To build or buy...that is the questions

[Vintage914Racer]

Long time listener, occasional caller here as they say...

I've decided it's time to do finally do something with the engine that's in my factory 914-6 street car. For background, the car is a bit of a taproot, and meaningful, car for me. It's been in my family since I was just a few years old and have great memories riding around in it between my parents as a kid. A bit more of a backstory on the car and the work I've done to it over the years can be found here.

But we're here to talk engines...The engine in the car is not original to the car, rather it's an engine of unknown spec built up on a 1968s aluminum case that's been in the car since the mid-eighties. Leakdown isn't great on one cylinder, and despite my replacing every seal and gasket possible without splitting the case, she still leaks a fair amount of oil. I'm ready to invest in a new engine that will keep the car going for the next 20+ years. I'm wavering on having it rebuilt, or finding something that's built to replace it. I dreamed of attending one of Tony's rebuild clinics and doing it myself, as I'm pretty mechanical, but with other things going on I just don't think I'll get it done anytime soon.

I browse this site and there regularly, and have seen lightly used, relatively rebuilt engines come through the classifieds that, at the time, I haven't been ready to pull the trigger on. Finding a built engine seems like the quick option to getting back on the road, but you don't always know what you're getting. That pushes me a bit towards getting the current engine rebuilt.

With folks retiring and dwindling air-cooled knowledge locally, I don't have a lot of options for rebuild in or around town here. I've seen some of the great work on these forums, and have an idea of good builders I could ship the engine out.
I guess I have a few questions:

1) In a similar situation, would you build or buy? Would you have any hesitation buying a used engine with back up stats (compression, leakdown) and 5-10k miles.

2) If sourcing something new, or brand new second hand, I’m inclined to stick to a smaller displacement engine under 3.0 liters, versus going to a 3.2 or 3.6. The ship has seemed to sail on finding reasonable versions of these, with more an more of the ones I see selling as cores with higher miles.

3) I do like the idea of keeping the current engine as the heart of the car, as its aluminum case with S origins, either sticking to a 2.0 or bumping to 2.2s specs. Assuming it is currently a 2.0, bumping up to a 2.2 would require case machining, right?

4) Rebuilding requires an investment that I’m prepared to make. My last rebuild on my track car was in 2016, and another in 2007 before that. Obviously prices have gone up, and I’ve browsed many of the “how much does it cost” threads, but few reflect 2025 numbers. Is it feasible, to do a rebuild on the current running engine for $20k? $25k?

[PeteKz]

Some questions for you: How do you use (or plan to use) the car? Weekend fun car for street on nice days? Racing (per your user name)? Autocross? Primarily as street car with occasional AX's or drivers events at the track? Do you want significantly more power? I assume it has carbs--do you want to stay with carbs or go to EFI? What else?

Big question: What's your budget (and whatever you say, it will end up higher)?

I'm a hardcore DIYer, so my advice will almost always be to do it yourself. Plenty of people here have done that. It not only saves money, but also time, as shops that can competently rebuild 911 engines are oversubscribed and you will have to get in line for them.

[mepstein]

Early aluminum engines are really cool. I would rebuild it and hot rod it but before I got started, I would talk with an engine builder you trust and figure out a good recipe for the rebuild. You can get a lot of suggestions on the forums but you don’t want to build an engine by committee, you want to build off a proven recipe.
We helped a friend rebuild his flared 914 with an early aluminum case into a 2.4 It really made a fun car even better.

[Vintage914Racer]

Originally Posted by PeteKz

Some questions for you: How do you use (or plan to use) the car? Weekend fun car for street on nice days? Racing (per your user name)? Autocross? Primarily as street car with occasional AX's or drivers events at the track? Do you want significantly more power? I assume it has carbs--do you want to stay with carbs or go to EFI? What else?

Big question: What's your budget (and whatever you say, it will end up higher)?

I'm a hardcore DIYer, so my advice will almost always be to do it yourself. Plenty of people here have done that. It not only saves money, but also time, as shops that can competently rebuild 911 engines are oversubscribed and you will have to get in line for them.

Car will be used solely as a street car spirited drives around and outside of town here. I'd love to do it myself, but with a lot of projects stacked up (car related and otherwise) I don't see the engine coming together if I do it myself for a couple years or more

[Vintage914Racer]

Originally Posted by mepstein

Early aluminum engines are really cool. I would rebuild it and hot rod it but before I got started, I would talk with an engine builder you trust and figure out a good recipe for the rebuild. You can get a lot of suggestions on the forums but you don’t want to build an engine by committee, you want to build off a proven recipe.
We helped a friend rebuild his flared 914 with an early aluminum case into a 2.4 It really made a fun car even better.

I have a 2.5ss built up on an aluminum case in my 914-6 vintage racer. It's a great engine, but I don't quite need it for my street car. My past engine builder has retired, as has a lot of folks with expertise in aircooled stuff around here so I do plan to find a new to me builder or otherwise to potentially take on the project.

