Building a Motor, how to figure out what you can do...

[RSTPerformance]

ok... I am trying to decide what to do. I toasted the motor at Mid Ohio and I have to decide to put in another junker (without cleaning it up with new rings or anything) and run another race or just throw in the towel this year and just build a real motor for next season. Time is my main issue this fall as I will be starting a new job in about 2 weeks and need to put 100% dedication into that rather than racing. One positive is that even if I throw in the towel, I will still be doing another race, the Last Chance Enduro in my brothers car, so I will get my fix, I think.

If I decide to build a motor, how does one go about doing it???

We have the restriction in the GCR that says we can not increase compression by more than .5. My understanding is that you can easily do this just by plaining the head?

What about .040 over pistons? If I have some made (they don't exist for our cars) will that effect CR? If so how does it effect it? Also how will the .040 pistons effect performance vs .020 or stock sized pistons.

When determining the allowance to not increase CR by more than .5 is that based on your modifications from the engines min specs or is that based on the manufacturers spec (as noted in the GCR where your vehicles classification is). How would I determine what my CR is before and after making any mods (during the planning stages with a pile of parts)? Is a stock motors CR generally less than the manufacturers # or is it possibly higher?

Besides planning the head, and putting in larger .040 pistons (obviosly new rings go with that), and reseating the valves for a tight fit, what else would you recomend to do for a "80%" build? What about a"90%" build or a 100% build?

Thanks for the input;

Raymond "Personaly I can't believe huge gains can be made legaly, and I want to put it to the test" Blethen

[Greg Amy]

Big, big subject here, my friend. Lots of details, lots of information. What you're asking for is roughly decades of engine-building experience...

But, to answer a few quick questions:

> If I decide to build a motor, how does one go about doing it???

Pay someone that knows what they're doing. Hey, you asked...

> My understanding is that you can easily do this just by plaining the head?

Maybe, depends on the engine. You have to keep the engine within service limits, and there's decisively a service limit on how much you can "deck" the block. Further, you have to make sure you don't run into any problems with piston extension and valve interference.

In other words, it's not as simple as "planing the head".

> If I have some [.040 over pistons] made...will that effect CR?

Maybe, depending on the piston design.

If all you did was make overbore pistons with no other changes, you WILL increase the compression. To counteract this, manufacturers of factory overbore pistons will move the piston pin "up" in the piston ever-so-slightly in order to keep the compression ratio the same. If you're having some built (hold on to your wallet) you can design them to suit your situation.

> ...how will the .040 pistons effect performance vs .020 or stock sized pistons.

No substitute for displacement...and you have a five-cylinder engine, meaning you'll increase the displacement 25% more than a comparable 4-cylinder...

> When determining the allowance to not increase CR by more than .5 is that based on your
> modifications from the engines min specs or is that based on the manufacturers spec (as noted
> in the GCR where your vehicles classification is).

It's whatever the manufacturer publishes, usually in the workshop manual. The GCR may or may not be correct on this, it's your responsibility to verify that and have the ITCS changed, if necessary.

Once determined, it is your responsibility to make sure the engine subsequent to modifications is no more than 1/2 point over that factory value.

> How would I determine what my CR is before and after making any mods...

Measure cylinder volume at BDC and divide it by volume at TDC. Don't forget to "cc" the head volume as well as the volume around the piston up to the top ring...

> Is a stock motors CR generally less than the manufacturers # or is it possibly higher?

Varies. Usually spot-on for any kind of stable production process. But, you never know until you measure it...

> ...what else would you recomend to do for a "80%" build?

Rebuild it with new stock parts.

> What about a"90%" build or a 100% build?

Pay someone that knows what they're doing.

Hey, you asked...

[RSTPerformance]

> How would I determine what my CR is before and after making any mods...

Measure cylinder volume at BDC and divide it by volume at TDC. Don't forget to "cc" the head volume as well as the volume around the piston up to the top ring...
[/b]

Greg-

Thanks for the reply... To measure the above, how in the world do you do this??? I have asked a million times but I still can't get it. Life would be easy if ieverything was flat but nothing is flat or easily measurable other than the diameter of the cylinder . Can a good engine shop measure this and what is a "normal" cost to do that?

If I do take the engine to a good machine shop do I bring the GCR in hand and just tell them to build it to the limit? How would I know what they did was legal?

What about port matching the intake/exaust? Do you get any real gains in IT trim?

Also on a side note has anyone actually had an experience in SCCA where someone did measure the CR on an IT car or any other class? How was it done at the track?

Thanks again, I know it is lots of long questions, but I bet thier are a lot out thier that are also wondering.

Raymond

[joeg]

Deck the Block a few Thou, clean-up cut on the head. Align hone the crank; polish the crank. New Pistons--if you cannot get 40 over, go with 20 over.

A nice port match; good valve job and the best balance job you can find.

Other than the port match and assembly work, all this is farmed out to a machine shop. So find a good one!

[Greg Amy]

> To measure [compression ratio], how in the world do you do this??? I have asked a million times but
> I still can't get it.

