3.2l rebuild, the quest for more power

[911pcars]

Originally Posted by fred cook

The point I was making was that the SSI exhausts will work well with the 964 cams. What was your point? Not sure you know what you are talking about.... just saying!
(I hate that expression!).

You said: "......So far, I haven't noticed any falling off of power at higher rpms"......

My point was that one shouldn't miss the extra power if the installed components aren't optimized/optimal in the first place. We all experience the limitations of the engine we have. Unless your engine previously produced more power with the same configuration, why would you miss a reduced amount that was never produced?

[fred cook]

Originally Posted by 911pcars

You said: "......So far, I haven't noticed any falling off of power at higher rpms"......

My point was that one shouldn't miss the extra power if the installed components aren't optimized/optimal in the first place. We all experience the limitations of the engine we have. Unless your engine previously produced more power with the same configuration, why would you miss a reduced amount that was never produced?

When I rebuilt my engine I added displacement, compression, different cams, larger port heads and modified the CIS system. Even with all of this, the SSI exhausts (which were on the otherwise stock 3.0 SC engine) still flow well enough to let the new engine configuration make increased power at higher (7,000) rpms. If the exhaust capacity was restricted, it would not do so. While an engine might make a marginal amount of more top end hp with larger diameter header type exhausts, they would take away from the bottom end and mid range torque levels. Engines are always a compromise, so you have to decide which is more important to you, good street driving characteristics or 5 extra horsepower at redline.

[Edelweiss]

Dear Sirs,

yes right and there is a clear tendency of thinking bigger is better.

This is not the case - you can see the majority of exhaust tubing being oversized.

A lot of the people doing this systems are reasonable welders but far away of being exhaust experts or constructors.

The Porsche engines like relatively small tubes - as an example a 45x1 mm tube is good for 400 plus hp out of a full spec 3,5 l RSR style race engine with 50 mm flat slides.

Max power is at 8.600 rpm and shifting is at 8.800 to 9.000.

So a bigger tube is not automatically making more peak power - it can also mean loosing everywhere.

Same with the ports - work at the seat / bowl area but do not open it up too much.

Ports also tend being too big not being too small !

Best reg.

Dirk

[911pcars]

Originally Posted by Edelweiss

Dear Sirs,

yes right and there is a clear tendency of thinking bigger is better.

This is not the case - you can see the majority of exhaust tubing being oversized.

A lot of the people doing this systems are reasonable welders but far away of being exhaust experts or constructors.

The Porsche engines like relatively small tubes - as an example a 45x1 mm tube is good for 400 plus hp out of a full spec 3,5 l RSR style race engine with 50 mm flat slides.

Max power is at 8.600 rpm and shifting is at 8.800 to 9.000.

So a bigger tube is not automatically making more peak power - it can also mean loosing everywhere.

Same with the ports - work at the seat / bowl area but do not open it up too much.

Ports also tend being too big not being too small !

Best reg.

Dirk

The configuration of Porsche's RSR track engine isn't necessarily a recipe for street-based engines, even uber-modified versions.

Not that PAG makes all the right calls, but one could take hints from the components they use (exhaust-wise specifically) in their production engines, some of which are pretty "uber". It appears the mods Fred made (displacement, compression increase, cams, etc.) would have provided a hefty boost to mid-range torque.

BTW, 45mm = ~1.77". Not sure if that dimension is tube ID or OD. If OD (as is typically used), the tube ID is typically 1-5/8" (41.27mm). By comparison, SSI tube OD/ID is 1.5"/1.375" respectively, not ideal for a 3.3 l engine according to "those in the know" and the more knowledgeable people here. I'm probably splitting hairs, but unless there are empirical test results, how does one know "my stuff" is not leaving untapped power on the table just because I can't feel the power loss?

Not to beat a dead horse, but unless there's a reference level, how does one feel a lack of e.g. +10-15 ft.lbs torque?

Sherwood

[Edelweiss]

Dear sherwood,

the comparison was just to make clear what gas flow volume is taking its way through a relatively small tube without restricting and causing the loss of power and torque.

And this is a strong argument to be considered when choosing from all systems available, or getting something build custom made.

A smaller system with smaller diameter is generating more velocity and a stronger pulse at the joining spots.

Looking at what Porsche did on street and race cars is telling exactly the same story.

We are working on our dyno every day and see evidently what happens.

Very often we change systems or adapt headers that we fabricate to be fitted on existing mufflers / silencers and in a lot of cases we use smaller tubes, if necessary, and produce more power and torque on a wider range.

At the end of the day the surface size under the power and / or torque curves makes the fast engine; whether it is a street or a race engine.

I was writing the tube diameter is 45x1 mm so the inner diameter is 43 mm !

