2.7 Hot Rod Engine Build (Advice Needed)
 

Hello Fellow Pelicans,
I’ve been lurking and searching through the forum ever since I purchased my first porsche.
I’m currently in the process of planning my engine rebuild (terrible leak down numbers) and I need some advice.

Here are the current engine specs.
2.7 7R Magnesium Engine Case
RS Spec pistons
S spec Cams
Already Time Sert or Case Savers

Here are my plans
Surface case and align back to standard
Shuffle pin
Insert all threads
LN Nickies
Mahle 10.3:1 Pistons (or 10.5 JE)
Keep S cams
Clewett ITB
Dual plug coil on plug ignition
Link Stand alone ECU and custom harness


I’m looking for a streetable car that I can enjoy in the canyons and the track(occasionally). Is my build over the top(in a bad way) or is it well suited for a fun street car. I will be assembling the engine myself but will be taking the engine to get machined by either Ollie’s or Competition Engineering.


Looking for advice or someone who has experience with the specs above and can provide feedback or recommendations.

Thanks
-Sirac Haile

Hi Sirac,

ARP or Raceware rod bolts.
Factory thermostat and lines to an 85 front cooler, or front valence cooler, depending on how hard you use it and ambient conditions.
Oil bypass mod, perhaps a "massaged" carrera oil cooler for a bit better flow.
Talk to John Dougherty to see if the S cam is right for your intended use.
Have Craig Garrett port and do a valve job on your heads + machine for 2nd plug.
You might need stronger valve springs.
KEP all aluminum clutch and RSR flywheel.

My good friend Gordon, is guiding me through the above work. We are going with JE 10.5 pistons in 92 mm replated Mahle cylinders. I went with Al Kosmal's Megasquirt EFI, with PMO ITB's and running EDIS twin plug, For exhaust, i got SSI's and a Scart Riva.

My use is very close to what you are planning, If you are going for more zoom, you might want to consider headers - talk to your head work guy and a good engine builder for cam specs.

How is your suspension/brakes/wheels/tires??

Have fun,
chris

Thanks for the information Chris,
I do plan on doing the oil bypass mods along with the other items you mentioned, so I’m glad to hear that.

I was planning to take my heads to either of the two machine shops I listed, but I’m having trouble finding more information about Craig and his pricing. Could you share his information?

The engine is on my first list of to dos, I’ll be tackling the other aspects of the car later but I do have stiffer TBs front and rear with plans of using the KW shocks. Brakes are still in the air, but the boxer calipers and adapters seem like a good affordable option. But I’m taking it one step at a time.

Consider Pauter rods - a lot lighter than standard

Having recently built an engine very similar to your existing engine for a friend and dynoed in the same car with a different engines I would offer these thoughts.
You can read build details for engine similar to your build here.
http://forums.pelicanparts.com/porsche-911-used-parts-sale-wanted/1074394-911-engine-sale.html

Having recently dynoed a 2.4 engine with similar head port sizes (36I 35E) but smaller cam (stock E) and compared to friends 2.7 I would suggest the following: Higher compression should be good, I would also consider a more efficient cam like MOD S cam or maybe even step up to next more aggressive with your higher compression plans. I would also consider some mild porting.

The dyno below compares a 2.4 with E cams and 2.7 with MOD S cams. 2.4 was 9.5 comp and 2.7 was 8.5. Same size ports on heads.

http://forums.pelicanparts.com/uploa...1651638445.jpg

Knowing the the MOD S cams are much more aggressive than E cams and seeing how the power is falling off on 2.7 at higher RPM would see what I could do to get the ports to flow better.

I also compared this 2.4 to previous 2.4 I built. The previous engine had lower compression 8.5 and smaller ports 33mm., but had the advantage of MFI compared to carbs with 30mm venturi. With a little more compression and larger ports power and torque was better everywhere with current engine.

http://forums.pelicanparts.com/uploa...1651639302.jpg

I am planning my own engine for my 914-6 conversion (car all the above engines were tested in) very similar to your plans. 10.5 JE pistons, twin plug, MOD S (or more) ITB, programable EFI, ported heads. Should be fun.

john


john

Suggestion: Consider just doing rings, valves, valve guides, and valve seals to fix the poor leakdown result?

