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Looking to buy a 94 Z28 with head gasket problem, what to look for?

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Looking to buy a 94 Z28 with head gasket problem, what to look for?

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Old 10-07-2018, 03:32 PM
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Re: Looking to buy a 94 Z28 with head gasket problem, what to look for?

Originally Posted by Chimera96 View Post
If you can find out what kind of springs are on this new motor they "may" be OK for the hot cam. The new motor should have new valve stem seals so those should be OK....unless you wind up changing springs that require a different spring locator than what you currently have sometimes removing the locator you need to pull the valve stem seals

Valve spring locators, retainers and keepers are not always "interchangeable" with other springs unless the replacement spring is same size. Often springs use the stock 7 degree keepers though.

If you are going to get RR its a good idea to go with 7/16" vs 3/8" RR studs (stock). No cost difference between 3/8 or 7/16 RR. ARP makes RR studs. If getting guide plates get RR studs for guide plates. They have a shouldered bottom for guide plates. ISKY adjustable guide plates are, IMHO, better on the LT1 heads. They allow each RR to be aligned dead nuts center vs the fixed two valve (intake/exhaust) type

If the new motor has a Mellig 55 in it than just leave that pump in it

If motor is out just bolt the flexplate on crank and use a screw driver in one of the holes that will hit the block that will prevent motor from turning if trying to get damper bolts off If its a stick car with flywheel you can do the same thing using one of the PP bolt holes. Just stick a screw driver through it and when motor rotates the screw driver will jam against block preventing motor from turning
Thank you. After your comments and general thinking, I'm going to hold off on upgrades until I can do it right. I might go Lloyd Elliots after a while but for now, I just want the car running.


I have a factory service manual and have been reading through it before I tackle this. I'm trying to figure out which parts I need to order at Rockauto for a full set so I can get to work without hiccups. I'm having trouble figuring out which gaskets I need.

So far I have the following for gaskets: Timing cover set (I think this covers the water pump, front main and opti but I'm not sure), water pump (theres 2 triangle ones), water pump coupler o-rings(?), rear main, oil pan gasket, valve cover gasket, exhaust and intake manifold gaskets. Anything else I am over looking for gaskets?

I do see full gasket sets for like $150-200 but that seems pricey considering I can piece it together at rock auto for around $50 and I don't need head gaskets or bolts.

I'm also ordering a full AC rebuild O-ring kit because I have a leak somewhere, AC dehydrator/drier, heater core, spark plugs, spark plug wires, new clutch kit and flywheel. Unsure about the opti, my opti is really greasy but works fine and is the original so I might just keep it rather than replacing with a junker chinese one.
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Old 10-08-2018, 06:58 PM
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Re: Looking to buy a 94 Z28 with head gasket problem, what to look for?

Originally Posted by ridiqls View Post
Timing cover set (I think this covers the water pump, front main and opti but I'm not sure), water pump (theres 2 triangle ones), water pump coupler o-rings(?).
The Felpro timing cover sets from Rockauto include the crank, cam (Opti drive) and water pump seals, the timing cover gasket itself, the two O-rings for the water pump drive and the water pump mounting gaskets.

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Old 10-09-2018, 04:12 AM
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Re: Looking to buy a 94 Z28 with head gasket problem, what to look for?

Originally Posted by pontiacstogo View Post
The Felpro timing cover sets from Rockauto include the crank, cam (Opti drive) and water pump seals, the timing cover gasket itself, the two O-rings for the water pump drive and the water pump mounting gaskets.
Ok thanks, perfect. Added that one to the cart.
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Old 10-10-2018, 11:17 PM
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Re: Looking to buy a 94 Z28 with head gasket problem, what to look for?

It's moving slowly but it is moving. My parts are on the way.

Here's a pic of the engine at the performance shop finished:





Progress: Removed all the accessories on the old engine and waiting for the oil pan gasket to get here tomorrow and I will switch out the oil pump, pan, etc. and then set the new engine on the k-member.


I removed the transmission and ran into this today:

The previous owner told me the clutch was a Centerforce Dual Friction and after research it appears to be the case.


Questions:
1) First time installing a clutch.... I was going to order a new OEM Luk clutch but I might just keep this in the car. Is there anything I should do to make sure I don't ruin the balancing of the clutch with the engine?

