2.8L N/A 318hp Build Recipe
-
michaelmount123
- Posts: 169
- Joined: Fri Jul 09, 2021 7:51 am
- Has thanked: 4 times
- Been thanked: 105 times
.0022" is absolutely fine. No worries. You could be slightly either side of .0025" and be fine. What connecting rods are you using? I typically open up the rod a bit to nail the oil clearance, as long as the big end is still within tolerance spec. Your method is fine too.
-
four0four
- Posts: 147
- Joined: Wed Feb 02, 2022 10:09 pm
- Location: Western WA
- Has thanked: 18 times
- Been thanked: 23 times
That's what I'd assumed, but that's good to hear for certain 
Brand new Wossner rods. They were slightly machined out, but I forgot to bring the bearings to the shop so they matched it to a set of Glycos which I assume explains the slight difference.
Brand new Wossner rods. They were slightly machined out, but I forgot to bring the bearings to the shop so they matched it to a set of Glycos which I assume explains the slight difference.
-
four0four
- Posts: 147
- Joined: Wed Feb 02, 2022 10:09 pm
- Location: Western WA
- Has thanked: 18 times
- Been thanked: 23 times
on topic:michaelmount123 wrote: ↑Sat Jun 03, 2023 8:29 pm Any interest in higher HP builds for 2.5, 2.8 or 3L? I have my old engine files and can share detail if it would be of interest. I won't ask about air cooled 911's, but could go there too. 2L, 2.4L, 2.5L, 3L, 3.4L.
Personally, I'm curious about (2.5L) mid-HP high reliability
There was a promising thread on RL, but it's drifted off into the weeds by now. More generally I'd be interested in any general findings around the valve train/cam you'd want to share. It's difficult to get anything beyond frustratingly qualitative info about available aftermarket offerings, and I've yet to find the time to sit down and learn enough to speak intelligently to someone about a custom one.
More info on 3L builds please, turbo too if it's ok in this section of the forummichaelmount123 wrote: ↑Sat Jun 03, 2023 8:29 pm Any interest in higher HP builds for 2.5, 2.8 or 3L? I have my old engine files and can share detail if it would be of interest. I won't ask about air cooled 911's, but could go there too. 2L, 2.4L, 2.5L, 3L, 3.4L.
-
Zirconocene
- Posts: 133
- Joined: Mon Apr 04, 2022 4:59 pm
- Location: PDX Adjacent
- Has thanked: 56 times
- Been thanked: 20 times
I second the desire for information about the 3L engines, but I'm also loving reading about the other engines. I don't understand most of it, to be honest, but that's what learning is all about.
Cheers, and thanks
Cheers, and thanks
Cheers
1990 928 GT
1990 928 S4
1991 944 S2
1993 968
2002 911 C2
1990 928 GT
1990 928 S4
1991 944 S2
1993 968
2002 911 C2
-
michaelmount123
- Posts: 169
- Joined: Fri Jul 09, 2021 7:51 am
- Has thanked: 4 times
- Been thanked: 105 times
OK, info on 2.5L and 3L builds coming. I've been tied up on a project that's gotten out of hand. I'll be back shortly.
MM
MM
-
michaelmount123
- Posts: 169
- Joined: Fri Jul 09, 2021 7:51 am
- Has thanked: 4 times
- Been thanked: 105 times
Here's a 3L that's relatively mild, but track only due to the compression ratio which required race fuel. It was a sleeved 968 block that was opened up to 4.125 bore (104.78mm) simply to make piston ring selection easier, custom JE pistons, stock 968 valve sizes in a ported and race-prepped head, big hydraulic lifter cams, and stock 968 intake/throttle body. A more streetable version with lower compression and perhaps a milder cam lobe would be lots of fun. I can provide more build detail if there's any interest.
- 968Dyno.jpg (909.52 KiB) Viewed 388 times
Last edited by michaelmount123 on Tue Aug 08, 2023 1:31 pm, edited 3 times in total.
Mr Mount
Thank you for sharing all of this. It's been a great read. I am about to start on a performance rebuild - my first Porsche engine build, so this is great timing.
