Cyl heads.

[bluefury361]

I may have more serious issues then I would wish for with my 67 Polara. I've been chasing a "miss" since I got it running and driving. I thought i'd run a compression check yesterday. Easiest access to plugs is #1, so I started there. No compression.... I thought perhaps the gage was defective but #3 had 125 lbs. I just stopped there.

I'm wondering when the first year hard seats were installed in the BB heads, 71/72?
Most likely scenario, I think, is a burnt exhaust valve. I may be fishing for a later model set of heads.

 

[detmatt]

I bought a great Depstech wireless camera with led lights that I can use with my iPad that fits right through the spark plug hole and gives a very clear image of what’s in front of it. Before I fired up the 413 in the ‘64 I sent that in to see what the cylinders looked like and to my surprise I could see the faces of the open valves clearly.

 

[67Monaco]

I bought a great Depstech wireless camera with led lights that I can use with my iPad that fits right through the spark plug hole and gives a very clear image of what’s in front of it. Before I fired up the 413 in the ‘64 I sent that in to see what the cylinders looked like and to my surprise I could see the faces of the open valves clearly.

I use this one attached to my phone.

https://www.amazon.com/Seesi-Endosc...s=usb+inspection+camera&qid=1588174470&sr=8-3


Burnt valve? Have to be one hell of a burn to have 0 compression. You should still see something, however slight.

 

[413]

Agreed, a burnt valve takes some time to happen and should still have some compression on a gauge.

Sounds like a valve not closing or a hole in the piston to have zero, like something major wrong. Doesn’t mean a hard fix though. Check it out,

Remove valve cover and make sure the valve stems are returning to closed height.

Blow compressed air in the cylinder with the valves closed and see where it comes out, exhaust pipe, out the carb, or valve cover breather.

 

[live4theking]

That's no fun Will. I hope you find something simple.

 

[ricks_RR]

My 68 imperial had a skip and i found it had # 5 cylinder valve guide was worn i put 440 source heads on and it runs great .

 

[bluefury361]

Thanks for the bore scope suggestion guys. I ordered one.

I figured perhaps a cracked ring, valve or valve guide. I wish I could have had control of the start up after the long storage. That took place about 11 years ago and who knows what precautions were taken.

It doesn't smoke and oil consumption sees normal so I doubt it is a piston, or even a ring. There is a noticeable miss on acceleration from the exhaust.
The proper way to check compression is to remove all 8 plugs. Once the scope arrives I will go through the compression check and "scope" the cylinders. Sounds like fun.
I will also shoot a little oil into #1 and see if that will give me a compression reading. Yes means a ring or piston issue, no should be a burnt or stuck valve.

I was hoping the next step would be a new top...... But engine repair and under hood detailing is just as good. Beats fixing rust....!

 

[78Brougham]

Cylinder leak down tester. Most accurate way of checking valves rings etc.

 

[413]

You don’t need all this fancy stuff for a zero compression cylinder. Blow shop air in the spark plug hole at TDC firing stroke and you will quickly know where the air is escaping. IE the problem

 

[HWYCRZR]

I may have more serious issues then I would wish for with my 67 Polara. I've been chasing a "miss" since I got it running and driving. I thought i'd run a compression check yesterday. Easiest access to plugs is #1, so I started there. No compression.... I thought perhaps the gage was defective but #3 had 125 lbs. I just stopped there.

I'm wondering when the first year hard seats were installed in the BB heads, 71/72?
Most likely scenario, I think, is a burnt exhaust valve. I may be fishing for a later model set of heads.

If you do find it is your heads, and they are not damaged i/e cracked a good valve rebuilding machine shop can add the hardened seats. You like original, so this gives you the option.

 

[4spd300J]

If you remove the valve cover, check that the rocker arms aren't worn out on the bottom of the shaft. Also check out the push rods on that cylinder, a sticking valve can bend or unseat one.

