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Richard Jemison
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7,106 Posts
Discussion Starter #281
Piston to liner question

In a message dated 3/29/2019 6:08:52 PM Central Standard Time, [email protected] writes:Hi Richard,  Mike Sabin here.  The cams are great, no questions there.  I would appreciate your thoughts on piston to liner clearance.  I have the Classic Alfa forged pistons made by Cosworth.  I asked them what the clearance should be and they said to just bore the liners to 84.5 and I’d be good.  That sounded kinda goofy to me but what do I know.  The pistons are 3.306 inches and 84.5mm is 3.326.  That is twenty which would be .010 thousandths piston to wall.  That seems pretty loose for a street motor.  What do you think?Thank you I really appreciate your help.MikeMichael Sabin
From: [email protected]: rmsabinsr/Cc: [email protected]
Sent: 3/30/2019 9:47:04 AM Central Standard TimeSubject: Re: piston to liner

I`m glad you ask!  That`s a poor response from CA or Cosworth who ever suggested that.
First, piston clearance in the liners should never exceed .004.-.005" and that is a bit looser than most road race engines are built. If the engine was being built for long runs at max RPMs where serious heat growth is expected, in excess of typical Road Race use (Turbo/supercharged/Bonneville and such), much less street driving, then clearances must be tighter. to control piston movement that reduces ring seal.

Cast pistons (like stock) should be happy at about .0025". But Forged pistons an a street motor set at .003" should have a long life. (that`s where I would clearance them) The Ross pistons (Forged Racing pistons) in the new race motor are clearanced at .0035".The measurement of the piston that should be used is the diameter of the skirt below the piston pin half way to the skirt bottom. (The piston top is generally as much as .020 smaller due to heat absorption growth.)Be sure the upper 2 rings are gapped correctly. Typically .004 per inch of bore for both top & 2nd ring. New 2nd ring designs are set with more gap than old design 2nd rings.
Rj
 

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Richard Jemison
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7,106 Posts
Discussion Starter #282
Re; Flywheel lightening

Got the question that is answered below, but with the thread that has been active on the on the Bb while I was away, clarification on the subject might help.

On non counterweighted flywheels, done correctly, and accurately, all the "casting surfaces" unfinished by machining when built will be machined to leave the entire piece a machined product. Commonly a accurately machined part will require only minor to no metal removal to achieve far better balance than found on the factory part.
Key to achieving "true" surfacing is the initial setup so the part is "true to the crank shaft center" when fitted. I use a the last main bearing and crank flange as a fixture in the lathe to insure that happens.

On Counter-weighted flywheels for the V6 applications re-balancing after lightening is critical as the large weight reduction of the flywheels require adjustment of the amount of "out of balance" on the crank due to the total weight of the unit. I made fixtures for the balancer to use to achieve the correct weights for the 3.0 liter and for the 2.5 liter engines.

Below is regarding the flywheel for a 1300/1600 application.


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In a message dated 7/14/2019 3:02:07 PM Central Standard Time,
Richard,

Good afternoon.

Do you have any lightened 1600 flywheels available?

Thank you and please advise.

Chip
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Sorry, I do not. I can lighten one if provided. However, I suggest using a 1750 core as a 105 tooth ring gear(1300/1600 fitment) will fit correctly on it, and the larger clutch design (larger disk and stronger pressure plate) will provide better torque capacity. Centerline sells an adapter to use the late type release bearing with the mechanical clutch release mechanism.

(to be clear the 110 tooth ring gear of a 1750 is the same ID but the OD is too large to fit in a 1300/1600 mech. release bell housing)

Typically lightening , re-balancing and return shipping is $340.00.
 

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Richard Jemison
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7,106 Posts
Discussion Starter #283
Clutch bleeding Problem??

This is from a post on my "Coupe" this am. Found a potential bleeding problem source...

In the coupe the tilton petal set up uses a 3/4"(19mm) master cylinder. The 105/115/119 (V6 cars) slaves are all one inch (24.5mm) bores. All of the ones above are interchangeable. Only the 116 Alfetta is a different design.

