Compression test. ..advice and next steps?

[Tonyclio]

I was thinking about putting 421 cams in my Clio 182 which is standard 130k mile engine, but with throttle bodies.
The results from a dyno earlier in the year were disappointing (186bhp at the flywheel) and it was recently suggested I perform a compression check on the engine:

I performed a dry and wet compression test this morning using a Gunson compression tester and here are the results give or take a couple of PSI counting from one being closest to the crankshaft pulley

Here are the results;
Dry
1 2 3 4
130 130 170 170

Wet
1 2 3 4
140 140 190 180

Not great?

So my options are; just keep going as it, source another second hand engine (hoping it's good) or have this one rebuilt.

I have the skills to remove and re-fit but not to rebuild this engine for the motorsport use.

My Clio is only used for hill climbing at Harewood and outwardly is running well no smoke, no apparent engine issues and putting in respectable times 66.60 being my best back in September this year (class record is I think 64.04. for comparison).

I have already sunk a fair bit into this car, ITB's Gripper, diff cage. etc etc so prepared to go a little further rather than call it a day and break as I'm quite attached to it.

Tony

 

[incy-spider]

Could just be leaking valves mate, do a leak down test.. head off... super techs.. go again?


Sent from my iPhone using Tapatalk

 

[R3k1355]

Was the engine upto temperature, throttle wide open and the battery fully charged?

 

[Tonyclio]

Could just be leaking valves mate, do a leak down test.. head off... super techs.. go again?


Sent from my iPhone using Tapatalk

Thanks for the advice.

I have a compressor and can buy a leakdown test kit for about £50 -£60. which is what a garage would likely charge, so probably the next step

Thanks

 

[David Stuart]

Yeah I would think it’s a top end thing. Either a few valves not sealing or a head gasket issue between the two cylinders with lower compression.

I would rather rebuild the head than chuck another engine in which is a complete unknown.

About £300-£400 in parts will have you going again. You know the rest works well and it’s about the same amount of work as putting another engine in.


Sent from my iPhone using Tapatalk

 

[bob the builder]

as said strip the engine you have then you know its all good.
fit new rings , relap all valves in , new head gasket kit and fit the 421 cams and you should easy see around 215bhp with your set up.
i was running standard engine in tricolore trophy with boddies,421 cams and omex ecu and always got about 210 to 218 bhp

 

[David Stuart]

as said strip the engine you have then you know its all good.
fit new rings , relap all valves in , new head gasket kit and fit the 421 cams and you should easy see around 215bhp with your set up.
i was running standard engine in tricolore trophy with boddies,421 cams and omex ecu and always got about 210 to 218 bhp

Yeah and probably not need to go to the hassle of new rings to be honest. It will be top end only 9/10 times.


Sent from my iPhone using Tapatalk

 

[Robbie Corbett]

Agree with all of the above. You want to do cams so have the head off and rebuild that (or send it off to be built). Get to have a good look over the bores while the head is off too.

Low compression results can only be down to:

Non sealing valves
Non sealing spark plug
Leaking head gasket (into water way, oil way, or adjacent cylinder - or very occasionally just out!)
Leaking rings due to ring wear, ring/bore glazing or more commonly bore scoring.
Failed piston - ring land failure etc.

So building the head eliminates all of those bar piston/bore related.

Also building engines to a regular spec is a very straightforward and pleasant task, if you can remove an engine you can rebuild one, plus you get to buy all sorts of interesting tools.

 

[JamesBryan]

Fit some Supertech valves if you've got the head off, for a bit of extra insurance.

 

[Martin_172]

As above if you have the skill to get the engine out you have the skill to build it get reading up or YouTubeing up!

 

[David Stuart]

Just get the head off it already.


Sent from my iPhone using Tapatalk

 

[Darren S]

Could just be leaking valves mate, do a leak down test.. head off... super techs.. go again?


Sent from my iPhone using Tapatalk

Yep - that's what affected mine. I had a new set of Supertech valves put in mine during the rebuild.

 

[Tonyclio]

Thanks everyone for your input, I,ve now got a leakdown test kit so I'll perform that in the next day or so then probably remove the head as the general consensus is that the problem may well lie in this area.

For those who fitted Supertech valves did you go for standard or oversize?

 

[Robbie Corbett]

I wouldn't fit oversized valves without having the head ported.

You will need to confirm this! But if you install std sized valves I do not think the seats need re-cutting, while over-sized obviously would.

 

[R3k1355]

You will need to confirm this! But if you install std sized valves I do not think the seats need re-cutting, while over-sized obviously would.

Well as long as the seats are undamaged and the guides are not worn.

If the heads coming off for valves anyway it's the perfect time to get it checked over and ported a touch.

 

[David Stuart]

I would have thought given you were happy with the performance and originally just going to Chuck another engine at it, standard rebuild would be the route.

Appreciate the one piece valve upgrade. But equally you could just get what you have fixed. We don’t even know what the issue is yet. If the valve seats are ok then a skim and new head gasket is your problem solved. If the valves are leaking you can usually get them refaced and seats recut fairly cheap.

Depends where you want to go. £000’s could be spend on bigger valves, porting, 3 angle valve seats solid lifters, high lift cams etc.

Your choice. I’ve been both roads in the past for different projects and the simple rebuild and more money in the bank tends to be the best bet.


Sent from my iPhone using Tapatalk

 

[Robbie Corbett]

Well as long as the seats are undamaged and the guides are not worn.

If the heads coming off for valves anyway it's the perfect time to get it checked over and ported a touch.

The seats won't be damaged and the guides are not worn

 

[Tonyclio]

Well just performed a leakdown test on a cold engine;

Cylinder 1 - 55% leakage - air from dipstick and inlet trumpet
Cylinder 2 - 55% leakage - air from dipstick and inlet trumpet
Cylinder 3 - 40% leakage - air from dipstick
Cylinder 4 - 50% leakage - air from dipstick and oil filler neck

Nothing blowing back through water and no significant noise between cylinders nothing from the exhaust but that's not suprising given it's at the other end of the car.

 

[JamesBryan]

50-55% loss!

That's a full rebuild job then.

 

[Robbie Corbett]

What was your procedure.

 

[Tonyclio]

What was your procedure.

I followed the instructions as per several youtube videos. I even performed the test twice on two of the cylinders. The compressor was reading 80-90 psi and I carefully re-calibrated the tester are each test. I also let the test run for a least a minute to ensure it stabilised.

 

[Robbie Corbett]

Im sure you did but just to confirm your not a dolt, you did place each cylinder at TDC?

*secretly hoping your a dolt, but suspect not.

 

[Tonyclio]

Hi Rob, don't mind the thoughts just pleased to receive advice. Yes, I placed each cylinder at TDC. You can tell when you have it 180 out as the leakage is even higher!

 

[David Stuart]

Or even 360 degrees out.


Sent from my iPhone using Tapatalk

 

[Robbie Corbett]

Hi Rob, don't mind the thoughts just pleased to receive advice. Yes, I placed each cylinder at TDC. You can tell when you have it 180 out as the leakage is even higher!

Ahh bugger. Was hoping for you that you hadn't done that. Sorry but it sounds like your going to have to do some winter surgery.