More rebuild questions.

[jdub]

Nope...just the math above.

Since you have rod knock, you will have to have work done to your crank shaft and rods. Make sure your mechanic sets the rod bearing clearances to the tighter side of the TRSM spec. The 7M does not like sloppy bearings...you will just get the knock again.

 

[jdub]

the thickness of the gasket affects the compression one way or the other. The studs won't come lose once you are heat cycled. The bolts will, I believe, in this car of mine. I'm not shaving my block but I am shaving the head...., they took 8 thousands off of it. I'm thinking 2.mm beaded. The only reason I ask is because this is the first time the stopper has seen the spot light.

If you want to know the differences between the different types of MHG's, look at this:

http://www.supramania.com/forums/showpost.php?p=216396&postcount=5

The amount of material does affect compression. A thicker HG than stock will decrease compression...thinner will increase compression. For an NA motor, you don't want to decrease compression...stock or a slight increase is better. For a turbo motor, it's the opposite...especially under high boost. The turbo has the effect of increasing compression as boost level increases.

 

[supramacist]

If I went with the stopper over the beaded and do the starter upgrade.....
This tacks on 200$ to the entire build tally. Damnit..., I was firm on the beaded until we started talking about this. I thought it to be the better choice for my car. Obviously the stopper is the better choice. But I am unsure of what diameter to go with. !.3 is stock you said and I had 8k removed from the head. A 2.mm should be fine. If I am wrong, correct me. Please.

 

[jdub]

If I went with the stopper over the beaded and do the starter upgrade.....
This tacks on 200$ to the entire build tally. Damnit..., I was firm on the beaded until we started talking about this. I thought it to be the better choice for my car. Obviously the stopper is the better choice. But I am unsure of what diameter to go with. !.3 is stock you said and I had 8k removed from the head. A 2.mm should be fine. If I am wrong, correct me. Please.

Actually, you would want a 1.5mm thickness....008" = .2mm + 1.3mm = 1.5mm. A 2mm will work, but you will lower your compression some...if I'm not mistaken, you have a N/A motor. You really don't want to lower the compression, but it won't hurt anything either...other than dropping your HP a bit

Something else to consider: The HKS stopper is without a doubt the best. However, to get full advantage you are looking at 500+ HP numbers...usually for a turbo motor. A guy like IJ def needs one of these, but if your goals are less (esp for a N/A) why spend the extra $$$? You can use the bead type with no problem and have a very strong motor.

 

[supramacist]

Actually, you would want a 1.5mm thickness....008" = .2mm + 1.3mm = 1.5mm. A 2mm will work, but you will lower your compression some...if I'm not mistaken, you have a N/A motor. You really don't want to lower the compression, but it won't hurt anything either...other than dropping your HP a bit

Something else to consider: The HKS stopper is without a doubt the best. However, to get full advantage you are looking at 500+ HP numbers...usually for a turbo motor. A guy like IJ def needs one of these, but if your goals are less (esp for a N/A) why spend the extra $$$? You can use the bead type with no problem and have a very strong motor.

Afterthought. What about the 1mm stopper. This would make me gain hp and that gasket...., more effective?

Tactfully said. Thanks for not callind me a retard. LOL. I'm not a mechanic and I don't claim to be. This maybe a prime example of why that is. I appreciate the input. I have been wrestling this for months. Indecision is a pain. We def. don't want to lower the hp, at all. 1.5 it is.

 

[jdub]

Afterthought. What about the 1mm stopper. This would make me gain hp and that gasket...., more effective?

Tactfully said. Thanks for not callind me a retard. LOL. I'm not a mechanic and I don't claim to be. This maybe a prime example of why that is. I appreciate the input. I have been wrestling this for months. Indecision is a pain. We def. don't want to lower the hp, at all. 1.5 it is.

I'd stick with the 1.5mm...the gain you'd get from the extra compression is very small and would increase the likelyhood of detonation.

And...LOL. I'd never call a Marine a retard...think I'm stoopid :naughty:
Besides, the only dumb question is the one you don't ask

 

[Sl1dewaysSupra]

Was there some sort of formula for figuring out the needed thickness? That is to stay close or a little higher compression than stock. I don't want to run too high of compression just because of the crappy gas here. Don't feel like hearing rod knock 15min. after I first start her up.

 

[IJ.]

1.37mm + what ever has been removed from the Head and Block.

 

[Sl1dewaysSupra]

So if I took .5mm off total(head and block) +1.37mm=1.87mm? So I could round up to 2.0mm gasket without losing too much compression?

 

[jdub]

So if I took .5mm off total(head and block) +1.37mm=1.87mm? So I could round up to 2.0mm gasket without losing too much compression?

That should be fine...just remember, there's .039" to 1mm. I use .040" and call it a day.

 

[IJ.]

Yep that would work out ok!

You need to measure the block and head to determine exactly how much has been removed as 7M's being known for head gasket issues you can never be sure if it's been machined already.

 

[87CandyBlueT]

You need to measure the block and head to determine exactly how much has been removed as 7M's being known for head gasket issues you can never be sure if it's been machined already.

Damn reading down through the first page I was wanting to mention measuring the head/block surfaces to figure HG thickness. IJ beat me to it and this last post made me laugh

 

[Sl1dewaysSupra]

Thanks a ton guys!!! You saved me a BIG headache trying to figure this out on my own.(Not that the mechanic rebuilding the motor wouldn't know.)

 

[Sl1dewaysSupra]

Hopefull I will have a few more questions in a couple days.

 

[Jaguar_5]

Don't over-estimate the machinists know-how
I had some amazing looking results, and then realised how many problems i had run into by assuming he'd do everything correctly!

 

[Sl1dewaysSupra]

^ Thats why I wanted your guys opinions. He said he has worked on 7M's but it has been awhile. I figure that if you have 4-5 7M's under your belt you either1) Know your way around a 7M better than you can walk. 2) you have done something terriably wrong and that forced you to replace the motor 4-5 times. The second option is very unlikley but you never know. With your guy's help I will be able to have mor specific questions and be able to tell him exactly what I want done to the motor. That was one of my main reasons for joining this forum, so I could get tons of diff. opinions and decide wich one best suits my needs.

 

[supramacist]

someone offered me 2k for the car as it sit's.
2k doesn't wipe my cars tail pipe.

 

[josh930]

Is the lowering of the compression enough to have to change the timing? If so, does it have to be advanced or retarded?

 

[Sl1dewaysSupra]

I think it would depend on how much you lowered it. Don't lower it unless you are running a big turbo or in the process of NA-T. If you only lower it a bit I would just start the motor and check the motor against factory specs.(10btdc) But that is only if you lowered it a little. If you know that the compression is going to be very low I don't what you would do.

 

[Sl1dewaysSupra]

So from what I hear on this forums and SF the clearances of the motor are finikey. From what I gather the 7M likes to spin bearings if the clearances are on the smaller side. Is this true? Should I have the mechanic go for the larger clearences that the TSRM calls for?