achalmersman stroker 4.1 build (291 block)

[achalmersman]

Well I figured it may be fun to document my 4.1 build in a thread. I have chosen to build a 291 block that I acquired a couple of years ago. Just got the block back from the machine shop so now I'm going to start thinking about the rotating assembly.

Machine work so far was done by Bill Coleman in Lithicum Maryland. Nice guy. I have him the block and asked him to check it over, final hone to 4" (was at 3.995), fit, bore and hone 2 new billet center caps with ARP studs, counter bore head bolt holes, drill and tap turbo return drain, clean up valley casting flash, etc. Found deck wasn't square so after squaring deck I finished with a deck height of 9.519". He installed my TA dual groove coated cam bearings and brass freeze plugs. The billet center caps came from David Husek

So next I need to figure out for sure what pistons, crank, and rods I want. Probably going to be a stroker 4340 crank and molnar rods from David Husek. I just haven't decided if I want to do a long rod combo. I probably will and welcome any tech discussion in this thread. I will probably be shooting for 9.5:1 compression

I have a set of aluminum CNC ported TA SE heads from Nick Micale that will reside on top of this engine as well as an intake ported to match by Nick. I also have a TA blueprinted front cover with oil pump assy from Nick.

Cam and turbo will be speced and bought from Bison. Don't have either yet. I doubt I will reuse my PTE Gen2 6266 S cover unless I run out of funds and decide to see how far I can push it as well as collect good data. I plan to log all important data such as drive pressure, intercooler pressure drop, etc.

Fuel system will be a double pumper racetronix 680lph dual feeding champion rails with external regulator. Pump kit is the new design hangar with Quick Disconnect fittings and -6 and -8 Teflon coated lines (made by Don Cruz). All purchased from Don Cruz

Transmission was built a year and a half ago from a DIY kit and instruction by David Husek by myself and help from my father. The build was only intended to support mid 10s so we'll see how she does. It is David's standard build kit and the direct clutch pack is not dual fed. Much of my work on my car is made easier by use of my father's shop and help. He was a GM tech for 25 years and worked on these cars under warranty when they were new. Aftermarket and modifications are not his specialty but his help is still appreciated.

Again I encourage any tech related discussion. Next step I believe is going to be getting a rotating assembly and mocking up and clearancing where needed.

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[Ttype6]

I did this same thing. My deck height ended up at 9.518". You need to determine what your combustion chamber volumes are. You'll want to use a .027" thick Cometic head gasket with Hylomar spray on both sides of the 3 layers. Once you determine your chamber volumes,call Dave Husek for the pistons and rods and crankshaft. The rods will likely need some material removed from the sides of the big ends to achieve the proper side clearance. They will also need one side of the big ends machined to eliminate cam to rod interference. Weber Racing is a good place to have the rods machined,the balancer modified, and the rotating assembly balanced. They use a specific procedure for the cam interference machining.

 

[achalmersman]

I'm hoping with molnar rods and a small base circle cam the oil galley and just a little bit of a rod bolt is all that needs touched? I see Weber sells clearancing for the Scat rods but don't see the option for Molars. Was hoping that meant the molnar already fit better. I have a neighbor that has a small machine shop and will be able to mill the side clearance of my rods as needed.

I am planning to measure chamber volume myself using a 60cc syringe from work and a sheet of plexiglass with Crisco and a small hole drilled in it. Anybody tried this before? Lol

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[seedling]

Following


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[bison]

Check your new rods big ends. I had an oversize one on the last engine. Make sure all touching up of the crank is done before installing


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[achalmersman]

Check your new rods big ends. I had an oversize one on the last engine. Make sure all touching up of the crank is done before installing


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Will do thanks. I am still in the market for a nice dial bore gauge with 0.0001" resolution. Would really like to find a sunnen. I have a nice set of mics. This is going to be a must have.

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[Ttype6]

I am planning to measure chamber volume myself using a 60cc syringe from work and a sheet of plexiglass with Crisco and a small hole drilled in it. Anybody tried this before? Lol

.

I tried the syringe method and found that the plunger doesn't move freely. Too sticky. You really need a burette.

http://www.ebay.com/itm/Borosilicat...834116?hash=item35fba001c4:g:heEAAOxyCGNTPHMH

I used a piece of plexi and silicone grease.