I'll second the call above for your wisdom and experience about a 2.5 16v build and since you have asked for input, I'll share my goals and thoughts and would appreciate any input. It's a bit to read through below, and I debated just keeping it short and simple but I decided, based on my ownership of these cars over the past 10 years that in 2023 there are a lot more people out there than me starting to want to give a lot of love to their previous underappreciated Transaxle engines, so if I type this all out now it just may help some future builder with similar goals, goals I think will become more common as these cars age.
First, the car and its purpose;
I have a 1987 944S which I use as an 'event' car. It's street legal, although has been stripped quite a bit. It does rally (both navigational and TSD), driving events, and a lot of miles of remote backroad exploration. I don't track it as I've wanted to preserve the engine for the events I really love, but after a rebuild, I would.
Because of the nature of these events - steady and precise speeds, typically fast, over very long distances with sudden micro adjustments to speed ... the motor lives at high rpm for hours at a time, and so far it loves it. It's been 5 years of this life and it has well over 250,000 km on the original bottom end, probably closer to 300k. A lot of those miles were above 4k rpm and does this 16v ever sing at those revs.
Now while the bottom end is original, it had a head rebuild before my ownership (2011). I have the receipts but they're not too detailed. It got a little polishing, but I can't see any items for the valvetrain being touched, so it's a bit of an unknown. It has a good enough for now msds header and a custom exhaust to match said header. Accessories have been deleted and will stay deleted (I don't need AC, and I like the depowered steering) but I do plan to keep the balance shafts, for the increased durability of their vibration cancelling.
For fuel management it has a Dinan tune in the factory Motronic 2.1 system. For a while I was running on megasquirt, but never got it dialed into factory drivability when dealing with certain transitionary throttle changes, which is a little important if you ever find yourself sideways on a slick ice-and-gravel hairpin next to a cliff...
I mention the tune because I do, critically, have a very reputable tuner in the region who wants to take on the tune when time comes. It will run whatever the tuner thinks is best. It may be motronic with a MAF conversion, or it may be standalone.
So... this high milage engine feels healthy and it makes great power for its miles, judging by how easily it keeps up with some of it's built air-cooled contemporaries... but it burns a disturbingly huge amount of oil on event days (1 or more quarts per tank of fuel). It also idles like a big cam 427 on startup until it's got a little heat in it, and It's got mediocre compression at around 150 across the board... although has been dead reliable despite what I think are clear signs of wear.
Everything else has been refreshed or maintained. Fuel system, electronics, even wiring is either new or refurbished. If it's in the engine bay or keeps the car on the ground, it's new or better. The beating heart itself is now ready for a new lease on life.
So to that end this winter I am removing the engine and tearing it down both as a diagnostic step and with the goal of rebuilding it to live another 10 years of this lifestyle it loves. I am not an expert. I have never rebuilt this motor although I do have a little comfort here, and will take on much of the build under the guidance of a very experienced air cooled builder locally. I have tried to learn as much as I can from local experts, although in my region there are none building transaxle cars, but plenty of air cooled folks. Frankly, I am hoping you can help me change that. There's a lot of folks growing their interest in these, and it already gets a lot of love when it goes out. To be able to show that these motors are so capable would be pretty cool.
So, that's the car's story. Now for the build thinking;
The goal is a durable high rpm build making a reasonable amount of power. A build that loves to rev and is very responsive. A driver's engine to match this driver's chassis. I do not have a power figure in mind, just a feeling. All of my best smiles have come from cars that have around 250hp and weigh around what this car weighs, so I guess that's the goal in a way, but it's really more about usable power, free spinning nature, feel and sound than a number to me. If it's 230 and just loves to rev, I'm happier than if it's 275 and feels like a tractor until 5700rpm.
That said... it doesn't need to be the most streetable. It's an event only car, but it will stay street legal and still has to be drivable enough to log thousands of mundane transit miles between events. It will be built to run on pump gas, as it's just not practical to run anything else in remote areas. (Sadly I don't have a pit crew with a support truck...).
My assumptions for the build:
I am thinking, based on consult, that the oil consumption and middling compression is just down to ring and piston wear. I will also not be surprised if I find bore wear, given the oil consumption and high rpm life, but the plan for now assumes the bores are ok.