Then drive it?

Seems like tackling everything all at once is a really hard way to go, so many things to get exactly right, so many potential mishaps and delays.

Add itbs and efi after the top end. If that doesn't get you where you want, you can change pistons and cams without cracking the case.

Not sure there's any reason to buy Nickies before inspecting the cylinders you have.

Baby steps will get you there just as fast and let you enjoy the car as you go?

Edit- I just read your introductory post- why not keep the carbs on there?

Sent from my Nokia 7.1 using Tapatalk

2.7 Hot Rod Engine Build (Advice Needed)
 

Thanks for the information John. I’ll be reading into that and I’ll check to see if the Cam will work well for my goals.

The heads do appear to look to be ported and I did get some confirmation from Craig that ok looks like light porting.

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As far as just doing a top end, I did consider that and that’s was an option. But since I never heard the engine run nor do I have any history on it I think it would be wise to tear it apart and inspect it.

The nickies are my preference since I wanted to start fresh. I’ll be inspecting the RS pistons and cylinders and posting them for sale to recover some costs.

The car needs a lot of work and I’m working on systems and the goal is to have a complete car when I’m done. I enjoy the journey and driving it at the end would make it so worth it.

But I appreciate the advice and feedback. There are a lot of very knowledgeable people in the forum so as a Newbie I’d like to absorb as much as possible.

More pictures of the engine as it sits

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Thanks
-Sirac

These kinds of posts bring a smile to my face. You asked and you will get a multitude of opinions. The only opinion that is important is yours.

What is streetable and occasionally track? This has always baffled me. Do you mean the engine will not be built particularly for the track , therefore when you are at the track you will drive it like you do on the street? I would bet every dollar for every doughnut that is never the case. Its the same as "boost fever" people get often. Some is OK, more will be better.

I used to ask 2 questions of my customers. The budget and performance goal. Now I have 4. The other 2 are, do you want to build the best engine or the cheapest?

Decide on a performance (including engine size) you want, then decide on the budget and see if they both fit. Then start making compromises (least first) to see if it all comes together. Then you know the costs, and then start buying.

Your list shows some work. Until you have disassembled, cleaned and measured, some may not be required. Be careful of some parts that may be required. Some have very long lead times now.

The performance level required will dictate the build. Any head work, port sizes, valves sizes, etc, along with dual spark plugs etc. Dual plugs changes the Ignition as well. My advice is to stick with CDI for these engines. Before you make any decisions, you should decide upon the Intake and have the heads and Intake flow tested as is. Then this will tell you what to build and what parts may be required. The air flow numbers will tell you the how much restriction is in the Intake system, how much the heads flow, what camshaft to chose etc.

Plan this, engineer this, don't rely upon what others have done.

nh

Thanks everyone for the input and the contacts. I have been been planning and seeing what worked for others to try not to reinvent the wheel. These engines and combinations have been around for along time so I would think there is a recipe that would work.

I’ve been in contact with the people mentioned here and I have a good plan on what I will be doing and I am thankful for those who provided the information.

I did tear the top end apart and the valves and seats were rusted from water that leaked past the carbs when the car sat under it’s previous ownership. So I was able to clear that up. It did have Web cams 149 grind that’s an s spec cam. And RS pistons too. The cylinders look in good condition with the exception of one that looks to have some spalling from the coating I think. So I think I have to replate or just get new cylinders.

I’ll update as I progress and let you all know the final recipe

Thanks
Sirac

For those who even care here is what I came up with.

