Milling Heads
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From: Clymer PA
Milling Heads
Hello again everybody!
College life is rough and I don't have the money right now to do the Camaro up the way I want to so I have decided to run the 'Vette with the big block for another year. I do however want to change my camshaft. I have always been upset with myself for picking the smaller 294S cam. The planned cam will be something like this:
Duration @ .050": 264/264
Gross Valve Lift: .630"/.630"
LSA: 110
Solid Flat Tappet
Now currently my compression ratio is around 10-10.2:1. I plan on pulling my heads and cc'ing them myself. Would it be possible to have them milled down enough to get me up to at least 11:1....without running into piston to valve clearance problems? I'm also running a deck height of about .020" and a steel shim head gasket of about .020".
Thanks.
College life is rough and I don't have the money right now to do the Camaro up the way I want to so I have decided to run the 'Vette with the big block for another year. I do however want to change my camshaft. I have always been upset with myself for picking the smaller 294S cam. The planned cam will be something like this:
Duration @ .050": 264/264
Gross Valve Lift: .630"/.630"
LSA: 110
Solid Flat Tappet
Now currently my compression ratio is around 10-10.2:1. I plan on pulling my heads and cc'ing them myself. Would it be possible to have them milled down enough to get me up to at least 11:1....without running into piston to valve clearance problems? I'm also running a deck height of about .020" and a steel shim head gasket of about .020".
Thanks.
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From: Sierra Foothills CA
Re: Milling Heads (bence13_33)
I doubt that anyone can give you a guarantee that you'll have enough valve/piston clearance since there are too many variables involved. You may be able to get in the ballpark if you know deck height, etc. but when it comes to clearances I wouldn't settle for ballpark. The only way to be sure is to bolt a head on w/ the cam installed & measure w/ the old clay method with the head gasket you intend to use.
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From: Just because I'm paranoid doesn't mean people aren't out to get me...
St. Jude Donor '09
Re: Milling Heads (bence13_33)
Great to see you posting on the forum again Shane. :yesnod: I'm the last person to ask about piston to valve clearance since you're the guy who helped me! :lol: BUT, and I know there's a lot more involved, the 294S had 0.595 lift, right? And the new cam has 0.63? That's an additional 0.035. What was your P-V clearance with the 294S?
I know it can't be that simple though.
I know it can't be that simple though.
Safety Car
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From: Severna Park Md
Re: Milling Heads (bence13_33)
Another thing to consider when milling heads is intake bolt hole and port alignment. The more the heads are milled the further out of alignment those things become. I dont know how far you can go but at a certian point the surfaces of the intake would also need to be shaved to keep things inline.
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From: In Dreams There Is Truth Ohio
Re: Milling Heads (bence13_33)
If you mill your heads, you should also mill the intake surfaces to keep port alignment. I think somewhere around .030 should get you to 11 or slightly above...with that much milling, you WILL have to mill the intake surfaces, unless you want to elongate the holes, but then Bubba is at work...
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From: In Dreams There Is Truth Ohio
Re: Milling Heads (bence13_33)
forgot...you want to have a minimum .1 piston to valve clearance...if I remember correctly, that's what I had with my cam, lift .623, without any milling. if you fall below that spec, you will have to fly cut the valve reliefs in the pistons.
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Re: Milling Heads (bence13_33)
Good to see you back Shane. And also great to see Vette is coming back out to play!
I have run cams SIMILAR to what you are planning and got by with it, BUT you HAVE to check it.
In the big scheme of things, LIFT is the least of your worries on P/V clearance. Duration and LSA along with intake centerline is what will determine P/V clearance.
Think about it....when max intake lift is achieved that piston is a LONG way down the hole. The critical area is just after TDC as the piston is descending and the valve is chasing the piston. The amount of duration and positioning of the cam affect this clearance.
Same on exhaust...the critical point is as the piston is ascending to TDC and valve is closing. Valve has to stay out of the way or it'll get smacked.
I've run cams in the area you are planning, but once again I'm going to say...REALLY check the edge of the pockets with the stock type TRW's and 2.19 valves. It is common for total P/V to be OK but when you look deep into pocket you see edge of valve is very close to edge of pocket and with piston rock it will eventually break a valve off.
If you have to open valve pockets up, Isky makes a neat little tool to do it while engine is in the car.
JIM
I have run cams SIMILAR to what you are planning and got by with it, BUT you HAVE to check it.
In the big scheme of things, LIFT is the least of your worries on P/V clearance. Duration and LSA along with intake centerline is what will determine P/V clearance.
Think about it....when max intake lift is achieved that piston is a LONG way down the hole. The critical area is just after TDC as the piston is descending and the valve is chasing the piston. The amount of duration and positioning of the cam affect this clearance.