Remaining with best regards

Dirk

de-de.facebook.com/edelweissmotorsport

[911pcars]

Originally Posted by Edelweiss

Dear sherwood,

the comparison was just to make clear what gas flow volume is taking its way through a relatively small tube without restricting and causing the loss of power and torque.

And this is a strong argument to be considered when choosing from all systems available, or getting something build custom made.

A smaller system with smaller diameter is generating more velocity and a stronger pulse at the joining spots.

Looking at what Porsche did on street and race cars is telling exactly the same story.

We are working on our dyno every day and see evidently what happens.

Very often we change systems or adapt headers that we fabricate to be fitted on existing mufflers / silencers and in a lot of cases we use smaller tubes, if necessary, and produce more power and torque on a wider range.

At the end of the day the surface size under the power and / or torque curves makes the fast engine; whether it is a street or a race engine.

I was writing the tube diameter is 45x1 mm so the inner diameter is 43 mm !

Remaining with best regards

Dirk

de-de.facebook.com/edelweissmotorsport

Dirk,
i actually agree with you, but tube size (small vs large) is relative, thus my initial response way back in #59.

Sherwood

[Edelweiss]

Dear Sherwood,

I went back to # 59 but could find no connection, anyhow:

" all is relative even mathematics " ( Albert Einstein )

Best reg.

Dirk

de-de.facebook.com/edelweissmotorsport

[michael lang]

This is unbelievably interesting. I'd never thought I would get so hung up in caring about what size tubing for an exhaust manifold I should be concerned about. But in actuality, I'm finding this stuff to be so interesting. I'm probably over thinking this because I'm not building a competition engine but it is really important to me to get this right so if it takes me a little longer to decide what is best for me, for my project and what I'll be doing with it, then it takes little longer. So I'd like to ask for all of your opinion, for a street engine that will see 5 maybe 6 DE weekends a season, what would you choose for exhaust (headers & muffler) w/out giving up heat?

[pooder]

Michael,
The rebuild of my 3.2 to 3.4 (Mahle P+C's) with 964 cams and extrude honed manifold is nearing completion and I am going with SSI's as heat is critical to me. I did speak with Brian at Rarly8 and given that my goal is midrange torque and his headers w/ heat have short length primaries, he told me that this would not be ideal for my intent. Thus my builder advised me to go with the SSI's. Project to be completed soon with dyno data to follow.
Peter

[michael lang]

Thanks Peter, I appreciate the info. I think I know which way I'm going with regards to "air out".

Since the heads are at the machine shop I wanted to do some reading up on what happens and what they do, just get some basic general information. So I pull open Wayne's rebuild book. I was reading camshafts and since my 964 cams had just come back from Elgin cams my interest was fairly peaked. Then the book started talking about the rockers and they should always be hardened and polished during a rebuild. I didn't think they needed to be redone as well especially sice when I took them out they were in next to perfect condition. How important is it to have them done? During the disassembly both the Bentley manual and Wayne's rebuild discuss the importance of marking the location as to which the rockers were removed from and reinstalling in the same location. If I sent them off to a machinist, how do I make sure they get put back in the same place so they are installed in the same location? If I installed them the way they are without any machining, what do I risk?

[jager911]

Mike,
I'm following your build with keen interest as I'm about to embark on rebuild, trying to make decision between Euro 3.2 or 3.4. I think you decided not to split the case, IIRC, did you do a leakdown before you started? I'm thinking I should get a base reading as I have a leakdown tester.

[michael lang]

I have to admit I did not do a leakdown test. I do know that I was experiencing zero engine problems prior to me tearing into this thing. What started out as simply pulling it out so I could save a little money because the body shop needed it out to fix some impact damage I had when I was hit coming out of T9 at Summit Main last season to some basic cleaning to where I am now. This has been quite the experience. There have been times that makes me doubt myself in being able to get it back together but at the same time I used to think that my meager tech skills would never get to where I am right now. It's a learning process and I'm trying to enjoy the ride because i think it will make me that much better when I get back to the track. The way I see it, this experience will give me a much better understanding of how things work in my car's engine therefore I will know how to apply that to my driving.

[michael lang]

Originally Posted by michael lang

So I pull open Wayne's rebuild book. I was reading camshafts and since my 964 cams had just come back from Elgin cams my interest was fairly peaked. Then the book started talking about the rockers and they should always be hardened and polished during a rebuild. I didn't think they needed to be redone as well especially sice when I took them out they were in next to perfect condition. How important is it to have them done? During the disassembly both the Bentley manual and Wayne's rebuild discuss the importance of marking the location as to which the rockers were removed from and reinstalling in the same location. If I sent them off to a machinist, how do I make sure they get put back in the same place so they are installed in the same location? If I installed them the way they are without any machining, what do I risk?

Can anyone comment on this? If I'm going to do this, now is the time. I was under the impression that they just went back in all I had to do was make sure they went back in the same spot. Is that not the case?

