Exhaust limits Options

[FJ1200]

Happy Friday,

I don't post here very often (crazy work schedule). I am considering engine options for my 72 this winter. It is currently, basically a bus 2.0 with a web 86 and 42x36 bus heads and 40 IDF's. I am contemplating throwing a set of 96mm jugs with flat tops in it this winter. I am also thinking about a set of new AA heads. The type 4 store stuff is beautiful but currently way outside my budget. The car has SSI 2.0 HE's with a Brush system. During this work I would like to get the heat functional again (I live in Maine). Is 125hp and comparable torque reasonable from what I talking about? Or who knows, maybe a little more. The lower end has about 20k on it, was lined bored and is oil tight and makes no "odd" sounds.

Thanks for any input.

Dan

[mrholland2]

Happy Friday,

I don't post here very often (crazy work schedule). I am considering engine options for my 72 this winter. It is currently, basically a bus 2.0 with a web 86 and 42x36 bus heads and 40 IDF's. I am contemplating throwing a set of 96mm jugs with flat tops in it this winter. I am also thinking about a set of new AA heads. The type 4 store stuff is beautiful but currently way outside my budget. The car has SSI 2.0 HE's with a Brush system. During this work I would like to get the heat functional again (I live in Maine). Is 125hp and comparable torque reasonable from what I talking about? Or who knows, maybe a little more. The lower end has about 20k on it, was lined bored and is oil tight and makes no "odd" sounds.

Thanks for any input.

Dan

My gentle suggestion is to remove that single carb and throw it away (or sell it, or use it as a paperweight). The extremely long runners cause a temperature drop and fuel falls out of suspension. This can cause fuel wash in the cylinders and excessive wear.

[FJ1200]

I dont have a single carb, it has twin 40's that I worked over and have the jetting pretty near spot on. The car runs great, economy seems good. Hard to say the odometer id kaput.

[Van B]

What’s the question here exactly?

[FJ1200]

Basically, what are the hp/tq limits of the stock 2.0 heat exchangers?

[Van B]

Oh, yeah way higher than what that motor will make. Especially with the organized flow you get from the collectors on the Bursch

[emerygt350]

I don't think the headers should be any kind of restriction till you hit close to 200hp. It's the fricking banana that sucks.

[Van B]

OEM primary size on a 996/997 is 1 5/8” (40mm) and they’re 300-350hp motors

[porschetub]

Happy Friday,

I don't post here very often (crazy work schedule). I am considering engine options for my 72 this winter. It is currently, basically a bus 2.0 with a web 86 and 42x36 bus heads and 40 IDF's. I am contemplating throwing a set of 96mm jugs with flat tops in it this winter. I am also thinking about a set of new AA heads. The type 4 store stuff is beautiful but currently way outside my budget. The car has SSI 2.0 HE's with a Brush system. During this work I would like to get the heat functional again (I live in Maine). Is 125hp and comparable torque reasonable from what I talking about? Or who knows, maybe a little more. The lower end has about 20k on it, was lined bored and is oil tight and makes no "odd" sounds.

Thanks for any input.

Dan

Mentioned later on you will be fine with current exhaust,bus heads with big valves ?could work but when the oversize valves were fitted was there any work done to improve flow in the ports? , these heads are cast for torgue in port size unlike the 914 heads with are for more power, so you could really have a limit there.
Appears the 1.8 914 head is a go to for flow of the EFI motor.
HP numbers are subjective really dependant a shitload of things but you should easily get over 100+hp with a 2056 and more with everything dialed in,cheers

[porschetub]

OEM primary size on a 996/997 is 1 5/8” (40mm) and they’re 300-350hp motors

Yes but that is a 6 cylinder and the tech in these motors has little to do with a T4 motor.

[Van B]

OEM primary size on a 996/997 is 1 5/8” (40mm) and they’re 300-350hp motors

Yes but that is a 6 cylinder and the tech in these motors has little to do with a T4 motor.

I wouldn’t over complicate it. Flow is flow… moving a mass of gas through a volumetric space.

[ChrisFoley]

Your exhaust is good to at least 140hp. It's not hard to reach that hp with a 2056, but extracting more power than that takes more cam than a Web86 with 96mm P&Cs.

[barefoot]

Switching to 2.0 heads will loose you compression ratio, they're 60cc vs bus heads of 48cc. If you've got big valves, not much to gain ??

[FJ1200]

So, the long and the short of it is. Stock 2.0 heat exchangers + bursch exhaust can make upwards of 140 hp and I would assume similar torque. As far as compression goes, I have to believe getting in the region of 9.0 - 9.5 : 1 would be a huge improvement. My leak down numbers are around 10% but yet static compression is only about 100 psi. Any experience with the AA replacement 914 2.0 heads? If I aim to shoot for the upper limits of the exhaust it sounds like a new cam is in order. Now we have content creep. If I am going to split the case, it really is starting to make sense to bite the bullet and do a 2270. I know the type 4 store stuff is kind of the benchmark, but I just can't swing their prices. What are peoples experience with other vendors. If I go down this road I am looking at p/c, crank, cam and heads. I think my credit card just winced in pain.

Dan

[rhodyguy]

Project creep. Was case machine work done during the last build? How much power do you feel you MUST achieve? Not the dream number. Power costs. Plenty. Adding 50- 60% more power stresses the other older components. Like CVs, transmissions, clutches, motor mounts.

[FJ1200]

I have the invoice from the last engine build. The case was line bored. As far as oil galley plugs and the like, I am not sure. I would be happy with 130-140 hp, not looking for a high rpm motor. 90% of the driving is commuting on secondary roads in Maine. Phase 2 of this (next winter) will be standalone EFI with twin IDF throttle bodies and a waste spark ignition system. I don't mind carbs, I am very good with them but as an almost daily driver I get tired of weberitis and having to "tweak" them every 4-6 weeks. Nothing scares me work wise. I was a Porsche/Audi shop foreman for 20+ years and I am a hobby machinist with a Bridgeport, lathe and the like.

[mepstein]

Even if you do not build out the engine, get the heat working. It will greatly extend your driving season and comfort and driving with the top off on a cold day while the heat is on almost feels like cheating. If you need any parts besides the heat exchangers, let me know. If I have them, you can have for the cost of shipping. (IMG:style_emoticons/default/beerchug.gif)

[FJ1200]

Thanks mepstein! I think I have most everything. I need the obvious all new paper tubes. Another project for this winter is to pull the tank, go through the heater box, service the wiper assembly (slow) and replace anything that fuel passes through. I should probably service the two heater valves in the engine bat while I'm at it. It still has the polyamide lines (fingers crossed), Mainly I need a defroster, I work at Bath Iron Works were we build the Arleigh Burke class destroyers. The dew point always seems to be around 60 deg, I come out from 2nd shift at midnight and the inside of the windshield is fully fogged. I will admit that I am guilty, often I leave the roof in the garage, so I don't seal it up.

[mepstein]

I’m a big fan of Tangerine Racing SS lines. 5 minutes when your engine is out of the car.
Rain-X on your windshield will help.

[emerygt350]

I wonder if there isn't a cheater heater you could use in the fresh air box. The exchangers are neat and all, but just a little electric heater in the fresh air box would probably work just as well without all the fuss. Anyone try something like that?