I read about people not getting it balanced which caused a major issue. One guy threw a rod bearing from driving it like that. So I plan to use a marker and mark the Pressure Plate/Flywheel/block so they are all in the same place when I re-install it on the new setup. And going to put the crank at top dead center when I do this in case that is somehow going to affect the balance. (Unsure if this is necessary so would like some input)


2) Should I replace the pilot bearing and throwout bearing when I re-install it? I plan to at least grease the shaft and the shift fork.


3) Ok, so when I test drove the car initially, the clutch pedal was REALLY stiff. Definitely felt aftermarket and thats when the previous owner told me that it's due to the Centerforce dual friction clutch. It wasn't bad but I can see this being really annoying when I'm commuting in LA traffic. Like 1 mph back to back traffic for 1.5 hours. I had a mustang with a stiff aftermarket clutch and it was really a bitch in that kind of situation.

So... is there anything I can do to make the pedal effort lighter? I am guessing no since it's all hydraulic other than welding a longer clutch pedal for increased torque. I read almost all LT1 pressure plates are the same (they all start OEM, which is why even aftermarkets were stamped VALEO) so what would happen if I removed those weights you see on the Centerforce clutch?

I'm guessing the weights are what helps hold the higher power #s but at the same time, they are what makes the pressure plate heavier to move with the pedal.

Just a thought...

Last edited by ridiqls; 10-10-2018 at 11:19 PM.
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Old 10-11-2018, 03:45 PM
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Re: Looking to buy a 94 Z28 with head gasket problem, what to look for?

I had a CF clutch on my car before moving to Spec, and felt no difference in how hard it was to push the clutch VS stock.
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Old 10-11-2018, 04:21 PM
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Re: Looking to buy a 94 Z28 with head gasket problem, what to look for?

Originally Posted by DrewHMS97SS View Post
I had a CF clutch on my car before moving to Spec, and felt no difference in how hard it was to push the clutch VS stock.
Thats what I read also. People say CF is only a little heavier or same as stock. But didn't feel that way when I drove it.. although I didn't drive it very long.

I'm going to remove the PP and Clutch today and take a look to see if anything worn out, etc.

Maybe it's a stiff/non-greased shift fork or slave cylinder affecting the pedal feel.



Anyway, I decided I'm going to keep this clutch setup instead of throwing in an OEM one. Since everything is the same just moving it to the other engine, would I have to get a new throwout bearing?
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Old 10-11-2018, 05:53 PM
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Re: Looking to buy a 94 Z28 with head gasket problem, what to look for?

As far as I know, the throw out bearing should last the life of the clutch. You will want to inspect the pilot bearing in the crank and replace if there is visible wear.
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Old 10-12-2018, 04:50 PM
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Re: Looking to buy a 94 Z28 with head gasket problem, what to look for?

What is the correct way to install and prime a new oil pump? I'm pulling the oil pan off the old engine and putting a new pump, oil pick up into the new engine.

I know you have to space it about 1/4" from the bottom of the oil pan but I'm not sure how to prime the pump. Can I just install it and then once the engine is in the car, pull the fuel relay and crank it over until oil pressure builds up?

I'm reading something about assembly lube (which I don't have)... is that just to be safe you stuff the oil pump with some lube to begin with?
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Old 10-12-2018, 05:47 PM
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Re: Looking to buy a 94 Z28 with head gasket problem, what to look for?

Originally Posted by ridiqls View Post
It's moving slowly but it is moving. My parts are on the way.

Here's a pic of the engine at the performance shop finished:





Progress: Removed all the accessories on the old engine and waiting for the oil pan gasket to get here tomorrow and I will switch out the oil pump, pan, etc. and then set the new engine on the k-member.


I removed the transmission and ran into this today:

The previous owner told me the clutch was a Centerforce Dual Friction and after research it appears to be the case.


Questions:
1) First time installing a clutch.... I was going to order a new OEM Luk clutch but I might just keep this in the car. Is there anything I should do to make sure I don't ruin the balancing of the clutch with the engine?

I read about people not getting it balanced which caused a major issue. One guy threw a rod bearing from driving it like that. So I plan to use a marker and mark the Pressure Plate/Flywheel/block so they are all in the same place when I re-install it on the new setup. And going to put the crank at top dead center when I do this in case that is somehow going to affect the balance. (Unsure if this is necessary so would like some input)


2) Should I replace the pilot bearing and throwout bearing when I re-install it? I plan to at least grease the shaft and the shift fork.


