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UGH... the problems of building a rare engine

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bluestang65
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UGH... the problems of building a rare engine

Post #1 by bluestang65 » Tue May 10, 2016 6:44 pm

I hate to say how much more I love building SBF, Modular and even the new Coyotes. This is a rant. If you can get through it, I'm actually asking for help.


Build is a 250 with the CI head and EFI.

I ordered a set of custom pistons and they came out with the compression distance at 1.600 instead of 1.511. When you buy custom pistons, you sign a waiver that you own them. Fault is on me because I just send them a link and asked them to make me a forged stock piston for a 4.1L Ford. Gave them the specs from summit racing including the 1.511 compression distance, but there's no way for me to prove that.

According to my calculations, that makes distance below deck .034" using 9.469 distance to center, 5.881 rod length and 1.955 (half of stroke). The machine shop kissed the block deck, so it's probably closer to .030" if I'm lucky.

Plug it all in and assuming the small side of CI's estimates for the heads of 48cc and I'm over 11:1. I haven't cc'd the heads yet.
I am building a cool-sounding, EFI, fun, street engine and I don't care about performance too much, but clearly the temperament of this engine doesn't match what I'm trying to do.

I'm pissed and venting a little. Help me come to some working solution...

New pistons - $500 sucks and of course the same 'no guarantee we do our job right' exists.

Copper head gasket - .094 gets me in the 9.5:1 but I've called 2 places and keep getting "huh, what motor... oh here it is... it's a 300, right?" I don't think I can explain to another human being what this engine is. I'm not keen on using these, but if somebody knows a source, lmk.

MLS - expensive but cheaper than new pistons, I guess. Did CI ever get Cometic to start making gaskets for these motors or is it a straight custom job?

Custom rods?

New cast pistons - bite yet another bullet and snag a cheap set of cast pistons just to get this job done. It's an NA build, but the idea of cast pistons isn't exciting. Plus, the block was machined to the piston's specs so it's set right at 3.710 instead of adding a couple thousandths to accommodate the .030" oversized pistons.

I could shave a little off the pistons like maybe .010 but this relies on also being able to squeeze a little more out of the heads. Anybody know if it's possible to get a few cc's out of the heads? I'll have to double check what's left to work with in the combustion chamber anyway.


I know we are building a dying breed here, but they built more than one of these motors, so it shouldn't be a total one-off. I'm about to put this whole mess piece by piece in the classifieds.

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Re: UGH... the problems of building a rare engine

Post #2 by DannyG » Tue May 10, 2016 6:51 pm

It sounds like a really cool build, I hope you get it all built and running to your satisfaction.
The truth lies in the metal, ya gotta cc the head first, then you can figure out the game plan.
250 pistons are the same as 200's, those pistons may have some resale value ?
Would you mind saying which piston company ?
Would you say "they" made the mistake, given what you wanted, is that something that happens often with custom pistons ?
I'll probably going to go with custom piston in a few months so I'm really curious about your experience.
Good luck, hang in there, " If it was easy, everyone would have one".
DannyG
C8 block, .040 over, zero decked. Forged Racetec pistons , D7 large log head .9:4 compression, CSC 264-112 cam going in a '65 Mustang one day...

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Re: UGH... the problems of building a rare engine

Post #3 by 78 granada » Tue May 10, 2016 7:11 pm

Just curious, have you picked your cam? If you cc the head you can figure the dynamic compression. I wonder how far out you will be? Good luck...you'll get it!

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Re: UGH... the problems of building a rare engine

Post #4 by bubba22349 » Tue May 10, 2016 7:49 pm

:hmmm: If they are forged you should be able to cut them down some or have the dish depth increased to get to the compression you want to be. With that Aluminum head and a good radiator 9.5 to 10 to 1 should be workable. The piston company should help you out some if they didn't machine them right to your plan specs by fixing or remaching the dish. The FelPro permaTorque head gasket is thicker then the Victor so that may help some too. Sounds like it would work great as a race motor if I had the extra money I'd sure buy it for my drag car project. Good luck :nod:
A bad day Drag Racing is still better than a good day at work!

I am still hunting for a project car to build but with my current low budget it's not looking so good. My Ex- Fleet of Sixes these are all long gone! :bang: 1954 Customline 223 3 speed with O/D, 1963 Fairlane project drag car with BB6, 1977 Maverick 250 with C4, 1994 F-150 a 300 with 5 speed.

