Author Topic: Mid- Engine Modified Sports  (Read 784792 times)

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Offline WOODY@DDLLC

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Re: Mid- Engine Modified Sports
« Reply #1635 on: April 18, 2019, 08:19:34 AM »
Youse guys are young enough to remember Pogo!  :x

"We have met the enemy and he is us!"  :-o :-D
"We are surrounded by insurmountable opportunities!"  :cheers:


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Offline Peter Jack

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Re: Mid- Engine Modified Sports
« Reply #1636 on: April 18, 2019, 08:47:28 AM »
Even before being trial assembled all cast and machined parts should be thoroughly inspected, deburred and cleaned. Very few parts are ever received ready to be installed if an engine is expected to be reliable and competitive.

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Offline ggl205

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Re: Mid- Engine Modified Sports
« Reply #1637 on: April 18, 2019, 09:15:55 AM »
This is one of those many small things FB was talking about when referring to building engines like a pro. It comes down to experience and knowledge, both of which Neil has more of. But it is a PITB getting there.

John

Offline fordboy628

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Re: Mid- Engine Modified Sports
« Reply #1638 on: April 18, 2019, 09:24:29 AM »
Neil,

The oldtime adage from long ago stated, "If it is not on time or doesn't fit, must be racecar parts..." still applies today. 8-) The finalization and detailed inspection of fit and finish is on the consumer, even if the parts are highly touted CNC super duper stuff. Important things such as valve seat concentricity are high on the hit parade for needing a detailed inspection to maintain any kind of QC. As I understand it you worked in aerospace stuff. The lack of QC is somewhat common in most (but not all) aftermarket parts. :roll: Buyer beware good old caveat emptor, my friend. :wink:

Looking at the bright side, at least you found the problem and it is easy to fix. :-D

Continue being careful and it will always pay off.

Best of Luck! :cheers:

Regards,
HB2 :-)

x 2!!   or x 3!!!

Neil,

I don't want to carp on this, BUT, there is no detail too small to check . . . . .

And it is NOT that the guys producing these parts are doing "shoddy" work.    The castings are especially complicated.      OR, your tappet bore in your block may be "out of position" by some amount that makes a difference.   Which is it?    The only guy who can say for sure is:  the guy who assembles it.

Part of my "sign off signature" used to be the phrase:   "Does checking all the little details matter?    I dunno, but I think you should ask the guy who finished second . . . . ."

I removed it from the bottom of my posts because I got tired of "folks" messaging me telling me I was wrong.   And then "they" wanted to argue with me about it . . . . . .  ( not going to "waste" my time on those "folks" . . . )

But, because I see this stuff ALL THE TIME, I'll provide you with a couple of examples:

1/
Just yesterday, a long time friend and client brings me a Cosworth BD head recently redone by a guy experienced in all things Cosworth.    All that was to be done was to check out a new set of valve springs, check the installed height, shim the springs and assemble the valves, springs, etc.    When checking, I noticed that the distance from the bottom of the retainers to the top of the seals seemed small.  So I checked a "little detail".    YUP, negative (-.040"  1mm) clearance between the bottom of the retainer and the top of the seal!!    This is not a cam grind change situation and the cam lift is .41" gross and ~ .40" net.    Further checking revealed early type guides installed in a later type head casting, so the guide top is .10" higher than specification.

When the client contacted the person (shop) that performed the work, his reply was: "No problem, just run it."   So, I then asked the client to bring me his dry sump pan.    In the trough, were 8 of the 16 valve seal collar springs . . . . .

2/
A few weeks ago, a client from a couple of states away dropped off a Cosworth BDH to be check over and then dyno tested.   This is a late 70's spec engine, now for vintage racing.    Replacement value ~ 35K to 40K . . . .
Needed to set the Lucas MFI, check a couple of things out, look it over, etc.   Having a problem setting cam belt tension . . . . . .

14 shop hours later:   (and these are just the "high points" . . . . .)

A/   Cams and tappets assembled with only "a smear" of assembly grease, no oil.    Oil flow to the top end of this engine is "restricted" . . . . . . .
2/   Wrong length or missing mounting bolts for the FI metering unit.    This engine is a "shaker".   Correct bolt length is critical to retention.
d/   Cam belt, as sold by a "Cosworth specialist" was a regular thickness (XL) belt.  Not thick enough to obtain correct belt tension adjustment . . . . .   Belt needs to be a XLH or better yet a special XLHH.     Inadequate belt tension on these engines can be a cause of belts "jumping" teeth and causing cam timing problems which result in a engine full of bent valves . . . . . .

and on, and on, etc . . . . .      When everything was corrected though, engine ran well on the dyno and achieved target bhp & tq.     Proving, to me at least, that: "little details matter".