3) Ok, so when I test drove the car initially, the clutch pedal was REALLY stiff. Definitely felt aftermarket and thats when the previous owner told me that it's due to the Centerforce dual friction clutch. It wasn't bad but I can see this being really annoying when I'm commuting in LA traffic. Like 1 mph back to back traffic for 1.5 hours. I had a mustang with a stiff aftermarket clutch and it was really a bitch in that kind of situation.

So... is there anything I can do to make the pedal effort lighter? I am guessing no since it's all hydraulic other than welding a longer clutch pedal for increased torque. I read almost all LT1 pressure plates are the same (they all start OEM, which is why even aftermarkets were stamped VALEO) so what would happen if I removed those weights you see on the Centerforce clutch?

I'm guessing the weights are what helps hold the higher power #s but at the same time, they are what makes the pressure plate heavier to move with the pedal.

Just a thought...
OP

If your new motor was "internally" balanced (aka neutral balanced) than the FW and PP also need to be zero balanced. If the motor the CF clutch came from was a stock motor it would be external (rear) balanced. The FW would have a weight on the back on one part and several drill holes to balance it. PP would also. That yellow paint dab on the CF is where you would line that up to the dowel pin on the crank on a externally balanced stock LT1.

Not a fan of CF clutches with the sliding weight thing. If anything it makes for harder pedal effort at RPM. If the clutch & FW look OK you can re-use it. Just get it zero balanced if your new motor is internal balance

Absolutely get a new pilot bearing in the new motor regardless of using the CF or new clutch

If the car the clutch hydraulics came from is using a aftermarket, larger bore, MC than pedal effort is about 10% more but not really something that makes stop/go traffic a PIA. Used clutches are like used brakes...make sure they are "worth" putting back in as a clutch swap is not a easy job later.

What ever clutch you get for a LT1 they all have the same China made (no more Valeo) PP with whatever spray paint color that clutch company uses so does not matter what clutch company you use, its the same PP. SPEC "claims" they increase PP holding by changing the angle of the diaphragm hat. This "may" be effective but certainly will add greater pedal effort. McLeod says they do no such thing for the LT1 PP. If the motor is mild a LUK replacement clutch is fine if it has a 5 spring hub disc. If you have a cam and intend to do some aggressive launches, especially with a drag tire, get a DF (dual friction) disc like the Centerforce. IMHO if I had to buy a single disc LT1 clutch for a car making 400 RWHP I would minimally get the SPEC 3+....but I have the McLeod Street Twin which is VERY good but costs about $1500 now. Drives like stock but holds the power. Not needed for milder builds

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Old 10-12-2018, 05:53 PM
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Re: Looking to buy a 94 Z28 with head gasket problem, what to look for?

Originally Posted by ridiqls View Post
What is the correct way to install and prime a new oil pump? I'm pulling the oil pan off the old engine and putting a new pump, oil pick up into the new engine.

I know you have to space it about 1/4" from the bottom of the oil pan but I'm not sure how to prime the pump. Can I just install it and then once the engine is in the car, pull the fuel relay and crank it over until oil pressure builds up?

I'm reading something about assembly lube (which I don't have)... is that just to be safe you stuff the oil pump with some lube to begin with?
You can just spin the oil pump while the pick up is submerged in oil on the bench

or use a oil pump drive rod on a drill and spin until oil pressure wuth the pump installed but before you put oil pump drive and gear on

or

On install crank the motor over with coil wire and FI fuses pulled until you have oil pressure. Use a solid oil pump drive shaft like ARP or Miloden vs re-using the stock on. The plastic collar cracks/breaks on re-install sometimes because it has aged and is brittle. Also be VERY gentle on tightening the one small bolt for the oil pump drive up top. You can even use a washer under the head of that bolt to help disperse the load onto the old brittle plastic top of the oil pump drive gear.
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Old 10-12-2018, 11:41 PM
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Re: Looking to buy a 94 Z28 with head gasket problem, what to look for?

