964 Engine rebuild
01-20-2011, 12:37 PM
#46
Rennlist Member
just my 2 cents
yours looks a lot like mine that I did a few years ago.
I reused my pistons and cylinders after thorough measurements. I had cylinders machined to same height as well as heads matched. I added a spacer from Bruce Anderson's shop under all the cylinders to compensate. Be sure to use the valve seals that actually allow a little oil to the stems.
Your cams look like mine. I had them reground and all new rockers. Elign did mine, that's where camgrinder used to work. I sent camgrinder my old parts for his use.
Used new head bolts.
Use adhesive sparingly on reassembly. Same for o-ring lube. Don't fall into the trap of "if a little is good, more is better". It ain't.
I was a little **** on mine.
yours looks a lot like mine that I did a few years ago.
I reused my pistons and cylinders after thorough measurements. I had cylinders machined to same height as well as heads matched. I added a spacer from Bruce Anderson's shop under all the cylinders to compensate. Be sure to use the valve seals that actually allow a little oil to the stems.
Your cams look like mine. I had them reground and all new rockers. Elign did mine, that's where camgrinder used to work. I sent camgrinder my old parts for his use.
Used new head bolts.
Use adhesive sparingly on reassembly. Same for o-ring lube. Don't fall into the trap of "if a little is good, more is better". It ain't.
I was a little **** on mine.
Last edited by stevepaa; 01-20-2011 at 02:09 PM.
01-26-2011, 05:56 PM
#47
Racer
Thread Starter
Thanks for all the advice guys, greatly received.
That's a good looking head Steve, seems it's a fine line between too little and too much adhesive when resealing - probably the bit I'm most nervous about, and setting up the timing of course!
Do you have any further photos or information about the compensation spacer you set under all the cylinders?
Quick question to anyone who might know - The previous owner has either cleaned up or enlarged the inlet ports on my heads. I gave them a quick measure and they are around 42mm dia, is that the stock size?
That's a good looking head Steve, seems it's a fine line between too little and too much adhesive when resealing - probably the bit I'm most nervous about, and setting up the timing of course!
Do you have any further photos or information about the compensation spacer you set under all the cylinders?
Quick question to anyone who might know - The previous owner has either cleaned up or enlarged the inlet ports on my heads. I gave them a quick measure and they are around 42mm dia, is that the stock size?
01-31-2011, 04:13 AM
#50
Racer
Thread Starter
I was reading another thread on here about harmonic balancers and it got me thinking - When I bought my 964 engine it had no harmonic balancer so I sourced a secondhand one and was planning on simply fitting that.
One thing that I have noticed about them is that they have different amounts of drilled holes in the front presumably to balance.
This must mean that the one I have bought is balanced to a different crank and needs to be rebalanced.
Does this mean that the best way to balance it is to dummy mount the flywheel and the pulley with harmonic balancer to the crank either in V blocks or in the case half and try to find a 'low point' where it settles then carefully drill the harmonic balacer a bit at a time until it seems weight matched or is there a better way that anyone knows of?
One thing that I have noticed about them is that they have different amounts of drilled holes in the front presumably to balance.
This must mean that the one I have bought is balanced to a different crank and needs to be rebalanced.
Does this mean that the best way to balance it is to dummy mount the flywheel and the pulley with harmonic balancer to the crank either in V blocks or in the case half and try to find a 'low point' where it settles then carefully drill the harmonic balacer a bit at a time until it seems weight matched or is there a better way that anyone knows of?
02-26-2011, 10:16 AM
#51
Racer
Thread Starter
Right, firstly a big thanks to everyone on here who has given me advice for my rebuild. It is much appreciated & I honestly have taken it all on board & been over and over it many times.
The final spec for my rebuild is:
Modified / Flowed case
Modified / Mooned stock cylinders
ARP rod bolts on weight matched stock rods
Weight matched stock Pistons
Lightweight Patrick Motorsport flywheel
993 RS Inlet Valves
993 Stock Exhaust Valves
Race springs with titanium retainers
DC21 cams with 114 lobes
Head inlets lightly ported (done by previous owner)
1.750" dia Headers
Lightweight fibreglass tinware
Exhaust / muffler TBD, 2-in 2-out probably.
I realise that there are limitations on the standard ECU and Motronic as have been pointed out in previous posts and plan to address this at a later stage when the motor is run in.
I've vapour blasted the outside of the heads and the cylinders after I ground out the 'mooned' section to match the case - Really gives a great finish, good as new!
One real issue I can't decide on is the one that keeps popping up on this site regarding whether to add the sealing ring between the head and the barrel or not as per the thread below. It seems that quite a few people in the US are doing it's not as common here in the UK. The chap who will probably do my heads says he can do it but would need dimensions to machine to. No idea where to get them and opinion is vry divided whether it's worth doing at all but the way I see it - Most early 964s leak in this area sooner or later and if there is anything that can be done to help prevent or delay this then now is the time to do it!
https://rennlist.com/forums/performa...ist-rings.html
The final spec for my rebuild is:
Modified / Flowed case
Modified / Mooned stock cylinders
ARP rod bolts on weight matched stock rods
Weight matched stock Pistons
Lightweight Patrick Motorsport flywheel
993 RS Inlet Valves
993 Stock Exhaust Valves
Race springs with titanium retainers
DC21 cams with 114 lobes
Head inlets lightly ported (done by previous owner)
1.750" dia Headers
Lightweight fibreglass tinware
Exhaust / muffler TBD, 2-in 2-out probably.