Another assumption is that I may need to guide my local aircooled machine shop a bit. They're reputable and have built some engines that I have experienced myself, they know their stuff, but they have not done any transxle family stuff really.
For other complimentary mods, besides the existing header/exhaust/accesory delete/tune, I will be converting the car to run a MAF, I will be porting the TB (or switching to a ford TB) and there's a very real chance that in a year or two this same longblock will be paired to a Hayward Performance ITB setup. He's in my region and although I have not yet contacted him, everything I've seen and read speaks towards a great product, so I'd like to end up on them with this motor one day.
So... that's the story so far and the goals.
So here's the plan -
if the bores are healthy and check out okay for roundness, I will plan to just have them lapped properly and fit a stock or near stock dimension piston set. I am hoping to avoid sleeving, because nobody in my region has sleeved the m44.40, and although I don't think it's really that exotic, at the end of the day if a shop isn't comfortable with something I'm not going to push them, it may just end in frustration on both sides. My power goals aren't lofty enough to really require them, I think.
If the bores are bad, I will change this plan and send it out to someone who can sleeve it, but that would be a dramatic change of plan and schedule so, I'm going to continue the rest of my post assuming the bores are okay and sleeving is not required. If you think this is a silly way to think, I'm open minded on this.
So I'd just have the bores lapped to create a fresh layer and put new pistons and rods in. I've seen some good logic talking about using modern piston coatings to compensate for the small clearances created by freshly lapped bores. So, I think I'd go that route with stock diameter pistons plus a coating and have the shop machine to the expected final diameter of the piston+coating. I was specifically thinking of Swaintech coatings.
I'm not against custom pistons sizes either, but don't think they'd be required?
For pistons and rings I could use your advice, because there's a lot of options and no clear standout choice to me.
For rods, I like the idea of a light rotating assembly, for the responsiveness and reduced stress on the other components so was thinking the Pauter lightweight rods, matched with a lightened crank.
I would need to figure out who I would send the crank to. Might have to ship it a ways. That's okay, but I always like to support local shops when I can.
For bearings, the ACL race bearings seem like a no brainer. What are your thoughts on having the load bearing side coated for durability?
I'd also like to get those additional oil ports drilled into the crank. Coupled with good bearings and maybe a trap door oil baffle in the oil pan, I shouldn't have to think about oiling much.
For the head, I'd like to get a good refresh done by the local aircooled machinist... a good port and polish and valve job, new seals and guides and then key item, a cam. I was thinking to go with the Web Racing cams 274/279 Grind.
For Redline, I had this idea that it would be a lot of fun, and useful, to be able to spin to 7500 or even higher but the more I read about the timing belt system and the valvetrain, the more I think I need to be more down to earth, remember my goals and keep the redline at what it currently is with the tune (7300 rpm) and just build the motor to peak before that.
So, what do you think and if you were to hot-rod for this car, how would you approach it?
Anything I'm thinking that is a bad idea?
Thank you for sharing all of this. It's been a great read. I am about to start on a performance rebuild - my first Porsche engine build, so this is great timing.
I'll second the call above for your wisdom and experience about a 2.5 16v build and since you have asked for input, I'll share my goals and thoughts and would appreciate any input. It's a bit to read through below, and I debated just keeping it short and simple but I decided, based on my ownership of these cars over the past 10 years that in 2023 there are a lot more people out there than me starting to want to give a lot of love to their previous underappreciated Transaxle engines, so if I type this all out now it just may help some future builder with similar goals, goals I think will become more common as these cars age.
First, the car and its purpose;
I have a 1987 944S which I use as an 'event' car. It's street legal, although has been stripped quite a bit. It does rally (both navigational and TSD), driving events, and a lot of miles of remote backroad exploration. I don't track it as I've wanted to preserve the engine for the events I really love, but after a rebuild, I would.
Because of the nature of these events - steady and precise speeds, typically fast, over very long distances with sudden micro adjustments to speed ... the motor lives at high rpm for hours at a time, and so far it loves it. It's been 5 years of this life and it has well over 250,000 km on the original bottom end, probably closer to 300k. A lot of those miles were above 4k rpm and does this 16v ever sing at those revs.