I see Weber sells clearancing for the Scat rods but don't see the option for Molars. Was hoping that meant the molnar already fit better.

They did my Molnar rods. Call them and send them out. This needs to be done and they do such a nice job.

 

[achalmersman]

I tried the syringe method and found that the plunger doesn't move freely. Too sticky. You really need a burette

Really? I have a medication syringe and I'm able to really deliver fluid 1 drop at a time. Of it doesn't work I'll buy a burette. Thanks for all advice!


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[Ttype6]

I am still in the market for a nice dial bore gauge with 0.0001" resolution.

I have a bore gauge from Central tools and I see that it is still offered on ebay for much more than I payed for it. It's their Storm 3D301 gauge. Here is a used one.

http://www.ebay.com/itm/Storm-Brand...665528?hash=item360ecec3b8:g:ei0AAOSw4GVYVBom

I wouldn't hesitate to buy this one.

Here is the exact same gauge marketed under a different name. I mean it is the exact same one in every way.

http://www.ebay.com/itm/Igaging-Eng...741994?hash=item20f06eba6a:g:jLQAAOSwMKpUZ4eY

If you search for bore gauges,you will find many different brands at many different prices and will easily be able to see that they are all the same as the two I've shown you. Eastwood sells the Storm 3D301 for $132.07 and you can find the same gauge on ebay under different names for $175.00 plus.
I used this gauge to determine the diameter that I needed my main bore to be. I asked my machinist for a specific diameter to one ten thousandths of an inch and when I measured his work,I found it to be exactly what I asked for to the ten thousandths of an inch. 2.6873"

 

[Ttype6]

Really? I have a medication syringe and I'm able to really deliver fluid 1 drop at a time. Of it doesn't work I'll buy a burette. Thanks for all advice!


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The syringe I used was for veterinary use. Looking back,I think I was using water when I tried it. Perhaps alcohol would have worked smoother. I did use isopropyl in the burette. The burette has .2 cc graduations and I was able to equalize all combustion chamber volumes at exactly 50.2cc.

 

[earlbrown]

Wow. I've never heard of combustion chambers that large before.



9.5:1 is easily doable with a stroker crank and a big bore. As long as you don't get stupid big with the cam, it'll be a screamer.


This is the bore gauge set I use at home and it's dead nuts with the Mitutoyo and Starrett units we have at the machine shop.
http://www.shars.com/products/measuring/bore-gages/2-6-dial-bore-gauge-1-1
If you look at my 'how to' post on modifying rods this same set is there with the same mics you have.

Looks like they're on sale too.


when it comes to CCing the heads, don't drill a hole. Just smear a thing layer of grease on the head and have it tilted a little. Leave the glass where it doesn't quite cover the entire combustion chamber and start letting the water run it. As it fills up, slide the glass over.

It's harder to describe in words, but after one pass, you'll see what I mean.


It looks like you already have cam bearings installed..... Did you grove the block at the front cam journal to send oil to the DS lifter channel?

 

[achalmersman]

This is the bore gauge set I use at home and it's dead nuts with the Mitutoyo and Starrett units we have at the machine shop.
http://www.shars.com/products/measuring/bore-gages/2-6-dial-bore-gauge-1-1
If you look at my 'how to' post on modifying rods this same set is there with the same mics you have.

It looks like you already have cam bearings installed..... Did you grove the block at the front cam journal to send oil to the DS lifter channel?

I took your advise and bought a Shars kit last night. This one actually http://www.shars.com/1-4-6-dial-bore-gage-0001

No I didn't grove the block but I used TAs coated dual grove bearings and they are installed correctly. There are 2 groves on the back side of the cam bearings that does the same thing right?

PS. Keep an eye open regarding pistons. Once I know what length rod I'm using. Probably 6.350" unless somebody like Bison tells me I would be better off with a shorter rod for velocity / cylinder fill.


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[Ttype6]

Leave the glass where it doesn't quite cover the entire combustion chamber and start letting the water run in.

Water has too much surface tension. Alcohol is much better for this.

