Difference in 67 289 heads and 77 302 heads?

Trent K. · Oct 29, 2019

So I have a 77 302 that is going into my mustang, I've mentioned this before. I have the factory 289 that came out of the car, would I be better off putting the 289 heads on the 302 or should I leave the 302 heads on it? The 302 heads were obviously during the smog craze and they're out of an f100 from the time. I just want to know if anyone thinks it would be better to go with the 289 heads or not. I could probably get them ported and polished and make some better power with them. Would I see a power gain from switching to the 289 heads, since they're pre smog?

Trent K. · Oct 29, 2019

I should clarify that both of these heads are 2v heads, and they'll both be stock more than likely. I don't have the money laying around to do anything with them at the moment, I was just wondering if I could get better performance out of the 289 heads over the 302 heads due to smog regulations.

Olivethefet · Oct 29, 2019

I can't answer your question about the heads, but I am curious. What is wrong with the 289?

2Blue2 · Oct 29, 2019

What yr casting makes a difference with older 289 heads having smaller chambers.

67 289 2v heads net about 9.3 compression in stock engine chamber volume about 63cc
77 302 2v heds net about 8.4 compression in stock engine chamber volume about 69cc

77 302 had a dished piston to help get lower compression

So yes 289 2v head might give slightly better performance than 77 2v head but not by enough to get really excited about or even notice

the stock head performance win goes to the 1993 to 97 gt 40 head

Trent K. · Oct 30, 2019

Olivethefet said:
I can't answer your question about the heads, but I am curious. What is wrong with the 289?

The 289 had low compression on about 4 of the cylinders. Bad piston rings and cam, and theres a small piece of crank that has a good groove in it so I just decided the 302 would be my best option.

Trent K. · Oct 30, 2019

2Blue2 said:
What yr casting makes a difference with older 289 heads having smaller chambers.

67 289 2v heads net about 9.3 compression in stock engine chamber volume about 63cc
77 302 2v heds net about 8.4 compression in stock engine chamber volume about 69cc

77 302 had a dished piston to help get lower compression

So yes 289 2v head might give slightly better performance than 77 2v head but not by enough to get really excited about or even notice

the stock head performance win goes to the 1993 to 97 gt 40 head

So is there a difference in the intake ports on the head? The engine is out of the car right now and I could replace heads fairly easily. Which heads would you pick? Looking for honest opinions on this.

Blue_Cheesehead · Oct 30, 2019

Are you sure the 289 heads were not contributing to the low compression? If the valves all seal fine, I would go with the 289 heads for a little more compression.

Any difference in intake ports will be insignificant.

Small block Ford's weak point is exhaust flow. Several hours with a Dremel tool can help by pocket porting the exhaust ports.

2Blue2 · Oct 30, 2019

We are talking 45 to 50 yr old engines, are all the pushrods, rockers, studs still good if you go 289 route?
Again what yr casting on 289 what piston in 302 block?

For either head to be worth a it will need screw in studs, roller rockers, and mild porting

go buy aluminum

Blue_Cheesehead · Oct 30, 2019

^^^ to make the heads worth a darn, add guide plates to that list of modifications as well...

Trent K. · Oct 31, 2019

2Blue2 said:
We are talking 45 to 50 yr old engines, are all the pushrods, rockers, studs still good if you go 289 route?
Again what yr casting on 289 what piston in 302 block?

For either head to be worth a it will need screw in studs, roller rockers, and mild porting

go buy aluminum

Everything is good on the 289 heads. I'm not sure what pistons are in the 302 block as it has been bored .030 over. My grandpa did the rebuild a while ago, so it's hard for him to remember exactly what went into it. How much is the average porting job?

Blue_Cheesehead · Oct 31, 2019

^^^ If you have a Dremel tool you can spend $20 on supplies and 6 hours of time. There are plenty of videos and articles out there. Just don't go too nuts.

Trent K. · Oct 31, 2019

Blue_Cheesehead said:
^^^ If you have a Dremel tool you can spend $20 on supplies and 6 hours of time. There are plenty of videos and articles out there. Just don't go too nuts.

I'd rather have a machine shop do it lol I don't want to be the one to mess it up.

Blue_Cheesehead · Oct 31, 2019

For the money you would pay a machine shop, you could buy a better flowing set of aluminum heads.

Trent K. · Oct 31, 2019

Blue_Cheesehead said:
For the money you would pay a machine shop, you could buy a better flowing set of aluminum heads.

It would cost that much?!?!

Blue_Cheesehead · Oct 31, 2019

Time is money... There used to be a place called Powerheads where you could send your heads and for $1k they would cnc port them. Looks like inexpensive aluminum heads have put them out of business.

Spending $ on porting iron heads just does not make sense these days. You can get aluminum heads from places like Skip White for $750. Are they the best? No, but will out perform a stock head with average port job.

rgsauger · Nov 29, 2019

Check out the Brodix ST5.0 heads from summit. Damn these are nice heads!!! About $1200 for pair and they are READY!

Have them on a 65 289. Love them.

rgsauger · Nov 29, 2019

Remember the ARP bolts!

Billm · Nov 30, 2019

Trent do a search for the Mustang Barn. They have a tech article on porting 289 heads. Cheap performance upgrade by opening up the exhaust. I did this to the engine in my Tiger and can't wait to start and break it in. I also have the C90z hydraulic cam. It's the hydraulic hypo cam. The owner Dan also will curve your your distributor to the proper specs. Another reasonable performance tip. A member on another Mustang forum got 320 hp. With this set up, using a 4 barrel carb and manifold. Bill

Difference in 67 289 heads and 77 302 heads?

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