How big are stock 302 valves?

Hack

15 Year Member
Mar 23, 2004
1,945
12
69
The size of 302 valves has varied a little in some performance versions over the years. D. Hearne is on the money as usual. Some additional 302 factory valve sizes:

69 Boss 302 intake 2.23 / exhaust 1.71
70 Boss 302 intake 2.19 / exhaust 1.71

E7 heads use 1.78 / 1.48 just like the 60s stuff.

GT40 heads use 1.84 intake / 1.54 exhaust
GT40P heads use 1.84 intake / 1.46 exhaust

Some people use factory 351W heads on a 302. 1.84 intake / 1.54 exhaust is a common size for them.
 

ForceFed70

That's why they call it "dope"
Founding Member
Dec 6, 1999
4,818
1
69
bad68coupe said:
could you stick the 69 boss heads on an 81-86 302? :SNSign:

The BOSS heads are a slightly modified version of the 351C heads. You could bolt them on, but you'd need to swap to a special intake manifold, and may need to change exhaust manifolds/headers (not sure on that one).

Generally, by the time it's all done with you'd be better off going with a set of aftermarket aluminum heads.
 

ForceFed70

That's why they call it "dope"
Founding Member
Dec 6, 1999
4,818
1
69
I had my local machine shop machine my stock 351W heads for 1.94/1.60 valves. Also did a port an polish job.

I like the results, but by the time it was over with it wouldn't have cost much more to switch to aftermarket heads.
 

bad68coupe

New Member
Jul 18, 2006
220
0
0
BottleFed70 said:
The BOSS heads are a slightly modified version of the 351C heads. You could bolt them on, but you'd need to swap to a special intake manifold, and may need to change exhaust manifolds/headers (not sure on that one).

Generally, by the time it's all done with you'd be better off going with a set of aftermarket aluminum heads.

any input D.Hearne?
 

Hack

15 Year Member
Mar 23, 2004
1,945
12
69
bad68coupe said:
could you stick the 69 boss heads on an 81-86 302? :SNSign:
You can but the port sizes are really big for 302 cubes. They are actually big for the 351 Cleveland, even. Like BottleFed said, you need a special intake that's the correct width for the 302 and has the Cleveland port sizes. Also exhaust manifolds for Cleveland heads. Also, the Cleveland intakes are dry, so you need the correct bypass so that water circulates properly.

The Cleveland block has a notch in each cylinder for the intake valve. It prevents the valve from touching the block and also helps to unshroud the valve. I expect that you would want to put similar notches into a 302/331/347.

You need Boss 302 special pistons for the canted valves.

You would want a cam shaft to take advantage of the heads. If you really want a good performing Boss 302 style motor, you probably want solid lifters and light, $$$ valve train, springs etc so you can wind it to the moon.

A rev limiter would be a very good idea, because air flow will not limit your rpm at all! I know the factory Boss 302s got rev limiters, and you would want them.
 

LMan

Founding Member
Aug 10, 2002
1,246
0
0
What you really mean is a set of 351C heads on a Windsor block (Clevor). This is a set, well-known procedure but with the profusion of good, aftermarket Al W heads its out of favor.

To do it you have to drill some water passages to match the heads and block. The FRPP catalog used to have a step-by-step process listed in it, I dont know if it still does or not.
 

bad68coupe

New Member
Jul 18, 2006
220
0
0
LMan said:
What you really mean is a set of 351C heads on a Windsor block (Clevor). This is a set, well-known procedure but with the profusion of good, aftermarket Al W heads its out of favor.

To do it you have to drill some water passages to match the heads and block. The FRPP catalog used to have a step-by-step process listed in it, I dont know if it still does or not.

not wure what you mean when you say " This is a set, well-known procedure but with the profusion of good, aftermarket Al W heads its out of favor" are you saying its worth it or not?
 

Hack

15 Year Member
Mar 23, 2004
1,945
12
69
bad68coupe said:
not wure what you mean when you say " This is a set, well-known procedure but with the profusion of good, aftermarket Al W heads its out of favor" are you saying its worth it or not?
It will cost you more money to build a 302 with Cleveland heads compared to a GT40 headed 302 or most other factory Ford heads. I was trying to make that obvious with my long list above. Also, if you are building a street machine only, it's not worth it. You'll end up with an expensive engine that's really lazy at lower rpms. Aluminum heads might even be close to the same money once you add up everything, and the right aluminum heads will work better in a 302 (power at usable rpms).

If you are doing all out race effort, that's another story. Or if you just want to do something really cool... :D

If you are in love with the idea of canted valves (like me!) you could buy the Aussie 302C heads or Edelbrock's Cleveland heads. They both have smaller valves than the original Boss 302 and smaller ports more suited to a 302 displacement engine. They will still require all the special parts above and cost more than just building a regular 302, though. Check out Powerheads web site.
 

D.Hearne

New Member
Sep 29, 2000
11,730
4
0
bad68coupe said:
not wure what you mean when you say " This is a set, well-known procedure but with the profusion of good, aftermarket Al W heads its out of favor" are you saying its worth it or not?
Listen to Hack, he's right on the money. I will add though, that the intake needed to use 4 bbl Cleveland heads on a 302 is a Boss 302 intake. The square coolant ports on the deck face of a Cleveland head have to be plugged and another port opened on the intake side to reroute the coolant when doing this head swap. And as the others have already stated, the Cleveland head swap is simply not a cost effective mod today with all the better aftermarket heads available now. Reworking a set of Cleveland heads, the cost of an intake (you're looking at $400 here for a good used Boss intake), pistons, rods (you'll not only need the longer 289 length rods, but better, stronger rods to handle the rpms that Boss heads are capable of) headers (Boss 302 headers) plus other costs, just make it an expensive proposition. Sure makes a sexy lookin' motor though :nice:
 

Max Power

Active Member
Jul 31, 2003
1,774
0
36
It's not even that easy finding good cleveland heads and definitely not easy finding Boss 302 heads.

There is a huge aftermarket for windsor based SBF heads, and prices are such that modifying for cleveland style heads, or ever porting and modifying 351w heads is just not cost effective for the results.
 
Jan 12, 2006
224
0
16
the pushrod length changed in 1969 to 6.905, slightly longer than 1968 and older engines.

If you are using 69 windsor heads on a 302 you'll want something close to that, When I did it I used 6.875 (.030 smaller) and they worked well. Stay away from the rail rockers when doing this swap as 69 heads usually have a bottleneck rocker stud meant for non-adjustable rockers. Go with screw in studs and guideplates and a decent roller rocker.
 

deadcarnahans

New Member
Sep 21, 2022
1
0
1
The size of 302 valves has varied a little in some performance versions over the years. D. Hearne is on the money as usual. Some additional 302 factory valve sizes:

69 Boss 302 intake 2.23 / exhaust 1.71
70 Boss 302 intake 2.19 / exhaust 1.71

E7 heads use 1.78 / 1.48 just like the 60s stuff.

GT40 heads use 1.84 intake / 1.54 exhaust
GT40P heads use 1.84 intake / 1.46 exhaust

Some people use factory 351W heads on a 302. 1.84 intake / 1.54 exhaust is a common size for them.
What about valve length? This is critical. Not putting 289 valves in my E7 heads. Not.
Can you tell us what length valve will be required in a E7 head build?
Thank you.