5K-C Head Gaskets For Race Use

[altezzaclub]

The pump has already been shimmed, so I gather if I just grind a bit off the washer/shim under the relief valve that'll drop it a bit?

 

Seems like an awful amount of work just to take the oil pump out :S

Both of those are true, toss the washer out and it is a pain to get to. I understand that too high an oil pressure strips white metal off the bearings, but I don't know what "too high" is in psi.

 

It would be odd if #3 is low on compression from a head gasket problem, but you'll find out when the head is off and the valves are out. You could hook a compressor up to #3 via the spark plug hole and listen for where the air leaks to..... inlet/exhaust via valves, sump via broken ring, water system via head gasket...

[ATOYOTA]

I doubt it would be valves due to the short period it was on the road after Phil cleaned all the carbon build-up off them last time. I'll run another compression test, this time wet and we'll see if it's something in the cylinder itself.

 

80PSI is a bit too high from my understanding so I think that will have to change if I have any hope of containing these oil leaks.

 

I've also had a quick gander on Innovate's website and came across this: http://www.innovatemotorsports.com/products/db.php

 

I'm not after fancy expensive gadgetry that can be hooked up to a laptop or give you eleven different user modes, and a hand controller is WAY over the top for me. I just need something very basic, but somewhat accurate, to help me keep an eye on the danger levels.

[philbey]

The spring chop is the wrong fix. It ups the rate and these don't run a lot of preload anyway, you will possibly choke bypass flow.

 

I don't think 80PSI at high revs (?) is an issue, filters will be rated to 100-150psi. Check to see if it has bulged out, if not I wouldn't worry about it.

 

I would at least get the head looked at to check runout on it every time I pull it off, alloy heads warp easily.

 

As for timing, just checking that you don't have too much advance, this could cause issues.

 

Again, I would definitely check plugs before spending big dosh on an O2 Sensor unit. that setup will be 250-300 by the time you get it here. That will only really tell you if it's running lean and at what revs. Then how do you fix it anyway? You'll probably get a dyno tuner to do it!!

 

You can get a good indication of how the tune is from the plugs, then for 250-300 a dyno tuner will dial it in, set it all up and off you go.

Edited July 4, 2013 by philbey

[GJM85]

Rich engines get flat spots through the rev range and lean engines cut out or bog down. White spark plugs mean it's lean. Blacks plugs are rich.

What ignition are are you running? Is it a standard k motor distributor?

Different shaped combustion chambers require different amounts of maxinmum advance. To much advance and you'll get detonation which will blow gaskets and damage the head and pistons.

 

[Taz_Rx]

I'm running an unmodified oil pump and get up to 80 psi max when cold, it will then drop back to 60-70 psi (at revs) once its warmed up. When exactly are you seeing 80 psi?

 

Other thing is I struggle to understand how high oil pressure would blow a had gasket when there's less area than a 5 centre piece under oil pressure! Plus from memory its between pots 1 & 2....nowhere near 3 were you reckon its blown this time.

Edited July 4, 2013 by Taz_Rx

[ATOYOTA]

Sorry about the late reply, been spending some late nights on the wiring but I'm starting to see daylight.

 

The spring chop is the wrong fix. It ups the rate and these don't run a lot of preload anyway, you will possibly choke bypass flow.

 

I don't think 80PSI at high revs (?) is an issue, filters will be rated to 100-150psi. Check to see if it has bulged out, if not I wouldn't worry about it.

 

I would at least get the head looked at to check runout on it every time I pull it off, alloy heads warp easily.

 

As for timing, just checking that you don't have too much advance, this could cause issues.

 

Again, I would definitely check plugs before spending big dosh on an O2 Sensor unit. that setup will be 250-300 by the time you get it here. That will only really tell you if it's running lean and at what revs. Then how do you fix it anyway? You'll probably get a dyno tuner to do it!!

 

You can get a good indication of how the tune is from the plugs, then for 250-300 a dyno tuner will dial it in, set it all up and off you go.

Cutting springs is never a good idea in my eyes; they have a particular rate and chopping only messes that up. Preloading is one other thing though.

 

I'm not worried about the pump or filter being up to the pressure, it's the fact that ALL the oil is fed via hoses and when there's about 10 of them that's a lot of hose ends to keep an eye on. Even IF the hoses are rated for 570PSI.

 

I mucked up the timing and retarded the exhaust cam by one tooth right before attempting to start it but I don't see how such a short period of dry cranking could have blown a gasket.

 

Oxy sensor's been a big priority ever since I did the swap. It's not so much a tuning thing; it's mainly for monitoring. Fact of the matter is, when it starts misbehaving and I'm away from the shed, a gauge on my dash is far more practical than pulling over to the side of the road and whipping out spark plugs and reading them by torch light.

