hi compression 4age16v losing compression

jakes_hachiroku
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hi compression 4age16v losing compression

Postby jakes_hachiroku » Mon Aug 29, 2016 10:21 am

I have a fully built 4age 16v that I built over the winter and its just got to 300 miles now. keep in mind this is my drift car so its beat on a lot.
now the other day after an hour or so of drifting with my buddy I noticed it didn't want to idle at all. so I limped it home did a compression test and cylinders 3 and 4 where much lower that 1 and 2. 225psi for the front two cylinders and 115psi for the back. so I put new rings on the cylinders that were low and its just about the same :'( now I did use a new head gasket and had the head shaved so I don't think its sealing issue. although the fact that its two cylinders next to eachother is worrying. is this a valve issue with the valves themselves or maybe valve seals??? :?: :?:

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Re: hi compression 4age16v losing compression

Postby totta crolla » Mon Aug 29, 2016 11:23 am

Explain what you mean by valve seals please.

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Re: hi compression 4age16v losing compression

Postby jakes_hachiroku » Mon Aug 29, 2016 11:59 am

the seals that sit under the spring in the head

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Re: hi compression 4age16v losing compression

Postby oldeskewltoy » Mon Aug 29, 2016 12:04 pm

did you check the valves? Did you check cam clearances?
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Re: hi compression 4age16v losing compression

Postby jakes_hachiroku » Mon Aug 29, 2016 12:30 pm

oldeskewltoy I haven't checked the cam clearance yet I that's first on my list after work today and the valves will have to be when I pull the head again.

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Re: hi compression 4age16v losing compression

Postby totta crolla » Mon Aug 29, 2016 12:50 pm

jakes_hachiroku wrote:the seals that sit under the spring in the head

:lol:

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Re: hi compression 4age16v losing compression

Postby jakes_hachiroku » Mon Aug 29, 2016 1:13 pm

I don't know why valve stem seals are funny haha just looking for some guidance but what ever. I am running 266 cams and never checked my cam clearance so that could be doing it to I suppose

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Re: hi compression 4age16v losing compression

Postby oldeskewltoy » Mon Aug 29, 2016 2:15 pm

jakes_hachiroku wrote:I am running 266 cams and never checked my cam clearance so that could be doing it to I suppose


possibly you have a few valves not closing entirely...

As to his laughing... the valve seals seal oil from getting consumed, a bad valve seal would leak oil, not air.
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Re: hi compression 4age16v losing compression

Postby jondee86 » Mon Aug 29, 2016 4:45 pm

jakes_hachiroku wrote:I am running 266 cams and never checked my cam clearance so that could be doing it to I suppose

Easy enough to check the clearances if you have a set of feeler gauges. Just pull the
cam covers and turn the engine until the cam lobes are pointing up on the valves you
are checking. Try slipping the end of the feelers between the cam and the shim. Use
different thicknesses until you find one that just fits (say 7 thou slips in but 8 thou
does not, then 7 thou is your clearance).

See if the clearance on the two problem cylinders is less than the two good ones. If
you have some clearance when the engine is cold, you should get good compression
if the valves are OK. If you have clearance and the compression is low, you most
likely have burned valves.

Cheers... jondee86
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Re: hi compression 4age16v losing compression

Postby jakes_hachiroku » Tue Aug 30, 2016 7:56 am

jondee86 wrote:
jakes_hachiroku wrote:I am running 266 cams and never checked my cam clearance so that could be doing it to I suppose

Easy enough to check the clearances if you have a set of feeler gauges. Just pull the
cam covers and turn the engine until the cam lobes are pointing up on the valves you
are checking. Try slipping the end of the feelers between the cam and the shim. Use
different thicknesses until you find one that just fits (say 7 thou slips in but 8 thou
does not, then 7 thou is your clearance).

See if the clearance on the two problem cylinders is less than the two good ones. If
you have some clearance when the engine is cold, you should get good compression
if the valves are OK. If you have clearance and the compression is low, you most
likely have burned valves.

