Pistons for Larger Valves?

MustangChile · 02-17-2003, 12:26 AM

I have a 1969 Mustang with a basically stock 302 CID engine.
I want to upgrade my valve train. Part of the upgrade includes the head.
In a few Ford V8 performance books(How to build Max Performance FORD V-8 on budget by George Reid and Mustang mustang 5.0 liter Performance Handbook by Peter C Sessler) Recomend using using 351W heads and using larger Chevrolet 1.94"/1.60" valves. I plan to follow this advice. That is, change my stock 302 heads, install the 351W heads with the larger valves, ported polished with other necessary modifactions, etc...

Now for the rest of the equation I will install screw in studs for roller rockers with 1.6 ratio, and will be running a cam with a max lift of .471". My pistons at the moment are stock however I will eventually change the to forged, but not for the meantime.

The QUESTION is: Will I have any clearance problems with the valves with my current stock pistons, taking into account increased valve lift and valve diameter?

When I will eventually change pistons to forged, what pistons are recomendable for the new head components

I have more information on my car at the following website>:
www.kovacic.tie.cl/mustang69
In the "model" link on the top bar are my VIN plate details.
The "modifaction" link also has other details as to what I have and what I wish to do.

All help and advice is very welcome and appreciated.

thunderbolt · 02-17-2003, 09:59 AM

Not an expert, but I don't think you are going to have problems. But to be sure and expecially with new pistons I would definately do a clay bar test to check for valve clearance. You might have to mess with head gasket thickness depending on how much is shaved off the block and heads.

hobgoblin351 · 02-17-2003, 12:05 PM

Like Thunder said, Always do the clay test! Even if they say the parts will match up check anyway. It's a easy thing to do and with the money you're spending you want to be sure you wont be throwing it away along with your motor.
Do you already have the 351W heads? You can go with one of the newer aluminum sets. They come with big valves and are set for screw in studs already. One thing about the cam though. If you're only going to go with .471 total lift(at the valve) why bother changing the heads? Yes it's probably a higher than stock lift but it wont take advantage of the bigger valve or port size. If you're going to the trouble of changing the heads so you can flow more air, flow more air! Dont let the cam be the restriction. You could probably run the cam with the heads that are on there and get similar results.

MustangChile · 02-24-2003, 09:37 AM

Thanks guys for the help.
A little question though. How would I go about doing a clay test?
I am concerned about the valvetrain geometry still. The chevrolet valves are supposed to be shorter. Do have any advice on how this might affect me and what I can do to no have problems concerning this.

Technick · 02-28-2003, 01:27 AM

Valve lift is not so much the problem as is duration. If you stay with 230 degrees duration @ .050 lift (NOT ADVERTISED) or less then you can run as much lift as you want! It is not the lift that causes the problems, it is WHEN the valves are open! Big duration cams leave the valve open longer and that causes the interference problems. That is why the factory went to roller cams, you can get lots of lift and keep the duration short.
As far as the heads go. For the same money you will never get the airflow out of the 351W heads that you can get out of aftermarket aluminum heads. Plus it's 50 lbs off of the nose of the car. Plus aluminum is repairable. How many people do you know that can sucesfully weld cast iron?

02-17-2003, 12:26 AM	#1
MustangChile Registered Member Join Date: Sep 2002 Location: Viña del Mar, Chile Posts: 3	Pistons for Larger Valves? I have a 1969 Mustang with a basically stock 302 CID engine. I want to upgrade my valve train. Part of the upgrade includes the head. In a few Ford V8 performance books(How to build Max Performance FORD V-8 on budget by George Reid and Mustang mustang 5.0 liter Performance Handbook by Peter C Sessler) Recomend using using 351W heads and using larger Chevrolet 1.94"/1.60" valves. I plan to follow this advice. That is, change my stock 302 heads, install the 351W heads with the larger valves, ported polished with other necessary modifactions, etc... Now for the rest of the equation I will install screw in studs for roller rockers with 1.6 ratio, and will be running a cam with a max lift of .471". My pistons at the moment are stock however I will eventually change the to forged, but not for the meantime. The QUESTION is: Will I have any clearance problems with the valves with my current stock pistons, taking into account increased valve lift and valve diameter? When I will eventually change pistons to forged, what pistons are recomendable for the new head components I have more information on my car at the following website>: www.kovacic.tie.cl/mustang69 In the "model" link on the top bar are my VIN plate details. The "modifaction" link also has other details as to what I have and what I wish to do. All help and advice is very welcome and appreciated.

02-17-2003, 12:05 PM	#3
hobgoblin351 Registered Member Join Date: Sep 2002 Location: NYC Posts: 245	Like Thunder said, Always do the clay test! Even if they say the parts will match up check anyway. It's a easy thing to do and with the money you're spending you want to be sure you wont be throwing it away along with your motor. Do you already have the 351W heads? You can go with one of the newer aluminum sets. They come with big valves and are set for screw in studs already. One thing about the cam though. If you're only going to go with .471 total lift(at the valve) why bother changing the heads? Yes it's probably a higher than stock lift but it wont take advantage of the bigger valve or port size. If you're going to the trouble of changing the heads so you can flow more air, flow more air! Dont let the cam be the restriction. You could probably run the cam with the heads that are on there and get similar results. __________________ 1970 Stang Conv: en:Boss351 (balanced/blueprinted) mech cam(240*@.050/.540 lift) Scrw in studs/comp cams rllr rkr Mldn valves 2.19in 1.71ex ported polished cc'd hrdnd ex Keith Black FT pistons(10.25/1) Weiand Excellorator manifold Holley700 DP mech 2nds MSD 6 box and Dis Headers/2 1/2 inch duels tr: modified FMX re:9-inch/3.89 limited slip

02-24-2003, 09:37 AM	#4
MustangChile Registered Member Join Date: Sep 2002 Location: Viña del Mar, Chile Posts: 3	How to clay test? Thanks guys for the help. A little question though. How would I go about doing a clay test? I am concerned about the valvetrain geometry still. The chevrolet valves are supposed to be shorter. Do have any advice on how this might affect me and what I can do to no have problems concerning this.

02-28-2003, 01:27 AM	#5
Technick Registered Member Join Date: Feb 2003 Location: Seattle, Wa. Posts: 175	Valve lift is not so much the problem as is duration. If you stay with 230 degrees duration @ .050 lift (NOT ADVERTISED) or less then you can run as much lift as you want! It is not the lift that causes the problems, it is WHEN the valves are open! Big duration cams leave the valve open longer and that causes the interference problems. That is why the factory went to roller cams, you can get lots of lift and keep the duration short. As far as the heads go. For the same money you will never get the airflow out of the 351W heads that you can get out of aftermarket aluminum heads. Plus it's 50 lbs off of the nose of the car. Plus aluminum is repairable. How many people do you know that can sucesfully weld cast iron? __________________ No matter how much you spend, or how much you prepare, there is ALWAYS someone else faster or quicker than YOU!!!!!!!!!!

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02-17-2003, 09:59 AM	#2
thunderbolt Registered Member Join Date: Oct 1998 Location: Houston, TX, USA Posts: 380	Not an expert, but I don't think you are going to have problems. But to be sure and expecially with new pistons I would definately do a clay bar test to check for valve clearance. You might have to mess with head gasket thickness depending on how much is shaved off the block and heads.