It's relatively easy for someone with the the right tools and understanding of the process. Those tools include flat clear plates, a Burette, a low-surface-tension oil, a bore gauge, and depth gauge (or calipers). You measure bore and stroke and you get the swept displacement; you use the other tools to measure the amount of oil displaced by the head and piston tops. Simple math after that, and...

> Can a good engine shop measure this and what is a "normal" cost to do that?

Absolutely they can, and it's about an hour's worth of work with the head off the car.

> If I do take the engine to a good machine shop do I bring the GCR in hand and just tell them to build
> it to the limit? How would I know what they did was legal?

Yes. That's why it's important to hire a trustworthy builder.

> What about port matching the intake/exaust? Do you get any real gains in IT trim?

Absolutely. The amount is dependent on how bad it is from the factory.

> Also on a side note has anyone actually had an experience in SCCA where someone did measure the
> CR on an IT car or any other class? How was it done at the track?

Yup, mine was done after the '06 ARRC, exactly as I described above.

Greg

[planet6racing]

Raymond:

If you are going to do this yourself (you should find someone to do this for you and do it right), go to the bookstore and get a book on high performance engine building. It doesn't really matter whether it is a V8 or Honduh engine book, the basics are all the same. It will explain how to CC the motor (with pictures, too), how to balance conn rods the right way (not just simply matching the weights of the overall rod), and so on.

[RSTPerformance]

Raymond:

If you are going to do this yourself (you should find someone to do this for you and do it right), go to the bookstore and get a book on high performance engine building. It doesn't really matter whether it is a V8 or Honduh engine book, the basics are all the same. It will explain how to CC the motor (with pictures, too), how to balance conn rods the right way (not just simply matching the weights of the overall rod), and so on.
[/b]

No no.... I have always built my own motors and had decent luck, however this sort of stuff I would just send out for someone else to do (as Greg suggested). I basically want a list of what I should do, or need to do to get the most out of the engine. I want to do as much homework as possible on my dime rather than their dime (I still don't want to spend more than $1,000 or so). I am sure that the engine builder would have suggestions, but in reality how many engine builders have built IT engines that limit what exactly you can do. How many engine builders will know what is more benefitial, .040 pistons or "decking" the head till it just about hits the pistons (within the limit of the rules, not the factory spec). I have no idea, but I do want to have some sort of understanding.

One thing I do need to do is figure out the measuring CR... I think it is one of those things I need to do once and I will be good. I am thinking we need to have an NER tech seminar at one of the upcoming races where an Audi motor is brought in to be measured. not only would it be a good test (education) for the tech inspectors, but also for the stewards as well as the competitors. - what are the thoughts? I have an old stock motor sitting on the floor that I would donate.

Raymond

[924Guy]

Seems to me that Shine Racing Service can't be too far from you - they seem to know their VW/Audis, and IT to boot... they're in Walpole, MA... I always said if I were a little closer and had the cash to spend on a pro-built motor, they'd likely get it. FWIW, it cost me nearly as much just to build my own anyway...

Some more thoughts... did you figure out what killed the old motor, and how long did it last??

[RSTPerformance]

Seems to me that Shine Racing Service can't be too far from you - they seem to know their VW/Audis, and IT to boot... they're in Walpole, MA... I always said if I were a little closer and had the cash to spend on a pro-built motor, they'd likely get it. FWIW, it cost me nearly as much just to build my own anyway...

Some more thoughts... did you figure out what killed the old motor, and how long did it last??
[/b]

I think this is the 4th season on the motor, never had an issue before that wasn't related to forgetting to put on the fan... It was/is basically stock. I did not have any guages on it as I had run out of funds to fix the broken ones ... All I had was Oil Pressure which was good till I parked it. I do know that our cars need the fan on at all times inorder to cool, and I know the fan was working. Stephens car was running around 260* (to high) when drafting and I may have toasted it trying to pull drafts off of people, not sure. Generally when the car overheats it blows a line, in this case it didn't for some reason.

As for Shine Racing Services, Shine is great with a lot of knowledge (although Eli is gone). I would buy any off the shelf product from them, but not sure if I could afford them ($$$ or length of time) for building something like an engine. I would probably use a local machine/engine shop that we have some experience with located in NH (Top Secret Place )

Certainly interesting that it cost you as much to do your own as to take it to a shop...

Raymond

On second thought... Maybe the issue!!! I havn't run a race with this car all season, so it was the first time out from winter. When prepping the little water that was left from the winter was orange (rusty) could this have a major effect on the cooling of the engine? I emptied the fluids and left the hoses disconected for the winter, then in the spring reconected the hoses and filled it with my special blend (water and slight bit of antifreeze), flushed out and it was still a bit rusty colored, but no flakes of rust to be found.

Raymond

[planet6racing]

Get the book, regardless. It will help.

I did mine half and half. The engine builder did the machining and balancing, I did the assembly and head work. With new rods, pistons, rings, seals, etc., it was well over $1000, and I ended up with a head that I do not know if I took off too much, too little, just right, etc. in the ports. Next head will be sent to him for flo-jetting.

