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head rebuild, comments sought

jerryc

jerryc

Active member
Joined
Jun 10, 2004
Location
SF Bay area
Edit;
Moot; head is warped 25 thou, need another, or is there a way to fix it? I read somewhere that maybe Volvo could/did twist them back into shape?

But I'll leave it all here for now as it will happen at some point.
Thanks for replies, I appreciate it.
-------------------------------------------

This may not qualify as performance but it's not stock so here goes.
93 940T, 275k mi. Decent compression last I checked, 165-175 range. All components such as AMM, plugs, wires, sensors, seem to be working well including O2 sensor several months ago. Car starts immediately, idles well, runs fairly strong. Mileage not so hot, 18 combined, 22 highway. Smog is an issue.
I am thinking that doing the below may take care of all at once.

I have a used head which I want to rebuild and do a swap, to make things happen faster. I don't have a good place to do a job like this.

Goals: several, including
preventive maintenance of doing a head gasket before it fails,
gaining a bit of performance, and
better mileage.
Also passing smog.
Perfomance/mileage may not be at the same time, but both are possible I believe with what I've read.
Smog, I need to get it done, got a pretest which showed I am probably over the limit for NOx at 825. Others, CO, HC, seem good. I am told that this situation can be due to exhaust leak, and I do have a broken ex stud. I am having other aspects of the ex looked at shortly.


Mods:
parts;
used 530 head off a turbo, that ms says is virgin.
*Cometic, (size to be determined when the head on the car comes off)
*Vcam,
*Dale's gear,
*Josh's phenolic man/head spacer,
*much lower mileage 90 ex manifold and stock size turbo that I have, 140k instead of 275k
*Also new valve springs and guides were ordered but they are not the same. I received the larger springs that I am told fit earlier cars, and that they can be used with the correct retainer and same keepers. ??? Should I do that or get the smaller springs? They are BeckArnley USA made.
*new timing belt etc, maybe water pump.

Machine work:
the used head is being evaluated for cracks etc. If good I am going to;
*change all int/ex studs
*mill flat ex manifold/head surface
*check the deck height, order the correct Cometic to get to 030-032,
*unshroud the exhaust slightly, (approx half the area between the chamber lip and the hg 'fire ring': 1mm maybe, and continue that semicircle)
*cc the chambers and accounting for gasket area,
*plan a cut to get to 9.1-9.5 scr

Machine shop says he does not believe the valves in the used head are sodium filled. Head came off a 90 or 91 740T. He has done many Volvo heads and really seems to know his stuff. He also says stellite coating can be machined. ?? The valves are not out yet so this may not be accurate right now.

Where to set the cam gear? 2-4-6 deg +- possible.
Any other comments welcome, Thanks
 
Last edited:
jerryc said:
Smog, I need to get it done, got a pretest which showed I am probably over the limit for NOx at 825. Others, CO, HC, seem good. I am told that this situation can be due to exhaust leak, and I do have a broken ex stud.
Click to expand...
I'd be looking at that cat with my eye lasers(pyrometer).
 
What MS are you using?
If you're gonna put yourself through deshrouding and maybe some DIY port work, why not get some bigger valves? Knox is practically your one stop shop... Lawrence sets up valve springs to a certain tension that allows for a little bit more rpm. He's a great source of info for this kinda thing. In the grand scheme of things, adding some high performance locks, guides, valves, etc really isn't that expensive with an 8v head. Think about it this way.... How often are you going to take the head off to tinker with it? Either go all out (it's only a few hundred more) or run the current head.

And... with the current head, it sounds like you're runnin just fine. I got a HF leak down tester if ya want to use it. If it was up to me, i'd get your exhaust system buttoned up properly and look into other reasons why your mileage is only so so. Maybe an aging AMM? Sometimes they die slowly, yet let ya run fine.

With regard to smog, there's a place in Oakland that lets you test until you pass. You can test as many times as needed for no extra fee. Might just be something simple...
 
