head rebuild questions

[68GEETEE]

decided to have my spare set of '68 302 4V heads rebuilt. Spoke with a machine shop locally, and they recommended, magnaflux, mill, valve job, hardened seats, new guides and seals, and a port and polish. He said I will pick up 30-35 horsepower , and that stock 178/145 valves are fine. The porting and polishing is going to increase air speed in the head, and that if I go with larger valves, the air speed slows down a bit. Unless I am building a race motor, which I am not, he says larger valves arent necessary. Is anyone here knowledgeable enough to agree or disagree with the machinist?

The car is driven on Sundays, I like to have power on demand, but I am not interested in racing the vehicle.


p.s. Please dont answer by telling me to buy aftermarket heads, staying with original equipment for date code reasons, thanks.

 

[6Stang7]

Ya he is right. If you increase your valve size, you will reduce the amount of air turbulance created, which will not give you the best atomization of the fuel. Besides, if they did, why would he tell you otherwise? He would be able to charge you more money to install larger valves, so it would be to his advantage to do so. To me, it sounds like this guy is being up front with you.

-Shaun

 

[HistoricMustang]

How much is he going to hit you up for? That is the key.

HistoricMustang
www.historicmustang.com

 

[D.Hearne]

He is correct, I did this with a set of E7 heads and it made a world of difference. Especially just opening up the exhaust passages, that's where the stock heads are the most restricted. I opened them up on the sides and raised the roof about 1/4 all around, then blended them into the bowls. The intake side just needs to be de-burred and the bowls cleaned up. If you need new valves, then by all means go larger on the size, but otherwise the stock size will work fine on a street motor.

 

[67GTCOUPE]

Buy aftermarket heads! Keep your "originals" as paper weights in your garage/shed.

Trying to do all that work to stock heads is like wiping your azz with $100.00 bills!

Anyone who tells you different is an idiot.....period.

 

[brianj5600]

I plan on filling in the cnc AFR on mine and painting them blue. I know it is not exactly stock, but a casual glance by most people won't notice. To me once you change anything, even wheels, it is pretty much over, but you can somewhat mask some things. Accessories hide heads pretty good. Blue paint and a dremmel hide an aftermarket intake from most people. Mine will look mostly stock until you look closer. What your machinist is telling you is about right, maybe a little optimistic on power though, but I hate to see anyone spend too much on stock heads. You can help them, but w/o major surgery on them ($$$$$) 15 or so hp is all I would expect.

 

[GaPonyFarm]

Buy aftermarket heads! Keep your "originals" as paper weights in your garage/shed.

Trying to do all that work to stock heads is like wiping your azz with $100.00 bills!

Anyone who tells you different is an idiot.....period.

That's the dumbest thing I've heard lately. Unless you're going to be running the streets racing, there is absolutely no need for aftermarket heads.

The man said in his post he was not interested in aftermarket heads or racing. He is definitely on the right track with his heads, and won't have wasted $1000.00 like many people who spend too much time reading magazines and "bench" racing.

 

[brianj5600]

Maybe 67GTCOUPE was a little harsh. If you want to go fast, he is right though. I want to go fast (low 10's), so stock heads were never considered. A good running street car on stock heads is not that hard to do.

 

[D.Hearne]

Buy aftermarket heads! Keep your "originals" as paper weights in your garage/shed.

Trying to do all that work to stock heads is like wiping your azz with $100.00 bills!

Anyone who tells you different is an idiot.....period.

I guess that makes me an idiot then, but at least I'm not a turd.

 

[68GEETEE]

He is correct, I did this with a set of E7 heads and it made a world of difference. Especially just opening up the exhaust passages, that's where the stock heads are the most restricted. I opened them up on the sides and raised the roof about 1/4 all around, then blended them into the bowls. The intake side just needs to be de-burred and the bowls cleaned up. If you need new valves, then by all means go larger on the size, but otherwise the stock size will work fine on a street motor.

that is exactly what the rebuilder was saying, thanks for clarifying it for me.

 

[68GEETEE]

Buy aftermarket heads! Keep your "originals" as paper weights in your garage/shed.

Trying to do all that work to stock heads is like wiping your azz with $100.00 bills!

Anyone who tells you different is an idiot.....period.

The '68 heads are date coded with my engine block, which means something in the car we are speaking of.

Standard compression with stock closed chamber '68 heads was 10:1 approx 58cc combustion chambers. While they may not compare to Dart heads, with a good port job they are far from paperweights.

I was trying to clarify the machinists statements, not interested in building a race motor at this time.

 

[D.Hearne]

The 68 4bbl 302 heads are basically a later casting of the older 289 heads with 53 cc chambers, not 58cc. Just open them up as I said and they'll work fine up to 5500-6000 rpms with a good cam.

 

[68GEETEE]

The 68 4bbl 302 heads are basically a later casting of the older 289 heads with 53 cc chambers, not 58cc. Just open them up as I said and they'll work fine up to 5500-6000 rpms with a good cam.

yep, i wasnt 100% sure about the chamber cc. I appreciate the replies, thanks!