I will show my knowledge. 1st what is the intake exhaust cross over and where is it located on the intake. 2nd. Why block it off? Does it help or hurt the engine and do you gain any thing by doing this. I am building a 390 FE bored .030 over and will be buying a new aluminum intake and carb when I get smart enough to figure out which one to get for my daily driver with a new cam a little hotter than stock hyd. flat tappet set up. My block is still at the machine shop so I have time to figure out what to do. I did save the valley pan for the intake area and will reuse that pan.

 

Center of the intake and heads, right under the carb. It is placed there to provide heat for the carb in stock engines. This helps eliminate icing, and helps the fuel atomize. It helps some and hurts some. Blocking it off helps maximum power performance as hot air and fuel are less dense than a cold charge. Other means can be used regarding icing, if that's an issue at all.

If you want more performance, be sure you get car spec pistons, not the pickup spec. 1.77" compression height is what you want, not 1.66".

 

It has been said here that using 360 pistons will also get you to a good compression for a 390. Search around, if you're interested.

 

"360" pistons are the same spec if not the same exact part out of the parts bin as 390 car pistons from '66 on. People report finding flat top and dished in 360s, and some flat tops marked "4V", as in 4 bbl carb, which was the flat top "Premium Fuel" motor.

Just as pickup 390 pistons are out of the Mercury 410 parts bin.

So if you go that way, it's probably easier to just tell the parts man you need 360 pistons rather than try to explain car vs PU, compression height etc

 

Order pistons for a 67 GT390 (Mustang/Fairlane) car engine. You should get flat tops with the correct pin height. Ordering for any other FE application, you're only going to end up with the wrong pistons, unless you know how to measure the pin height when you have them in hand, even then you may have to send them back when you get the wrong pistons. You do not want to expose an aluminum intake to corrosive exhaust gasses. Unless you want the intake to develop cancer. The only time the exhaust crossover is beneficial is in wintertime sub freezing driving. Any other time, it's not needed. I would choose a Performer RPM topped with either an 80783 650 cfm Holley or a 3310 750 cfm Holley. As far as I know the RPM does not have an exhaust crossover passage.

 

I will say, I ran my highboy's 390 at 11:1 compression, with an Edelbrock Performer 390 with no exhaust crossover, and even in the dead of winter, it would be just fine. I did, however, run a Holley 750, so it's larger venturis (and serious lack of vacuum at idle) might have made it less prone to icing

 

The '67 GT 390 piston is certainly a winner. But according to this info, into which few holes have punched over the years as I have posted it a million times, the FE in cars had 3 basic compression heights: 1.8s for the 352, 1.7s for the 390, 1.6s for 410/428. Flat top, or dished varied, and 406/427 had some variations, but were still in the 1.7s.

OP needs to measure deck height and combustion chamber volume. That will help decide flat top or dish for his pistons. Nothing wrong with a dished piston near zero deck.

http://www.fastfairlane.com/Engines/fespechart2.html

 

Agree, but measuring the pin height is the most important thing to me. I've only seen two 390 4 bbl pistons in the engines I've torn down. The early ones ala 1964 were true flat tops without valve reliefs, the later 60's had 4 reliefs as in the 67 GT390 I had and the 68 Merc 390 2bbl I had later (this was the 2 bbl premium fuel engine exclusive to the Mercs)

 

Living here in Texas we very seldom get any sub-zero temp and then since I am retired I have plenty of honey do jobs that I don't need to go out side. Thanks for the piston info and the carb and intake I will use that for sure I did go with the GT 390 flat tops with the valve reliefs in them. I will next get a carb and intake a long with the cam.

 

I got my truck heads and got most of the grease and dirt off of them and took some pics of them. I did notice that I have two sets of springs on each valve, is this common on ford heads? I did spray WD40 inside of the valves and two intake valves leaked. There are also different caps on top of the valves for the intake compared to the exhaust. I will also be removing a bolt that is on the exhaust manifold side that decide to break off in the head. I will take to the machine shop friend of mine who I am installing 15 tons of ac in his shop and let him do the valve job.








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Those are 1963 heads. The 3D23 is the date code for that one head, translates to April 23, 1963. The inner spring is a damper spring, normal thing to have. the valve stems should all be the same height above the deck. Sometimes Ford used lash caps on either the intake or exhaust valves (I don't recall offhand, but think it was the exhausts) so the caps would make the short valves the same height as the others. Looks like two different retainers were used here, accounting for the stems looking different. "DIF" is Detroit Iron Foundry where the head was cast. C3AE-6090C is the engineering number.

 

The thicker retainers are valve rotators used on the exhaust valves in truck apps.
Each time the exhaust valve opens and closes it rotates the valve slightly so that it never seats in the same place.
This was supposed to help prevent the exhaust valve from burning.
These retainers don't work well with high lift cams, if a aftermarket performance or RV cam is planed you'll need a set of matching non rotator style retainers.

 

I will be installing an Edelbrock Streetmaster intake on my FE 390; it has the exhaust crossover and it isn't corroded from use. I want to keep the crossover for winter start up, it gets to 30 below overnight sometimes in the winter. Will the hot exhaust corrode the crossover as I have heard a bit. The reason I see mostly for blocking the passage is to keep the manifold cooler. I don't want the exhaust to destroy the manifold, but winter starts are important too.

 

Several aluminum intakes have been ran for years without damaging the crossover, look at the ear systems on newer vehicles with aluminum intakes.
That said I'd use a block off with a 1/2" hole in it to restrict the exhaust but still let it warm the intake for you cooler climate.

 

I've had several aluminum intakes that were severely corroded from exhaust gasses. Last was a 428PI that I had to have the ports welded shut because of it. No, the length of time it took to do the damaged is debateable, but it WILL happen over time. Maybe the newer EFI intakes are a different alloy that prevents the damage. But that Streetmaster won't be, that one's been out of production for at least 30 years. If you want to heat the carb, find one of the O.E carb spacers that had a coolant passage through it, that'll kill two birds with one stone. You'll get the heat without the corrosion.