 

[67Monaco]

Thanks for the bore scope suggestion guys. I ordered one.

I figured perhaps a cracked ring, valve or valve guide. I wish I could have had control of the start up after the long storage. That took place about 11 years ago and who knows what precautions were taken.

It doesn't smoke and oil consumption sees normal so I doubt it is a piston, or even a ring. There is a noticeable miss on acceleration from the exhaust.
The proper way to check compression is to remove all 8 plugs. Once the scope arrives I will go through the compression check and "scope" the cylinders. Sounds like fun.
I will also shoot a little oil into #1 and see if that will give me a compression reading. Yes means a ring or piston issue, no should be a burnt or stuck valve.

I was hoping the next step would be a new top...... But engine repair and under hood detailing is just as good. Beats fixing rust....!

Pull the valve cover and see if the valve is stuck. Or if a pushrod got stuck and holding the valve open. Be worth it during the delay for shipping.

 

[bluefury361]

To darn many projects going on.... LOL. I'm headed up to where Connie has been for the past 8 months to do some maint and repair on her. I'm still optimistic about Carlisle and she has to be made ready. Also gearing up for the final assult on Virgil. Complete the finish body work, cut in the paint color, restore the stub frame and reassemble to, hopefully, running condition. Maybe even final paint.
I'll get on the Polara next week.

I thought retirement and living at the beach would be easier then this.

 

[monaco75]

Beats fixing rust....!

Just rub it in!! LOL

That sucks Will. Hopefully it is something fairly “simple”.....

 

[FURYGT]

Will, Sorry to hear you might have a problem. I am going by memory and believe that your '67 383 has the 516 closed chamber heads with the small exhaust valves (whereas the 440's used 916 heads with larger exhaust valves). My recall is that from '68 & up, open chamber heads were used. As I recall using closed chamber heads on your engine would kill your compression and power as I believe that different pistons were used. Someone with a better a memory can confirm and expand on this and make sure that I don't have the open and closed chamber heads backwards.

 

[detmatt]

Will, Sorry to hear you might have a problem. I am going by memory and believe that your '67 383 has the 516 closed chamber heads with the small exhaust valves (whereas the 440's used 916 heads with larger exhaust valves). My recall is that from '68 & up, open chamber heads were used. As I recall using closed chamber heads on your engine would kill your compression and power as I believe that different pistons were used. Someone with a better a memory can confirm and expand on this and make sure that I don't have the open and closed chamber heads backwards.

On 440s The 516s were used through ‘66 and early ‘67(my silver Imp is very early and had 516s). For ‘67 the 915s were used with the same 1.60 exhaust valve of the 516 except in HP applications where the 915s had the 1.74 exhaust valves and were actually stamped HP.
The Director is a late build and has 915s with the 1.60 exhaust valves.

 

[70bigblockdodge]

Only the 452 castings are true hardened seats 76-78. 902, 241, 346 are all only surface hardened, couple thousands, meh.
The 452s will drop the compression in the toilet on a 383 with closed chambers on it. I would just rebuild and up grade what you already have IMO. I would open the exhaust up to 1.74 and also get new one piece intake valves. With no lip on the valves, the larger virgin cut seat on the exhaust, power increase for little to no cost and no down side that will last beyond you, me and some of the younger members on here. Oh, and you still keep the closed chamber anti detonation resistance you already have and would lose with a open chamber later head.

 

[Wollfen]

Closed chamber heads will give you higher compression, if you go with later heads expect to lose some compression. If it is a burnt valve i recommend getting hardened seats fitted. 516 heads are not that common anymore.

 

[65sporty]

Well this sucks Will, I hope you find something simple. I am afraid though it's going to be a valve. Happy wrenching when you get to it. It sounds like you don't have any shortage of other projects though.

 

[commando1]

Will, for your use, I can't see worrying about CR's. Keep it so it uses regular octane gas. 9.0 would be my choice. It will be simpler to tune.