So I’ve did enough research to start ordering parts.
Heads were sent off to Craig for his magic. They were mildly ported/smoothed
Twin plug
Aasco Springs and Ti retainers
Cams are Dougherty DC43x
Pistons Mahle Motorsport 2.7 10.3:1
Cylinders Nickies
Refreshed bottom end with all the reliability updates
40mm Clewett ITBs
Link ECU
SSI heat exchanger (maybe upgrade to bursch)
Muffler still pending.

Hopefully will see it running before the end of the year lol.

I would just drop off with Henry at Supertech in Fallbrook California. He will setup your 2.7 better than anyone. Good luck!

Sirac,

Great to meet you before Luft8 and thanks again for bringing me those ignition parts. Following your build with interest. Keep us updated on how progress goes. Pics too!

Small update! Got my case and parts from Ollie’s took a while but worth the wait.

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A little update for those who care.
Got a lot of parts WPC treated, bearings rockers and shafts, cams, pistons and cylinders. It’s a surface treatment that adds micro dimples onto the surface to reduce friction and wear.
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Measured the Carillo Rods and the crankshaft to verify clearances.

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CC’d the heads and they came within spec and equal at 67cc. Heads machined by Craig Garret with Aasco valves and minor port to s spec.

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Sorted all the parts to start the assembly

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Getting ready to finish up and seal up the case soon.

Rods look nice and light

Sent from my Pixel 7 using Tapatalk

Continued on the assembly this weekend.
Forgot to add the photo of ccing the head
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Added Driven assembly grease to main bearings. Assembled the case and sealed it up.

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I like your post I have the same engine I will be rebuilding in the future I will be keeping up with you post.
I want to see a cost break down on your build if you can show that and maybe what options you looked at before you pulled the trigger on parts ?
Looks Good look forward to progress

I do have a spreadsheet that I was keeping track of that needs to be updated. But I’m way over budget with all the unforeseen upgrades and impulse purchases.

I’ll be updating it soon and can share. But I’m over $30k in the build so far. Without the intake and exhaust system

More progress with the engine. Working on the top end now.

Installed ARP studs
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Brand new Mahle Nickies set from LN Engineering

WPC treatment on the pistons, cylinders, rings and pins.
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Measured deck height to 1.4mm for an effective 10:1 compression

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Assembled the updated idlers with new sprockets and Supertec idlers
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Next up measure piston to valve clearance

Great thread, keep the updates coming

Quote: Measured deck height to 1.4mm for an effective 10:1 compression

I would recommend reducing your base gasket by .025mm , I target 1mm and go for it .
.055" is what you have , remove .010" (.025mm) and you have .045" (1.143mm) and this is a much better deck height. your engine will be happy for your efforts

The 1mm deck height is a very important number , the larger the deck height the more heat and pressure will go to the rings . This extra clearance can also add to the potential for knocking .

2.7 Hot Rod Engine Build (Advice Needed)
 

I tried multiple shims and targeted 1mm. The issue I had was I would be under or over. I currently have the supplied shims from the engine builder and that got me around 1.4 to 1.5. I purchased 1mm shims and also used the factory shims to try to get to the 1mm but got tired of the multiple attempts and stuck with the final originally supplied shims 1.5mm. The engine will have dual plugs to aid with the higher compression but I’m trying to make progress.

Will the 1.5mm height really have detonation? Do I need to tear it back down? Those shims aren’t cheap at $200 a set.

I have not read all but I must have missed something here.

If you have 1.50mm Piston deck height are we talking positive or negative deck height?

If the piston is below the top of the cylinder at the edges we are talking positive. If it sits above the deck its negative. Be careful here as different people have this reversed. Just make sure where the piston sits when the crank is at TDC.

If its below the surface if the cylinder top, and you have 1.50mm clearance, your static CR will be less than if the clearance was 1.0mm. A simple way of checking is to use some plug numbers into your calculation. Increase the Volume at TDC and see where the CR comes.

Find the 1.0mm shims if that is what you need. What is the bore size of the gaskets required? I may have some. PM me and I will help you.

Another way to del with this is the bottom of the cylinders can be cut to remove 0.50mm. Not the better way, the gaskets are.