Now while the bottom end is original, it had a head rebuild before my ownership (2011). I have the receipts but they're not too detailed. It got a little polishing, but I can't see any items for the valvetrain being touched, so it's a bit of an unknown. It has a good enough for now msds header and a custom exhaust to match said header. Accessories have been deleted and will stay deleted (I don't need AC, and I like the depowered steering) but I do plan to keep the balance shafts, for the increased durability of their vibration cancelling.
For fuel management it has a Dinan tune in the factory Motronic 2.1 system. For a while I was running on megasquirt, but never got it dialed into factory drivability when dealing with certain transitionary throttle changes, which is a little important if you ever find yourself sideways on a slick ice-and-gravel hairpin next to a cliff...
I mention the tune because I do, critically, have a very reputable tuner in the region who wants to take on the tune when time comes. It will run whatever the tuner thinks is best. It may be motronic with a MAF conversion, or it may be standalone.
So... this high milage engine feels healthy and it makes great power for its miles, judging by how easily it keeps up with some of it's built air-cooled contemporaries... but it burns a disturbingly huge amount of oil on event days (1 or more quarts per tank of fuel). It also idles like a big cam 427 on startup until it's got a little heat in it, and It's got mediocre compression at around 150 across the board... although has been dead reliable despite what I think are clear signs of wear.
Everything else has been refreshed or maintained. Fuel system, electronics, even wiring is either new or refurbished. If it's in the engine bay or keeps the car on the ground, it's new or better. The beating heart itself is now ready for a new lease on life.
So to that end this winter I am removing the engine and tearing it down both as a diagnostic step and with the goal of rebuilding it to live another 10 years of this lifestyle it loves. I am not an expert. I have never rebuilt this motor although I do have a little comfort here, and will take on much of the build under the guidance of a very experienced air cooled builder locally. I have tried to learn as much as I can from local experts, although in my region there are none building transaxle cars, but plenty of air cooled folks. Frankly, I am hoping you can help me change that. There's a lot of folks growing their interest in these, and it already gets a lot of love when it goes out. To be able to show that these motors are so capable would be pretty cool.
So, that's the car's story. Now for the build thinking;
The goal is a durable high rpm build making a reasonable amount of power. A build that loves to rev and is very responsive. A driver's engine to match this driver's chassis. I do not have a power figure in mind, just a feeling. All of my best smiles have come from cars that have around 250hp and weigh around what this car weighs, so I guess that's the goal in a way, but it's really more about usable power, free spinning nature, feel and sound than a number to me. If it's 230 and just loves to rev, I'm happier than if it's 275 and feels like a tractor until 5700rpm.
That said... it doesn't need to be the most streetable. It's an event only car, but it will stay street legal and still has to be drivable enough to log thousands of mundane transit miles between events. It will be built to run on pump gas, as it's just not practical to run anything else in remote areas. (Sadly I don't have a pit crew with a support truck...).
My assumptions for the build:
I am thinking, based on consult, that the oil consumption and middling compression is just down to ring and piston wear. I will also not be surprised if I find bore wear, given the oil consumption and high rpm life, but the plan for now assumes the bores are ok.
Another assumption is that I may need to guide my local aircooled machine shop a bit. They're reputable and have built some engines that I have experienced myself, they know their stuff, but they have not done any transxle family stuff really.
For other complimentary mods, besides the existing header/exhaust/accesory delete/tune, I will be converting the car to run a MAF, I will be porting the TB (or switching to a ford TB) and there's a very real chance that in a year or two this same longblock will be paired to a Hayward Performance ITB setup. He's in my region and although I have not yet contacted him, everything I've seen and read speaks towards a great product, so I'd like to end up on them with this motor one day.
So... that's the story so far and the goals.
So here's the plan -
if the bores are healthy and check out okay for roundness, I will plan to just have them lapped properly and fit a stock or near stock dimension piston set. I am hoping to avoid sleeving, because nobody in my region has sleeved the m44.40, and although I don't think it's really that exotic, at the end of the day if a shop isn't comfortable with something I'm not going to push them, it may just end in frustration on both sides. My power goals aren't lofty enough to really require them, I think.