 

I could try tweaking it to a somewhat drivable state but the blow has got me spooked. Besides, this isn't an asian 4K carb we're talking about. These are BST38SS CV's, and there's 4 of them! I've gotta dick around with main jets, pilot screws, idle screws, air screws, jet needles...

 

As for a tune, there's this bloke around the corner from my work whose main line of work is carbies. He's pretty old school and doesn't use dynos.

 

Rich engines get flat spots through the rev range and lean engines cut out or bog down. White spark plugs mean it's lean. Blacks plugs are rich.

What ignition are are you running? Is it a standard k motor distributor?

Different shaped combustion chambers require different amounts of maxinmum advance. To much advance and you'll get detonation which will blow gaskets and damage the head and pistons.

Distributor's an electronic 4K modified for the 4A-GE head.

 

Apart from that balls up with the one tooth on the pulley, I haven't so much as nudged the timing whatsoever since procuring the engine from Phil.

 

I'm running an unmodified oil pump and get up to 80 psi max when cold, it will then drop back to 60-70 psi (at revs) once its warmed up. When exactly are you seeing 80 psi?

 

Other thing is I struggle to understand how high oil pressure would blow a had gasket when there's less area than a 5 centre piece under oil pressure! Plus from memory its between pots 1 & 2....nowhere near 3 were you reckon its blown this time.

It's been some months since I had the thing running properly but from memory it used to start out at 80 and drop to 60 (full noise, fully warmed up), but now it only drops to about 70 under the same circumstances.

 

It's blown between 1 & 2 before, which is a common area in these engines, being that the bores are closer together on 1 & 2 and 3 & 4 than 2 & 3. Dunno why the front blows more often than the rear. I'm yet to run another comp. test but when I do I'll give you the readings before I take the head off.

[ATOYOTA]

Ran a wet com. test today and it read the same. #1, #2, & #4 @~150PSI and #3 @ ~60PSI.

 

Took the head off and the gasket doesn't seem blown, as such. But it's a little burred on the side of #3, but not fully blown :S

 

I've got the head upside down with kero sitting in the combustion chambers and although the valves are as black as the name Shaniqua, none of them seem to be leaking due to carbon deposit.

 

What the hell else could be the cause of a compression drop in #3?? If the wet/dry compression tests brought the same results that points away from rings, the gasket isn't really blown (not enough to cause such a drop, anyway), and the valves don't appear to be leaking. And if the head was warped it would have blown a gasket.

[altezzaclub]

I do hope it had a tappet gap on #3.... Something not sitting square in the tappet?

 

It might be that little burr. #2 wasn't affected so its not between cylinders, so not warped. It wasn't from the cylinder to the oil drains or the water jackets, so there's not much else apart from broken rings or a valve/seat.

 

Pop the valves on #3 and take a look.

Edited July 13, 2013 by altezzaclub

[philbey]

Cracked block?

 

It can be bloody hard to see the leak on a head gasket that's only freshly blown as well.

[ATOYOTA]

Doesn't have tappets, it's DOHC. I did ʞ©$ɟ up the timing when attempting to start it though, one tooth out on the exhaust pulley. Pistons don't have any marks on them, so let's hope I didn't bend any valves? There's bugger all gap between the valves & piston crowns so I'm really not sure.

 

Kero test showed the valves aren't leaking so that can be ruled out.

 

#1, #2, and #4 were all very consistent through the compression test, so I doubt it's blown anything between cylinders. This includes cracks in the block, which I've also had a look for.

 

Wet compression test would have shown at least SOME variation if it was the rings, so it can't be that.

 

There is just one thing left that may have been a cause.. The stud bores have been elongated in the head to match with the block and as a result it's just never quite fitted properly. Head bolts have always bound up for a fraction of a turn and aligning things up is very painful. It's a possibility that I got the wrong torque readings and lead to a blow that way.

 

I spoke to an engineer about plugging up the bores in the block and redrilling/tapping but he said it would be a major job and difficult to get right. I reckon what I'll do is take the head into this bloke and get them to elongate the stud holes a little more to allow for smoother torquing. It would probably be pretty tricky to get the milling bit in between the valves to recess the washer but we'll see how it goes. I'm sick of grinding 3/4 of the circumference of the washers to size.

[altezzaclub]

Don't forget to do a compression test before you start it.

 

I have had bent valves that gave no visible evidence of being bent and there were no marks on the pistons, I had to roll them across a desk to see the stem wobble, they stood up straight and looked OK except the seating area was worn on one side. The car ran, but didn't want to start. All valves were the same, two cyl had about 100psi and two had 30psi, but you're only losing one cyinder.

[Evan G]

my money is on cracked rings/ring lands