Will 318, 340 or 360 heads fit on a 273?

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DodgeA100Van

DodgeA100Van

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Will 318, 340 or 360 heads fit on a 273? I have a 1966 A100 van with a stock 273/727 auto. After a lot of searching I see this question gets asked a few times but I can't seem to find an actual answer. Most people advise to upgrade to a larger cube motor but I want to keep the 273. I have the motor yanked as of today and I want to do an affordable rebuild with a little more power than bone stock. I am finding that the cost of aftermarket 273s heads is very steep, while 318/340/360 heads are much more affordable. What will actually fit without spending too much $$$ in the machine shop? Also, what configuration of cam/carb/heads etc will get me the most bang for my buck? Thanks in advance!

IMG_20190311_110455.jpg
 
I have 318 heads on my 1965 Barracuda 273. I believe the valves are a little larger on the 318 heads. Check it out.
If you ever want to use the Performer aluminum intake manifold on a 273, the 318 heads match the angles of the intake manifold whereas the 1965, and I think the 1966, 273 head angles do not exactly match this manifold. You can bolt them up, but you will have vacuum leaks. Edelbrock says this manifold fits the 1965 273. Uh-Uh.
 
340 or 360 heads wont work without notching the cylinders for the larger valves. Try to find 318 heads with 302 casting and closed chamber design.
Check the heads you have now, 65 and older have the different intake angle from 66 and up( more common)
 
318 heads only and only the early closed chamber heads or the mid 80's #302 casting heads that 4 speed mentioned. If you put open chambered heads on a 2 barrel 273 your static compression will be in the 7:1 range and it will be a gutless wonder.
 
toolmanmike said:
318 heads only and only the early closed chamber heads or the mid 80's #302 casting heads that 4 speed mentioned. If you put open chambered heads on a 2 barrel 273 your static compression will be in the 7:1 range and it will be a gutless wonder.
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Pls explain the difference in design between closed chamber heads and open chambered heads.
 
Flip the heads upside down with the valves up.
Open chambers will have a big round "open" design that the piston can pop into quite far without hitting anything. Whereas
a closed chamber will not allow the piston to enter it at all, as there is a big wedge of material on the one side of the valves.
The open chamber heads could have a capacity to hold as much as ~72cc of water, whereas the closed-type comes in at 57 to 60cc
For a normally-aspirated 273, forget any open chamber big-port heads.

A stock-bore 273 has a swept volume of ~562cc. Even if you install flat-tops at zero-deck and an .039 gasket, the TCV (total chamber volume), with uncut open-chamber heads might total 80cc and your Scr will be in the basement at 7.95; that's at zero deck, which you would have to make happen. More likely, without decking, the TCV might come in at 90cc, dropping your Scr to 7.2 like Toolman said; hopelessly inadequate for anything but supercharging
Whereas;
with closed chambers of 57cc and pistons down .057 in the holes, she might make 8.7. That you can work with.
BTW
AFAIK all 318 heads will bolt onto all 273s. The angle error talked about is in the bolt angles that draw the intake down. The older heads are set up for the older intakes, and vice versa. IIRC the change happened in 66. There is nothing inherently wrong with the bolt angle, except 4bbl intakes are hard to find. The bolts are in the same place, and I have heard that some guys have modded their late intakes to fit on early heads.
You can install the newer 318 closed-chamber heads circa 1966/67,on your 273 as long as you also bring along any later matching intake. But I think 318 heads are spec'ed at 60cc, versus 273s at 57cc; I think.
AFAIK all 273/318 heads were closed chamber up to 67. (or maybe 68). And
AFAIK all 273/318 heads had the same valve sizes of 1.78/1.50 ..
 
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My thoughts..........

Don't worry about about changing heads........keep yours, do a good valve job, cut them .030 to reduce chamber volume, put a Performer intake on with a 500 cfm Eddy carb, install a stock 360 Hydraulic cam, try a set of 360 exhaust manifolds........a little wake up not alot of money

BTW, nice van
 
The are 302 heads see how they have the heart shaped chamber. I will post a separate pic of an open chamber head
Closed chamber head

20181109_084617.jpg


Opened chamber head

20190310_090550.jpg
 
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Having done the swap, I put 340/360 heads on "64" 273 .040 over. Not even close to a dog. I used "72" 340 "J" heads with 1.88 intake valves. Topped off with "71" 340 intake, TQ and the "72" 340 cam. The heads were milled .040 and .038 on the intake side to min cc, 64.7. I also had TRW forged 10.5:1 pistons and mocked up the heads to the block using offset dowels to center the chambers on the bore. I would not recommend doing that with your van though. Your "66" 273 heads flow about 10-15 cfm less than J heads throughout the range till .500 lift. 302's flow 10-18 less than your heads, and 318 heads flow in between the two with larger chambers. All 273 and 318 heads have the same valve sizes. So, I'd have your heads rebuilt, Get a nice 4 barrel intake, including a factory 340 and any 4 barrel carb, I find Carter/Edelbrock more reliable. Get a cable operated kickdown set up. Use a 340 throttle cable bracket. Put in an Isky E-4 solid lifter cam, or similar and enjoy. Use your exhaust manifolds and run duals or go the Commando route and go single with a 2.5 pipe from the Y with 2 glass pack mufflers in series.
 
