4.2 performance
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Junior User
Joined: Feb 2004
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From: earth
4.2 performance
i was curious if any1 has experiance porting the stock heads? also ive read some threads on roller rockers some said they used mustang style rollers. im assuming pedestal mount? what ratio is the 4.2?
302ho mustang is 1.6.since there really arent any cams to choose from would 1.7 rockers work better with ported heads? any valve clearance probs or coil bind with 1.7 ratio? also does any1 know the stock valve size on the 4.2?
thanks for your replies!
302ho mustang is 1.6.since there really arent any cams to choose from would 1.7 rockers work better with ported heads? any valve clearance probs or coil bind with 1.7 ratio? also does any1 know the stock valve size on the 4.2?
thanks for your replies!
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Joined: Sep 2003
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There are several companies that sell ported heads for our engine, but I do not know anyone who has tried them. To take full advantage of ported heads you would also need to upgrade the cam to maximize flow.
If I remember correctly, the stock rockers are 1.73 and the typical upgrade is to 1.80 ratio rollers. No problems with valve clearance or stock springs from the change. While this is a cool mod, you will probably only see a couple HP improvement from the small increase (0.020”) in lift the RR give you. Far more substantial gains can be had if you bundle a cam + springs + roller rockers. There are quite a few options for street and street/strip grind cams for our engine. Gains of 20 to 40 HP are easily achievable without sacrificing dependability or daily drivability.
If I remember correctly, the stock rockers are 1.73 and the typical upgrade is to 1.80 ratio rollers. No problems with valve clearance or stock springs from the change. While this is a cool mod, you will probably only see a couple HP improvement from the small increase (0.020”) in lift the RR give you. Far more substantial gains can be had if you bundle a cam + springs + roller rockers. There are quite a few options for street and street/strip grind cams for our engine. Gains of 20 to 40 HP are easily achievable without sacrificing dependability or daily drivability.
Senior User
Joined: Oct 2003
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From: Cincinnati
There are a couple companies that sell ported stock heads. Unfortunately nobody makes aftermarket heads for us 
Those same companies also make cams that will work for your 4.2. You might want to email them about your setup and let them pick the best cam for you. 1.73 is the stock rocker ratio, and if you do decide to go with a reground cam then there really is no need to switch to 1.8's (although you still might want to switch to roller rockers). If you decide to just go to 1.8's you won't have any problems with coil bind, but if you decide on getting a reground cam new springs are always recommended to avoid bind and valve float.
Stock intake valve size is 1.86", exhaust valve is 1.45". I know RPM-Mustangs sell big valve heads with 1.94" intake and 1.55" exhaust valves
I will be installing a set of ported heads this spring (whenever the temperature reaches above freezing!!). I plan on taking a lot of pictures and doing a write-up. I'll let you guys know when it's up on the web and hopefully it will help a couple of you guys in the future
Those same companies also make cams that will work for your 4.2. You might want to email them about your setup and let them pick the best cam for you. 1.73 is the stock rocker ratio, and if you do decide to go with a reground cam then there really is no need to switch to 1.8's (although you still might want to switch to roller rockers). If you decide to just go to 1.8's you won't have any problems with coil bind, but if you decide on getting a reground cam new springs are always recommended to avoid bind and valve float.
Stock intake valve size is 1.86", exhaust valve is 1.45". I know RPM-Mustangs sell big valve heads with 1.94" intake and 1.55" exhaust valves
I will be installing a set of ported heads this spring (whenever the temperature reaches above freezing!!). I plan on taking a lot of pictures and doing a write-up. I'll let you guys know when it's up on the web and hopefully it will help a couple of you guys in the future
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