Cheers... jondee86


and if If the clearance is to little will I need smaller shims to get the valves to close? or the other way around? because I do have a spare head I can rob the shims from if I need to do some assorting

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Re: hi compression 4age16v losing compression

Postby oldeskewltoy » Tue Aug 30, 2016 8:49 am

jakes_hachiroku wrote:
jondee86 wrote:
jakes_hachiroku wrote:I am running 266 cams and never checked my cam clearance so that could be doing it to I suppose

Easy enough to check the clearances if you have a set of feeler gauges. Just pull the
cam covers and turn the engine until the cam lobes are pointing up on the valves you
are checking. Try slipping the end of the feelers between the cam and the shim. Use
different thicknesses until you find one that just fits (say 7 thou slips in but 8 thou
does not, then 7 thou is your clearance).

See if the clearance on the two problem cylinders is less than the two good ones. If
you have some clearance when the engine is cold, you should get good compression
if the valves are OK. If you have clearance and the compression is low, you most
likely have burned valves.

Cheers... jondee86


and if If the clearance is to little will I need smaller shims to get the valves to close? or the other way around? because I do have a spare head I can rob the shims from if I need to do some assorting


you will need thinner shims.... from my expereince Toyota was pretty good with their machining equipment and most often the valve shims are generally between 2.85mm to 3.05mm. Toyota does have shims as thin as 2.3mm, and as thich as 3.5mm. Other places to get shims... 4AFE engines, as well as many motorcycles. The shim is more commonly referred to as a 25mm shim, 25mm referring to the shims diameter.
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Re: hi compression 4age16v losing compression

Postby jakes_hachiroku » Wed Aug 31, 2016 5:09 am

oldeskewltoy wrote:
jakes_hachiroku wrote:
jondee86 wrote:Easy enough to check the clearances if you have a set of feeler gauges. Just pull the
cam covers and turn the engine until the cam lobes are pointing up on the valves you
are checking. Try slipping the end of the feelers between the cam and the shim. Use
different thicknesses until you find one that just fits (say 7 thou slips in but 8 thou
does not, then 7 thou is your clearance).

See if the clearance on the two problem cylinders is less than the two good ones. If
you have some clearance when the engine is cold, you should get good compression
if the valves are OK. If you have clearance and the compression is low, you most
likely have burned valves.

Cheers... jondee86


and if If the clearance is to little will I need smaller shims to get the valves to close? or the other way around? because I do have a spare head I can rob the shims from if I need to do some assorting


you will need thinner shims.... from my expereince Toyota was pretty good with their machining equipment and most often the valve shims are generally between 2.85mm to 3.05mm. Toyota does have shims as thin as 2.3mm, and as thich as 3.5mm. Other places to get shims... 4AFE engines, as well as many motorcycles. The shim is more commonly referred to as a 25mm shim, 25mm referring to the shims diameter.


And what if the clearance is too big? will I still have a low compression issue?

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Re: hi compression 4age16v losing compression

Postby totta crolla » Wed Aug 31, 2016 5:15 am

jakes_hachiroku wrote:
oldeskewltoy wrote:
jakes_hachiroku wrote:
and if If the clearance is to little will I need smaller shims to get the valves to close? or the other way around? because I do have a spare head I can rob the shims from if I need to do some assorting


you will need thinner shims.... from my expereince Toyota was pretty good with their machining equipment and most often the valve shims are generally between 2.85mm to 3.05mm. Toyota does have shims as thin as 2.3mm, and as thich as 3.5mm. Other places to get shims... 4AFE engines, as well as many motorcycles. The shim is more commonly referred to as a 25mm shim, 25mm referring to the shims diameter.


And what if the clearance is too big? will I still have a low compression issue?


Possibly but at least you know it's not the valve clearances causing the problem.
Did you really build this engine ?