[brighton911]

The way I see it, buying an engine that is "rebuilt" has too many question marks attached to it. Unless the builder has a solid reputation with references, you really don't know if it has been done properly. I would go with having your engine re-built with a well vetted builder.

[Turbo_pro]

Originally Posted by Vintage914Racer

I have a 2.5ss built up on an aluminum case in my 914-6 vintage racer. It's a great engine, but I don't quite need it for my street car. My past engine builder has retired, as has a lot of folks with expertise in aircooled stuff around here so I do plan to find a new to me builder or otherwise to potentially take on the project.

if your goal is to find a competent engine builder for a 914/6 I would highly recommend Supertec Performance.
They built an absolutely incredible engine for my six. Although they didn't start with an aluminum case, (a great starting point BTW) they built me a 2450cc on an early case.
They used a 70.4 crank, 9.5:1, 86mm Ps&Cs, 36mm ports and mod "S" cams. It pulls strong from 2500 and makes 180 rear RWHP @ 6400. It's the best running street Six I've ever driven. Crazy fun!
With a core aluminum engine to start, 20-25K is very feasible, I think?

[Vintage914Racer]

Originally Posted by brighton911

The way I see it, buying an engine that is "rebuilt" has too many question marks attached to it. Unless the builder has a solid reputation with references, you really don't know if it has been done properly. I would go with having your engine re-built with a well vetted builder.

The more I think about it I am definitely leaning more that way. Knowing what you have is important, as is trusting who did the work.

Originally Posted by Turbo_pro

if your goal is to find a competent engine builder for a 914/6 I would highly recommend Supertec Performance.
They built an absolutely incredible engine for my six. Although they didn't start with an aluminum case, (a great starting point BTW) they built me a 2450cc on an early case.
They used a 70.4 crank, 9.5:1, 86mm Ps&Cs, 36mm ports and mod "S" cams. It pulls strong from 2500 and makes 180 rear RWHP @ 6400. It's the best running street Six I've ever driven. Crazy fun!
With a core aluminum engine to start, 20-25K is very feasible, I think? .

I've heard many good things about Henry at Supertec. Sounds like he built a fun engine for your six.

[Billiam 911 2.8]

Two old favorites are the 2.2S (84 x 66) or 2.4S (84 x 70.4) with 40 webers.

[zztot]

You have gotten some good advice from very competent people.
I am going to throw in some non technical input based on my current and past experience. Building an early spec engine is cool, (just had one done for my six) but since yours is not numbers matching there are better choices IMHO.. Both 3.0
and 3.2 have a lot of benefits over the early (2-2.7) engines. …..well documented and they have broader range of parts availability. You can dissect that position til the cows come home but with that in mind I would go with a more “modern” engine.
Sell the early engine to help fund the project. Just my 2 cents to help blur the lines

[Henry Schmidt]

If I'm reading your current engine description properly, it's a 68 aluminum case.
That's a pretty cool starting point. It's unique in that the 68 was the only aluminum case that used the later chain boxes. That's good for two reasons, better sealing and an easier time installing Carrera chain tensioners. (Although we also make covers for early covers to use Carrera tensioners).
As long as your gold is 240hp or less, there is no reason not to use what you have.
That early case is strong (all be it heavy) and doesn't suffer many of the issues you have with a mag case.
We recently built a 2.8 short stroke (66X95mm) engine using one of those case that offered incredible performance for a 914/6.
The main issue with installing a 3.0 or larger in the 914 is the flywheel required to join the 901/914 to the engine. Many people have solution for this dilemma but most are crazy heavy and very expensive. The lightweight racing clutches that suit the conversion are generally too high-strung for street use.

[Vintage914Racer]

Originally Posted by zztot

You have gotten some good advice from very competent people.
I am going to throw in some non technical input based on my current and past experience. Building an early spec engine is cool, (just had one done for my six) but since yours is not numbers matching there are better choices IMHO.. Both 3.0
and 3.2 have a lot of benefits over the early (2-2.7) engines. …..well documented and they have broader range of parts availability. You can dissect that position til the cows come home but with that in mind I would go with a more “modern” engine.
Sell the early engine to help fund the project. Just my 2 cents to help blur the lines

Appreciate the input. I've thought about going the 3.0 route. Not against it.

[Vintage914Racer]

Originally Posted by Henry Schmidt

If I'm reading your current engine description properly, it's a 68 aluminum case.
That's a pretty cool starting point. It's unique in that the 68 was the only aluminum case that used the later chain boxes. That's good for two reasons, better sealing and an easier time installing Carrera chain tensioners. (Although we also make covers for early covers to use Carrera tensioners).
As long as your gold is 240hp or less, there is no reason not to use what you have.
That early case is strong (all be it heavy) and doesn't suffer many of the issues you have with a mag case.
We recently built a 2.8 short stroke (66X95mm) engine using one of those case that offered incredible performance for a 914/6.
The main issue with installing a 3.0 or larger in the 914 is the flywheel required to join the 901/914 to the engine. Many people have solution for this dilemma but most are crazy heavy and very expensive. The lightweight racing clutches that suit the conversion are generally too high-strung for street use.