Before you do anything. have you measured thew chamber and dome volumes?

I'll throw in my two bits: I like to keep the piston to head clearance even tighter, shooting for .75mm. This increases squish and combustion chamber mixing. I know it helps with single plug heads. I don't know if it gives you any advantage with dual plug heads. It might not.

As far as the cylinder base shims go, the stock ones are .25mm and you can stack several of them. It's not necessary to have custom shims.

Thanks everyone for their input it’s good to know there are several knowledgeable people here. I spoke with Ian and he gave me some valuable advice. I do have 1mm shims that I did purchase from LN engineering and the effective number was around .85-.90 left to right.

Given my pistons and rod combo that may be okay. And I will be measuring and trying that once more. If I get the same values I feel that may be a good combo.

I’ll keep you all updated on the progress.

Thanks

I noticed that you used a GT3 oil pump in an air-cooled, two valve 911.
Why? Isn't the enter section simply an additional pump designed to create crank case vacuum. How would that benefit your engine?
Wouldn't an air-cooled engine benefit from more scavenging instead?

2.7 Hot Rod Engine Build (Advice Needed)
 

The extra screen is another scavenge pump.

I have read that the addition scavenging on a Naturally aspirated engine would help in reducing windage in the crank case and reduce resistance freeing up horsepower. Also beneficial at the higher RPMs. Another plus was the price I got it for was comparable to a new turbo or 964 pump.

GT3's also have a check valve in the top to keep 10 in Hg of vacuum in the crankcase. Yes, there's power to be had by having a vacuum in the crankcase on any engine. In nascar we ran over 20 in Hg, but we also had supplemental pin oiling and extra piston squirters, otherwise the crankcase vacuum will cause those parts to run dry.

On boosted engines, the blowby under boost is always high enough to overcome the vacuum generated by the extra scavenge stages, so it's not even possible under high boost.

Even with the benefit of a discount price, the pump is not appropriate for your build. Don't feel bad, a lot of inexperienced builders think more is always better.

All true but no benefit on this particular build.

Thanks for your input, but it’s staying inside. Couldn’t hurt and probably won’t.

Of course. When building these cool little projects we should all use what we have.
My comments were offered so others wouldn't make the same error.

Care to elaborate on its inappropriateness. I may learn something.

I'll take a shot at this question.
The scavenge pump in the 911 was designed to scavenge as much crankcase oil as necessary. Moving parts like oil pumps create parasitic loss so limiting that loss is a design imperative. Porsche improved the oil pump around 1975 by reducing the scavenge side and increasing the pressure. This had little effect on internal loss. Obviously, Porsche design engineers deemed the scavenge reduction beneficial when balanced with increased pressurized volume.

In or around 1978, Porsche decided that a larger pump was necessary for the increase challenges generated by the turbo engine. They increased both the scavenge side and pressure side probably to compensate for the pressure loss do to larger oil squirters and the increase sump oil that followed. Now keep in mind, Porsche now had a larger pump but they continued to use the smaller (what I call the 908 pump) in normally aspirated engines. In fact they continued that practice for 11 years. Why? I would assume that they deemed the turbo pump "inappropriate".

Now lets move on to the GT3 pump. By the time the GT3 engine arrived on the scene, Porsche had modified the oil flow to the top end, reducing it some 25%?
The pump they used was a 9000 rpm racing development that would create crankcase vacuum and theoretically more horse power. They created so much vacuum that they had to redesign the flywheel seal. Because of the spacial limitations of the Mezger case, they had to reduce the scavenge side of the pump by about 30%.

The new GT3 pump, had less scavenging volume than the turbo pump but now, in conjunction with other design features, it could make negative crankcase pressure. Because of the higher location of the vacuum pump pickup, it offers very little oil scavenging effect but will add to the parasitic loss (by the shear nature of it's size) of an engine that doesn't benefit for the vacuum.
More parasitic loss, no scavenging benefit, no need for larger oil pressure side (unless larger squirters are installed), no horse power producing vacuum creation, might just deem the GT3 oil pump an inappropriate pump for a 7200RPM engine.