If the bores are bad, I will change this plan and send it out to someone who can sleeve it, but that would be a dramatic change of plan and schedule so, I'm going to continue the rest of my post assuming the bores are okay and sleeving is not required. If you think this is a silly way to think, I'm open minded on this.
So I'd just have the bores lapped to create a fresh layer and put new pistons and rods in. I've seen some good logic talking about using modern piston coatings to compensate for the small clearances created by freshly lapped bores. So, I think I'd go that route with stock diameter pistons plus a coating and have the shop machine to the expected final diameter of the piston+coating. I was specifically thinking of Swaintech coatings.
I'm not against custom pistons sizes either, but don't think they'd be required?
For pistons and rings I could use your advice, because there's a lot of options and no clear standout choice to me.
For rods, I like the idea of a light rotating assembly, for the responsiveness and reduced stress on the other components so was thinking the Pauter lightweight rods, matched with a lightened crank.
I would need to figure out who I would send the crank to. Might have to ship it a ways. That's okay, but I always like to support local shops when I can.
For bearings, the ACL race bearings seem like a no brainer. What are your thoughts on having the load bearing side coated for durability?
I'd also like to get those additional oil ports drilled into the crank. Coupled with good bearings and maybe a trap door oil baffle in the oil pan, I shouldn't have to think about oiling much.
For the head, I'd like to get a good refresh done by the local aircooled machinist... a good port and polish and valve job, new seals and guides and then key item, a cam. I was thinking to go with the Web Racing cams 274/279 Grind.
For Redline, I had this idea that it would be a lot of fun, and useful, to be able to spin to 7500 or even higher but the more I read about the timing belt system and the valvetrain, the more I think I need to be more down to earth, remember my goals and keep the redline at what it currently is with the tune (7300 rpm) and just build the motor to peak before that.
So, what do you think and if you were to hot-rod for this car, how would you approach it?
Anything I'm thinking that is a bad idea?
-
michaelmount123
- Posts: 169
- Joined: Fri Jul 09, 2021 7:51 am
- Has thanked: 4 times
- Been thanked: 105 times
Hello Remi,
Your approach is spot-on, IMO. Good planning makes for good results, so I'm optimistic you'll be thrilled with your fresh and modified engine. I'll follow the format in your post and try to add my thoughts.
Your engine is surely old, worn, and tired. That said, it has served you well and you are wise to freshen it before any internal failures. I imagine the bores will be well worn, and likely out of round. The proper refinishing with the Porsche Alusil process is problematic since I don't know of anyone that does it properly/successfully. (Perhaps others on Carpokes can make referrals?) However, creating nice, round, refinished cylinders by simply lapping with the silicone paste cannot happen. See the Porsche Workshop Manual for more info on this process.
Consider having the bores Nikasil coated by someone like Millennium Technologies. The bores will have a great wearing finish, and be round to maximize ring seal and power. If you go with Nikasil and keep the 100mm bore, you can use Porsche 964 rings which will seat quickly and last a long time. I'd use a custom JE piston, bump the compression a few points (still using street gas), have sufficient valve pockets for performance cams, and a lighter piston. I can help with piston specs if you like. Your stock pistons will be worn out; primarily the ring grooves, so replacement is a must.
Good performance connecting rods will give you peace of mind. I like both Pauter's and Molnar. Both are high quality and will serve you well. Whatever you choose, have them checked dimensionally, and set your ROC by adjusting the big end dimension. Definitely use the ACL race rod bearings, and I see no need for any bearing coating. I used to lighten a lot of 944 cranks, but decided they are more durable with stock counterweights. Do check your crank for straight and journal dimensions, but I'll bet it will be fine. I do cross-drill #2 and #3 rod journals which seems to help. I do this on a Bridgeport Mill and a hardened drill. It's not a complicated process, but it's easy to break drills (sux), so the machinist who hasn't done it before can easily get in trouble. A crankshaft shop will have no problem.
I'm not convinced the trap door in the oil pan provides measurable improvement. I left them alone if one came in, but never did the mod myself. You can make that decision. The stock Porsche pan seems to work well.
