High compression high RPM 7M-GE build

[NegativeGeForce]

Interference means if a belt breaks a valve hits a piston, NOT that the relief is the wrong size,placement to begin with, get a clue before you start giving your sage advice...

We all know you're a knowledgeable person in the supra community but there's no need to step on anyone like that just because they have a different view on building motors. I provided an option that andrew hasnt even considered. Since I was in a similar situation I thought id chime in and say what I did in my case. Rather than attacking me maybe you can provide your own advice so andrew can decide on his own.

Another option I guess is to see if CP can fix that set for you but that will probably set the build back another month or more.

 

[TurboStreetCar]

Unless im reading his post wrong, I think the problem is that the valves kissed the piston with the timing belt still on and timed as the motor would normally run. Not with the valves held at full lift and rotating the crank to check for interference.

 

[NegativeGeForce]

If the valves hit with the timing belt on then that's definitely not acceptable. What kind of cams are you running andrew?

Sent from my SPH-L720 using Tapatalk

 

[andrew_mx83]

yes correct the valves just kissed the piston with the belt on. actually im pretty sure it hit when the timing was at the extreme end of its adjustment on the cam gears but it is still too close for comfort. i gotta do something, wont run it like this.

cams are stock cams reground to 280* adv duration and 228* @ 0.050", 8.5mm max lift. this is the most you can get out of grinding stock cams without welding up the lobes and starting over ($$$). the base circle has had 0.060" off and is just above the bearing journal.

i wouldnt send the pistons back to CP to get modified, i have enough toys to do this myself. its a decent amount of work though, and NOT something you would want to get wrong considering the cost of getting custom pistons made. one wrong keystroke on the CNC can see the cutter plunge straight through the workpiece in a flash. cutting through the ceramic coating may be fun though, and then i would probably have to get them recoated (and balanced).


in regards to interference, with the previous pistons i timed it up with no belt at first and couldnt even rotate the crank to TDC with the valves fully closed. my valves sit out past the head surface so as i said everything is VERY close and all the clearances etc really need to be spot on.
im pretty sure this will end up as an interference motor no matter what i do, although i would really prefer it to be non-interference i cant see how i can do it and still keep uber compression


rollus, thats a neat spreadsheet! thanks! do you mind emailing me a *.xls file so i can edit the cells and play with the values (cant seem to do this online)
ill post up my valve clearance spreadsheet when i can find it as you guys may find it useful.

 

[SeeUSmile]

where'd did you get your pistons coated btw? how much did they cost?

 

[IJ.]

yes correct the valves just kissed the piston with the belt on. actually im pretty sure it hit when the timing was at the extreme end of its adjustment on the cam gears but it is still too close for comfort. i gotta do something, wont run it like this.

cams are stock cams reground to 280* adv duration and 228* @ 0.050", 8.5mm max lift. this is the most you can get out of grinding stock cams without welding up the lobes and starting over ($$$). the base circle has had 0.060" off and is just above the bearing journal.

i wouldnt send the pistons back to CP to get modified, i have enough toys to do this myself. its a decent amount of work though, and NOT something you would want to get wrong considering the cost of getting custom pistons made. one wrong keystroke on the CNC can see the cutter plunge straight through the workpiece in a flash. cutting through the ceramic coating may be fun though, and then i would probably have to get them recoated (and balanced).


in regards to interference, with the previous pistons i timed it up with no belt at first and couldnt even rotate the crank to TDC with the valves fully closed. my valves sit out past the head surface so as i said everything is VERY close and all the clearances etc really need to be spot on.
im pretty sure this will end up as an interference motor no matter what i do, although i would really prefer it to be non-interference i cant see how i can do it and still keep uber compression


rollus, thats a neat spreadsheet! thanks! do you mind emailing me a *.xls file so i can edit the cells and play with the values (cant seem to do this online)
ill post up my valve clearance spreadsheet when i can find it as you guys may find it useful.