Why do I say 7200 rpm? The 2.4/2.7 crank has a design flaw that limits it's functioning RPM range. The rod journals are so wide that it created a thin flyweight that flexes during higher RPM. That flexing creates an imbalance (a rocking couple) that creates a destructive harmonic that limits engine longevity.

I know "but I rev my 2.7 all the time". Well if you really work it hard, the engine will do it's best to spit off the flywheel. 2.8 RSR could rev because it had very special crank. A crank with narrower rod journals, wider fly weights and reduce rotating mass. They also ran a really cool light weight flywheel.

Thank you Henry. That's interesting.

We did a lot of Oil flow testing on the dyno some years ago when Stefan did the big pump for us. We compared the stock pumps at the time and the GT3 to his prototype pump. I need to dig out all that data and re read what we found.

Is it inappropriate for this particular engine. No not at all. The wording inappropriate reads as if it would not work. Could it be said "over the top" for the application, yes for sure. But at the cost it certainly will not fail the engine.

I can say this from experience and a lot of testing. The GT3 pump has played apart in saving the middle rod journals.

But then, according to the post that suggested it is inappropriate, and inexperienced engine builders use it, I guess I just found my position in life.

Crap, I'm too old to start over. What do I do now. Anyone need their lawn mowed?

So the word "inappropriate" has your panties in a bunch. You didn't take my comments personally did you? Oh my, maybe you did.
If so I apologize.

Henry, I think Neal's sarcasm is directed at this post.....
"Even with the benefit of a discount price, the pump is not appropriate for your build. Don't feel bad, a lot of inexperienced builders think more is always better.

It's not really how he portrayed my words but I think that's what has "his panties in a bunch"

I saw no panties in a bunch. Neil's post was lighthearted and self-deprecating, and also substantive. Henry you seem to be spoiling for a fight of some kind. I don't get it.

Henry, no offence taken. You have no need to apologize.

In all the years I have never heard a part called inappropriate. It was something that caught my eye. Seemed an unusual way of telling someone he had chosen the wrong part.

I come on here knowing most are DIY home builders. Sometimes you can advise and be helpful. I know that I have been blessed to do this work professionally and at times at a very high level. Those times and now, professionally, we have to make the right decisions as all too often it comes around and bites us in the rear end. We push what works but more often, what does not. My "failed did not work" pile is so high you need a 10ft step ladder to see over. That's how we learn. I remember in my F1 days, Niki used to say, you learn more from failure than you do from success.

This is the world I live in. The DIY guy lives in the "one time" world that either works or does not. There is never any room for failure. So when I read the person was using a GT3 pump, I look at that this way. Will it work or will it fail. I know for sure it will work and not fail him and his engine. The wording inappropriate stood out as to say, neither but to add a whole lot of confusion.

For the home built DIY, the fact it will work, not fail and its a good price, what's gained by suggesting anything other.

BTW, its commando all the way.

I guess I opened a can of worms. Not my intention.
I was just asking why and offering a thought about why the GT3 pump might not be the best choice for this type of build. Others will read this thread and hopefully will have more information to evaluate their own choice.
This looks like a great build and a cool thread, it was not my intention to derail it.

Well I’m glad my choices created a great discussion. Either way there’s a gt3 pump in there and it’s staying.

I spoke with Ian and he advises I reevaluate my piston deck height. After many combinations of shims. I got to a .89 deck height. With my current Rod and piston selection I’ll be fine. And the static compression ratio is at 10.6:1

As I continued to assemble the engine I installed all the pistons and cylinders.

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Rebuilt rockers by Craig Garr and WPC treated. Turbokraft rocker locks

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All timed. The Stomski tools are amazing

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Carrera tensioners installed using Supertec idlers.

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Sealed and ready for the next step.

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More updates to come. Thanks for all your input