Head maching questions

[Supra_Villan]

well, i'll be taking my head to the machinist on monday, i need to know; since my head gasket is 2mm thick, then i will have to have 2mm(or 78thousandths) shaved off the head correct?(btw, don't worry the block has already been prepped and resurfaced for it but none was taken off, just a resurfacing) And when i called the machinist he wanted to know if he will have to do any valve grinding.....will he? he says most likely yes because the lifters are solid, but like i said i wouldn't know, any input would be appreciated, thanks alot!
charles

p.s. for those of you who will say that i need to make sure he can/will do the right RA on the head, its all good i got it, but thanks for thinking about saying it before you read this!:icon_bigg lol

 

[jdub]

The block...when you say "re-surfaced" what exactly was done?

I would have a valve job done (3 angle mininum), replace the seals and have the guides checked for wear. Also, get Comp Cam Springs...you need to order 2 sets of 975-12 (12 = # in the package), they are ~$35 per set. Excellent upgrade over stock.
http://www.compperformancegroupstor...reen=CTGY&Store_Code=CC&Category_Code=SPRNGSI

You should never shave the head to match the MHG...you match the MHG to how much was removed from the head.

 

[Supra_Villan]

The block...when you say "re-surfaced" what exactly was done?
You should never shave the head to match the MHG...you match the MHG to how much was removed from the head.

okay well the first part...it has all of the old gasket surface gone, and is pretty smooth, not a mirror surface, but the only thing i can see on the top is the casting flaws, but they aren't raised.

and the second part.....i don't get it if i get 2mm taken off of the head, then that means i need a 2mm head gasket....but if i get a 2mm head gasket i'm NOT supposed to get 2mm taken off of the head....? elaborate please, i'm scared...:1zhelp:

 

[Supra_Villan]

and by cam springs do you mean valve springs? not trying to correct you, i'm just making sure cuz i haven't heard of them being called that,
thanks, charles

 

[zachm611]

yes he means valve springs and by matching the HG to how much removed is so you can get it closest to stock compression. and im sure theres a few other things im not sure exactly but i would guess its to retain compression as close to stock as possible.

edit i just looked it over.. comp cam...is the company and he simply said springs after that.

 

[jdub]

Comp Cams IS the name of the company that sells them...yes, they are the valve springs
They are the inner springs from a small block Chevy...they happen to fit our valve train.

When determining thickness for a MHG, you have to know a couple things. First, a stock HG is 1.37mm compressed. Now lets say you get 0.007" of material removed when surfacing the head and 0.003" removed surfacing the block...that equals 0.010" total. 0.039" = 1mm...you've removed 0.25mm of material. Add that to 1.37 and you get 1.62mm as the required thickness to retain stock compression. If the MHG is thicker, cylinder compression drops...thinner, compression increases. You want to get as close to calculated MHG thickness as possible to retain stock cylinder compression. That's the basics...if you're planning to run big boost numbers, you'll see guys use a thicker MHG to drop compression on purpose to help prevent detonation at WOT.

Concerning your block...the surface RA requirements are the same as they are for the head. It's a crap shoot if it's smooth enough in stock form to meet spec. That decision is up to you, but I've seen a lot of crying when it didn't work. FYI - HKS RA spec is 30, Cometic RA spec is 50...the lower the number, the smoother it needs to be.

A couple of other things:
- Don't get the idea a spray sealer will help...the chemicals in them attack the Viton coating on new MHG's. Not a good idea IMO
- Make sure you apply RTV at the locations shown in the TSRM, top of the front plate...READ the TRSM a couple times before you do this
- Torque your ARP hardware to the specs ARP provides with the bolts/studs....READ the instructions and use the moly lube included. ARP bolts are limited to 75 ft/lbs on an aluminum head
- Check your valve lash clearances before you install the head...easier to do out of the car and if you need to order shims, you can walk away to come back and do it.