I do like the uniqueness of the case as a starting point. A 2.8 SS would be fun. I have a 2.5 SS in my track car built on a similar aluminum case and it's very fun. Does this case need machining for anything larger than a 2.0? I vaguely remember that the case would accept up to 2.2 cylinders, but my memory could be failing me.

[Henry Schmidt]

Originally Posted by Vintage914Racer

I do like the uniqueness of the case as a starting point. A 2.8 SS would be fun. I have a 2.5 SS in my track car built on a similar aluminum case and it's very fun. Does this case need machining for anything larger than a 2.0? I vaguely remember that the case would accept up to 2.2 cylinders, but my memory could be failing me.

The uniqueness of the case and you own it. A great place to start given the cost alone.
The cool thing about the 2.8SS is that the size offers performance so you can down play compression and cam spec for a more pleasant throttle response.
The 2.0, 2.2 and 2.4 cylinders all fit in the same case spigot. The reason we build so many 2450 (like Jim talked about) is that 86mm cylinder also fit the 2.0 spigot. It allows us the largest size without permanently altering the case. Most often on matching number builds.The optio to reverse the optional spec generally seems appealing.
2.5 SS requires a 90 cylinder ( 89mm for racing accuracy) which means you have to bore out the spigot. Too far for may taste in most applications.
The 90 cylinder has historically been the largest cylinder you could fit in the early aluminum case but we started manufacturing a Biral cylinder in 95mm that fits. With a 70.4 stroke crank the 95mm cylinders will make a 3.0. Imagine a 3.0 built on an early aluminum case....
Back in the day, Mahle made an 86.7 and an 87.5mm cylinder for the 911ST that you could also fit in that case. Those sets are long gone.
If you really wanted that configuration, LN Engineers will make them for you, "no matter how much it costs".

[Vintage914Racer]

Originally Posted by Henry Schmidt

The uniqueness of the case and you own it. A great place to start given the cost alone.
The cool thing about the 2.8SS is that the size offers performance so you can down play compression and cam spec for a more pleasant throttle response.
The 2.0, 2.2 and 2.4 cylinders all fit in the same case spigot. The reason we build so many 2450 (like Jim talked about) is that 86mm cylinder also fit the 2.0 spigot. It allows us the largest size without permanently altering the case. Most often on matching number builds.The optio to reverse the optional spec generally seems appealing.
2.5 SS requires a 90 cylinder ( 89mm for racing accuracy) which means you have to bore out the spigot. Too far for may taste in most applications.
The 90 cylinder has historically been the largest cylinder you could fit in the early aluminum case but we started manufacturing a Biral cylinder in 95mm that fits. With a 70.4 stroke crank the 95mm cylinders will make a 3.0. Imagine a 3.0 built on an early aluminum case....
Back in the day, Mahle made an 86.7 and an 87.5mm cylinder for the 911ST that you could also fit in that case. Those sets are long gone.
If you really wanted that configuration, LN Engineers will make them for you, "no matter how much it costs".

Thanks for the insights, Henry. The 2,450 sounds like a great engine that doesn't alter the case. Based on my chainsaw math, that would use the later 70.4 crank, right?

Is there a general rule for when an external oil cooler becomes necessary, versus the engine mounted cooler?

[Henry Schmidt]

Originally Posted by Vintage914Racer

Thanks for the insights, Henry. The 2,450 sounds like a great engine that doesn't alter the case. Based on my chainsaw math, that would use the later 70.4 crank, right?

Is there a general rule for when an external oil cooler becomes necessary, versus the engine mounted cooler?

Yes, the 2450 uses a 2.4/2.7 crank. 70.4 X 86mm. Since high rpm (7K+) isn't the goal in a spirited street car, the flaws in the crank are not as noticeable.
The general rule for front cooler installation in 911 powered cars was 160hp.
The factory installed a front cooler at that mark until they got to the 2.7 mid year cars. They were trying to accommodate smog challenges so they tried running the engine a little hotter. Now the 914 chassis has an added challenge. The air to the fan is supplied through the engine cover and the engine cover is located directly below a low pressure area created by the air crossing over the Targa bar.
The issue isn't so much oil temperature but head temperature. I have always found it difficult to keep the heads cool enough to avoid detonation in this low air pressure environment. That is why controlling the dynamic compression in the 914/6 is so much more critical.

[Geneulm]

This would be a no brainer for me personally: build, don't buy.

You have a great starting point with the case and all the ancillaries. You will know what you have when it's done; something that will never be 100% if you buy. It would be a great project. Just find the level of your abilities. Whether it be doing it all yourself, having a pro put together a short block or long. If you have a builder pick one with a great rep and you can be involved with. If you are going to hotrod it to some level some planning and decisions will have to be made to get what you want.

It will be a good time.

We just finished a 2.9 built on such a case for my car. The intent was to clear out the stash of NOS parts that I've been hoarding for years. 2.9 isn't my fav but the Andial P and C's have been in my closet for 30 years so in they went! And I couldn't be more happy!