with a 300...
Lead Driver
Joined: Mar 2008
Posts: 7,172
Likes: 376
From: Near Los Angeles
Ah, that looks like it'd work nicely.
Last question (for now)
Which bolts would you suggest using to pick one of these engines? head and manifold, or head and head? I've never pulled anything bigger than a 20r previously, and we just wrapped a come-along around that and strung it to a rafter.... dont think that method will work with a 300...
Last question (for now)
Which bolts would you suggest using to pick one of these engines? head and manifold, or head and head? I've never pulled anything bigger than a 20r previously, and we just wrapped a come-along around that and strung it to a rafter.... dont think that method will work with a 300...