66fs said:
Having done the swap, I put 340/360 heads on "64" 273 .040 over. Not even close to a dog. I used "72" 340 "J" heads with 1.88 intake valves. Topped off with "71" 340 intake, TQ and the "72" 340 cam. The heads were milled .040 and .038 on the intake side to min cc, 64.7. I also had TRW forged 10.5:1 pistons and mocked up the heads to the block using offset dowels to center the chambers on the bore. I would not recommend doing that with your van though. Your "66" 273 heads flow about 10-15 cfm less than J heads throughout the range till .500 lift. 302's flow 10-18 less than your heads, and 318 heads flow in between the two with larger chambers. All 273 and 318 heads have the same valve sizes. So, I'd have your heads rebuilt, Get a nice 4 barrel intake, including a factory 340 and any 4 barrel carb, I find Carter/Edelbrock more reliable. Get a cable operated kickdown set up. Use a 340 throttle cable bracket. Put in an Isky E-4 solid lifter cam, or similar and enjoy. Use your exhaust manifolds and run duals or go the Commando route and go single with a 2.5 pipe from the Y with 2 glass pack mufflers in series.
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I don't think we should go there. You used big port, small valve, open chamber heads on your 273 build and made them work. It sounds like you built your engine around the heads. From what I see, the OP is a beginner. He is learning here and doesn't know the difference between open and closed chamber heads. Let's not confuse him with a fairly complicated combination. It sounds like he should keep it simple.
 
273 & 318 have the same size valves. the 273 heads will NOT have hardened seats for todays unleaded fuels. I'd put 318 heads on it with hardened seats. A good pair of 302's would be nice IF you can find them not cracked. Otherwise, I think I'd just go with a typical 318 smog head. You can bolt any intake you want on them.
 
318willrun said:
273 & 318 have the same size valves. the 273 heads will NOT have hardened seats for todays unleaded fuels. I'd put 318 heads on it with hardened seats. A good pair of 302's would be nice IF you can find them not cracked. Otherwise, I think I'd just go with a typical 318 smog head. You can bolt any intake you want on them.
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I typically skip hardened seats and replace the exhaust valves with stainless steel. No problem so far. The exhaust valves usually need replacing anyway. Use what you have. He does not need much more than what he has.
 
66fs said:
I typically skip hardened seats and replace the exhaust valves with stainless steel. No problem so far. The exhaust valves usually need replacing anyway. Use what you have. He does not need much more than what he has.
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I've seen exhaust seats beat 1/16 into the heads... just say'n. that's why I prefer hardened exhaust seats.
 
toolmanmike said:
I don't think we should go there. You used big port, small valve, open chamber heads on your 273 build and made them work. It sounds like you built your engine around the heads. From what I see, the OP is a beginner. He is learning here and doesn't know the difference between open and closed chamber heads. Let's not confuse him with a fairly complicated combination. It sounds like he should keep it simple.
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You will see I answered his question, then recommended he use the "66" heads he has.
 
Only 64 and 65 273 heads had the 5/16 odd angle intake manifold bolts. They take a 1/2 in socket. 66-69 273 heads use the same intake manifold as 318 heads.
 
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I’d have the original heads rebuilt if they have the newer style intake mounting configuration, and aren’t cracked.

Have hardened ex seats installed.
 
66fs said:
Were they stainless steel valves?
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Not sure I understand the question. Are stainless valves softer and cushin' the seat? The seats get beat in because there is no lead to cushin the valve hitting the seat, and it will beat the seat into the head if they are not hardened seats. It's the hardness of the seats that protect the seats.
 
318willrun said:
Not sure I understand the question. Are stainless valves softer and cushin' the seat? The seats get beat in because there is no lead to cushin the valve hitting the seat, and it will beat the seat into the head if they are not hardened seats. It's the hardness of the seats that protect the seats.
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The cast iron head sticks to the stellite exhaust valve face and acts as a cutter. I have seen Chevies about 3/8 down or more from the top. Good stainless steel does not pick up cast iron on the valve head.
 
OP, since the enigne is out, pull the heads, put a piston carefully at TDC. Measure how far down the piston is from the block's deck at TDC.I bet is going to only a few thousandths if it is a 2 BBL engine. Those early 273's & 318's had higher pistons than later 318's. If so, then with a .028" head gasket, then the static CR is going to be over 8:1 with the 675 heads, WITH THOSR STOCK PISTONS. If you use aftermarket pistons, then that will change.

675 is the last 3 digits in the casting number on the head for the later open chamber 2 BBL heads on 273's. They have chamber volumes that are typicaly around 68 cc's. Look at you heads and find the casting number, it is a 7 digit number and is usually cast on the intake runner. Let us know what you find there. And if you would please, can you post some pix of the tops of the pistons and the chambers in the heads?

675's have 1.78" intake valves and were used in the earlier 318 2 BBL engines. You can upgrade these to 1.88 valves with little or not notching of the tops of the bores.

I'd do as advised before and have yours re-worked, since you just want a modest improvement in HP. A modest cam upgrade and a small carb will help. The cam selection needs to be carefully done.
 
nm9stheham said:
675 is the last 3 digits in the casting number on the head for the later open chamber 2 BBL heads on 273's. They have chamber volumes that are typicaly around 68 cc's.
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I thought -675 open chamber heads didn't come around until 68

OP's 1966 stock 273 should have -920 closed chamber heads,no? Which IIRC are speced on 273s, closer to 57/60cc,no?
 
A stock 66 273 will have closed chamber heads. Pistons should be around .020 in the hole at TDC. The 66 heads flow better than the 68-70 675 heads. 1.88 valves in a 273 is a must check. I would advise keeping the stock valve sizes. Probably not 920's but about equal. 57cc is NHRA minimum and it takes a .040 cut to get there.
 
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