Originally Posted by Chimera96 View Post
You can just spin the oil pump while the pick up is submerged in oil on the bench

or use a oil pump drive rod on a drill and spin until oil pressure wuth the pump installed but before you put oil pump drive and gear on

or

On install crank the motor over with coil wire and FI fuses pulled until you have oil pressure. Use a solid oil pump drive shaft like ARP or Miloden vs re-using the stock on. The plastic collar cracks/breaks on re-install sometimes because it has aged and is brittle. Also be VERY gentle on tightening the one small bolt for the oil pump drive up top. You can even use a washer under the head of that bolt to help disperse the load onto the old brittle plastic top of the oil pump drive gear.
Thanks for the tip. Ok I will order a new shaft and probably the easiest way to do this is to just install it and crank it with the fuses pulled until there is oil pressure.

Are these 2 parts the same? It looks the same but might be categorized differently..

https://www.rockauto.com/en/catalog/...ump+shaft,5588
https://www.rockauto.com/en/catalog/...te+shaft,14256


I'll be careful when installing that top driveshaft gear bolt thing, thanks for the heads up.



Originally Posted by Chimera96 View Post
OP

If your new motor was "internally" balanced (aka neutral balanced) than the FW and PP also need to be zero balanced. If the motor the CF clutch came from was a stock motor it would be external (rear) balanced. The FW would have a weight on the back on one part and several drill holes to balance it. PP would also. That yellow paint dab on the CF is where you would line that up to the dowel pin on the crank on a externally balanced stock LT1.

Not a fan of CF clutches with the sliding weight thing. If anything it makes for harder pedal effort at RPM. If the clutch & FW look OK you can re-use it. Just get it zero balanced if your new motor is internal balance

Absolutely get a new pilot bearing in the new motor regardless of using the CF or new clutch

If the car the clutch hydraulics came from is using a aftermarket, larger bore, MC than pedal effort is about 10% more but not really something that makes stop/go traffic a PIA. Used clutches are like used brakes...make sure they are "worth" putting back in as a clutch swap is not a easy job later.

What ever clutch you get for a LT1 they all have the same China made (no more Valeo) PP with whatever spray paint color that clutch company uses so does not matter what clutch company you use, its the same PP. SPEC "claims" they increase PP holding by changing the angle of the diaphragm hat. This "may" be effective but certainly will add greater pedal effort. McLeod says they do no such thing for the LT1 PP. If the motor is mild a LUK replacement clutch is fine if it has a 5 spring hub disc. If you have a cam and intend to do some aggressive launches, especially with a drag tire, get a DF (dual friction) disc like the Centerforce. IMHO if I had to buy a single disc LT1 clutch for a car making 400 RWHP I would minimally get the SPEC 3+....but I have the McLeod Street Twin which is VERY good but costs about $1500 now. Drives like stock but holds the power. Not needed for milder builds
Thanks .. Hm what is your opinion on the following pictures?

I marked with a sharpie so I know where to align everything exactly the way it was. I also aligned the flywheel with the dowel pin on the crank so I know where that goes. The new engine is just a stock LT1 with forged pistons and .30 bore that's it.


Clutch disc padding visible




Flywheel




Clutch disc - Flywheel side. Can't tell depth here but from the side you can tell it has padding left (See below)



Clutch Disc - Flywheel side (bottom).. clutch life left




pressure plate side of the clutch disc




Pressure plate




If I'm installing a new clutch, I would resurface that flywheel or get a new one and replace everything new. However, I would like to keep this clutch if at all possible given that I don't plan on doing hard launches at the drag strip and the engine is only pushing stock Horsepower.

I might get Lloyd Elliot LE package later down the road, maybe a year or two but it's not really urgent. I can revisit the clutch issue later but if this clutch lasts me regular street driving for the next 2 years I'll consider it a win.


Driving wise I haven't had much experience with this car because the minute I drove it home from the previous owner it was overheating like crazy so that's why I pulled the engine out. But the clutch itself didn't chatter or slip or have any issues. I plan on putting it back into the tranny with the new engine exactly the same it is (with new pilot bearing) unless there's something you see that's highly not recommended to reinstall this clutch.

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Old 10-13-2018, 11:57 AM
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Re: Looking to buy a 94 Z28 with head gasket problem, what to look for?