Same on exhaust...the critical point is as the piston is ascending to TDC and valve is closing. Valve has to stay out of the way or it'll get smacked.
I've run cams in the area you are planning, but once again I'm going to say...REALLY check the edge of the pockets with the stock type TRW's and 2.19 valves. It is common for total P/V to be OK but when you look deep into pocket you see edge of valve is very close to edge of pocket and with piston rock it will eventually break a valve off.
If you have to open valve pockets up, Isky makes a neat little tool to do it while engine is in the car.
JIM
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From: B'Ville NY
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St. Jude Donor '05
Re: Milling Heads (bence13_33)
I do think you can also gain some clearance by having the valve seats cut to lower the valves up into the head for a bit more clearance ;) .
Shane not sure what the difference in duration is between cams, but you can gain addition lift by going with the next ratio higher rocker arm also. :cheers:
You may be ahead by not milling the heads and just going with the cam swap. Your not going to achieve much more HP by going from 10:1-11:1 compression (all things being the same) so if you have the clearance for the new cam as it is maybe just the cam swap would be the safest (no piston/valve damage or detenation). the money spent to mill the heads could be used for a valve job for added clearance and improved air sealing/ flow ;) .
[Modified by SmokedTires, 3:13 PM 11/30/2003]
Shane not sure what the difference in duration is between cams, but you can gain addition lift by going with the next ratio higher rocker arm also. :cheers:
You may be ahead by not milling the heads and just going with the cam swap. Your not going to achieve much more HP by going from 10:1-11:1 compression (all things being the same) so if you have the clearance for the new cam as it is maybe just the cam swap would be the safest (no piston/valve damage or detenation). the money spent to mill the heads could be used for a valve job for added clearance and improved air sealing/ flow ;) .
[Modified by SmokedTires, 3:13 PM 11/30/2003]
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From: Waterloo ontario Canada
Re: Milling Heads (bence13_33)
Nice to see you back again Shane. Besides piston to valve clearance really watch retainer to seal. At .648 lift I really need to cut the guides down. I even machined the bottom of all the retainers to gain extra clearance.
The duration is good, my favorite cam as you know is 256, 264 @ .050 with 108 lope centers. This is close.
Once agian really watch the retainer to seal clearance and installed spring height.
Hope you and Robyne are still together.
We still have an unfinished bet going.
The duration is good, my favorite cam as you know is 256, 264 @ .050 with 108 lope centers. This is close.
Once agian really watch the retainer to seal clearance and installed spring height.
Hope you and Robyne are still together.
We still have an unfinished bet going.
Thread Starter
Safety Car
Joined: Aug 2000
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From: Clymer PA
Re: Milling Heads (bence13_33)
Thanks for all of the responses.
I pulled a head off of my motor today and here is what I found out. With the current 294S cam I have 1/2" (without the head gasket) of piston to valve clearance and while I had the head off I decided to cc the combustion chamber, as it turns out I have 106.6cc combustion chambers :( .... I need more compression.
Does this information help any?
I pulled a head off of my motor today and here is what I found out. With the current 294S cam I have 1/2" (without the head gasket) of piston to valve clearance and while I had the head off I decided to cc the combustion chamber, as it turns out I have 106.6cc combustion chambers :( .... I need more compression.
Does this information help any?
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From: Sierra Foothills CA
Re: Milling Heads (427Hotrod)
Good to see you back Shane. And also great to see Vette is coming back out to play!
I have run cams SIMILAR to what you are planning and got by with it, BUT you HAVE to check it.
In the big scheme of things, LIFT is the least of your worries on P/V clearance. Duration and LSA along with intake centerline is what will determine P/V clearance.
Think about it....when max intake lift is achieved that piston is a LONG way down the hole. The critical area is just after TDC as the piston is descending and the valve is chasing the piston. The amount of duration and positioning of the cam affect this clearance.
Same on exhaust...the critical point is as the piston is ascending to TDC and valve is closing. Valve has to stay out of the way or it'll get smacked.
I've run cams in the area you are planning, but once again I'm going to say...REALLY check the edge of the pockets with the stock type TRW's and 2.19 valves. It is common for total P/V to be OK but when you look deep into pocket you see edge of valve is very close to edge of pocket and with piston rock it will eventually break a valve off.
If you have to open valve pockets up, Isky makes a neat little tool to do it while engine is in the car.
JIM
I have run cams SIMILAR to what you are planning and got by with it, BUT you HAVE to check it.
In the big scheme of things, LIFT is the least of your worries on P/V clearance. Duration and LSA along with intake centerline is what will determine P/V clearance.
