BUGA Community
Technical => Driveline => Topic started by: Rothu on December 02, 2009, 06:01:05 PM
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Ok, I have a 1976 Bedford fitted with a holden 186.
I replaced the head with a 173, which made it run bloody well! Then blew a head gasket.
Got the head totally rebuilt, and put on extractors. running like shit ever since.
It idles fine and smooth but loses all power under load. I'ts running on LPG, changed the LPG convertor, rebuild the carby, changed HEI leads, changed the coil (has constant 12volts). Still loses all power under load. What the hell could it be??
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whups , accidently modified ur post , but fixed it and posted reply as shoulda done first, :)
are ur valves adjusted correctly?
looses power under load? up hills?
can u get full power on a straight or does she get to 3/4 throttle then there,s no more?
sounds like she,s reaching full gas flow and might need more? = is it a 6cyl converter. 4cyl ones might not give enough flow.
or valves may need adjusting?= might not be gettin full compression.
= have u done a compression test? valves might not be sealing correctly.
just 2 thoughts at the moment.
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does it only loose power on LPG or don't you have dual fuel?
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It is a new 6 cylinder gas convertor. Can't get it going on petrol just yet. Been on gas for years.
the head was totally rebuilt. Bled the lifters.
Idles beautifully! But as soon as you apply load it dies badly. Barely makes it up hills. I've tried 3 other coils, same situation.
What gets me is that it was running amazingly before the head gasket blew. Since then, I've tried new head gaskets, got the head checked again, all valves perfect. Compression on cylinders are 110,120,110,80,150,95. Slight gas oil on number 6 plug, went up a grade.
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can u hook petrol up to her?
if u have the carby but no fuel tank just use a boat fuel tank to get her runnin on fuel to see if she still has the problem under petrol.
that way u could rule out engine/ elec/ignition problems and then know its gas related.
it will take a boat fuel tank, elec fuel pump(if mech one is removed), and a length of fuel line.
make sure all fuel lines are clamped tightly and dont smoke in the cabbin when ur doin the test.
ive done this test a few times on gas only vehicles still fitted with a standard petrol carby.
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wow you recon 173 head on a 186 goes well.. then im gunna put a 173 head on a 202. should go real hard:)
another thing to try is make sure engine timing is right. and not a tooth out.
we had a motor running with the dizzy a tooth out, but had no power, we could rev it and all that it was just like it was strangled.
cheers
ben
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sounds like the bottom end is worn out it should have around 160 -180 psi compression with a 173 head on a 186 and you shouldnt have more than 20 psi fluctuation between cylinders try sticking oil in the bores and crank it with no plugs for 4 or 5 revs then do a compression check if it improves then ya rings are shot Cheers Neil
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if its not mech/elec,
sounds like its gettin enough air but not enough gas.
might be a silly question but u checked that a hornet hasnt built a mud nest in the gas line from the tank to converter or anywhere else while the converter was out,
believe it or not its bloody happened to me.
and had the little b#@$ards build nests in whipper snipper exhursts 2, took me about a hour to find it, lol. gets the thinker mass thinkin.:)
ive had them build nests in = fuel lines, gas lines, carby,s whipper snipper exhursts, spray guns, air tools = they just dont care as long as the holes the right size.
disconnect the converter tank feed line and get someone to turn the tank on n off quickly to test the feed line. make sure theres no one smokin and disconnect the battery, etc, no ignition things near u like things that spark.
if there,s a hornet nest it should blow most of it out, but bear in mind that just 1 tiny fragment on forign material can cause a blockage.
especially in the final gas injector, its a small hole.
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hey merlin where do you find out what sort of psi you should expect from engines? or do you just know:)
ben
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google it ben, the psi compression of a motor, its amaising what google dosent know.
p.s. its not so much the compression but the fluctuation between cylinders.
but i think that overall compression should get no lower than 90 to 100psi
ive got a 2 stroke 15hp evinrude outboard that has 80psi in both cylinders and still runs smooth as. and it lived up the hawksburry river at brooklyn before i bought it being flogged by a young guy wake boarding every possible chance.
its on my 11ft savage tinny and still fly,s.
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Try the simple things first.
The fact that you say it idles fine but as soon as you put load on it it barely makes it up a hill, and that you have changed coils and plugs leaves either points or timing.
My guess is timing, I use a very finely tuned device (my ear) and a 9/16th spanner to do my timing.