This Melling shaft will be fine
https://www.rockauto.com/en/moreinfo...=1035874&jsn=9

The clutch looks "OK"...I would just use some emery cloth on FW & PP. Wrap a small wood sanding block (or piece of wood) with emery cloth

Confirm with the machine shop who rebuilt the motor if it was "internal" or "external" balanced motor. MOST are internal if rebuilt. They would have needed your FW to balance it if it is external

You can have your FW & PP zero balanced at a machine shop for about $40

Make sure you confirm how the rotating assembly was balanced. A stock FW on a internal balanced motor will vibrate like a dog shiating razor blades
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Old 10-13-2018, 12:30 PM
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Re: Looking to buy a 94 Z28 with head gasket problem, what to look for?

Originally Posted by Chimera96 View Post
This Melling shaft will be fine
https://www.rockauto.com/en/moreinfo...=1035874&jsn=9

The clutch looks "OK"...I would just use some emery cloth on FW & PP. Wrap a small wood sanding block (or piece of wood) with emery cloth

Confirm with the machine shop who rebuilt the motor if it was "internal" or "external" balanced motor. MOST are internal if rebuilt. They would have needed your FW to balance it if it is external

You can have your FW & PP zero balanced at a machine shop for about $40

Make sure you confirm how the rotating assembly was balanced. A stock FW on a internal balanced motor will vibrate like a dog shiating razor blades

If the engine is built to stock specs, wouldn't it be externally balanced? (I'm reading internally balanced front/externally balanced rear on stock lt1)

So to clarify... if it was built differently than stock and is purely zero balanced internally, then my FW and PP need to be also zero balanced where they remove the weights, etc.

If it is externally balanced like stock, then I can just add my stock flywheel and clutch setup AS-IS?

I imagine any time you change a flywheel when an externally balanced stock engine is already in the car, they just look up factory weight specs and apply it to the flywheel since most of the time you don't pull the engine and strip it down.

I just emailed the shop so we'll see what he says but def good advice. Might have him just machine the flywheel if we're going to zero balance it.


EDIT: I found this in the service manual


So I guess if you replace the flywheel and it's externally balanced like a stock engine, you just take the same weights and put it in the same location on the new flywheel.

Last edited by ridiqls; 10-13-2018 at 01:01 PM.
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Old 10-13-2018, 01:19 PM
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Re: Looking to buy a 94 Z28 with head gasket problem, what to look for?

The machine shop that rebuilt the motor had to balance the rotating assembly. If they did not have a donor or your FW than it would have been "internal" balance.

The shop that did it should be able to tell you immediately or it would have been noted on the "build sheet"....if there was one.

If it is a internal balanced motor now you must run a zero, aka neutral, balanced FW. Either have a stock one re-balanced or but a "zero" balance aftermarket FW. IMHO even if buying a expensive billet zero balanced FW...have it checked by a machine shop. My McLeod billet FW was 26 grms off.....

You have new pistons....they must have balanced the rotating assembly

pic of stock FW. The cast in weight and some drill holes are what they have. Machine shop would initially grind off the cast in weight and either drill some material out where needed...or better, use steel pins in the outer holes around the FW of various lengths (weight) to balance it. What the shop did to my stock one when I was running a single disc clutch

Last edited by Chimera96; 10-13-2018 at 01:21 PM.
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Old 10-13-2018, 01:24 PM
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Re: Looking to buy a 94 Z28 with head gasket problem, what to look for?

Originally Posted by Chimera96 View Post
The machine shop that rebuilt the motor had to balance the rotating assembly. If they did not have a donor or your FW than it would have been "internal" balance.

The shop that did it should be able to tell you immediately or it would have been noted on the "build sheet"....if there was one.

If it is a internal balanced motor now you must run a zero, aka neutral, balanced FW. Either have a stock one re-balanced or but a "zero" balance aftermarket FW. IMHO even if buying a expensive billet zero balanced FW...have it checked by a machine shop. My McLeod billet FW was 26 grms off.....

You have new pistons....they must have balanced the rotating assembly

pic of stock FW. The cast in weight and some drill holes are what they have. Machine shop would initially grind off the cast in weight and either drill some material out where needed...or better, use steel pins in the outer holes around the FW of various lengths (weight) to balance it. What the shop did to my stock one when I was running a single disc clutch


This is what I received from the machine shop: "Just like factory the front is internal balance the rear fly will will be external balance"

So I'm guessing since he knew it was internal in the front and external in the rear, he knows what he's talking about with the LT1 so I think we're clear to use flywheel and clutch setup as is.

Thank you for the explanation.
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