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#1782704 - 06/04/09 04:58 PM Engine swap advice for CNG model Crown Vic
CNGBiker Offline
Rookie

Registered: 04/02/08
Posts: 50
Loc: CA
The engine in my 2000 Crown Vic CNG (compressed natural gas) has blown a head gasket. I'm hoping you folks can help me pick the best donor engine for a swap.

I'm not interested in spending money to fix this engine. It's got 172k on it and it's had a low oil pressure problem (5 psi at idle) that I confirmed by installing a mechanical pressure gauge. Surprised it made it this far!

So I think it's new engine time for me. Does everyone agree?

There seems to be some conflicting information regarding the CNG engines.

This Autotrader page says, "The Crown Victoria can be ordered with the V-8 retuned and dedicated to operate on compressed natural gas (CNG). The CNG engine has been reworked to increase the compression ratio from 9.1 to 10.1 for the natural gas version."

I searched around this site and and found this but this doesn't seem to confirm the information.

Also, I'm aware of another CV.net member who successfully swapped in a '04 Town Car PI engine.but it seems there were issues with the intakes lining up.

I also spoke to the owner of AFV in Huntington Beach and he told me the compression ratio is no different than a normal gas powered CV.

What engine do you guys suggest?

I was hoping to make this as straight forward as possible. My best guess right now is something from a 98 Crown Vic, Town Car or Grand Marquis.

Why do I say this?
-NPI motor should hopefully be the easiest to fit.
-98 had apparently no timing chain issues compared to 99 & 2000
-2001+ is PI and the intakes aren't an exact fit.

Can someone confirm the above info? I need to get the engine ordered ASAP..

Many thanks in advance!

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#1782718 - 06/04/09 05:27 PM Re: Engine swap advice for CNG model Crown Vic [Re: CNGBiker]
interceptor1985 Offline
Poobah

Registered: 02/07/08
Posts: 5825
Loc: OREGON
So what all is different about the nPI CNG intake vs the regular intake? Personally I'm all for making more power and when its broke upgrade it....If a PI intake could be modded to work with CNG that would rock! Then you could go with a PI engine or even a nPI engine with PI heads for a compression boost;)

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#1782732 - 06/04/09 05:46 PM Re: Engine swap advice for CNG model Crown Vic [Re: interceptor1985]
CNGBiker Offline
Rookie

Registered: 04/02/08
Posts: 50
Loc: CA
As I understand it, my CNG intake is aluminum with the throttle body at the rear towards the firewall. I'm pretty sure with a NPI engine, I just swap my intake over/rails/injectors/harness and ECU. I'm hoping that everything underneath that (heads, compression ratio) is the same. That is what I'd like to confirm.

As much as I'd like to take this opportunity to upgrade, right now, I'm just looking to go back to stock as cheaply as possible.

I'd love to go with a PI engine but the last person I've heard of that did this had issues with the CNG intake lining up with the PI heads. You can click on this link to check out his posting. He had to use RTV to make it work. Not that there's anything wrong with that, but I'm just looking for bone stock if possible.

The PI heads on a NPI block sounds interesting, but now were talking about buying those parts + labor to do the head swap. Then I'd still have to face the fit issues with the CNG intake and PI heads. After that, I'd have to find someone to tune it to work with the increased compression ratio, right?

I'm a gearhead at heart and I think there's a lot of potential for high performance CNG applications. It's rated at 130 octane so it is very resistant to detonation. I just don't have the time or money to be the guinea pig.

I use my CV as a daily (60 mile commute) driver and also to haul my 2 young children around, so I'm just looking for a reliable, stock car.

I get my thrills on 2 wheels, hence my SN. I appreciate your enthusiasm and suggestions and 4 years ago when I didn't have kids and had plenty of disposable income, I'd been all over a hi performance CNG build, but it's just not for me right now.

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#1782779 - 06/04/09 07:07 PM Re: Engine swap advice for CNG model Crown Vic [Re: CNGBiker]
Stick Offline
Climber

Registered: 11/29/07
Posts: 969
Loc: Oshawa Ontario Canada
Use this link to find another CNG engine near you. http://www.car-part.com/ or a newer NPI will work with no problems switching the intake over.


Edited by Stick (06/04/09 07:17 PM)
_________________________
2010 CVPI Black ]Jmod/rear bumper tuck /Head light harness upgrade /2015 Taurus 114 kms and more too come

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#1782783 - 06/04/09 07:14 PM Re: Engine swap advice for CNG model Crown Vic [Re: Stick]
CNGBiker Offline
Rookie

Registered: 04/02/08
Posts: 50
Loc: CA
Thanks for the suggestion. I tried that link and unfortunately, there are no CNG model engines near me. (zip 90278) Also, the CNG engines are typically more expensive.

I'd really like to confirm if there is a difference between the CNG block and nPI engines.

I can find nPI engines everywhere for cheap.

