340 with edelbrock heads overheating

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That looks like an Oregon Cam Grinding sheet. They are very good, shouldn't have any concerns about them. Not that they couldn't make a mistake but not likely.

Sounds like you did everything to get air out of the system. Can't remember how many miles are on the engine but rings could be tight causing heat. Mine took over 1000 mikes to cool down after my rebuild. My guess it was a combination of air and rings.
 
At this point it's a good time to put the cast iron X heads back on with a 3 angle valve job and watch that baby cool right down.

No more guessing, no more what ifs?

Just do: X heads and done. The way Ma Mopar intended it.

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if you dont want to centerline the cam, install it dot to dot and use it that way. checking lifter height at tdc is not precise enough to set a cam. your intake lifter being higher than the exhaust only means your cam is advanced, but you dont know how much. your cam requires 104 degrees intake centerline, which would be 4 degrees advanced ( 108 lobe separation minus 104 intake centerline). i would think your cam grinder is right in saying to leave it alone if you set the gears dot to dot. the cam you got is not for racing use, where you would want that last ounce of hp. for a street application, you wouldnt FEEL the difference if you centerlined it.
your cam is probably already ground for 4 degrees of advance already.
 
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your overheating problem is probably caused by tight piston to wall clearances. it will improve as you put more miles on it.
another thing : check your piston to head clearances . the piston shouldnt have touched the head anywhere, especially in the chamber . i believe it may be contributi
ng your engine to overheat , especially because you said that it didnt overheat before you switched heads. cometic gaskets are available in thicker sizes, although more pricey. you dont have to have the heads nor the pistons machined if you find that you dont have enough clearance, just use a thicker gasket.
 
since your heads are off of the engine, here is a quick test in order to find out if you have enough piston to head clearance. install the head with a few bolts WITHOUT a head gasket. turn the engine BY HAND, it should turn freely. you dont even need to use the rockers for this test. if it hits and jams, it means that you have less than the gasket thickness (.039 in.) for piston/head clearance when everything is assembled . the mopar bible calls for .055 in. MINIMUM.
 
7e5hangten360 said:
since your heads are off of the engine, here is a quick test in order to find out if you have enough piston to head clearance. install the head with a few bolts WITHOUT a head gasket. turn the engine BY HAND, it should turn freely. you dont even need to use the rockers for this test. if it hits and jams, it means that you have less than the gasket thickness (.039 in.) for piston/head clearance when everything is assembled . the mopar bible calls for .055 in. MINIMUM.
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If you read the entire thread, you will see all of this and more has been suggested. I would like to see him get some clay measurements which would put it to bed for good....and that has also been recommended already.
 
Why isn’t the compression ratio change between X-heads and edelbrocks being addressed?

He could be detonating and not hearing it.

If he was at 8.88 before he likely would be at 9.88 now.
 
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I do not read sideways too well, but I am seeing a 292 Adv Duration cam, 241 @ 050.
A very poor choice in a small block for a car that will be street driven.
It needs compression, heaps of timing at idle [ about 35* or more ] & probably carb work on the T slot position.
Retarding the cam would be the WORST thing you could do, like putting lipstick on the pig. Since this is a single pattern cam, when the cam is 'straight up', ie at TDC the int CL equals the exh CL equals the LSA, 108 in this case. When the cam is advanced, the ICL# is lower. 104 ICL means the cam is 4* advanced. With a single pattern cam [ which this is ], easy to check the grinding accuracy. Most cams have about 4* ground in to them. With the timing chain dot to dot & #1 at TDC on the overlap stroke, the int lifter will be slightly higher than the exh by about 0.005" to 0.030". The exact # does not matter. Cam is advanced. If the int lifter is lower, cam is retarded. Bear in mind a discrepancy could be in the timing chain set as well as the cam. There is no way of knowing what THIS engine will like in terms of cam adv/ret, only experimentation will determine that. Check V/P clearance if moving the cam around.
 
ok did first cam degree attempt. came back at 105.5 so that's good. Will try again to see if it replicates. If good then i am good with the cam.
 
ok, checked then rechecked the cam and it is good each time comes back at 105.5. it does not appear to be the cam. Heads are at the engine builder he is going to make sure there are no problems with those. If all is good will slap everything back together. Then have an excorsism to remove the evil spirits. Say a little prayer and fire it up
 
autoxcuda said:
Why isn’t the compression ratio change between X-heads and edelbrocks being addressed?