And this is not just Cosworths that I see this on.    The shop I am affiliated with is drag centric.    Some "recent" issues:

A/   BBC drag engine comes in for dyno test.    Won't roll over smoothly, no dyno.    Valves hitting pistons as engine is turned by hand.
2/   SB Pontiac comes in for dyno test.     Rolls over OK initially.    When filling with water, water rains out between the heads & block.    Customer customer wants to add "block seal".    I suggest rolling engine again.  Won't turn by hand.  Removing spark plugs results in jets of water shot out of several spark plug holes.    Uh, NO dyno . . . . .
d/   SB Ford for dyno test.   Disappointing bhp.     Cam timing check reveals cam 8 degrees advanced from cam grinder's spec.    Owner builder states: "he lined up the marks", why is there a problem?"

I could go on until you puke, but I'll spare everyone.     I think everyone will agree that some of these examples are not "little details" . . . .

Almost 50 years ago, my first mentor opined the a really good engine builder is just: "A perfectionist looking for a place to happen."     It was sage advice then, as it remains today . . . . .

Neil, do not despair.    Checking all the "little details" is ALWAYS the right thing to do.   It can be a PITA, though.

 :cheers:  :cheers:  :cheers:
Fordboy
« Last Edit: April 18, 2019, 09:32:19 AM by fordboy628 »
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Offline fordboy628

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Re: Mid- Engine Modified Sports
« Reply #1639 on: April 18, 2019, 09:35:21 AM »

Youse guys are young enough to remember Pogo!  :x

"We have met the enemy and he is us!"  :-o :-D
"We are surrounded by insurmountable opportunities!"  :cheers:


Yes, I recall.     I thought at the time that it was "profoundly correct"

 :cheers:
M
Science, NOT Magic . . . .

I used to be a people person.  But people changed that relationship.

"There is nothing permanent except change."    Heraclitus

"Only two things are infinite, the universe and human stupidity, and I'm not sure about the former."     Albert Einstein

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1640 on: April 18, 2019, 11:50:08 AM »
Youse guys are young enough to remember Pogo!  :x

"We have met the enemy and he is us!"  :-o :-D
"We are surrounded by insurmountable opportunities!"  :cheers:




Yes, I remember Pogo. My best recollection of that strip was their Christmas carol "Deck us all with Boston Charlie. Fa La La La La, alley- gay- roo..."

I don't remember that last one but it reminded me of a quote by a US Marine general, "Retreat hell! We're just attacking in another direction!"


Seriously, thanks for the advice and encouragement, fellows. As you have all advised, I'll check everything.

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1641 on: April 18, 2019, 09:21:50 PM »
This afternoon I ground about 10 to 15 thousandths off the edge of the head pushrod hole and cleaned the head carefully. Now there is no interference between the head casting and the #6 E pushrod.

I found that CRC Brake Cleaner works very well for removing K & W Copper Coat so cleaning up the copper head gasket was not difficult at all. Denatured alcohol works too but the spray can is more convenient. I re-applied the gasket sealer, this time with a cheapo artist's paint brush instead of the dauber that comes in the lid of the Copper Coat can. The small brush does a much neater job. Now both heads are torqued to 60 ft lbs. Tomorrow I'll pull them up to 70 ft lbs.
Regards, Neil  Tucson, AZ

Offline Stan Back

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Re: Mid- Engine Modified Sports
« Reply #1642 on: April 18, 2019, 09:49:32 PM »
I quit cleaning paint brushes.  Harbor Freight has 4 assorted in a package for $1.49 (or so).  Use 'em, throw them away.  Lacquer thinner will break the bank nowadays.
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Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1643 on: April 19, 2019, 07:10:11 PM »
The rockers were cleaned, installed, and set to 0.026" intake and 0.028" exhaust per Crower specs. The crank rotates as it should- no clunks, or squeals.  :-) I checked the inside of the timing gear cover and it showed some evidence of the cam gear lightly scraping the inside of the cover. I wonder if it was supposed to have a gasket? I didn't get one when I bought it so I made one and sealed the cover on with the homemade gasket and Ultra Black RTV.