 

[achalmersman]

Water has too much surface tension. Alcohol is much better for this.

Makes sense. I'll give alcohol a try. May do this today if I have time

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[Nick Micale]

Once I know what length rod I'm using. Probably 6.350" unless somebody like Bison tells me I would be better off with a shorter rod for velocity / cylinder fill..........

Over many years I have researched and discussed "long vs. short" rod in a turbo Buick V-6 as it pertains to performance, and a couple expert engine builders have told me there is no advantage over either one.

Kenny D. has published his findings in a national magazine that even high HP Buick V-6 engines long vs. short rods make no noticeable difference in HP.

In a big displacement V-8 NA race engine application at 7-9000 RPM there can be 30-40 HP improvement according to other builders.

Most all our engine builds are stock length rods as we like to keep the pin as low as possible in the piston, especially in a stroker crank application.

 

[achalmersman]

Most all our engine builds are stock length rods as we like to keep the pin as low as possible in the piston, especially in a stroker crank application.

I've kind of gathered performance is negligible but I figured the less side loading of the cylinder walls was worth a consideration esspecially if there was any chance of power advantage. If I already had stock length rods the choice would be easy I'd use them. I don't have any rods so I can use whatever I want. I do want to pay attention to pin height which you bring light too. Will the pin fall below the oil ring land with stock length and into the land with 6.350" ? I guess it will come down to pin placement vs side loads (which I know isn't increased greatly)



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[Ttype6]

Makes sense. I'll give alcohol a try. May do this today if I have time

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You'll quickly figure out what will and won't work. I did drill a hole in the plexi and positioned it at the edge of the combustion chamber with the head tilted.

 

[Ttype6]

Will the pin fall below the oil ring land with stock length and into the land with 6.350" ?

Correct. I used the 6.350" Molnar rods. If you do everything wrong (according to the experts),you are going to have an engine that will put such a big smile on your face. Everything will happen sooner and bigger. I am excited for you and eager for you to experience what you're going to experience. There will be nothing useful about first gear on the street and second gear will be difficult,but you can burn that bridge when you get there. After all,Rome wasn't burned in a day.

 

[achalmersman]

This post here combined with the advantage of not having the pin in the oil ring land may lead me to go stock length rod. This combo is most likely going to stay 3 bolt so cylinder fill with regards to high pressure ratio should be considered.

[quote uid=24950 name="charlief1" post=3518181]The same effect as EGR Brian. You will get a dirty mix of sorts and if you're running that big a cam then hypothetically, it's a race car, not a street car. What type of ratio are you wanting to plug in there?[/QUOTE]<br />I know what happens I'm wondering if a longer rod will further exasperate the problem because of added dwell. Every cam we've analyzed had some overlap near tdc. There's no way around it. Close the ex valve sooner. Does a longer rod hurt the engines efficiency with higher exhaust pressure and longer dwell at tdc? Theoretically it should because the cylinder can't begin to fill till the pressure in the intake is higher than the pressure in the clearance volume. But it may also help if the CR is high enough and the ex valve closes nearer to tdc The lowest pressure you can have at tdc is the lower of the two pressures. High pressure flows toward low. Most everyone is running higher ex pressure and usually at radios of 1.3:1 or higher. Speeding the piston up near tdc faster theoretically would help because the pressure in the clearance volume would equalize at less crankshaft rotation. We will probably never know for sure but theoretically speaking a shorter rod with a higher CR should increase cylinder fill with higher drive pressures because of the cylinder pressure relative to crankshaft position will equalize sooner. The ex closing relative to crank degrees is very important to look at in a turbo engine. We've definitely seen positive effects by closing the ex valve at the proper time. <br /><br /><br />Sent from my iPhone using Tapatalk

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[achalmersman]

Looks like I am right around 50cc chamber volume as a rough measurement. I need to verify my syringe with a graduated cylinder at work tomorrow to make sure I am actually starting with 60cc like I think I am. I also don't have valvesprings installed so they are seeping a VERY tiny amount. I suppose I could try a very thin coat of Crisco on the backside of the valve being careful not to allow the valve to extend into the chamber.

And yes....my wife looked thrilled when I brought a cylinder head into the kitchen and laid it on her countertop lmao

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