FIrst Post

[klmustang67]

Hey everyone,

I have actually been on this forum for quite some time now, but I just search all of the past posts to find what I am looking for instead of bugging everyone here every five minutes.

Anyway I am the process of deciding whether or not I should rebuild the head on my engine (200 CID) or just replace it with another. I did a compression test and got some wacky readings with cylinders 3 and 4 being holding about 30% less then the other cylinders. My car has also been backfiring through the carb, along with serious loss in power, which leads me to believe that it is a result of my poor compression test. My car is my daily driver so whatever I need to do it has to be relatively quick. So should I have the head rebuilt or replace the engine? If I replace the engine can I get a later model 200 and what would you suggest?

Thanks,

Kyle

 

[170-3tree]

Well it would depend on what engine and head you have. If it's earlier then getting a later head will result in more performance, but without knowing what is the cause if the compression loss it's really in the air as to whether or not a new engine as a whole would be better.

Best bet for deciding the beat approach for you would be to run a leak down test and see where the compression is being lost from. If you do this and hear air coming from the intake or exhaust then the head should keep you going for a while. Air from the radiator or dipstick tube will necessitate the bottom end being rebuilt most likely.

Gerald.

 

[klmustang67]

Opps I should've said that I have a 1967 200 CID Coupe.

I am thinking that it may be a blown head gasket between cylinders 3 and 4, but I still have to confirm that.

Is there a place where I can just get a leak down test done?

 

[170-3tree]

Any decent shop should have the manifold to do the task.

 

[Frankenstang]

Welcome aboard klmustang67

I am thinking that it may be a blown head gasket between cylinders 3 and 4, but I still have to confirm that.

That's not a bad supposition, and if it is 'the cause' then a head gasket replacement can be done in an afternoon...provided everything goes smoothly<<famous last words

However, as 170-3tree mentioned, a leakdown test would be the next logical diagnosis procedure...you do need some equipment, cmpressor, fittings, gauge, etc.

Last head gasket leak I had was not between cylinders, but isolated to one, and I would not have described it as a "serious" loss of power...this leads me to wonder what else could be causing your "backfiring through the carb and serious loss of power" issues.
How about a little more backround on when & how these two issues first raised their heads?

Additionally those symptoms make we wonder about the condition and setup of your other engine components, primarily ignition...what's the low down on that setup?

In short 30% between two cylinders is not insignificant, or considered as normal as say 10% difference...eg 130-130-100-100-130-130...but is not also as glaring as one might expect(more like 50%) from a head gasket blow out eg 130-130-70-65-130-130...and these are just examples. It could turn out to be a blown head gasket, but more diagnostics should probably prelude head removal IIWIYS.
...

So should I have the head rebuilt or replace the engine?

If you look to rebuild your head, then you may want to consider an upgrade to a later model head, but that could involve swapping carbs, head milling to raise compression to early head stnds, etc. An engine rebuild is a wholesale 'leap' beyond that If you have an earlier block, you'll have forged rods as at least once incentive to stay with that lower end...
...so in short more info, when you can :
Good luck

 

[klmustang67]

Thanks for your input Frankenstang,

I replaced the head gasket this past winter and that is why I am thinking that it may be that, but it's not a difficult procedure as you mentioned and I don't know how I could've messed it up, but it is certainly possible.

As far as the ignition setup goes it is a stock setup, however it has been well maintained. My girlfriend's dad (airplane mechanic) and I went over it and did a thorough tuneup. We will be rebuilding the carb sometime this week and we hope that it will take care of some of the problems. Although I feel like it is much bigger then just the carb.

The problems arose 2 1/2 months ago while on my way home from college. I started noticing hesitations when I pushed the gas pedal and I started noticing a serious lack of power. I am not sure what may have caused this problem, but it has gotten increasingly worse as time goes on. Every once in a while the carb back fires and the car returns to normal driving conditions for a few minutes.

I feel like we are chasing the wind here...