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Re: UGH... the problems of building a rare engine

Post #5 by pmuller9 » Tue May 10, 2016 8:46 pm

You need another 5-7 cc to get close to 10:1

The combustion chambers in the aluminum head are not finished and the user is expected to complete the chamber work and to make sure all the chambers have the same volume
You should easily be able to pull a few CCs out of the chambers.

Bolt the head to the block and scribe the cylinder bore on to the head surface.
The chamber wall area that was machined for the valves needs to be blended into the un-machined wall area approaching the spark plug hole.
That same area around the valves needs to be angled back to the scribe line representing the cylinder bore.
Then the entire chamber needs to be polished.

If you still need more after the chamber work then you can work in the piston dish.

Please post a picture of the combustion chamber and the piston dish.

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Re: UGH... the problems of building a rare engine

Post #6 by Econoline » Tue May 10, 2016 9:33 pm

You're deck height is .030" or better w/ the new pistons. Are the pistons flat tops? If so, call Cal at Cal Spec in CO and have him mill some D dishes in them to your volume. Imo, if you were having custom pistons made you should have brought the deck to near zero and had them mill D dishes to whatever was called for. Best of all worlds. But whatever to late now.

Measure the chambers after the head is done, measure a piston in the hole and have them dished. Cal is very reasonable. Assuming .030" now, w/ 55cc chambers, Corteco gasket @ .053" you're @ 10:1 w/ 7cc dishes, 10cc's w/ a .035 oem composite, 8 w/ a Victor.

Pick your cam then decide what you need for the dishes. Base it on DCR not SCR
Last edited by Econoline on Tue May 10, 2016 9:35 pm, edited 1 time in total.
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bluestang65
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Re: UGH... the problems of building a rare engine

Post #7 by bluestang65 » Tue May 10, 2016 9:35 pm

It is still my fault for not sending them information. I asked for a 'stock' piston. They acted like it was impossible. I sent them a link to the stock cast piston on Summit Racing's website to match it up. All the specs matched, but not the compression height. It came out 1.600 and should have been 1.511.

Racetec was the supplier.

Pics forthcoming. Need to figure out a host for them.

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Re: UGH... the problems of building a rare engine

Post #8 by Econoline » Tue May 10, 2016 9:37 pm

Dishes? 6.5 like the stock you'll be fine with a 262/262 cam
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bluestang65
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Re: UGH... the problems of building a rare engine

Post #9 by bluestang65 » Tue May 10, 2016 9:38 pm

Econoline wrote:Dishes? 6.5 like the stock you'll be fine with a 262/262 cam


7 supposedly... I need to measure those out too.

bluestang65
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Re: UGH... the problems of building a rare engine

Post #10 by bluestang65 » Tue May 10, 2016 9:42 pm

Image

Image

Image

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Econoline
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Re: UGH... the problems of building a rare engine

Post #11 by Econoline » Tue May 10, 2016 10:32 pm

That's a groovy dish ;) I bet you're going to be fine with the available gaskets once you know where you stand w/ all the variables. Quench is not going to be there but the aluminum head will help. What are your goals for the engine? Idle quality, HP, transmission, use?
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bluestang65
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Re: UGH... the problems of building a rare engine

Post #12 by bluestang65 » Tue May 10, 2016 10:43 pm

It's a fun street motor. I've had the car fast before with a 351W. Now I just want it EFI, reliable and running right. Power isn't a concern but the when it had an L6 in it the car was unbearably slow.
T5 transmission.

I've read the articles on SCR vs DCR and just curious what I will get out of this:
http://www.summitracing.com/parts/hrs-280938-10

http://www.summitracing.com/parts/hrs-280998-10

I much prefer to build proven, trusted combos. I'm out on a limb here. I

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Econoline
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Re: UGH... the problems of building a rare engine