So I was getting insufficient movement at the slave (about 3/8") due to the smaller displacement MC going to the larger slave. All the adjusting on the MC`s push rod to move the piston so it stopped just at the "bleed back" hole helped but didn`t resolve the lack of full release which is death for the syncros. As well it required a full petal movement to the floor to even get that. This is a race car and clutch release should happen at the top of the petal movement to allow faster shifts and positive clutch disk release.

I decided to sleeve the factory slave reducing it to a 7/8" bore. On removing the factory slave for modification I noticed a design/build problem with the bleeder opening into the bore of the slaves. I looked at both the factory aluminum and steel ones, both had the opening to the bleeder about 3/32" below the top of the cylinder`s bore. Since the slaves are mounted horizontally this would allow a small amount of air to be trapped after bleeding.

To correct this it can be improved by drilling a relief exposing the hole to the top edge of the bore. I used a 1/4" drill so the drill`s tapered entry created a path from the top to the existing hole, just to see if it helped, and it did other than still not enough movement...

I took an aluminum slave and bored it a bit and sleeved it to 7/8 inch bore. The piston from an aftermarket 7/8" slave was fitted, and put on the trans. This allowed the full release point to be about 3" from the floor. Movement of the arm at the outer end was now 5/8" (rather than 3/8 inch), which is about 1/4" at the clutch fingers...

Clutch problem solved.
FYI the clutch in this car is a Quartermaster 7.25" single disk race unit.
 

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Richard Jemison
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7,106 Posts
Discussion Starter #284
Suspension setup ideas

There`s seems to be lots of interest in suspension setups recently.
Here`s some thoughts:

Spring Rate: Because of the angle of the spring there is a reduction in the actual "spring rate" which has to be considered. That "rate" is used in the equation to determine the actual "wheel rate" which is a factor of the center of the springs position relative to the full distance between the inner bushing on the lower arm and the center of the tire`s tread. Commonly I`ve found that most 105/115 Real Race cars are using 1200 inlb to 1300 inlb springs. to control listing.

Spring rate needed will be different if the factory spindle is dropped. Typically a 1" drop will fit in any 14" or 15" wheel, and the resulting angle of the lower arm closer to level and the increase of the angle of the upper arm and the point of their angles crossing will be significantly higher than stock. Lowering the car with only shorter springs has the opposite affect. Roll centers below ground.

My 105 Duetto has 1" drop spindles, but another mod, the lengthened lower ball joint (.5" each side) to widen track, reduces the 1300 inlb spring`s effective wheel rate.

My "Coupe" springs are 1150 inlb, but the effective "spindle drop" is is 2.5" (The pivot center difference between stock and the
underslung Chrysler ball joints) mounted under a stock spindle after reaming correct size taper from the bottom of the upright. As well those Chrysler BJs are extended 1" longer than stock Alfa BJs,
and using 8' wide rims with massive offset (to the inside) and 215 section tires my wheel package still fits in the unmodified fenders.
The big rise of the roll center with the weaker springs still leave the car very flat cornering.

Caster: the more negative caster you can put in it within the limits of the sides of the chassis box where the upper arm exits, will result in more negative camber gain on the outside wheel and positive gain on the inside wheel. This occurs regardless of other settings.

Camber; there is no specific perfect starting point. It is tire dependent (bias or radial) and suspension mod dependant. Start at
negative 2.5 degrees and chalk the sidewalls to see "rollover" which should be limited to the tread`s depth on the sidewall.

Ackerman; The steering arms can be bent to increase the inside wheels angle of attack relative to the outside wheels, which assist pulling the nose into a turn.

Rear Suspension: Loosing the factory Trunion is step one. A properly built Panhard system with an upper arm in the correct angle to negate both squat on acceleration, and lift under braking is the best and easiest locating system. Watts is nice but complicated to fabricate and space is limited for it.

De-cambering the axle tubes is quite easy. On the top center of the tubes weld a bead 1/4" wide from bell to the outer flange. This repeatedly has pulled a .5 degree negative in both sides. Jim Steck does a prettier method by heating that line in "spots" till red hot then quinching the spot. Seems it has to take too long to finish for me...
 