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Re: hi compression 4age16v losing compression

Postby jakes_hachiroku » Wed Aug 31, 2016 6:31 am

totta crolla wrote:
jakes_hachiroku wrote:
oldeskewltoy wrote:
you will need thinner shims.... from my expereince Toyota was pretty good with their machining equipment and most often the valve shims are generally between 2.85mm to 3.05mm. Toyota does have shims as thin as 2.3mm, and as thich as 3.5mm. Other places to get shims... 4AFE engines, as well as many motorcycles. The shim is more commonly referred to as a 25mm shim, 25mm referring to the shims diameter.


And what if the clearance is too big? will I still have a low compression issue?


Possibly but at least you know it's not the valve clearances causing the problem.
Did you really build this engine ?


yes I built it myself haha! BUT... this is also my first engine and race motor all at once so im learning as I go! :( but I did have the block and pistons sent to a machine shop to be bored so the pistons match the block so that's why im confused that the back to cylinders are low now :?: but this I did start with just a bare block no head or anything so this is a used head off ebay that I sent to be resurfaced and plopped on put bigger cams and called it a day so idk lol

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Re: hi compression 4age16v losing compression

Postby totta crolla » Wed Aug 31, 2016 9:48 am

Check the clearances and post them here if you get the chance.
Clearances have a small effect on the cam timing.

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Re: hi compression 4age16v losing compression

Postby davew7 » Thu Sep 01, 2016 5:14 am

A quick check if you have an air compressor, is to apply air pressure to the cylinder(s) and listen to the intake, exhaust and crankcase for leaking air. Should help narrow down the problem. Dave W

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Re: hi compression 4age16v losing compression

Postby jakes_hachiroku » Thu Sep 01, 2016 11:46 am

ok so here is where I get mad at the kid I bought these cams off of or I hit my self for buying "modded" cams in the first place and not measuring anything.
so I dug up my oem cams and measured the lobs the long way. the new cams I put in were 1mm shorter than oem that's why I have the biggest gap ever! so today im putting my factory cams back in and guna re check with my feeler gauges and see what I come up with

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Re: hi compression 4age16v losing compression

Postby Ratranger » Thu Sep 01, 2016 1:51 pm

They might be regrinds. Best bet would be to check them for marks of who did it, if they are marked write or call the company and see what you can find.
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Re: hi compression 4age16v losing compression

Postby jondee86 » Thu Sep 01, 2016 3:49 pm

jakes_hachiroku wrote:So today im putting my factory cams back in and guna re check with my feeler gauges
and see what I come up with

As regrinds most likely don't take anything off the top of the lobe, and would be
looking to get an extra mm of lift, I'd guess they took 1mm off the base circle. You
can check by measuring at right angles to the lobe and comparing the base circle
diameter with your stock cams.

Theoretically that would mean that you need shims 1mm thicker. Using the shims
that you had would mean you actually were getting less valve lift than stock, so
there should not have been any chance of holding a closed valve slightly off its seat
to lose compression or burn valves.

So the the reason for the loss of compression is still a mystery :? Take a look at
the shims and lifter buckets on those back two cylinders and see if there are any
signs of the shims trying to escape from the bucket.

Cheers... jondee86
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Re: hi compression 4age16v losing compression

Postby jakes_hachiroku » Fri Sep 02, 2016 4:53 am

jondee86 wrote:
jakes_hachiroku wrote:So today im putting my factory cams back in and guna re check with my feeler gauges
and see what I come up with

As regrinds most likely don't take anything off the top of the lobe, and would be
looking to get an extra mm of lift, I'd guess they took 1mm off the base circle. You
can check by measuring at right angles to the lobe and comparing the base circle
diameter with your stock cams.

Theoretically that would mean that you need shims 1mm thicker. Using the shims
that you had would mean you actually were getting less valve lift than stock, so
there should not have been any chance of holding a closed valve slightly off its seat
to lose compression or burn valves.

So the the reason for the loss of compression is still a mystery :? Take a look at
the shims and lifter buckets on those back two cylinders and see if there are any
signs of the shims trying to escape from the bucket.