Post #13 by Econoline » Tue May 10, 2016 10:54 pm

The calculator download at the bottom of the page on this link for Patrick Kelly is the one I've been using. With a T5 you'll be able to have a pretty sweet ride and run the freeway. I don't think you need the duration to be that long, but you'd be fine I bet C/R wise with either of those cams. 208 @ .050" is probably doable if you want more power down low. You're 250 build isn't to different than mine except the head and whatever your chamber size is. I'm @ .020" deck, ~61cc chambers, 8 cc dishes. I'm going to be running 8.2 DCR iirc w/ an iron head and the vistor gasket. Still waiting for my new cam. It's 204/208 duration @ .050". I'm running an AOD w/ 3.7:1 in the rear. It's all theory till it hits the road though.

http://cochise.uia.net/pkelley2/DynamicCR.html
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Re: UGH... the problems of building a rare engine

Post #14 by pmuller9 » Wed May 11, 2016 12:52 am

That definitely looks like an Autotech piston.
The dish looks like 2.300" diameter by .100" deep.
If the dish diameter was increased to 2.8" the dish volume would be increased to 10 cc.
That would still leave close to a .500" wide squish ring around the top of the piston.

Here are the two areas that can be angled out closer to the edge of the cylinder bore which also unshrouds the valves.
Click on photos to enlarge.

Image

You will also notice the ridge around each valve where the valve seats were installed.
The entire chamber surface can ground or polished until those ridges are gone and the surface is smooth.
As a reference here is a photo of a finished Jeep Six head chamber which is similar in shape.
If you duplicate this chamber finish you will be good to go.

Image

If the Static compression ratio gets close to 10:1 then the Howards 275* cam installed 4 degrees advanced will yield a dynamic compression ratio just over 8:1 which will work fine on pump gas.

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Re: UGH... the problems of building a rare engine

Post #15 by rocklord » Wed May 11, 2016 9:33 am

One step at a time.

CC the head and the pistons to determine the volume of each.
If necessary, the head volume can be increased by unshrouding the valves and smoothing the chamber.
There should be enough meat in the piston to increase the diameter of the recess to gain a few more cc's.

Definitely check the head and piston volumes first to determine what path to take.

Good luck.
Dan

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Re: UGH... the problems of building a rare engine

Post #16 by bluestang65 » Wed May 11, 2016 10:10 am

Thanks a lot for the tips. I'll run the head to the machine shop and ask them about unshrouding the valves.

I will update on progress.

Here's the crank going in it

Image

Image

Image

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Re: UGH... the problems of building a rare engine

Post #17 by Econoline » Wed May 11, 2016 11:14 am

If they just took a light pass on the deck I'd be surprised if you're much less than .050" in the hole. I had .035" taken off my deck, 1.556" compression height pistons and ended up @ .020"
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Re: UGH... the problems of building a rare engine

Post #18 by BCOWANWHEELS » Wed May 11, 2016 12:06 pm

who made your pistons for 500.00 ? all I,ve priced is 100.00 per piston / pin.
thanks
bob
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Re: UGH... the problems of building a rare engine

Post #19 by pmuller9 » Wed May 11, 2016 4:11 pm

BCOWANWHEELS wrote:who made your pistons for 500.00 ? all I,ve priced is 100.00 per piston / pin.
thanks
bob


AutoTec makes a custom forged 4032 alloy piston which is less expensive than the 2618 alloy piston.
The 4032 alloy requires less piston to wall clearance than the 2618 piston.
The spiral machine work in the piston dish is a telltale sign of their work.
The piston also includes an accumulator groove in between the 1st and 2nd ring groove.

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Re: UGH... the problems of building a rare engine

Post #20 by rbohm » Wed May 11, 2016 4:51 pm

OP, if you are still having issues getting your compression ratio down, you can always spec the cam lobe separation angle at 108 degrees. this increases the valve overlap and reduces cylinder pressure at low speeds. this reduces the engines dynamic compression ratio at low speeds helping to prevent detonation.
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Re: UGH... the problems of building a rare engine

Post #21 by BCOWANWHEELS » Wed May 11, 2016 4:58 pm

thanks
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Re: UGH... the problems of building a rare engine

Post #22 by bluestang65 » Sun May 15, 2016 10:53 pm

The head turned out to be right at 50cc.

The piston is .055" below deck. I'm not sure how that happened. Compression distance is right at 1.600". Crank is turned .010" under so that would account for another .005" but I had it calculated at .034" I believe.

Using those calculations and a standard .041 gasket from felpro, I'm sitting at 10.3:1 if my calculations are correct.

The machine shop is going to unshroud the valves for me and taper the ridge off the valve opening. I might gain a cc or two.