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Richard Jemison
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7,106 Posts
Discussion Starter #285
Hydrolic clutch release issues

This was posted on another thread, but his was a mechanical clutch release system.

Having a clutch that releases close to the top is very important in a race car scenario where full clutch release is critical to syncro life, and it happening quickly is key to faster shifting without syncro damage.

I tried adjusting the clutch rod to get the maximum clutch disengagement as possible. I virtually have all the rod linkage backlash removed. At the pedal I have the clutch starting to engage about 1" off the floor? I have about another 1" of pedal travel from rest to where I feel the T.O. bearing pressure. Am I adjusting the linkage correct. Should I remove more play?
I had the same issues with my coupe. Jim Steck gave me some advice that helped but not enough in my application

The issue exist primarily due to the clutch master cylinder (Stock) being 5/8" diameter cylinder and the stock slave being 1". (for a soft petal)

Jim suggested that the MC adjusting rod can be lengthened until it just allows the fluid to gravity bleed out the slave cylinders bleed screw. That will make a big improvement as it can be extended several turns out before closing the bleed back hole under the reservoir.

Additionally bleeding the system takes a bit of fluid to get the air out. When you think it`s done with pressure on the petal crack the connection up at the master cyl. IE burp it. You will feel a difference... If you can pump the petal a few times and get full release, but get drag with a single push you likely have air still in the line. Burp the top!

Lastly the factory push rods are too short. and the Piston in it needs more room to move. I pulled my push rod out by forcing the leaver forward to make the piston retract to its full range of travel and helded the rod in that position. Then returned the lever to it`s position in contact with the TO bearing. Noting the clearance between the pushed in rod`s rounded end and the socket in the lever.
I pulled the push rod out of the rubber bellows and added 1/2 inch to it`s length. All of the above AND sleeving the slave to 7/8" diameter got me at least 2.5" off the floor for full release
Also. I left the clutch petal pressed to the floor overnight. The next morning, with it still on the floor I blead the connection to the MC. Got a bit more air out! Now full release is much higher.
 

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Hi Richard !

I would like to have your opinion about the 44/45 DCOE, you knows ? Theses are good carburetors ?
Your cams must be installed with a graduated disk or there are "marker" ?

Have a nice day !
 

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Richard Jemison
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7,106 Posts
Discussion Starter #287
Carbs / Cams

Well there are no 44 DCOEs but 45 DCOEs are very appropriate for
1750 & 2 liter Alfas. 40 DCOEs are best suited for the smaller engines if performance is the goal.

I provide set-up info for my cams and commonly you can do that without a degree wheel using the timing templates down loadable from Centerlinealfa.com.
 

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Thank you for your answers !

hunttheshunt is right, I wanted to say "40 DCOE 44/45 series", it gives me great to know the 44/45 are good for modded engines !

With the timing templates it's not necessary to pull up the engine ?
 

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Richard Jemison
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7,106 Posts
Discussion Starter #290
Timing cams.

Correct, the cams can be timed with only the cam cover removed and the timing chain opened if new cams are being installed. But even that isn`t necessary as you can remove the cams with the tensioner pushed back to the head surface, and raising the rear of the cams to remove them from under the chain. Do the intake first..
 

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Richard Jemison
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Discussion Starter #291
Fueling issues and air horns

From my post on another thread:

One day last week I was on the phone with Russ Jones while he had his GTA that has the very short stroke 1300 cc engine with the German built narrow angle head on the dyno.

His AFRs were rich at the lower RPMs went into the 12s about 5500 RPMs but at 7000 the AFRs went totally lean (14s).

We tried different jet pairings but with all changes the AFRs were similar with 7000 being the end to proper AFRs and abruptly going lean.

The engine was fitted with long curved Airhorns with screen covers, and no cold air box.

I told him I thought the airhorns were the issue, and suggested removing them. He was a bit reluctant as "they all ran airhorns back in the day". He was going to call Pierce Manifolds for different air correctors and I suggested that he question them on this issue.

Well he called Jim who also suggested removing the airhorns as he thought that reversion of fuel/air mixture at lower RPM was being contained in the long air horns causing richness and not so at high RPM. He mentioned lengthening the runner length after the butterflies is more likely to improve the power curve.