[michael lang]

Getting to this point has been slowed to say the least. The bolts for the rocker arms were buttass tight and I kept thinking that I was going to round off one of the 5mm heads and I would totally in the toilet as far as getting it out.


But with a little but of patience, some penetrating oil & heat and talking real nice to them I was able to get them all out with no damage.


Now it was on to getting the cam towers off






Being very careful in keeping everything together just the way it was originally put together





I've been using both the Bentley manual and Wayne's book as my guides and working the two together. On one side I took the cam tower off first and then the heads as suggested by the Bentley manual. On the other side I took the cam tower and heads off at the same time and then separated the two on the bench. I liked doing it that way better. If I ever have to do it again I'll have to remember to loosen the nuts and bolts first before removing the two together, it was a pain in the ass getting them loose with the heads wanting to slide around on the bench top when torque was put to the bolts.



Now the heads have already been sent to the machine shop, the cams have already returned from Mr. Elgin being regroup and polished. As soon as I gets the heads back and the fuel injectors back I can pretty much get started on putting everything back together. Although I do see more cleaning in my future.

[DSPTurtle]

Did you decide to get your rockers rebushed and polished? It's not very expensive. The theory behind keeping the rockers in the same place has to do with the wearing of the cam and the rocker pad together over the last 25 years. Since you had the cam reground, that's now no longer relevant but you do want the rockers to be as flat as possible to make new wear patterns with your "new" cam. Check the bushes too, they will probably show some wear. The rocker shafts will also show some wear and can also be polished just like the rocker pads. Definitely consider the RSR rocker seals when reassembling the cam rack. These can develop annoying leaks for sure! They slip into the little grooves on the rocker with a little persuasion. Just make sure they don't invert as you are sliding them on.
Keep trucking... You're doing great so far!!!
Btw... If you want those aluminum parts to look new, and you don't want to buy an air compressor, drop them off at a powder coating or metal shop and ask for them to be bead blasted. All the elbow grease, mineral spirits and simple green in the world, will never get the parts to look like they will after bead blasting. And it's not that expensive.

[jager911]

Looking good, giving me inspiration to tear into mine, take lots of pics and keep posting. What cam grind are you going with? What's the approx estimated cost with cams and heads being sourced out?

[michael lang]

Thanks for the encouragement DSPTurtle, like I said for a 1st timer, it's a little overwhelming. I did find a shop in my area that has the type of cleaning equipment and solution that I have been looking for. Gunther's Machine & Speed Shop in Walkersville MD is cleaning them for me. I'm particularly interested in the cam towers as I spent the most time. He did tell me that he wasn't sure how much cleaner they would get since they were already fairly clean. I can't wait to see them. I did decide to send the rockers in for polishing. I figure if I've gone this far I should skimp on something like this. And yes I did think, if I'm replacing the cam why am I worried about making sure they go back in the same spot, but what do I know.

jager911, the cam I'm installing is a stock 964 cam. I wanted to stay mild as my plan was to not replace the pistons and I was concerned about having valve clearance issues. A stock profile allowed me to not have to worry about those issues. I did tell the machinist what I was doing so he knew what my goals were and would know what to do to match everything up.

[michael lang]

Here's what the inside of the cylinders look like



That's #3 cylinder & this is #2



All six cylinders are pretty much identical to one another so I think for the most part my engine is very healthy. Other than having the piston tips bead blasted, is there any way the carbon can be cleaned off the piston tops.



I really don't want to remove the cylinders if I don't have to.

[hyperkinesis]

Any recommendation? I have to open the engine because it have the exhaust valves blowout

now the engine is open what I can do to get more HP from it.. what I need to change or what to do some help Im not doing the job is a mechanic but I don't want he told me something to get more money ... I need the more efficient upgrade to get the more HP possible without spend a lot $$$

thanks for the help

[911-32]

Always interesting to hear of 3.2 owners searching for more power. I had mine rebuilt with similar aims a few years ago. My recipe was euro Ps&Cs, supercup cams and SSIs plus the usual rod bolts, race valve springs, Ti retainers etc and a custom SW chip. I saw 260fwhp, but never saw more than about 220lbft of tq. Fast forward a few years and I decided to put a 964 plastic intake with working resonance flap, hot film maf and 1 5/8 headers on. Once that was live mapped on the dyno I am at 283fwhp and 250lbft. Getting this to work was neither inexpensive nor trivial, but it is now a strong engine that pulls much harder in the mid to upper ranges. I am also running an aluminium pressure plate and 930S spring centred clutch which together with the cams makes this engine much more akin to the early, revvy engines in character. Ignoring the dyno numbers (notoriously unreliable), the change in character and the seat of the pants difference certainly do make it all worthwhile.

What I have learned, is that changing just one thing (say exhaust) makes little difference. To make a real difference in hp/tq, you kind of have to go through the whole system and change everything to step up to the next level.