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline Dynoroom

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Re: Mid- Engine Modified Sports
« Reply #1644 on: April 19, 2019, 07:48:26 PM »
The rockers were cleaned, installed, and set to 0.026" intake and 0.028" exhaust per Crower specs. The crank rotates as it should- no clunks, or squeals.  :-) I checked the inside of the timing gear cover and it showed some evidence of the cam gear lightly scraping the inside of the cover. I wonder if it was supposed to have a gasket? I didn't get one when I bought it so I made one and sealed the cover on with the homemade gasket and Ultra Black RTV.

Regards, Neil  Tucson, AZ

Neil, you might want to revisit the valve lash. I'm betting that's .026 / .028 HOT.
You should probably tighten them up to .012 / .014 cold being that you have an aluminum block & heads. The lash will grow about that much when warm. When the engine is warmed up and ready recheck the lash & set to the required hot lash if needed. Then recheck when cold to know where the actual cold setting should be for future reference.
Michael LeFevers
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Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1645 on: April 19, 2019, 07:56:57 PM »
Yes, Crower specs the lash HOT. I thought that an aluminum block would expand more than the steel pushrods and decease lash but I guess I have that backwards. I'll take your recommended initial COLD lash figures for start-up.

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline Harold Bettes

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Re: Mid- Engine Modified Sports
« Reply #1646 on: April 20, 2019, 01:24:02 AM »
Neil and others that might think about this stuff, :-D

Coefficient of linear expansion for aluminum is 22.2 x 10^-6. Starting temp at 75F and ending temp at 200F yields the aluminum growing and the lash will get wider, just like Mike said. The number for reference is the length of the pushrod (on aluminum column), roughly 8" x the delta T of 125F x 0.0000222 = 8.0222" or pretty close to that. Unless I moused up a decimal point.  :?

Good Luck to you.

Regards,
HB2 :-)
« Last Edit: April 20, 2019, 01:29:52 AM by Harold Bettes »
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Offline jacksoni

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Re: Mid- Engine Modified Sports
« Reply #1647 on: April 20, 2019, 07:45:07 AM »
My iron block, 4 cyl, aluminum headed engine had lash grow reliable 0.006" cold to hot. Of course checking hot is a PITA to work on smoking motor getting valve covers off etc but once you have done it you can set cold as Dynoroom has outlined. Worth the work.
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Offline fordboy628

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Re: Mid- Engine Modified Sports
« Reply #1648 on: April 20, 2019, 08:29:22 AM »
Something to consider . . . .

When you start "opening up the lash", for whatever reason, you can make dramatic changes to the "valve motion".    Racing cams, in general, have lash ramps that are short to very short.    When lash "opens up", valve motion can begin and end, on the cam flank.    NOT a good idea.    One of the big problems becomes "seating velocity", which varies with lash.    Once seating velocity is "too high", the valve beats up the seat, in short order.    IMO, NOT a good idea.

The cam grinder knows what the grind spec might tolerate within the engine, and it always pays to heed their "instructions".   The general rule is that you can typically "tighten lash" more than you can "loosen lash".   Tightened lash during the "warm-up" period is tolerable.   

How much?  It depends on the valve train type; rocker ratio, if any; ramp height; base circle runout; etc; etc.

So yes, it is worth the effort to figure out how much it will change from cold to hot.

 :cheers:
Science, NOT Magic . . . .

I used to be a people person.  But people changed that relationship.

"There is nothing permanent except change."    Heraclitus

"Only two things are infinite, the universe and human stupidity, and I'm not sure about the former."     Albert Einstein

Offline Dynoroom

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Re: Mid- Engine Modified Sports
« Reply #1649 on: April 20, 2019, 11:32:32 PM »
As a note for others, like Jack said Iron block with aluminum heads do not require you to tighten the lash as much as the aluminum block & heads engine.
So, for a reference using a SB chevy, if running an alloy block & heads tighten the lash cold .012 to .016 (I used .014 in my example above)
If running an iron block with alloy heads tighten the lash about .006 to .008.
This is for pushrod engines. Carry on...  :cheers:
Michael LeFevers
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Without Data You're Just Another Guy With An Opinion!

Racing is just a series of "Problem Solving" events that allow you to spend money & make noise...