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Re: UGH... the problems of building a rare engine

Post #23 by rbohm » Sun May 15, 2016 11:41 pm

bluestang65 wrote:Crank is turned .010" under so that would account for another .005"


no t wont unless the crank was offset ground.
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Re: UGH... the problems of building a rare engine

Post #24 by bluestang65 » Sun May 15, 2016 11:51 pm

You're right.

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Re: UGH... the problems of building a rare engine

Post #25 by DannyG » Mon May 16, 2016 9:03 am

FWIW, I mic'd a takeoff felpro headgasket @ .045", not sure if that helps your equation...
DannyG
C8 block, .040 over, zero decked. Forged Racetec pistons , D7 large log head .9:4 compression, CSC 264-112 cam going in a '65 Mustang one day...

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Re: UGH... the problems of building a rare engine

Post #26 by Gene Fiore » Mon May 16, 2016 11:53 am

DannyG wrote:FWIW, I mic'd a takeoff felpro headgasket @ .045", not sure if that helps your equation...
DannyG

Huh...I always thought the felpro was .050
1971 Maverick, 250I6, crank knife-edged, Clay Smith 278 solid cam, .040 over 255 V8 pistons, 10.5 to 1, Custom 500 Holley 2V on Classic Inlines Aluminum cylinder head, 1.6 rockers, Hooker header, DUI dizzy, C-4 w/2800 stall, 8" 3.55 det locker

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Re: UGH... the problems of building a rare engine

Post #27 by DannyG » Mon May 16, 2016 12:51 pm

That's why I wanted to post my takeoff/used gasket measurement. Taken with a known reliable micrometer I got .045".
DannyG
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Re: UGH... the problems of building a rare engine

Post #28 by RichCreations » Mon May 16, 2016 12:52 pm

Gene Fiore wrote:
DannyG wrote:FWIW, I mic'd a takeoff felpro headgasket @ .045", not sure if that helps your equation...
DannyG

Huh...I always thought the felpro was .050


It is, until you install it, then they compress to .046 or so...

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Re: UGH... the problems of building a rare engine

Post #29 by rbohm » Mon May 16, 2016 1:30 pm

RichCreations wrote:
Gene Fiore wrote:
DannyG wrote:FWIW, I mic'd a takeoff felpro headgasket @ .045", not sure if that helps your equation...
DannyG

Huh...I always thought the felpro was .050


It is, until you install it, then they compress to .046 or so...


yep, danny gave the compressed thickness, which is what you need to know to do proper compression ratio calculations.
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Re: UGH... the problems of building a rare engine

Post #30 by Gene Fiore » Mon May 16, 2016 2:54 pm

Ok thanks. I have been erroneously under the impression the felpro was .050 compressed. :|
1971 Maverick, 250I6, crank knife-edged, Clay Smith 278 solid cam, .040 over 255 V8 pistons, 10.5 to 1, Custom 500 Holley 2V on Classic Inlines Aluminum cylinder head, 1.6 rockers, Hooker header, DUI dizzy, C-4 w/2800 stall, 8" 3.55 det locker

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Re: UGH... the problems of building a rare engine

Post #31 by cr_bobcat » Mon May 16, 2016 3:08 pm

I understood the Felpro to be 0.050 as well. I thought it was the Corteco that was 0.044. I've read that a number of places here on the forum. Good to know!
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Re: UGH... the problems of building a rare engine

Post #32 by Econoline » Mon May 16, 2016 3:52 pm

Interesting. The Corteco/ROL gasket is the thickest, I've got all 3 here, I just mic'd the felpro @ ~.050" @ the printo seals and fire rings/~.046" @ the flat, the corteco @ ~.058"@ the flat and the Victor @ ~.047" @ the flat.

If you get another 2-3 cc's and go with a corteco/rol gasket you can get the SCR down to 9.8:1 or less
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Re: UGH... the problems of building a rare engine

Post #33 by pmuller9 » Mon May 16, 2016 9:53 pm

bluestang65 wrote:The head turned out to be right at 50cc.
The machine shop is going to unshroud the valves for me and taper the ridge off the valve opening. I might gain a cc or two.


Please post pictures of the combustion chamber after it has been worked.
It looks like the compression ratio will turn out OK.

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