Might want to consider making your self a cutter out of an old valve, you then use a dummy head and a positive stop collar set to the required depth and spin it up with a drill, you do this with the piston/crank locked at it's point of maximum interference this way the pocket ends up in the exact right spot on the crown not where someone thinks it should be.

where'd did you get your pistons coated btw? how much did they cost?

A Mate of mine owns Competition Coating in Coburg, Give Andrew a call and tell him you're a friend of Ian Johnston and he'll look after you.

 

[SeeUSmile]

Cheers IJ!

 

[Rollus]

rollus, thats a neat spreadsheet! thanks! do you mind emailing me a *.xls file so i can edit the cells and play with the values (cant seem to do this online)
ill post up my valve clearance spreadsheet when i can find it as you guys may find it useful.

Here you can select File/Download (Ctrl+S): https://drive.google.com/file/d/0B0PDVhGu1l7bQjNDOWFqYWNkQlU/edit?usp=sharing
Please PM me your mail if it doesn't work

++

Reynald

 

[TurboStreetCar]

Might want to consider making your self a cutter out of an old valve, you then use a dummy head and a positive stop collar set to the required depth and spin it up with a drill, you do this with the piston/crank locked at it's point of maximum interference this way the pocket ends up in the exact right spot on the crown not where someone thinks it should be.

Genius!

 

[andrew_mx83]

Pistons were coated by CP. Only 'local' one i knew of was HPC in leongatha. they do good work but cost an arm and both legs. to get everything coated in a 24v I6 (piston crowns & skirts, valves, chambers, ex ports and manifold) comes to around 2k last i checked.
good to know there is someone a bit closer, will give them a call.

ive heard of this method to cut pistons but of course it is never that simple.... this block is assembly clean, so i wont be making anymore chips in it. so have to setup a dummy block... not sure what blocks i have at 0.040, would have to see if there are any in the stash. i have plenty of other bits to mock up the rest of the motor (and another 9 or 10) so no issue there. i probably wouldnt use this head either, not sure how good it would be for the guides and fresh VSS.... then would do one valve pocket at a time and R&R the head in between? could do all 12 but its more cutting tools to make (out of oversize valves, dont have heaps of these laying around)
if i can figure out a clever way to make a fixture i think ill just do it in the CNC. dead easy to repeat the process at any time in the future then too.

still havent decided if i should do that or just buy a 2mm HG and drop the CR to a more sane level

 

[andrew_mx83]

Ok, some background and a general rant about valve interference and why this motor has come to be (and why im so pissed about the latest round of fails).

Many moons ago I decided I wanted more compression for LPG so I marched into my engine shop with a not-so-great cylinder head and told them to "mill it down to the valve seats". Which they did. Chamber ended up at 30cc and gave me around 11.5:1 on the motor I then stuck it on. The valves sit proud of the deck surface, and it becomes in interference motor but it all works just fine.

Bought a new car, pulled the head and replaced it with the high comp one and enjoyed happy fun times on LPG. Spun a b/e bearing not too long after.
Built a nice new bottom end for it with oiling upgrades and ARP rod bolts plus the usual balance/blueprint etc. Took around 0.030 off the block while I was at it and ended up at around 12:1CR, on stock GE pistons. Lapped the valves in and fitted heavier springs but otherwise left the head alone.
It lifted the head shortly after, I reinstalled it with studs (none of my hot NA motors run studs but I'm starting to push things a bit now so why not).
Started blowing out spark under load so I put some bigger cams in it and upgraded to waste spark, did some 8k rpm shenanigans for a while.
It lifted the head again, decided it had gone soft and needed to be replaced. My high comp experiment had worked and it was now time to build a proper head.

In the same week, I picked up the new milling machine for my next CNC project -main prerequisite was enough travel to port a 7m head.
Spent 6 months building the CNC, then another 5 or 6 weeks writing code, porting and building the head.
Had it all assembled, went to go bolt it to the built bottom end (only has about 10k km on it) and that's where the fun started.