Once the ecu rule passes (ha ha! I knew I could sneak that in there and not de-rail this thread! Oh, wait...), I plan to have a long, serious talk with my engine builder and his dyno (yes, his dyno can talk! Well, ok, maybe not. What do I know?).

[JeffYoung]

There is power in the bottom end (crank scraper, torque plate on "flexible" blocks, good seal with the rings, etc.) but I think most IT gains are made in the heads. The port matching is a big deal, at least on my motor, and improved flow on my heads by a documented 10%. Heads and exhaust are were you still see most improvement over stock; focus on that.

By the way, yes, you do see HUGE gains on some motors in IT trim. Mine is rated at 133 crank hp stock; I make 160 whp now with lots left to do. A good L24 Datsun (240z) motor will make 170 whp, with a 150 crank rating. See also Greg Amy's car for another example (150 whp IT, 140 crank stock).

In particular for 80s motors, I think just the attention to detail and "clean up" helps get power.

For what it is worth, I spent about $1500 on outside parts and services on my present motor. $900 for the head, and about $600 for bottom end parts. I assembled the bottom end with the help of a friend, and then put the heads on myself. I consider this to be about a 80% IT build. On a "V" motor, it's probably best to have the guy doing the port matching on the heads to install them on the block, etc.

[joeg]

Jeff--Do you mean honing[i] with a torque plate? I would not think you can add a plate to an open deck block under IT rules.

Finding a commercial honing torque plate for a 5 cyl. Audi would be a bit of a challenge. You could actually make one (or have one made) from an old cylinder head and a milling machine. Chop the head in half lengthwise and hog out the combustion chambers. I have also heard that simply stacking some good washers on a bolt for each head bolt hole in the block and torquing to spec actually imparts the same distortion for round honing purposes.

[JeffYoung]

Correct, I mean using a torque plate to make sure your honing of the cylinder bores is "true."

I've had at least one engine builder indicate that these things can be made using even just a head gasket as a pattern, for about $200 to $300.

[77ITA]

I do not have much to contribute to this discussion as I am not an expert engine builder, but I do have a few points that I would like to add.

To start with, I think we can agree that high performance engine building is a rather precise science. It's not outside any of our physical abilities, but there is not a lot of room for error and you must have the requisite tools and knowledge for the job. If you do not posses said tools and knowledge (and do not have the time/money/space to gain them), the job is better left to a professional; someone that has the ability to do the job correctly.

The above being said, I would like to provide a frame of reference. We all need trailers to go racing just like we need engines. I'm sure I could design and fabricate my own trailer, but I'm not willing / able to invest in doing so. Trailer manufacturing is a job best left to Haulmark and thus I 'paid someone else' to build my trailer.

[Ron Earp]

You'll want to use a torque plate and any decent machine shop can make you one. Steel piece thick enough to not distort, bored on your bore spacing and diameter, with holes for head bolts.

We farm our machine work out, assemble the motors, and then do the install. While not a super racey setup it doesn't cost a fortune and thus far has worked pretty well. Jeff's motor is pretty decent and will be stronger next go around, and I hope my Z motor turns out pretty good.

R

[Sandro]

how to determine your CR

http://www.valvoline.com/carcare/articlevi...g=pht20020701cr

this makes it easy to mess around with how much you need to take off to get where you want to be.

http://www.csgnetwork.com/compcalc.html

[tom91ita]

scca actually has a spreadsheet for CR:

http://www.scca.com/_FileLibrary/File/compratio.xls

tom

[RSTPerformance]

Thanks for all the reply's...

So do we have an ordered list of things to do for the best "bang for the buck" in order of most needed to least needed to get to a 100% build?

1- Pay someone if you don't have the right tools (possibly assemble yourself though)
2- New bearings and rings
3- Clean up the valve seats
4- Deck the head
5- Increase piston size
6- Port match
7- Balancing
8- New parts (what difference does it make beside prevent failure?)
9- Start the expensive stuff, such as balancing as well as flow testing?
10- Add the turbo or custom ecu

Thanks for the additional comments, please fill in or move around the ist for me!!!

[Rabbit07]

Thanks for all the reply's...

So do we have an ordered list of things to do for the best "bang for the buck" in order of most needed to least needed to get to a 100% build?

1- Pay someone if you don't have the right tools (possibly assemble yourself though)
2- New bearings and rings
3- Clean up the valve seats
4- Deck the head
5- Increase piston size
6- Port match
7- Balancing
8- New parts (what difference does it make beside prevent failure?)
9- Start the expensive stuff, such as balancing as well as flow testing?
10- Add the turbo or custom ecu

Thanks for the additional comments, please fill in or move around the ist for me!!!
[/b]

Don't Forget New Valve Springs! I also like new oil pumps and pick-up screens. Don't forget a good windage tray, my understanding is the Volvos get about 2 HP from oil control!

Be sure to properly break in the engine, One good intial heat cycle for the rings and springs before you put any load on it is also a good idea.

[gran racing]

What type of gains can typically be seen by adding a crank scraper?