He could be detonating and not hearing it.

If he was at 8.88 before he likely would be at 9.88 now.
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Aluminum heads are more resistant to detonation than iron and therefore they can typically be run at higher compression than iron. I don’t know how good the gas is where the OP is, but I’ll bet the increased compression is not the issue.
 

lilcuda said:
Aluminum heads are more resistant to detonation than iron and therefore they can typically be run at higher compression than iron. I don’t know how good the gas is where the OP is, but I’ll bet the increased compression is not the issue.
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I believe RAMM or another engine builder here did a dyno comparison. And the aluminum resistance was in tenths. Not a whole number.

If he was 10:1 before and now it's 11:0, the detonation resistance will not cover that on 91 octane pump gas typically with that cam.

It all depends where the x-heads were at. If before was under 9.0:1, he may be ok.

And the number he's at right now may be ok in theory. But the compression jump may be bringing to light other issues.
 
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Higher compression increases the heat.

It's a hotter fire with more energy released.

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George Jets said:
Higher compression increases the heat.

It's a hotter fire with more energy released.

☆☆☆☆☆
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So? Higher compression can lower exhaust temperatures and the quicker the burn the more heat works to turn the crank and not end up in the exhaust port.
 
Depends on how efficient the chamber is and if there's quench. A good quench engine can run cooler at a higher compression ratio than one with crappy chambers and lower compression ratio.
 
Bewy said:
Exactly. Higher CR burns quicker, needs less timing advance.
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It depends on how you get the higher compression. If you have a large dome on the piston it can slow down the burn rate and require more ignition lead.
 
ok, got the heads checked out. They were both bowed. He had to take out .6000 off each head. Keep in mind the heads never got hotter than 215 or so based on my ir gun. so it may have been warped heads the entire time. not sure how much these heads can take in terms of heat but this was a very interesting development.
 
Early a body said:
ok, got the heads checked out. They were both bowed. He had to take out .6000 off each head. Keep in mind the heads never got hotter than 215 or so based on my ir gun. so it may have been warped heads the entire time. not sure how much these heads can take in terms of heat but this was a very interesting development.
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I’m guessing you really mean .060 off because .600 is damn near 5/8 inch.

I’ve seen heads move that far without getting too hot. If the fasteners get a bit loose (this was a big deal in the 1980’s when everyone and their mother was making composite gaskets that needed to be to retorqued at least twice stay tight (if you were lucky).

Once the fasteners got loose the head would bow up right quick and the poop fest was off and running.
 
ok, got it back togeher . same thing is happening.

one thing i did while playing around trying to figure what the heck is going on is i disconnected the pvc at the carb . the idle increased. Then i took it off at the valve cover while still plugged into carb, it did not like that. When i disconnect at the carb and plug the pvc at the carb with my thumb it wants to die. am i on to something?

finally i noticed the metering rod was jumping up and down while at idle. I went to the blue spring and that solved that.

last the ide mixture sceews are now very little responsive. IF I turn them all the way in they will not kill the car. SO I may still have an issue of some sort.

I am using a mid 80s chevy pvc because it fit in the grommet. Have not found another yet that does.

any suggestions?
 
There are many possibilities here. Met rods jumping around at idle means low vacuum. So does the PCV behaviour.
Low vac could be cam installed retarded, wiped cam lobes or just a long duration cam, where low vac would be normal. Or valves not seating. Many suspects!!
If you remove the carb, I suspect a large amount of the t-slots will be visible below the t/blades [ more than 1/16"] .
This fits with the above scenario. This would not be a faulty carb problem, but a result of the above.
12* at idle with a big cam is NOWHERE near enough & will give above symptoms. But is it a big cam? PCV will also act erratically with a big cam. You can feel this by idling the engine with your finger on the PCV; if you feel movement [ vibration ] , then the vac is insufficient to pull in the internal pintle [ the PCV is just as valve that closes off against a spring ]; engine must have enough idle vac to overcome the spring & pull in the pintle.
 
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