351c head id markings

pabear89 · Jul 20, 2003

Does anyone know if there is anyway to tell the Heads apart from open and closed chambered. Short of taking them off.

I have been looking for some kind of telltale mark to let me know so I can continue to collect parts for motor rebuild.

I have the large 4V heads, there is a 4 cast in the corner with a dot a little smaller than a pencil size diam.

does anyone have a set of these heads off to look for me,
am in need of help. thanks

D.Hearne · Jul 20, 2003

If your heads are original to your 70 Stang , then yes you have the quench chambered heads. The open chambered heads didn't come out till 71. I don't think the CJ 351 was available til 71 also.

pabear89 · Jul 20, 2003

DH, The motor is not the orginal, it came with a 351c 2V auto. when i got the car there was a rod thru the block and trans was shot.
the 351c was transplanted in it from?
was a deal from a freind of a friend, he did not know what it came out of other than it was a 351c 4V and also had a rug toploader 4speed with it and it ran. we slapped the motor in and it has been running good for the past couple of years. i did not check any of the code stamps before putting it in, and only found out it has a 4 bolt main from changing the oil pan, Had a Hard hit on a steep driiveway one foggy night.

D.Hearne · Jul 20, 2003

Do a compression check. I know someone hear could possibly translate the results into the comp ratio. Does it ping readily? Open chamber heads are notorious for pinging, the quench heads are more tolerant of lower grade gas.The CJ heads also had screw-in studs and guide plates from the factory, they were just open chambered versions of the Boss heads

pabear89 · Jul 20, 2003

last time i ran test was when it started having a crappy miss in mid range rpm. they all ran about 135-145.
found the breaker plate in the dist was bad, so installed a axcell duel point that was new and on the shelf from a box i got at a auction. [good find at the bottom of the box]
have not pulled the v/covers yet.

I was happy to find the motor/ trans for it and for 500.00 it was a deal cause the guy was moving and had to get rid of it quick.

we hooked a battery to it and a shot of ether just to see if it would fire, it came to life and we loaded it up.

all the guy could remember was the orig car had less than 70k miles on it.

kid vishus · Jul 21, 2003

If the heads are the factory heads that came on the block, you should be able to tell from the casting numbers on the block that should be visible from underneath. If it is 72 or older (first digits D2), they are open chamber. If it's a 70, then they are closed, 71, could be either. The only real way to tell is to pull them off. If someone changed them before you got the motor there is no way of knowing which they are.
The dot on the head means nothing.

Regardless of which they are, they are good heads.

pabear89 · Jul 21, 2003

I may have found the answer, while searching thru Ebay I can accross a set of heads for sale that have the same markings that are on mine.
they are the Boss 351 adjustable closed chambered 61cc heads.
there are 4 or 5 sets on Ebay and thes are the only ones with the dot in the casting after the 4.
with any luck this is a Boss motor.

'69coupe · Jul 21, 2003

pabear89 said:
I may have found the answer, while searching thru Ebay I can accross a set of heads for sale that have the same markings that are on mine.
they are the Boss 351 adjustable closed chambered 61cc heads.
there are 4 or 5 sets on Ebay and thes are the only ones with the dot in the casting after the 4.
with any luck this is a Boss motor.

So the dot next to the 4 means they are closed chamber heads?

I'm wondering because I also have some 4V cleveland heads with the dot and don't know if they are open or closed chamber. They do have ford guideplates, screw in studs, and stud girdles though.

Also, what is the difference between a normal 351C and a 351 Boss?

stackz · Jul 21, 2003

I could have sworn it was the other way around hearne?? the quench heads give the higher compression ratio and give the pinging with pump gas and the open chambers give the lower ratio and better on pump gas (at least this has always been my experience with clevelands).

the most cj motors and boss 351's (hell half of 4v engines) used the same block with 4bolt mains so that will be the same if you've got a 4-bolt main. what is the block casting number? you can pop the valve cover off the head and get the part number and I can tell you if you've got closed chamber or open chamber heads...

the markings on the 4v heads are all the same except for the part numbers so don't get your hopes up as I doubt you've got a boss engine (with heads)...was it a completely stock engine when you tossed it in?? did it have the stock ford intake manifold on it?? if it did and the manifold is aluminum and a quadrajet setup then you've probably got a boss engine or at least an H.O. engine which is the de-tuned 72 boss...

as for the dot that just means you've got early 72 4v or earlier heads...ford retooled for the gas crunch after about february 72 and the dot dissappeared so odds are they are closed chamber heads.

pabear89 · Jul 21, 2003

guess that i will have to pull the valve cover off to find out.
was hoping that i could find out without doing that, but.
will have to see what is under there to be sure.

will hope for the best, and see if there is studs and guide plates already installed.