The cylinder head is a critical component for increased performance and reliability. You may be aware of the cracking issue with the S head, but the only alternative is to start with a LATE S2 head and modify the front water port to match the 2.5 block. I encourage you to send your head to someone very familiar with the 4V head so your $ is well spent. I still do a few heads and have a lot of experience with them. Reach out if you like. The port shape is the issue, as well as proper guides and valve job. A performance job takes more time and knowledge than the typical automotive machine shop will admit, and they are not always equipped with suitable equipment.
I'm not a fan of the MSDS header, but clearly there's value in what you already own. The best header is available from Racer's Edge. Karl will fix you up. www.racersedge-inc.com
The Web 274/279 will provide a very healthy increase in power and will easily to 7300 and higher without sacrificing the low end grunt. Use new followers. They're very pricey from Porsche, but many are using VW lifters which are lighter and much cheaper. Part numbers are 034109309AD, 050109309J, INA 420002210. (Other Carpokians, please confirm.)
Your final results will be the result of proper tuning. Reach out to John at Vitesse Racing. His products and support are second to none. Let him know your mods and he'll fix you up.
I hope this is helpful to you and others. If there are more questions / comments, fire away.
MM
Your approach is spot-on, IMO. Good planning makes for good results, so I'm optimistic you'll be thrilled with your fresh and modified engine. I'll follow the format in your post and try to add my thoughts.
Your engine is surely old, worn, and tired. That said, it has served you well and you are wise to freshen it before any internal failures. I imagine the bores will be well worn, and likely out of round. The proper refinishing with the Porsche Alusil process is problematic since I don't know of anyone that does it properly/successfully. (Perhaps others on Carpokes can make referrals?) However, creating nice, round, refinished cylinders by simply lapping with the silicone paste cannot happen. See the Porsche Workshop Manual for more info on this process.
Consider having the bores Nikasil coated by someone like Millennium Technologies. The bores will have a great wearing finish, and be round to maximize ring seal and power. If you go with Nikasil and keep the 100mm bore, you can use Porsche 964 rings which will seat quickly and last a long time. I'd use a custom JE piston, bump the compression a few points (still using street gas), have sufficient valve pockets for performance cams, and a lighter piston. I can help with piston specs if you like. Your stock pistons will be worn out; primarily the ring grooves, so replacement is a must.
Good performance connecting rods will give you peace of mind. I like both Pauter's and Molnar. Both are high quality and will serve you well. Whatever you choose, have them checked dimensionally, and set your ROC by adjusting the big end dimension. Definitely use the ACL race rod bearings, and I see no need for any bearing coating. I used to lighten a lot of 944 cranks, but decided they are more durable with stock counterweights. Do check your crank for straight and journal dimensions, but I'll bet it will be fine. I do cross-drill #2 and #3 rod journals which seems to help. I do this on a Bridgeport Mill and a hardened drill. It's not a complicated process, but it's easy to break drills (sux), so the machinist who hasn't done it before can easily get in trouble. A crankshaft shop will have no problem.
I'm not convinced the trap door in the oil pan provides measurable improvement. I left them alone if one came in, but never did the mod myself. You can make that decision. The stock Porsche pan seems to work well.
The cylinder head is a critical component for increased performance and reliability. You may be aware of the cracking issue with the S head, but the only alternative is to start with a LATE S2 head and modify the front water port to match the 2.5 block. I encourage you to send your head to someone very familiar with the 4V head so your $ is well spent. I still do a few heads and have a lot of experience with them. Reach out if you like. The port shape is the issue, as well as proper guides and valve job. A performance job takes more time and knowledge than the typical automotive machine shop will admit, and they are not always equipped with suitable equipment.
I'm not a fan of the MSDS header, but clearly there's value in what you already own. The best header is available from Racer's Edge. Karl will fix you up. www.racersedge-inc.com
The Web 274/279 will provide a very healthy increase in power and will easily to 7300 and higher without sacrificing the low end grunt. Use new followers. They're very pricey from Porsche, but many are using VW lifters which are lighter and much cheaper. Part numbers are 034109309AD, 050109309J, INA 420002210. (Other Carpokians, please confirm.)
Your final results will be the result of proper tuning. Reach out to John at Vitesse Racing. His products and support are second to none. Let him know your mods and he'll fix you up.
I hope this is helpful to you and others. If there are more questions / comments, fire away.
MM