 

[Frankenstang]

The problems arose 2 1/2 months ago while on my way home from college. I started noticing hesitations when I pushed the gas pedal and I started noticing a serious lack of power. I am not sure what may have caused this problem, but it has gotten increasingly worse as time goes on. Every once in a while the carb back fires and the car returns to normal driving conditions for a few minutes.

I feel like we are chasing the wind here...

I know what you mean Kyle...it can feel like that at times...but I'm sure you'll get it figured out. '67 should be a points & load-o setup, so you might want to put a timing light on it and see how it's behaving at idle and under rpms. Although I don't tend to think of ignition when a problem is intermittent (or in this case 'normal' operation is intermittent)...ignition failures or malfunctions seem to be more binary (on/off).

An issue encountered before with regards to the fuel system is crud building up on the pickup sock, robbing power and hurting performance, but that problem usually goes away after a brief sit, then rares right back up after sufficient driving.

Your initial thought is certainly worth investigating further...30% loss across two cylinders is nothing to sneeze at Good luck

EDIT: And not to endorse a 'tiger by the tail' strategy to diagnosing above, but sometimes never hurts to check back over the basic stuff, eg stuff like a faulty plug wire (pull one at a time and see if operation is 'unaffected'), etc. Point being there are a number of simple tests like fuel delivery, or plug readings that can still be gone about methodically, and might help steer you in the right direction. I'm sure you'll get it whooped.

 

[klmustang67]

An issue encountered before with regards to the fuel system is crud building up on the pickup sock, robbing power and hurting performance, but that problem usually goes away after a brief sit, then rares right back up after sufficient driving.[/quote]

I took it for a drive last night and this is exactly what happened. It ran great for a little while and then after a bit of driving it started running like crap again. I think I am going to check out the pickup sock!

Thanks,

Kyle

 

[MPGmustang]

putting the compression test aside, I think your igntion is loose or your vacuum canister is leaking. this would get the jerk like hesitation when you're maintaining speed and accelerating. but this is just speculation, a simple test is to take the vacuum hose from carb and blow into the canister, if it holds air its good, if not then replacing that will help restore some power.

your recent post would suggest a carb issues, mainly with the choke. but as you menttioned lower compression in your 3/4 cyls, then I think it's getting water or compression is being lost once warmed up. sometimes it's the procedure of replacing the head gasket, I lost one 6 months after I replaced it cause I didn't know to drive it for 2-3 days and 'retighten the head bolts' after those full heat cycles. tot est this you can take thevalve cover off and use a torque wrench up to IIRC 70lbs? if it's not 70 then it wasn't tightened properly. I even doulbed checked mine after 14 days to find some just a hair under 70lbs.

something to check, the trans, if it's an auto c4 then check the fluid, low fluid will hurt the trans and any kind of acceleration. but if manual then you have nothing to look at. and of course a vacuum leak, take some starting fluid and spray around the vacuum lines, carb base, anywere the engine is sucking in air, not too much though as you want to concentrate it in an area to find if there is any leak. if auto then you have a vacuum line going to the back of the trans.

 

[69.5Mav]

It ran great for a little while and then after a bit of driving it started running like crap

Two other common things that can go wrong are a bad coil and stretched timing chain.

The coil can heat up with the engine running and cause insufficient ignition voltage. Test by swapping or maybe freeze spray on the carb.

The timing chain stretches as it wears. when it heats up it stretches a little more. This can be enough to make the engine run badley. Test by turning the crank oneclock wise then reversing dirrection while watching to see how many degrees of rotation it takes for the distributor rotor to folow suite. The timing chain stretch can cause back firing out the carb as well.

If it is the timing chain and you need to remove the head you could consider swapping the cam as well as you will be almost there any way.

As for your loss of compression It is most likely a blown head gasket but I would pressurize each cylender to see where the air is coming out first before removing the head.

 

[klmustang67]

This is good stuff guys, I am just going to keep trouble shooting to see what I can find. I will be sure to keep you updated!

-Kyle