 

[Supra_Villan]

oooooo....that sucks, i purchased the mhg long ago anticipating that the thicker the better so i could avoid going too thin, but i'm also only planning on a max of 500 hp, so that concept was dumb....:3d_frown: i can dig up the old paperwork from the block and get the exact specs, so am i totally screwed if i have the machinist match the head to the mhg?(and the block which has already been done, and is now assembled)

 

[jdub]

Well...better lucky than good
I see you're using JE pistions...I looked at their website a few weeks ago and found out these pistions are an 8.8:1 CR (stock is 8.4:1). That means, you can afford to drop the CR a bit using a 2mm HG. Have your machinist take the min necessary off to straighten the head deck and get it to RA spec. Have him test for hardness 1st...a bad overheat can anneal the head, making it soft.

I saw your block too...looks to be re-surfaced to me. Can you run a fingernail across the machine marks and feel them?
(not very scientific, I know)

 

[Supra_Villan]

Well...better lucky than good
I see you're using JE pistions...I looked at their website a few weeks ago and found out theie pistions are an 8.8:1 CR (stock is 8.4:1). That means, you can afford to drop the CR a bit using a 2mm HG. have you machinist take the min necessary off to straighten the head deck and get it to RA spec. Have him test for hardness 1st...a bad overheat can anneal the head, making it soft.

I saw your block too...looks to be re-surfaced to me. Can you run a fingernail across the machine marks and feel them? (not very scientific, I know)

will do, thanks alot, the block has been decked, but i'm not sure what the ra is on it, i'll find out if i can, and no i don't recall any feelable(is that a word?) raised surfaces on the block, but i'll double check this week end, once again, thanks a ton for the help, much appreciated:icon_bigg

 

[jdub]

NP
Get those springs...excellent, inexpensive upgrade.

 

[Supra_Villan]

well i'm back again with more questions....the head i'm using was disassembled long ago and i'm not sure which order i took the cam caps off in..will this be an issue as long as they're the same ones?

 

[nosman4]

As long as you have all the cam caps that came off that head, then you should have no problem putting them back on. All the cam caps have numbers on them, (I1-I7, E1-E7) "I" being intake cam and "E" being exhaust cam. I believe they also have arrows on them that you install pointing toward the front of the motor and of course #1 starts at the front of the head.

 

[Supra_Villan]

god bless you nosman and all the other local geniuses:icon_bigg without you guys i'd most likely be::hang::
thanks alot, its much appreciated

 

[JAB89]

As long as you have all the cam caps that came off that head, then you should have no problem putting them back on. All the cam caps have numbers on them, (I1-I7, E1-E7) "I" being intake cam and "E" being exhaust cam. I believe they also have arrows on them that you install pointing toward the front of the motor and of course #1 starts at the front of the head.

Here it in the TSRM (you are of course using the TSRM for assembly):
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=EM&P=52

 

[Supra_Villan]

well, we have another issue....i was going over my block today, and i noticed that when i put the timing cover on it it wasn't level with the block.....on one side.... and on the same side it is level with the block, there is some gasket(very little but enough to feel with my fingernail), so my guess is that it was done unevenly because if one side of the unmachined timing cover is higher than the other that means that the block wouldn't be completely even especially if there are gasket remains on the left side and not the other....i have a few alternatives
1. pray to god you genuises say that this will be okay
2. take it back to the machinist, who is a good guy and will back up his work and correct his mistakes for free(at least he should), but at the same time, he's very backed up and he said any more work won't be done for almost a month due to his load he has right now
or
3. take it to the machinist who is doing my head and pay even more

 

[MassSupra89]

Take it back to the machinist who did your block. The front timing cover MUST be level with the block or you will be taking that engine out much sooner than you'd like.

 

[Supra_Villan]

Take it back to the machinist who did your block. The front timing cover MUST be level with the block or you will be taking that engine out much sooner than you'd like.

well, i had planned on machining the cover, BUT my main issue is if the blcok is totally level

 

[cuel]

The timing cover should be bolted on the block, and both machined together. If it wasn't, you need to have it surfaced again, correctly.

You could measure the block, from the deck to the oil pan on each side, and see if they're the same. I believe Home Depot sells a tape measure that is both metric and standard.