I'm helping a nefew do a valve job on a 1966 390 T-bird. His heads would cost too much to repair so he got some replacement heads. My question is that the replacement heads have smaller intake and exhaust ports and I wonder if that would be a problem. He only uses it as a driver so power change is not a problem. My concern is that there would be pooling of fuel as goes from the larger intake ports then hitting the smaller head ports.

 

That's a big no no, get the proper heads or rebuild the old.
Small to big yes but never big to small as this is worse than
both being smaller than the smallest runners.
Don't let those heads get away in a exchange, you lose and
someone wins at the rebuilders.

 

Well Q one is why did he buy heads that didnt match his intake?? Number 2 is you never run a larger intake port into a smaller Head port.. (thats Induction reversion) Thats like trying to push 10lbs of air thru a 3lb tube!! It will work..but not worth a *****...

Have the newbie take the heads back to where ever he bought them from and order the right heads for the intake...If you have too take the intake down to the parts house and show them the size..I dont know what Intake you have off hand ..but numbers Dummy and FFR428 can give you the intake port size to match the heads.. If I'am not mistaken any later C5AE-g head and above will work with that T-Bird Intake..C6AE,C8AE,...

There is probably more..I dont use a book just try and go by memory..So I'm sure the guy will give you somemore head #s.... Right now I have 3 Drag race builds in my head..and I keep wanting to think after market parts..LOL..I have been away from stock too long!! Sorry!

RJ

 

The heads will work with the intake, just not as well as the correct heads. The intake charge is being drawn thru here, not pushed so it's not as big a deal as some think. This would also be a good time to upgrade the intake to aluminum like in an Edelbrock Performer or RPM. The ports will match up better, but still not be perfect, unless he port matches them.

 

For a low-torque daily driver, it's not.

But anything after a certain RPM it would fall on it's face. The port length makes for a ram effect at higher RPMs. The air/fuel is traveling so fast that the cyilnder isn't drawing so much as allowing the flow. Much like exhaust scavenging...

But for a daily driver, I wonder how much that matters...

Not sure where the FE lies in that territory, but I know it matters in most of today's motors that have a pretty long intake runner length per cylinder.

 

Back in the 70's Ford recommended using a 429CJ intake on std 429/460 heads. Even with that port mismatch, there was still power to be gained. They even did this on the Marine 429/460's in jet boats. These came from the factory with the CJ intake with std heads.

 

Anytime you use a larger port into a smaller port your going to get reversion.. It will work..but not as advertised!! Thats like running a High Compression motor on pump gas..It will run..but not up to what it should be by far..

RJ

 

Thanks for your responses! So if he just wants to be able to drive this car it should be OK? It won't make it run bad to the point he can't drive it because of fuel pooling at the head or cause a bad flat spot under normal driving?

 

Who knows, it might do both... in my opinion, better to be safe than sorry after all that work.

but if you're stuck for money, let us know how it works out

 

It's a 66 T-Bird, a "cruisin" car, not a drag strip terror. I doubt he'll notice any difference. Bolt em on and forget it. The engine will likely never see the far side of 3 or 4,000 rpms so there will be no adverse effects.

 

Hey Russ; after grinding 14 hours on the C4 heads and F427 intake the heads match the Victor Reinz gaskets (2.355" x 1.400"), intake is .032" smaller on roof, sides and .110" on the floor than the heads. No bell mouth on intake to heads. Seems the floor of the C-4's have a rise of .110" inboard .600" from the exhaust port flange going in towards the valve from factory. The intake floor is .110" taller and the port is parallel from the port floor runners on 1,4, 6 and 7 being they are fed from the upper plenum, would be foolish my thinking to bell mouth the intake floor that .110" to match head floor to only go back up to that .110" rise again in the head and mess up a F427 intake. I can see why the F427 was rated so low on that intake shootout with the crappy port dimentions, flashing and casting joints that can be corrected big time.
All opinions welcome be it good or bad, LOL.
Next to wash and paint heads then figure how to clean intake without bead blasting, thinking "acid brightner" like they use on big rig wheels and fuel tanks.
Has anyone used "acid brightner" on an Edelbrock intake and your results?
On a Zinc based BMW carb it will become a black fizzy, bad idea trust me as I
scrubbed for hours with cleanser and nylon brush to get the factory cast finish and color again.

Summit stiffed me, half the Manly viton valve seals and my machined keepers not shipped until the 16th of the month, springs shipped 2nd day I got 'em.
Sunnit sucks at times, best part the seals were located in Jeg's but summit pulled their catalog and matched price. Pirates, AARRRGGG!

 

Aluminum "brite" will turn it white. I'd get it bead blasted then clean it good to remove any residual beads. Done this with lots of aluminum intakes and had zero problems.

 

Lots of soap and water afterwards, with a big bottle brush to get inside the runners.

What's funny is the guys who glass-beed the inside of their oil pan and don't clean it out afterwards. But then, those were Chevy guys...

 

Ouch!
Years ago when I baffled and deflectored the FT pan I had a friend
ultrasonic the pan at Alameda's Naval Air Station aircraft rebuilding
department (O&R). Clean enough to eat off in and out when done plus free.
My heads were just bead blasted, another scrubbing job ahead.
I don't trust these blasters tossing a F427 intake on metal grates screwing
up machined surfaces and corners as everythings dressed and nick free.
I don't want a sharp surface on the intake from blasting making cleaning harder, rather keep the factory finish.
"Acid brightner" test on the old Performer coming up me thinks as it's just wall art.
May also try Off Oven cleaner it's caustic base.

 

Carl, I removed that duplicate post.

EZ-Off Oven Cleaner, from what I can tell, is mostly lye.