Use the spanner to loosen just slightly the bolt that holds down the base of the dizzy.
with the engine running on a fast idle twist the dizzy one way until the motor starts to falter, then twist it back the other way it will idle smoothley again, keep twisting and it will start to falter again. From memory twisting clockwise retards and counter clockwise to advance - could be vice vesa.
Now set it in the middle of those two extremes.
Lower the idle speed and repeat. Rev the engine and listen to how easily it revs.
If you take the engine cover off you can actually drive along and udjust the timing as you drive - do this on quiet straitght roads though.
I try and get the motor to ping under load and then back it off a bit, that should have it set pretty well right.
Works for me anyway.
Warren
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hey mate, you've said it idles, and dies under load..
Does it die when given some revs while parked? or only when driving?
What was done when the head was pulled off?
Did you touch the dizzy or anything else?
The compression on the various cylinders is worrying, however, the motor should still run fine, just not as well as it would if they were all higher.
With the head, what did they actually do to it? How did you test that the seats were fine?
If they have only ground the valve seats with a stone, they are likely to be out of true, if you've tested this by filling the combustion chamber with petrol and lost none, they are a good seal.
There are a number of things it could be, but before i write an essay of possibilities, i'd appreciate some more info.
Cheers
PS. there are some good tips above, i advise taking note.
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Ok, further information: The battery has slid forwards earthing out the live connector onto the wall. but has slid back, but shows some 5mm of arcing, actually removing brass to that extense.
The fuses are all okay. What else could it spike? the HEI?
The head had a full regrind, was a Repco recoed head, needed valve stem regrinds to naturally fall, and all valves and seats reground for proper fit. Do not by any old Repco recoed heads, they will cost you $285 for total rebuild.
The head was tested by vacuum, all sealed well. I did my own tests with metho into each chamber to see leakage. None.
it does not die revving in idle.
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ive got a small block of wood stopping mine from doin that.
if u suspect the hei bein damaged thus causing ur lacking power try a points dissy n see if it works better.
p.s. try running a single wire from ur power side of battery straight to the power side of ur coil 2 just in case there is some fried wires causing the power lack.
pp.s. i run a elec disy 2 but always carry a recond points disy under the passanger seat just in case the hei one fries 1 day while im traveling or even just drivin local.
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Ok, good stuff. So the engine will rev while parked? can you rev it right up to 6000rpm or so?
If the motor is revving freely as you please while parked thats as much of a good thing as a bad thing..
A quick question, on your coil it should say 12V use with resistor, or use without resistor.. Are you using a resistor?
Is the car an auto or a manual?
Did the motor ever run well after the head went back on? or did the battery hit the body and arc pretty much straight away?
The main things you'll want to start looking for are burnt wires, if it's done damage to the terminal, you want to check the cable attached and consider a new fitting if need be. you want to have a look at the power wire going to your coil from both ends if accessable.
If the car is an auto, have a look at any electrical cables attached to the box, as the fact it'll rev when parked leads me to believe it will be transmission related..
If you can get a good photo of the wiring around the motor, and under the dash and bonnet this may give us a better idea also.
Also, when you said you checked the fuses, was that just under the dash or under the bonnet too?
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12volt coil, no resistor, direct line from battery. All fuses good.
5 speed supra gearbox.
Will try a points dizzy today.
Don't know when the battery arced but it would have been after head got recoed.
It runs the same as when the head gasket blew out between 5 and 6. Replaced it of course!
Can rev it to 6000 no problems. Just dies under load.
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Compression on cylinders are 110,120,110,80,150,95 = those compression readings are a big worry especially 4 and 5 .
thats 70psi difference, could u have made a mistake with the readings?
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tried points dizzy, even worse than before! Put HEI back in, smooth as.
Also noticed a couple of bent pusher rods, replaced those, still the same.
A friend mentioned the timing gears might be worn. anyone?
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bent push rods means their too tight, are the rockers adjustable?
sounds like the valves arnt closing up, thats prob why there is low compression in some cylinders.( would make it run but no power under load)
if their unadjustable rockers like on the 202 maybe the head being shaved itsnt giving enough clearance on the rockers where they touch the valve stem ends?
even moreso when ur lifters pump up with oil there would be no clearance at all thus valves not closing and would bend pushrods. and bugger all power a result.
marty
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The pushrods were out of another engine (same length), but I didn't check them properly, obviously.
Bled the lifters so they're fine and there is clearance on all the rods when valves are at rest, ie: you can easily twist them, that's how I found the bent ones.
It's a 173 head so it a matter of simply bolting down the rockers to 40nm.
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Ok, got another set of push rods, pulled out the old ones, Bugger me they were bent!