Russ removed the airhorns and with the same jetting the mixtures were greatly improved & perfect from 5K to 8K & beyond. (little short stroke mouse motor requires high RPM to make any power. The cams were "Unknown" that came with the new head)

When I built my larger air box I used some 2.5 inch long 55mm airhorns (to match the flared opening to the 50 DCO carbs.
I pulled them off and in the lathe cut the length down to 1". I measured my "choke tubes" as Ed ask me what size they were while he was here this past weekend. They are 42mm modified into a correct airfoil cross section. As well the ports are raised and large.

I should have listened to my own advice re: airhorns, but thought the added length with big carbs and porting might help.
I wanted to test the short 1" ones before totally removing them.

Both Ed`s engine and Hayes Flynn`s (229 HP) engine were dyno`d by Jim with only modified factory air boxes opened to 50mm to match the flared openings to 45 DCOEs.

Something to think about...
 

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Reversion!! Well, duuhh. Of course that makes good sense. But what to use as a spacer downstream of the butterfly? Could you double up using first an oem style rubber mount combined with an AH aluminum carb mount?
 

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Jim wanted to put 2" spacer blocks between the manifold and the carb adapters on my car but I declined because I thought that there would be insufficient room to get at the plenum fasteners. I probably lost out on some torque. I have since thought that I should have had some made out of plastic to insulate the Webers a bit from engine heat.

My motor should have less reversion than some similar ones because of the small diameter intakes which increase the speed of the charge. It would be even better with longer intakes as that would increase the momentum of the charge column and so less of it would be reversed.
 

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We used pipemax and a few other programs to help determine intake and exhaust lengths when we were competing in Engine Masters Challenge. We usually could get within 1% of the computed power numbers. We had significant intake reversion on one of our early velocity stack arrangements. We made some cam alterations in order to cure it.

Anyhow, here is the inexpensive program, you can scroll down to see the inputs and outputs. There is a complete table based on which harmonic to use and the resulting lengths of intake and exhaust tracks.


www.maxracesoftwares.com ? View topic - PipeMax Professional Engine and Header Design - Updates
 

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Richard Jemison
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7,106 Posts
Discussion Starter #295
Problems with aftermarket syncro parts

From one of my post on another thread....

NOTE!:
The response from the maker of synchro rings and dog teeth was as follows:

The ones we make fit '68-'94 Trans. (not 164). These use moly coated synchro rings.

3.008" (76.4 mm) installed major diameter is the spec. we use for new dog rings with new synchros. +/- .002" is probably OK. Don't have any info on wear limits. These synchros are very similar to early 911 but they are wider.
Hope this helps.
Problems with aftermarket syncros is the inability to engage gears.
Tightness between the dog assembly and the snap ring interfere with compression. As well the aftermarket syncro bands are thicker at the crown of the bands making the compression for the slider to "ride" over the crown and engage the teeth of the dog assembly impossible.
Spruell`s "suggestion" to grind away the excess was just another attempt to shrug off his responsibility for selling bad parts.

I`ll not ever again use aftermarket syncro parts on any transmission I build.

Now for your information. Long has lived the rumor that non moly (pre 1963) syncros are incompatible with modern "Moly type components.
In my race boxes, both those of Transmissions and Transaxles, I have used late Moly type dog assemblies and Slider rings (both small ID 105/115 and larger ID 116/119 type which are better(harder) alloy, fitted with the harder alloy "non-moly" syncro bands.

This pairing gives much longer service than the fast wearing "Moly" bands.

Be aware that the "brake bands" under the syncro bands are not all the same width. If installing the snap rings over the aftermarket syncros is "difficult to impossible" measure both the width of the brake bands as well as their length which can make compression of the wider & thicker aftermarket syncros an issue.

The length of the bands used when "converting" the 1st gear 'one directional" syncro is critical. Do not use any part of it's internal assembly. That single brake band is too short. Use only the "lock, bands, and engagement slider" of 2nd through 5th gear assemblies.
 

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The butter with the best lubricating properties is the one that Marlon Brando used in "Last Tango in Paris" :surprise:
 
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