• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

OMG stop smoking already!!!!

Share this page

Haha, I like the way you think Roy. A break sounds like just what the Dr. ordered. I'll try the revised compression test and get back to you guys when I have my new #s. I think i'm going to drain the oil a bit as well to see if that helps at all.
 
Hooper11772 said:
Does anyone know the recommended compression for these cars?
Click to expand...

I don't know the 'recommended' but I can tell you this -

my 62 Sprite w/ a 1098 was @ 150 across all cyl.
my Bugeye w/a 948 must have had some work done to it cuz I'm averaging about 170-180 for each.

Good luck!

BillW
 
This was posted by ROSCOE in the AH forum....
The compression check should be done with an engine that is warm. So if you can run it, get it to temperature, and then turn it off. Remove all of the spark plugs. Put the compression tester in the first spark plug hole and being careful not to let the fan catch anything, crank the engine for 4 or 5 seconds (a good battery helps here), do this with the throttle wide opened, so as not to restrict the intake air. (You can do this with the starter solenoid button in the engine bay if you have one, and open the throttle by hand on the linkage). Your tester should have a check valve in it so it will hold the highest pressure reading you get. Do the next cylinder and so on. There are threads on this site, if you do a search for compression test, that will help you interpret the readings you get. All cylinders should be within a few PSI of each other, and you like to see readings over 130 PSI. You should read the other threads for more information. Hope this helps.

Search for other threads, there are quite a few ISTR.
 
Since I assume you have the SU carbs, besides having the throttle wide open, which is the butterflies, prop open the carb pistons so you have a clear path for the incoming air. If you do one without the other you may still get low readings due to intake constriction.
 
How did this turn out?

mark
 
Hey Guys sorry for the late response have been crazy at work lately. Got to the garage this past week and was able to perform the new revised compression test (thank you for all the advice on the correct way to do this). The numbers were better: cylinder 1= 155,2= 125,3=90,4=130. definitely better numbers than before so I was happy about that however the smoking is still a problem. I'm beginning to agree that the head might be the culprit. I also shined a light down all the spark plug holes and all the cylinders had a heavy coating of oil and all plugs were wet with oil. I figured this would be a sign that although #3 is a little lower than the others it wasn't the only one so rules out blowbye.

I took the valve cover off the head and there was oil pooled over the area that the valve stems come through the head to attach to the rockers. Not a ton of oil but a decent amount. Is this normal?

Is there a way for me to test the head for lack of a better term to see if this might be the cause. As stated prior Chris S gave me a hand with this during the initial build we replaced a couple exhaust valves as well as lapped all the valves. I also replaced the rubber caps that go on to of the guides. Thanks for all the help with this to it keeps me plugging along.
 
Is it possible the rings never seated?

The way to test the head (and rings)is with a leak down tester Harbor Frieght has One cheap, if the oil is leaking DOWN from the head peeking in the side of the head it <span style="font-style: italic">may</span> be visible, of course this means removing the manifolds.

judging by your compression numbers i would be real interested in #2 and #3 cylinders. Have you set your valve clearances? better a bit loose than too tight.

m
 
I am starting to suspect valve guides or valve guide seals.
 
There is actually a harbor freight a few towns over i'll have to read the article to see how these things work since i've never used one before but it looks allot like the compression tester so Is should be all right.

When you say have I set the valve clearances? Chris and I did this together but it's been over as year and i'm not really sure how to do it anymore. Is there an article on this or can someone point me to a good resource? Id like to try this before I buy anything else if possible. Do you think that would cause the problem? Sorry for the ignorance i'm still pretty new to this.
 
Thats a great thread and video. I'm going to set the valves tonight hopefully that will boost my compression a bit.

I was also thinking is it possible that the vacuum I have going to the crankcase from the manifold is creating to much suction and is pulling the oil into the cylinders from my head? I know I bypassed this a bit but I have an oil catch can setup that is pulling from the can on the timing cover to the vacuum from my carbs. It's relatively straight forward but I included a picture below. I was thinking could it be that the suction pulling to the timing cover is too great and should be restricted some? If there is too much negative pressure could this cause my issue?
I know oil vapor is not being pulled directly into the intake for sure since I used clear line originally and the oil catch can stays empty but could the suction alone cause my issue?


[image]https://share.shutterfly.com/action/welcome?sid=0Bbsm7dq1asX3Q[image]
 
No, the suction, if the line is dry (swiped with a q-tip) you aren't sucking excess.
If you swipe the line and you need to wring out the q-tip, yes.

I think you'll see a big drop off in performance and engine idle with tight valves before it drops the compression that much.

Oil going past the guides will oil up the cylinders, and actually give you better compression (wet/dry).

Unless the valves are shot, guides aren't going to help low compression on the order you have.

Leak-down is really the way to go.

In a pinch, just to find where the leak is, I've backed off rocker assemblies, fitted 100-120 PSI (and that's lower than comression, so it won't hurt) into an adaptor, and into the plug hole.

Out of gear!
Fingers clear of belt and blades!

Then go listen to the tailpipe.
Open the throttles.
Then listen up past the pushrods.
You'll know right away.
Do all 4.

#3 is the low one, with 2-4 right behind.

When you're doing a leakdown, listen to the adjacent plug hole....you never know, could be a head gasket.

Lordalmighty, looking at those photos.....I've done so many head gaskets, valve and guides, rings, carbs, ignition......

Flashback!
Yeah, that's what it was!

Dave
 
Well I set the valaves to .12 car runs the same I havent checked compression yet. I was hoping that the smoke would clear a bit but no luck. I'll check compression in the AM and see if the numbers on 2 and 3 rose at all. The car is running great good even exhaust note accelerates without popping. This is sooo frustrating.

I'm going to have to buy a leak down tester I tried renting but no luck. I'll head to harbor frieght next week and continue. More to follow thanks for the ideas so far guys it definitely helps!
 
Call HF first. Not all stores stock what they show on the internet. I went for Hylomar wednesday; they had no idea what I was talking about.
 
Call Harbor first, the one up the road from me was out. Oops sorry, previous post is the same as this, I look up the SKU number and the website then call the store. I want a leak tester too, but I don't have a "proper" air compressor but I wonder if couldn't pressurize it with my little portable emergency compressor somehow.
 
It's pretty easy and cheap to build a leakdown tester. If you search around on the web you can find some pretty good tutorials.
 
Morris said:
It's pretty easy and cheap to build a leakdown tester. If you search around on the web you can find some pretty good tutorials.
Click to expand...

I did but not having a spare pressure gauge or anything else lying around, $40 seems like the easy way out.
 
Haynes or orginal maintance manual.
 
Don't want to rain on your parade but, since I was a mere lad, I was told that if compression varies by more than 10% a overhaul is in the cards. Don't know what may be the trouble but those compression readings look rather dismal. Do the leak down to confirm. If recently overhauled maybe the rings are'nt seated or maybe they were broken on installation.
Just my opinion,
KA
 
Back
Top