^ Stirtz in Oakland.
I am not going for big dog performance obviously :rofl: I did talk to Knox, who were very helpful. Part of my issue right now is timing; this project was going to be in a couple of months, add a bigger turbo and mbc, but I want to solve the smog at the same time, now. I can do the others later, and will have the proper basis for them.
I have no interest in hitting 7k rpm, and in the mods that go with big valves. I like stealthfti's ideas and am going mostly that way. I know JV likes big valves and I like some of his ideas but this motor is not going that way.
I want mostly to play just a little bit, be able to get out of the way of johnnyracerboy and his buddies on I80 and the Bay Bridge/high speed test track, and save gas the rest of the time.

Leakdown; that's interesting, I'm coming to Sac on Monday, will pm you.
Place in Oakland, do you recall the name?
AMM; I have tried several, have a bunch of spares. Mileage does not seem to change with any, but I'll try another anyway. I get similar mileage out of my 92 745T which is the same exact setup and axle.
 
jerryc said:
^ Stirtz in Oakland.
I am not going for big dog performance obviously :rofl: I did talk to Knox, who were very helpful. Part of my issue right now is timing; this project was going to be in a couple of months, add a bigger turbo and mbc, but I want to solve the smog at the same time, now. I can do the others later, and will have the proper basis for them.
I have no interest in hitting 7k rpm, and in the mods that go with big valves. I like stealthfti's ideas and am going mostly that way. I know JV likes big valves and I like some of his ideas but this motor is not going that way.
I want mostly to play just a little bit, be able to get out of the way of johnnyracerboy and his buddies on I80 and the Bay Bridge/high speed test track, and save gas the rest of the time.

Leakdown; that's interesting, I'm coming to Sac on Monday, will pm you.
Place in Oakland, do you recall the name?
AMM; I have tried several, have a bunch of spares. Mileage does not seem to change with any, but I'll try another anyway. I get similar mileage out of my 92 745T which is the same exact setup and axle.
Click to expand...

Hy Jerry, since I'm stuck in the 1880s maybe you should look up some info posted here by the sharp Finnish guy "Wagner" on the subject of % loss of powerz when LARGE BORE >90mm motors must compromise best ignition to mitigate detonation---and of course run pissy low boost vs powerz lost from slightly lower static compression, but correct ignition timing and more bewests.

Have you fingered what you actual comp will be with that cam you have vs say the much despised T cam----it could be the T cam with lower static---and hence real close dynamic to static comp, might be a better set up for what you seem to want to do...

It might not be baller enough to impress the boys here but soem of the guys who have done motors with T cam have made well over 250 BHPs AND had torque like a truck in the real world, every day rev range...

But I reallyu don't know anything since air flow and hos combustion works was only discovered by new technology in the late 90s on a discussion forum.

So look for what Wagner posted---it was very enlightening--as always.
 
John V said:
Have you fingered what you actual comp will be with that cam you have vs say the much despised T cam----it could be the T cam with lower static---and hence real close dynamic to static comp, might be a better set up for what you seem to want to do...

It might not be baller enough to impress the boys here but soem of the guys who have done motors with T cam have made well over 250 BHPs AND had torque like a truck in the real world, every day rev range...
Click to expand...

Thanks John, I always appreciate your take on things. I noticed some time ago that you thought the Tcam was good in many ways, thus I had thought of using the old one in my NA car, which pulls a small trailer.

No I have not calculated the dcr of the Vcam. I do see great reviews from people I also respect, like Hans and TF.
Edit; head is bad, will readdress later
 
That is the exact mileage I am getting from my 91 940T.

Keep the larger springs. You will have to get the correct larger retainers and larger spring seat washers. I have been running a set on my 740T for well over 100K.

New keepers are cheap insurance.

HIgh NOX means your tune up is not correct. As stated maybe a lazy O2sensor or carboned up chambers. Try either seafoam or water tourture and recheck the NOX.

My 740T was high on NOX the last smog check and the water torture cleaned things right up.