Installed the new ones, BINGO!! Power is back! One very happy camper! ;D
Thanks for all your advice guys! ;)
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good 2 hear,
i bet the compressions good on all cylinders now?
post some pictures of the bent pushrods, be cool 2 have a look.
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cool as! good to hear!
ben
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hey mate, good to hear you've got it sorted!
I thought about the push rods when i first saw the thread, but i couldn't see how they'd have been bent by blowing a head gasket.. so i passed it off as something else..
Goes to show, you need to look at all the small things..
Well done!
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sounds like ur tappets were tightned down 2 much resulting in the pushrods bending when the lifters pumped up with oil resulting in valves not closing properly causing power loss.
161,173,179.186 heads have fully adjustable tappets and u can run into this problem by not giving enough clearance.( tightning them down 2 much)
(ask ben about bending pushrods and what causes it.
he had a bad expereance with them 2 on maria,s van.
and the pushrods bent and smashed through a few tappets. )
but 202 heads its hard to go wrong as the tappets are non adjustable and bottom out when the rocker gear n bolt is tightned down solid.
only way u can go wrong with a 202 head to block surface is ground down heaps. could need a shim spacer between the rocker gear post n rocker bolt hole surface.
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i would be having a look see in a week... if the new push rods are the same size then you have fixed the symptom.... not the problem.
they didn't bend because they thought it was a good idea so logic tells you that you are on the road again but will be back in trouble in roughly the same time it took the other ones to bend.
that's what would be going through my mind.
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good thinkin able:))
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Guys, this is what I've worked out the history of the bent rods.
It's a 173 head with NON-adjustable rockers which I got from ebay. it was totally recoed by Repco, but they did a pigs breakfast of it.
When I blew the head gasket, I had the head checked and then forked out to have it totally recoed again... The valve stems weren't "falling" naturally, needing a valve stem guide regrind.
THAT'S where the rods bent, trying to open up valves that were sticking.
I got new hardened push rods and it just jumps up and goes now!
Up a wall in 5th gear? No problem!
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sounds like a bad reco first off.
who did the second reco?
non adjustable rockers on a 173 never heard of them before.
got any pictures u can post up?
or can u give the ebay item number? ( might be able 2 see from the item pictures)
im interested 2 see the rocker setup.
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The first photo show the first head with receded valve seat on the exhaust on No.1 cylinder.
It was a 202 head with adjustable rockers. I checked the casting number and it matches. 2811930
the next 2 show the one I bought, the guy thought it was a 202 head, but it was a 173 HC head!
Again matched the casting number. 2811929
here's some links that I found to help match the casting numbers.
http://oldholden.com/node/78628 (http://oldholden.com/node/78628)
http://www.allhead.com.au/Identification/ID_Red%206.html (http://www.allhead.com.au/Identification/ID_Red%206.html)
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And of the rockers in the 173 head. and yes, they are mismatched but they measured and fitted. Replaced them when I had the dosh.
The push rods ARE ALL the same length for all the red and blue motors. 230mm
I bled the hydraulic lifters after the head was shaved 7 thou. These are what adjusts to the new conditions and sort themselves out.
If they were SOLID lifters THEN you have to critically adjust the rockers to suit with both valves at rest and tightened enough to just barely turn the push rods.
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well that clears up any doubts i had, thanx.
check out the difference in the combustion chambers of the 202 and 173.
be interesting 2 see the compression readings on each cylinder now .
and 2 compare them with a standard 202.
i bet it fly,s now.
cool so the 173 heads had the 202 rocker gear fitted.
sounds like its gunna be a very powerfull 6 cylinder motor now.
be interesting 2 see if there,s a big difference in fuel economy
good stuff Rothu thanks for the pictures.
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my engine guy is putting over sized exhaust valves in my 173 hc head. as well as new springs and the rest. so you used the the 202 rockers?
how is my 202 with a 173 head going to go with the vk inlet manifold and straight gas cam? poor mans v8 i have been told ;D
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hey Rothu, sounds like you've got it all sorted now. Good to hear!
Did you get a CC on the head before it was fitted by chance? I'd be keen to hear what volume they are around standard.
Anyway, enjoy the motor, you sound happy with it so far.
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how is my 202 with a 173 head going to go with the vk inlet manifold and straight gas cam? poor mans v8 i have been told
you know why its a poor mans V8! cause you dont have to folk out 1000+ dollars for engineering certicicate!!!!!! plus all the extra cost of v8 gear. not a bad option if you ask me brother!!!!
cheers
ben