Cheers... jondee86


will do my friend! but yea now im at a point where I STILL need to find where my compression is going would there be anything else beside the cylinders and pistons themselves I know wiseco are built to expand a little but the back to wouldn't be that off hahah :?: :?:

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Re: hi compression 4age16v losing compression

Postby oldeskewltoy » Fri Sep 02, 2016 7:39 am

davew7 wrote:A quick check if you have an air compressor, is to apply air pressure to the cylinder(s) and listen to the intake, exhaust and crankcase for leaking air. Should help narrow down the problem. Dave W

aka leakdown test...... do it
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Re: hi compression 4age16v losing compression

Postby jakes_hachiroku » Fri Oct 14, 2016 6:58 am

so hear is the update... so on my head almost all of the valves were not water tight and the new valves I bought weren't seating right either so through my work I was able to pick up a re-manned smallport for pretty cheap. new everything came with it obviously. still low comp in same cylinders (3 and 4) so im gunna find a straight edge and check the block surface and pull the block and check for a crack between 3 and 4 because that's all that's left to check haha FML. so if anybody else has any thoughts chime in lol

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Re: hi compression 4age16v losing compression

Postby oldeskewltoy » Fri Oct 14, 2016 8:13 am

jakes_hachiroku wrote:so hear is the update... so on my head almost all of the valves were not water tight and the new valves I bought weren't seating right either so through my work I was able to pick up a re-manned smallport for pretty cheap. new everything came with it obviously. still low comp in same cylinders (3 and 4) so im gunna find a straight edge and check the block surface and pull the block and check for a crack between 3 and 4 because that's all that's left to check haha FML. so if anybody else has any thoughts chime in lol



agree... if you have now used a different head, with the same results... odds are there is a problem with your block..... :(
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Re: hi compression 4age16v losing compression

Postby jakes_hachiroku » Fri Oct 14, 2016 10:14 am

oldeskewltoy wrote:
jakes_hachiroku wrote:so hear is the update... so on my head almost all of the valves were not water tight and the new valves I bought weren't seating right either so through my work I was able to pick up a re-manned smallport for pretty cheap. new everything came with it obviously. still low comp in same cylinders (3 and 4) so im gunna find a straight edge and check the block surface and pull the block and check for a crack between 3 and 4 because that's all that's left to check haha FML. so if anybody else has any thoughts chime in lol



agree... if you have now used a different head, with the same results... odds are there is a problem with your block..... :(



now before I tore the motor down it was building up a crazy amount of pressure in my cooling system like waaay to much pressure. sound like a crack to you?

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Re: hi compression 4age16v losing compression

Postby oldeskewltoy » Tue Oct 18, 2016 2:41 pm

jakes_hachiroku wrote:
oldeskewltoy wrote:
jakes_hachiroku wrote:so hear is the update... so on my head almost all of the valves were not water tight and the new valves I bought weren't seating right either so through my work I was able to pick up a re-manned smallport for pretty cheap. new everything came with it obviously. still low comp in same cylinders (3 and 4) so im gunna find a straight edge and check the block surface and pull the block and check for a crack between 3 and 4 because that's all that's left to check haha FML. so if anybody else has any thoughts chime in lol



agree... if you have now used a different head, with the same results... odds are there is a problem with your block..... :(



now before I tore the motor down it was building up a crazy amount of pressure in my cooling system like waaay to much pressure. sound like a crack to you?


could be.... but one thing is certain, you have tried just about everything else...
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Re: hi compression 4age16v losing compression

Postby SR85DET » Mon Nov 28, 2016 6:22 am

[quote="jakes_hachiroku"]so hear is the update... so on my head almost all of the valves were not water tight and the new valves I bought weren't seating right either...quote]

Just curious, did you lap the new valves in or just put them in yourself and move forward? Also, I know its a big late now but valve lash is critical when putting new cams or valves in. Any new part to part clearance can change if the parts are changed. You live and learn but you might have a good head on your hands that just needs a valve job and some new shims.