Like the others have stated, ensure the exhaust system is sealed.
X2
If you are going to unshroud and equalize combustion chambers, get some larger valves also. Correct pocket shaping goes a long way toward helping off boost power. I did not get a mileage increase but I did notice that the car would accelerate much easier in traffic when off boost not to mention when on boost. Night and day difference between the stock head and a ported head. I still got 22mpg after I installed the ported head (46X38).

Oversized valves (46X38) can also be used to restore valve face height and help save a slightly overcut seat.
 
That is the exact mileage I am getting from my 91 940T.

Keep the larger springs. You will have to get the correct larger retainers and larger spring seat washers. I have been running a set on my 740T for well over 100K.

New keepers are cheap insurance.

HIgh NOX means your tune up is not correct. As stated maybe a lazy O2sensor or carboned up chambers. Try either seafoam or water tourture and recheck the NOX.

My 740T was high on NOX the last smog check and the water torture cleaned things right up.

Like the others have stated, ensure the exhaust system is sealed.
X2
If you are going to unshroud and equalize combustion chambers, get some larger valves also. Correct pocket shaping goes a long way toward helping off boost power. I did not get a mileage increase but I did notice that the car would accelerate much easier in traffic when off boost not to mention when on boost. Night and day difference between the stock head and a ported head. I still got 22mpg after I installed the ported head (46X38).

Oversized valves (46X38) can also be used to restore valve face height and help save a slightly overcut seat.
 
89740GLT said:
That is the exact mileage I am getting from my 91 940T.

Keep the larger springs. You will have to get the correct larger retainers and larger spring seat washers. I have been running a set on my 740T for well over 100K.

New keepers are cheap insurance.

HIgh NOX means your tune up is not correct. As stated maybe a lazy O2sensor or carboned up chambers. Try either seafoam or water tourture and recheck the NOX.

My 740T was high on NOX the last smog check and the water torture cleaned things right up.

Like the others have stated, ensure the exhaust system is sealed.
X2
If you are going to unshroud and equalize combustion chambers, get some larger valves also. Correct pocket shaping goes a long way toward helping off boost power. I did not get a mileage increase but I did notice that the car would accelerate much easier in traffic when off boost not to mention when on boost. Night and day difference between the stock head and a ported head. I still got 22mpg after I installed the ported head (46X38).

Oversized valves (46X38) can also be used to restore valve face height and help save a slightly overcut seat.
Click to expand...

I've done water torture 3x since last year, including half an hour before the reading above. It never has given off the clouds of smoke that many others have noted, but I always notice a slight improvement in how it runs.
O2 sensor is a new Bosch/Ford 3 wire from the list of interchanges, and crimped connectors done right. Also added a casing ground strap. Voltage measured correct.
Exhaust is going to get more lookage.
 
jerryc said:
^ Stirtz in Oakland.
I am not going for big dog performance obviously :rofl: I did talk to Knox, who were very helpful. Part of my issue right now is timing; this project was going to be in a couple of months, add a bigger turbo and mbc, but I want to solve the smog at the same time, now. I can do the others later, and will have the proper basis for them.
I have no interest in hitting 7k rpm, and in the mods that go with big valves. I like stealthfti's ideas and am going mostly that way. I know JV likes big valves and I like some of his ideas but this motor is not going that way.
I want mostly to play just a little bit, be able to get out of the way of johnnyracerboy and his buddies on I80 and the Bay Bridge/high speed test track, and save gas the rest of the time.

Leakdown; that's interesting, I'm coming to Sac on Monday, will pm you.
Place in Oakland, do you recall the name?
AMM; I have tried several, have a bunch of spares. Mileage does not seem to change with any, but I'll try another anyway. I get similar mileage out of my 92 745T which is the same exact setup and axle.
Click to expand...



Ah yes, good ol' Carl... The machine shop to the Volvo guys in the Alameda area... You really need to be clued in... Drop me a PM with your email addy and phone number.
Oh yea, i'm in the Bay Area on weekends. Probably much, much easier to do a leak down back in the Bay.
 
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