67 383 rebuild suggestions

Just did a compression test...pretty happy with the results. D123 128 125 130 P130 130 125 128. This was done warm with no oil added to the cylinders. 4 hits. Reached these numbers by the second or third hit. Plugs are old...worn out...running a bit rich. Some blow by on two cylinders but not extreme. This was also right after warming it up till it came off choke....so that may be some of the richness I'm seeing but I think the carb is rich anyway. Going to change the plugs...recheck and adjust for the moment. Then change the timing gear set.
 
413 said:
You would be wise to stay with closed chamber heads. You will give away too much compression with open chamber heads. It would be a losing decision.
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The heads on my 67 383 sport fury were 915 castings but had the small valves. I had them completely redone and changed to hardened later/larger 1.74 exhaust valves. I plan on putting them on my 68 440 HP one of these days. The OPs might be 915 castings as well.
 
swisherred said:
915...what can anyone tell me about these
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Have them re-done and swap to larger 1.74 exhaust valves ... or perhaps with luck yours are already 1.74 and just put in hardened seats and the rest of the work.

They are closed chamber and were used on the 67 440 HP engines ... those had 1.74 E valves. in 68 they changed to open chambered heads w/ the 1.74 valves.
 
swisherred said:
915...what can anyone tell me about these
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They’re one of the more sought after castings in the Mopar world but I can almost guarantee you have 516s. The good news is that these have the same potential as the 915 HP heads.
 
detmatt said:
They’re one of the more sought after castings in the Mopar world but I can almost guarantee you have 516s. The good news is that these have the same potential as the 915 HP heads.
Click to expand...

take some pics of the casting numbers swisherred
 
2780915-1

20190209_103815.jpg


20190209_103824.jpg
 
Score.

I had a set done, new valve guides, valves, springs, retainers, expanded valve to 1.74, hardened seats, very minor bowel work on exhaust, and slight milling to to true surface. $900. That was about 5/6 years ago.
 
swisherred said:
They are 915....very clear casting towards upper front between 1st and 2nd set of valves.already changed the gasket and reinstalled
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I’m really surprised and happy to be wrong in this case.
 
swisherred said:
Just did a compression test...pretty happy with the results. D123 128 125 130 P130 130 125 128. This was done warm with no oil added to the cylinders. 4 hits. Reached these numbers by the second or third hit. Plugs are old...worn out...running a bit rich. Some blow by on two cylinders but not extreme. This was also right after warming it up till it came off choke....so that may be some of the richness I'm seeing but I think the carb is rich anyway. Going to change the plugs...recheck and adjust for the moment. Then change the timing gear set.
Click to expand...
I'm just going to throw this out there...

The car is running. Change the timing gear set to give you some peace of mind. Then just go out and drive it. Have some fun, work on a couple other things that aren't going to put the car into pieces. The car will run better with good plugs and getting it tuned right.

Too many times I see cars taken apart with good intentions and next thing you know, it's a massive, expensive project that drags on and the fun goes away.
 
Leave the small exhaust valves in there. You will have better throttle response and low speed torque. Sounds like it fits with your planned use of the car.

Bigger valve’s will only be noticed at higher RPM and with the throttle close to wide open.
 
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Changing the rear end gear ratio will make a big improvement. It is like riding a 10 speed where you have to work hard to hold a speed, then shifting down 1 or 2 gears and it becomes much easier.

I always. It notice improvements when moving up numerically from the 2.76 gears.
 
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With those compression test readings look pretty good!! If it was mine I would leave the heads alone.
 
swisherred said:
I only want to do the heads because of the valve seats...maybe this car wasn't abused...
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Well... If you have the heads apart, it's a great idea to install hardened seats, but in reality, they aren't as necessary as you might think. The idea is that the unleaded gas will shorten the life of the valve seat. That's true to some extent, but you won't see the effects for tens of thousands of miles. Even then, the Mopar heads aren't as soft as, let's say a SBC head. Chances are it will never cause you a problem.

Taking the head off just to replace the valve seats isn't worth the effort or money.
 
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