Piston to Valve clearance

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2nd Dart 67

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Hello everyone,

I am building a 340 for my '67 dart GT. I opted for the KB hyperutetic pistons .040 over. Will I have a problem with piston to valve clearance with the factory "big valve" heads? I haven't chosen a cam yet, but I want something mild, since this is just a street car. Thanks!
 
I always check V-P clearance, but with KB pistons and 2.02 int valves the relief in the piston should be big enough. Which pistons and what camshaft?
 
I have the same pistons in my .030 over 340.
I am running stock "X" heads.
I have a .513 lift with no clearence issues.
 
I run KB 107's in my 360, they stick .008 out of the hole, MP .557 cam advanced 2 deg, Hughes 1.6 rockers, Mr. Gasket composition head gasket that crushes at .038. When I clayed P to V with out the head gasket I had over .07 I and E. The pocked in KB's are deep and very generous, go for it.
 
2nd Dart 67 said:
Hello everyone,

I am building a 340 for my '67 dart GT. I opted for the KB hyperutetic pistons .040 over. Will I have a problem with piston to valve clearance with the factory "big valve" heads? I haven't chosen a cam yet, but I want something mild, since this is just a street car. Thanks!
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While you have gotten excellent answers, your question is ridiculously vague and continues to laughable because you have not selected a cam even in theroy.

The piston height also must be known along with head gasket thickness and the cams valve lift height plus lash if it applies. Also cam style. IE: Hyd. Solid, Roller type.
 
rumblefish360 said:
While you have gotten excellent answers, your question is ridiculously vague and continues to laughable because you have not selected a cam even in theroy.

The piston height also must be known along with head gasket thickness and the cams valve lift height plus lash if it applies. Also cam style. IE: Hyd. Solid, Roller type.
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Sorry it was so vague. I bought the Fel pro master gasket kit, so I assume that its close to stock style. Also the cam as I said in first post is going to be mild, just barely over stock. Hydraulic lifters, cam.
 
Just so you know .Lift is not the only thing that can cause V/P clearence issues with a camshaft choice.Long duration and lobe seperation angles as well as advancing or retarding the timing set can cause things to get close also.The solid flat tappit i just installed in my stroker Bracket car is only .507 lift on boths sides ,but it is 254 duration @ 50 on both sides with a 108 lobe seperation angle.My previous cam of .510 lift cleared just fine ,but with a 112 lobe seperation angle and only 234/244 duration @50 ,i know things are gunna be closer.I think im good ,but for peace of mind i will be claying it prior to bolting the heads down for good.My motor has KB quench type pistons BTW.
 
The Shocker said:
Just so you know .Lift is not the only thing that can cause V/P clearence issues with a camshaft choice.Long duration and lobe seperation angles as well as advancing or retarding the timing set can cause things to get close also.The solid flat tappit i just installed in my stroker Bracket car is only .507 lift on boths sides ,but it is 254 duration @ 50 on both sides with a 108 lobe seperation angle.My previous cam of .510 lift cleared just fine ,but with a 112 lobe seperation angle and only 234/244 duration @50 ,i know things are gunna be closer.I think im good ,but for peace of mind i will be claying it prior to bolting the heads down for good.My motor has KB quench type pistons BTW.
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I guess I'll have to wait until I decide on a cam. I am going to clay it before I put everything together, but if so many things about the cam are factors and you won't know for sure until you mock it up, how do you know what cam to choose? If you get the wrong one its possible to have issues.
 
You're right, choose the wrong cam and you will have issues.

Cam choice is is defined by what, where, when, and how you want to drive your car; simply it defines the performance characteristic's of the car. When you climb into the drivers seat, where are you going? Saturday night/weekend cruze, stop-light bandit, drag race? What are you willing to put up with as relates to driveability?

You stated this is a "street car", I'll go out on a limb and guess your intent is Saturday night/weekend cruze. A cam slightly bigger than factory 340 may be what your looking for. The car would be fun/snappy to drive, have a little "thump" in the exhaust tone, pin you to the seat a little when you step on it. There are dozens of catalog cams in that catagory, plus just as many custom grinds. Call the cam tech lines, define you car to them, tell them what you want; it's what they get paid to do.
 
For what i think your after i would look for a camshaft close to .490-.500 lift and a duration @50 of no more than about 230-240 duration with a lobe sep angle of around 112 .The duration of 235ish will make it sound plenty tough ,but the lobe seperation of 112 will make it have plenty of vacume at idle,plus better manors in traffic jams.If your interested i have an Edelbrock performer Rpm hydraulic flat tappit cam that i just pulled from my motor i would sell dirt cheap.

Its .488/.510 lift with 234/244 duration @50 with a 112 lobe seperation.This is what i would call a nice street /strip cam ,but it aint no race cam IMO.Athough my Dart ran 11.40 flat with it in the 1/4 ...
 
The Shocker said:
For what i think your after i would look for a camshaft close to .490-.500 lift and a duration @50 of no more than about 230-240 duration with a lobe sep angle of around 112 .The duration of 235ish will make it sound plenty tough ,but the lobe seperation of 112 will make it have plenty of vacume at idle,plus better manors in traffic jams.If your interested i have an Edelbrock performer Rpm hydraulic flat tappit cam that i just pulled from my motor i would sell dirt cheap.

Its .488/.510 lift with 234/244 duration @50 with a 112 lobe seperation.This is what i would call a nice street /strip cam ,but it aint no race cam IMO.Athough my Dart ran 11.40 flat with it in the 1/4 ...
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Thanks for the offer, My funds are needed elsewhere at the moment. I'm just trying to think ahead.
 
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