See you can mill 0.085" off the head, and it will all clear with the stock pistons/valve pockets no problems, even though the valves actually sit a fair way proud of the deck surface.
You can also fit bigger valves into a 7m head and have it clear the pistons no worries.
You CANT do both. The 7m gods will frown at you and everything will turn to shit.

I weighed up my options and then remembered that i had some custom flat top pistons sitting there which had been specifically spec'd for oversize valves. They would solve all my problems! Decided to throw all the other nice hardware at it and shoveled money at the machine shop again to get a block prepped to suit, crank ground, everything balanced etc. Made sure they took minimum off the block to keep some clearance.

Started to put it all together, mock up for piston to valve clearance. Valves fully closed I cant even get the crank to TDC. Swear loudly.
Spend a day fucking around with different combinations of valves and head gaskets etc trying to get SOMETHING to work and have it turn over. Finally figure out the pistons were made incorrectly with the valve pockets at the wrong spacing and swear even louder. The neighbours learnt some new words that day.
And that brings up to this week, when the new pistons turned up that were supposed to just drop in and work, solving all the problems of the world and i would finally get my car running again. Aaand once again, it's kicked me in the balls instead.

I'm getting tired of this game.....

 

[SeeUSmile]

1.3mm won't clear?? I remember titan having some.

Unless you tried already then never mind ;D

 

[Backlash2032]

1.3 is stock sized

Sent from my HTC6435LVW using Tapatalk

 

[SeeUSmile]

1.3 is stock sized

Sent from my HTC6435LVW using Tapatalk

ohh yeah shyt forgot about that.

 

[andrew_mx83]

No progress on this recently, been snowed under with work. Have another 2x 7m-ge's to build for customers this month so mine may be sitting a little while longer

I was having some evil thoughts last night about my customer's big hp turbo build, and was wondering if anybody makes a 1 piece crank girdle & main cap(s) or if its something ill have to do myself? Rough numbers say the billet would start out in excess of 150lb which is a little daunting :/
I know you can buy billet caps already but if we are going to shoot for the moon then we may as well tie it all in properly.

 

[Rollus]

I don't think it already exist.
What would be the price tag of a one piece crank girdle & main cap?
If line bore of the assembly is not required after installation, I may be interested ;-)

Envoyé de mon Nexus 5 en utilisant Tapatalk

 

[TurboStreetCar]

Considering even changing stock main caps from one block to another "should" be line bored because there no longer matched to the block im sure a one piece girdle would need to be line bored to ensure proper clearances and alignment.

I really can't wait for this to be done and see how it does!

 

[IndigoMKII]

I know a few people have made a crank girdle but I think they all went on top of the mains. I thought about making a girdle with the mains integrated out of some 4340 PHT. It would definitely need to be line bored though. Also need longer main studs and pan bolts.

 

[andrew_mx83]

Would definitely require line boring/line honing. If you ever want to lock up a crankshaft, simply turn one cap around and torque it down, or swap it with another cap from the same block. Crank will be locked up tight (great for removing stubborn gallery plugs). Dont ever mix or swap caps from another block (without lineboring), and i never store a block or head without its caps, its too easy to get em mixed up otherwise.... i do have a few of each hehe
Any aftermarket main cap or integrated girdle has to be made undersize so the machine shop has some meat to play with and bore out.
In the case of a 1 piece unit you would have them dowel it to the pan rail before boring to ensure perfect alignment every time.
Pan bolts would either have to be longer, or offset, or some other clever trickery.
I would probably try and make it to suit stock length main studs.
Also not 100% sure about the need for 4340 or other 4xxx series alloys, ideally id like to make it out of a free machining steel to keep the time ($) down.

Price -f*cking expensive! Its still just a pipe dream at this stage, although i did get some mean new teeth for the CNC this week which would be quite handy on a huge part like this

 

[Backlash2032]

Couldn't you skip the dowels and have it locate into the block just like the factory main caps? Ie close tolerance fit with the sides of the caps against the blovk

Sent from my HTC6435LVW using Tapatalk