Polo motor build for junkyard coupe 58367

[Blechquäler]

Nice to see how it grows Justin!

[Blechquäler]

Well I see Justin, I need to do the same milling work as you on an old 911 case because I believe the development of the required parts will
be easier when I can do it directly in sheet metal, what do you think?

[JTR70]

Thanks Gerd! My plan was to send you "1 to 1" models in fiberglass but absolutely your job would be made easier with a mock-up engine there on hand. Hell, you probably wouldn't even need my models then. We have a few months yet for sure so you can round up a donor block so just let me know on that.
Thank you again! Justin

[merbesfield]

This pic made me think of Darth Vader.

[Blechquäler]

Well, a little bit... LOL!

[William Crowell]

Justin, please forgive me if you think I'm being a Nattering Nabob of Negativism, but you say you hope to obtain good low-rpm performance from the engine; however, with all that porting and the big valves, isn't the intake charge velocity going to be pretty slow at low rpms?

Pardon me if this has already been discussed. I confess to not reading the entire thread.

[JTR70]

Yep, its shape (and color of course) has always put me in mind of Darth Vader as well Mark.

William,
I'm more suited to rust then I am technical motor questions but I'll try and get Tony to jump in here or if any other resident motor head would like to chime in its of course welcome. My basic understanding(and I could be wrong) is that this will be a grunter due to the long stroke crank and the cam grind that will be used. It would make sense that the larger ports could slow down velocity at low RPM's but the barrels are huge(102mm)and were designed to run with these heads as a matched set from the factory. If were using lets say 93mm barrels that might cause a draw problem down low as they would not be big enough to take advantage of the heads. It reminds me of my 912 engine way back when, it had a 1720 kit in it and I bought a 44Idf kit from the Maestro. It had no low end and wouldn't come alive until way into 3500RPM. A versed mechanic helped me by installing smaller venturies so it was now choked down to a basic 40IDF like it should have been for that size displacement and pulled much stronger down low. Now with this engine I believe there to be more than enough bore and stroke to take advantage of those heads down in the lower ranges. Justin

[Jack Staggs]

At close to 2.7 liters, each barrel will be drawing nearly 675cc. That's a pretty big slurp. Do you have an idea of your final compression ratio? Have you decided on a fuel delivery system? Mappable ignition?

[JTR70]

Thanks for confirmation on that Jack! I of course want to raise the compression as high as we can while on Super Unleaded; not sure what ratio that would be? The ignition system will be an electronic crank-fired system for sure.
The fuel system is still in question at this point. I'm partial to EFI myself but

I've had this pair of early Weber 48IDF's on hand in case we decide on old school. If I use them I'll send them to Jaycee racing to be bored out to 51.5 MM and all the other upgrade tricks they offer for these carbs.

If we go EFI maybe something like these throttle bodies from Jenvey.

It was always a rule of thumb in my mind that more power and performance was had with EFI but according to Tony that's not always the case so its in the air at this point. Thanks again Jack!
Justin

[merbesfield]

I am no expert for sure, but I would think the most compelling reason for EFI would be that it starts every time and doesn't require the services of a mechanic nearly as often. I have always said I would love to have an old Porsche the starred and ran as well as my Toyota Land Cruiser. Dream?

[Tony G]

Good to see some the interest in Justin's Polo engine and Speedster metal work endeavors. I am impressed with Justin's work and progress.

I just recently met with Justin at his shop to look at his new 4-cammer shroud and I was really impressed with the quality of the fabrication. We also discussed his Polo engine and he is creating a list of components that he already has at hand to see what kind of configuration he currently has and what we might have to acquire or possibly change/modify. That being said, we will look at all of the current components to determine what is the present configuration looks like.

We are still somewhat early in putting together the right combo for the right targeted use. Justin and I have quite some homework to still do and there will be more to come before we can continue to move forward. At this time we need to see what he really wants/needs performance wise and in order to determine what parts and specs will enable him to attain his wishes, we have to consider many other variables such as final vehicle curb weight, how car is to be driven, transaxle selection and gearing, bearings (Clevite most likely), ideal rod-ratio, connecting rods, bore and stroke, compression ratio, deck height, valve-train components, camshaft durations and lifts (maybe consider custom split durations and lifts), head details, crank specs, where he wants the power band to be, ideal compression ratio; valve-train, valve sizes , exhaust diameter, and design for optimum breathing and exhausting, oiling system, ignition system (most like crank triggered), carburetion vs. EFI, etc.... It is all in the combo and how the combo is expected to be used. One has to look at the big picture and not get too fixated on only one element of the entire many elements of the targeted combo; at this moment, until Justin and I go through several iterative thought processes, calculations, and decisions, we are evaluating what we have and will not procure any additional parts until we know what will work and benefit Justin's functionality and performance goals. Like the few who have built a variant of this Polo engine, there are a lot of things to work out before one can arrive to the point where the engine assembly commences. Also, at this point, we have not ruled out either EFI or Justin's 48 IDA's.

I am really excited about getting more and more involved with this engine. Now off my little smartphone I go to have lunch.
engine.

[Tony G]

By the way, I am not shy about using healthy Compression ratios. Efficiency increases as the CR increases but of course, there are some variables that need to be considered before arriving to the final CR.

[JTR70]

I agree Mark, That is another vote for EFI; I too like the idea of just hitting the key and the motor firing right up with no ceremony.

Thank you Tony!!
Did I mention how impressive Tony is with his insights and detailed knowledge of building air cooled engines? I was telling him today that I am so fortunate to have him here. I'd be lucky to just get this engine "assembled" but because of his expertise this motor is going to be "built"...Big difference. We are(actually Tony)beginning the process of blueprinting this engine as of today. Will have updates as they come. Thanks for looking!
Justin

[William Crowell]

Have you got your quench all figured out, Justin? Once I built an engine with a high compression ratio, before I knew anything about quench. Man, did that thing ever detonate!

[neilbardsley]

I agree Mark, That is another vote for EFI; I too like the idea of just hitting the key and the motor firing right up with no ceremony.

Thank you Tony!!
Did I mention how impressive Tony is with his insights and detailed knowledge of building air cooled engines? I was telling him today that I am so fortunate to have him here. I'd be lucky to just get this engine "assembled" but because of his expertise this motor is going to be "built"...Big difference. We are(actually Tony)beginning the process of blueprinting this engine as of today. Will have updates as they come. Thanks for looking!
Justin

I'm not an expert or even novice intermediate but is starting first time a reason for EFI? My 356 has a mechanical fuel pump / carbs but start pretty well even if leave for a few weeks. My 912 has an electric pump so fill the carbs for you and starts well too. However, it also has a opticial distributor which if you get the programmable type can have many of the benefits of EFI but without the added complexity? Just my 2 pennies worth back to the experts.