D.Hearne · Jul 21, 2003

stackz----- the open chambered heads I'm running on my kid's 400 ping like crazy, even ping a little with 93 octane. The 390 in my 68 Monterey has quench heads and running a 10.5 to 1 comp ratio, it runs fine on 87 octane mixed with CD2 lead substitute. My brother had a quench headed 351C back in the 80's and it too would ping but, it had the stock 4 bbl Clevland cam, which had relatively little overlap to bleed off some of the 11 to 1 compression. My Monterey would ping before I overhauled it and stuck in a Crane 272 degree Energizer cam. I think based on my experiences that it's better to run quench heads than open with lower octane fuel as long as you don't get too radical on the comp ratio.

hungrymonkey · Jul 22, 2003

anyone know the cc size on a set of 73 2v heads?

hungrymonkey · Jul 22, 2003

oops. the picture is of a set of aussie 2v closed chambers.

i didnt think it would let me hot link it.

D.Hearne · Jul 22, 2003

The open chambered heads are around 76 cc's , to know for sure you'd have to cc them. Get a thick piece of plexiglass from your local glass company, that's large enough to cover one chamber. Then drill a small hole in it. Get the bigest syringe from your favorite nurse and some fluid ( I can't remember what works best) , seat a pair of valves in a chamber, using white grease to seal them. Then cover that chamber with the glass also using white grease to seal it and keep it in place. Inject whatever fluid you've chosen to use thru the hole and fill the chamber, keeping track of how much fluid it takes to fill it. Nuttin to it!!

stackz · Jul 22, 2003

hungrymonkey said:
oops. the picture is of a set of aussie 2v closed chambers.

i didnt think it would let me hot link it.

lol, I was about to say something on that too...

wow hearne, I've never had problems with pinging on open chamber heads...only closed chamber heads

and yeah, that cc method is easy and cheap, can't beat it

D.Hearne · Jul 22, 2003

Stackz----- part of the problem with my kid's 400 is there's too much deck clearance. The piston sits .050 down the hole at TDC and combined with a .040 head gasket, there's virtually no quench with that and the open chambers. I used a set of 351C forged flattops in it, but it really needs taller pistons. I milled the heads .030 and polished the chambers but it still pings.

stackz · Jul 22, 2003

D.Hearne said:
Stackz----- part of the problem with my kid's 400 is there's too much deck clearance. The piston sits .050 down the hole at TDC and combined with a .040 head gasket, there's virtually no quench with that and the open chambers. I used a set of 351C forged flattops in it, but it really needs taller pistons. I milled the heads .030 and polished the chambers but it still pings.

oh ok...400M....nuff said. I don't even wanna know how low that compression ratio is

have you tried advancing the timing any over stock and running a colder thermostat??

D.Hearne · Jul 22, 2003

The comp ratio on this 400 is now 9.7 to 1 ( if my calculations are correct) We've set the timing everywhere from 8 degrees initial to 12-14. Pings like crazy with 87-89 octane at 12-14, 93 octane cuts the pinging almost out. Backing the timing down to 6-8 gets rid of it too, but cuts the power as well.Can't run a colder T-stat due to the forged pistons and a little too much piston to wall clearance. Motor will rattle soo much you can't stand the noise. But it does run like a spotted ape.

pabear89 · Jul 25, 2003

Ok, took off the covers and this is what is under them.
would use Super Daves RTM, but this is not in the ford manuels that i have for this car.
the drivers head has 2J2 cast on it and the pass side has 2H8.
no other # am able to see short of removing the heads.

The adjustable push rods seem that they would be the weakest link in this valvetrain.
any help ID ing these heads would be great.

stackz · Jul 25, 2003

pabear89 said:
Ok, took off the covers and this is what is under them.
would use Super Daves RTM, but this is not in the ford manuels that i have for this car.
the drivers head has 2J2 cast on it and the pass side has 2H8.
no other # am able to see short of removing the heads.

The adjustable push rods seem that they would be the weakest link in this valvetrain.
any help ID ing these heads would be great.

crap...that's what I was afraid of...sigh...my bad man. Being here in atlanta away from the shop in charleston and not having been able to mess with any cleveland stuff in the past year my mind got foggy. Couldn't remember if the part number was in the rocker area or under the intake ports...apparently it must be under the intake ports.

so unless you wanna pop off your intake manifold and use a mirror to read the numbers then we'll just be happy they're 4v heads and not 2v heads

351c head id markings

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