I realise that there are limitations on the standard ECU and Motronic as have been pointed out in previous posts and plan to address this at a later stage when the motor is run in.
I've vapour blasted the outside of the heads and the cylinders after I ground out the 'mooned' section to match the case - Really gives a great finish, good as new!
One real issue I can't decide on is the one that keeps popping up on this site regarding whether to add the sealing ring between the head and the barrel or not as per the thread below. It seems that quite a few people in the US are doing it's not as common here in the UK. The chap who will probably do my heads says he can do it but would need dimensions to machine to. No idea where to get them and opinion is vry divided whether it's worth doing at all but the way I see it - Most early 964s leak in this area sooner or later and if there is anything that can be done to help prevent or delay this then now is the time to do it!
https://rennlist.com/forums/performa...ist-rings.html
03-27-2011, 07:09 AM
#53
Racer
Thread Starter
Decided against machining the cylinders for the 993 gasket in the end as I think it removes too much surface area so I'm now in the 'doesn't need to be done' school of thinking!
Had the crank assembly re-balanced as the engine is getting a new harmonic balancer and Patrick Motorsports flywheel and was quite surprised how much material had to be taken from both the balancer and flywheel.
Bottom end now back together (not by me) and waiting for my valves and cams to come back to finish the top end.
Had the crank assembly re-balanced as the engine is getting a new harmonic balancer and Patrick Motorsports flywheel and was quite surprised how much material had to be taken from both the balancer and flywheel.
Bottom end now back together (not by me) and waiting for my valves and cams to come back to finish the top end.
05-17-2011, 05:44 PM
#54
Racer
Thread Starter
The final spec for my rebuild is:
Modified / Flowed case
Modified / Mooned stock cylinders
ARP rod bolts on weight matched stock rods
Weight matched stock Pistons
Lightweight Patrick Motorsport flywheel
993 RS Inlet Valves
993 Stock Exhaust Valves
Race springs with titanium retainers
DC21 cams with 114 lobes
Head inlets lightly ported (done by previous owner)
1.750" dia Headers
Lightweight fibreglass tinware
Exhaust / muffler TBD, 2-in 2-out probably.
Modified / Flowed case
Modified / Mooned stock cylinders
ARP rod bolts on weight matched stock rods
Weight matched stock Pistons
Lightweight Patrick Motorsport flywheel
993 RS Inlet Valves
993 Stock Exhaust Valves
Race springs with titanium retainers
DC21 cams with 114 lobes
Head inlets lightly ported (done by previous owner)
1.750" dia Headers
Lightweight fibreglass tinware
Exhaust / muffler TBD, 2-in 2-out probably.
I know the profile of the stock 964 pistons that I am using don't have the pockets that the RS valved pistons have but didn't think it would be that close. I think that machining the pistons for clearance screws up the compression ratios so I'm looking for advice or opinions what the best way forward is?
Any ideas?
Last edited by ALEX P; 07-30-2011 at 05:21 AM.
05-17-2011, 06:23 PM
#55
Nordschleife Master
Join Date: Feb 2011
Location: Deep Downtown Carrier, OK
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Dammit Alex, I'm sorry. I think you're right about machining the pistons...but we both may be wrong.
Perhaps a trusted pro here could offer advice; I'd like to know also.
Best 'o luck - but you really wanted cool pistons anyway, huh?
Perhaps a trusted pro here could offer advice; I'd like to know also.
Best 'o luck - but you really wanted cool pistons anyway, huh?
05-17-2011, 10:02 PM
#57
RL Technical Advisor
The pistons must be clearanced to run the RS cams with bigger intake valves, especially at the outside edge of the intake valve pockets.
Make sure your deck height is spot-on at 1mm (.040").
05-17-2011, 11:31 PM
#58
Is it interfernce or no clearence?
Have you clayed it and measured the profile?
Likely the fix is to cut the valve pockets bigger for the larger valve, which is no big deal, it's when you have to go deeper it gets a little more hairy.
You will lose a little compression but it's nominal. Likely not even a tenth of a point. A few mls of volume, unless you have to do a lot of cutting on them you wont even notice it.
just have the pockets radius out, what do NOT want in the camber is any sharp edges.
If you have to do a lot of cutting you probably want to rebalance the assembly.
Yes make sure the deck measurement is on.
And have you timed the cams yet? Where are you there?
For what it's worth, the mirror polish finish is over done.
A good port match, blending the seat and removing any casting lines will do more than anything else.
Have you clayed it and measured the profile?
Likely the fix is to cut the valve pockets bigger for the larger valve, which is no big deal, it's when you have to go deeper it gets a little more hairy.
You will lose a little compression but it's nominal. Likely not even a tenth of a point. A few mls of volume, unless you have to do a lot of cutting on them you wont even notice it.
just have the pockets radius out, what do NOT want in the camber is any sharp edges.
If you have to do a lot of cutting you probably want to rebalance the assembly.
Yes make sure the deck measurement is on.
And have you timed the cams yet? Where are you there?
For what it's worth, the mirror polish finish is over done.
A good port match, blending the seat and removing any casting lines will do more than anything else.
05-18-2011, 03:40 PM
#59
Racer
Thread Starter
My fault for not doing my homework properly.
Options were to machine the pistons or buy a set of JEs and while both are solutions in their own right I went for the JEs and hopefully get a little back for my original set.
Lesson learnt the hard way I guess, thanks for the help guys.
Options were to machine the pistons or buy a set of JEs and while both are solutions in their own right I went for the JEs and hopefully get a little back for my original set.
Lesson learnt the hard way I guess, thanks for the help guys.