Think about it....when max intake lift is achieved that piston is a LONG way down the hole. The critical area is just after TDC as the piston is descending and the valve is chasing the piston. The amount of duration and positioning of the cam affect this clearance.
Same on exhaust...the critical point is as the piston is ascending to TDC and valve is closing. Valve has to stay out of the way or it'll get smacked.
I've run cams in the area you are planning, but once again I'm going to say...REALLY check the edge of the pockets with the stock type TRW's and 2.19 valves. It is common for total P/V to be OK but when you look deep into pocket you see edge of valve is very close to edge of pocket and with piston rock it will eventually break a valve off.
If you have to open valve pockets up, Isky makes a neat little tool to do it while engine is in the car.
JIM
It's essentially just like a valve & you insert it into the guide before dropping the head onto the block. It does work but.... the cutting face of it is much thicker than a valve & therefore it protrudes more deeply into the cylinder. With the amount of clearance I had, due to having closed chamber heads, there wasn't enough room to bring the piston all the way up w/o hitting the face of the cutter. My buddy(performance engine builder for about 30 yrs) decided to get the pistons as high in the bore as possible, use the cutter, & do any finish work by hand. There was a small area at the edge of the valve pocket that required finishing & then he polished the entire piston dome to remove any potential for hot spots.
It sounds like you have open chamber heads, so clearance may not be an issue for you if you need to use this tool. I still have it & they are NOT cheap, so if you end up needing one let me know & I'll be happy to send it to you if it's the size you need.
:cheers:
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From: In Dreams There Is Truth Ohio
Re: Milling Heads (norvalwilhelm)
I would think it would have been wiser to just fly cut the valve reliefs in the pistons than to go through all that hassle with the tool.
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Re: Milling Heads (GDaina)
First off..you're at 106 cc so that's not all bad. Are those open chamber heads that have been ,milled already? Or are they closed/semi-closed ones?
I would hesitate to sink valves into seats much. Unless you do some flow work that typically hurts airflow. If you are in a really tight spot you can shave the heads of the valves some. Good thing cause it makes them lighter too. But there goes compression. I once shrunk cc's by 5cc by installing new intake valves. They were thicker and they placed them deeper into chamber. But there goes P/V.......!!!
Of course disassembling engine is the best way to do it all so you can flycut pistons, but I've used one of those tools at least three times and had no trouble other than it's a long process if you're aas **** as I am about things like that.
You can retard cam to get intake valve clearance, but that might defeat the whole purpose.
But if you have that much P/V right now (is that with clay?) then you have lots of room to play with.
JIM
I would hesitate to sink valves into seats much. Unless you do some flow work that typically hurts airflow. If you are in a really tight spot you can shave the heads of the valves some. Good thing cause it makes them lighter too. But there goes compression. I once shrunk cc's by 5cc by installing new intake valves. They were thicker and they placed them deeper into chamber. But there goes P/V.......!!!
Of course disassembling engine is the best way to do it all so you can flycut pistons, but I've used one of those tools at least three times and had no trouble other than it's a long process if you're aas **** as I am about things like that.
You can retard cam to get intake valve clearance, but that might defeat the whole purpose.
But if you have that much P/V right now (is that with clay?) then you have lots of room to play with.
JIM
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From: Sierra Foothills CA
Re: Milling Heads (norvalwilhelm)
I used one of those tools on a 302 mustang to increase valve to piston clearance and ended up destroying/cracking all the guides.
Thread Starter
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From: Clymer PA
Re: Milling Heads (427Hotrod)
Jim:
The heads are "206" castings from 1966. Supposedly they came with 96cc combustion chambers from the factory. I would say the heads are a semi-closed head design. Yes, I got the piston/valve clearance by using the clay method plus I have another .020" when you add in the head gasket.
So what's going to be the easiest method to figuring out how much I need to shave off of my heads to get me to 11:1 compression? I was thinking probably installing the new cam and then doing the clay method again to determine how much I can shave off the heads. What do you guys think?
The heads are "206" castings from 1966. Supposedly they came with 96cc combustion chambers from the factory. I would say the heads are a semi-closed head design. Yes, I got the piston/valve clearance by using the clay method plus I have another .020" when you add in the head gasket.
So what's going to be the easiest method to figuring out how much I need to shave off of my heads to get me to 11:1 compression? I was thinking probably installing the new cam and then doing the clay method again to determine how much I can shave off the heads. What do you guys think?
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From: Living in the Hartland
Re: Milling Heads (bence13_33)
Personally I would wait till you are ready to drop it in the Camaro for the little extra comp and bigger cam, you might decide to go blown and not want the extra comp or the cam.