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#1782788 - 06/04/09 07:21 PM Re: Engine swap advice for CNG model Crown Vic [Re: CNGBiker]
Stick Offline
Climber

Registered: 11/29/07
Posts: 969
Loc: Oshawa Ontario Canada
You would need to use your injectors in the NPI engine.The Compression is the same.


Edited by Stick (06/04/09 07:22 PM)
_________________________
2010 CVPI Black ]Jmod/rear bumper tuck /Head light harness upgrade /2015 Taurus 114 kms and more too come

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#1782799 - 06/04/09 07:37 PM Re: Engine swap advice for CNG model Crown Vic [Re: Stick]
CNGBiker Offline
Rookie

Registered: 04/02/08
Posts: 50
Loc: CA
Awesome!! Thank you!!

How were you able to confirm the compression ratio is the same so quickly? I've put in a few hours of research on this and still haven't found anything conclusive.

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#1782844 - 06/04/09 08:50 PM Re: Engine swap advice for CNG model Crown Vic [Re: CNGBiker]
Stick Offline
Climber

Registered: 11/29/07
Posts: 969
Loc: Oshawa Ontario Canada
I have worked at St Thomas and have seen the conversions done.They use a stock engine and just add the CNG parts. Same up here when the taxi companys and limos have there cars converted over privitely.
_________________________
2010 CVPI Black ]Jmod/rear bumper tuck /Head light harness upgrade /2015 Taurus 114 kms and more too come

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#1783132 - 06/05/09 03:20 AM Re: Engine swap advice for CNG model Crown Vic [Re: Stick]
TheShadow Offline

Over the Hill

Registered: 05/01/07
Posts: 1781
Loc: SoCal High Desert
Regarding knowledge and research: I cheat. I have a Ford shop manual!!

The only difference I could find between normal and CNG engines is the piston pin. The CNG specs increase the diameter of the pin 0.0003" and shortens the length of the pin between 0.0008" and 0.013". Those dimensional changes are very insignificant. The pistons' pin bore, diameter, ring end and side gaps, clearance to bore, etc., and all the head specs regarding valves, displacement of combustion chamber, etc., are all the same.

So, yes, your only concern could be a changeover from NPI heads (used by the CNG engines and a lot of gasoline engines) to PI heads and the intake situation. You could get a PI engine, requiring a new PI intake with no fit issues. Or you could stick with an NPI engine and keep your existing intake. The change to a PI engine would cost you an intake manifold.

Don't know what, if any, price differences you'll encounter between an NPI and a PI engine.
_________________________
'95 P71, 5xx,xxx miles, Rebuilt tranny, 2.73. Lives as a cab, and will die as a cab. (Died-FrontEnder)
'96 P71, 640,xxx on original drivetrain. (Now parts car - T-bone & roll)(You should see the roof - A,B & C-pillars chopped on driver side)
New to list: '96 MGM (Nice! @ 35x,xxx), '97 CV P71, '98 CV P71, '00 CV P71, 01 P71 (2 of 'em) '03 CV P71 (Nice so far) (All Ford Zinc Yellow w/Black decals & trim) And the list is growing...........
Taxicab mechanic: I HATE DRIVERS!

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#1783206 - 06/05/09 08:27 AM Re: Engine swap advice for CNG model Crown Vic [Re: TheShadow]
Chevyguy Offline

Poobah

Registered: 01/05/04
Posts: 9449
Loc: Winchester Mass
I would imagine that fitting all the CNG gas rails/regulator and whatnot on a Plastic PI intake may prove troublesome.

For this project just SEARCH around for the lowest mile 98-99 Panther NPI 4.6 you can find.

http://www.car-part.com/

Oh lookie first hit in Boston

1999
Engine
Ford Crown Vic 4.6 AUTO RUNS LIKE NEW 46K CNG 46,000 A 060089 $850 Brookside Auto Parts Inc. USA-MA(Orange) E-mail 1-800-245-1229


A little closer to you

1998
Engine
Ford Crown Vic 200-210AVG,VAC18 39,679 A T0215B $700 Pacific Auto Salvage, Inc. USA-CA(American-Canyon) Request_Quote Local Calls only or Email sales Request_Insurance_Quote

Better hits search for 99 Towncar in Cali pulled up Merc and Vics 99 and 98 Found lots of high mile units on the search that's the hardest part.

1999
Engine
Lincoln Towncar *(8-280, 4.6L, VIN W)-39K 39,000 A J487 $1000.28 All Auto Parts Co. -- Gold Seal USA-CA(Fontana) Request_Quote 1-800-797-4595 Request_Insurance_Quote


1999
Engine
Lincoln Towncar *-(8-280, 4.6L, VIN W)-49K TESTED GOOD 49,000 A V034 $975.28 All Auto Parts Co. -- Gold Seal USA-CA(Fontana) Request_Quote 1-800-797-4595 Request_Insurance_Quote


So found some under 1K with under 50K miles that should work!!


Edited by Chevyguy (06/05/09 08:30 AM)
_________________________
2004 MarauderM79 155K miles Jmod!! Rockin Stock tune Daily, Muscle Merc tune for track 14.85 @95.63
2004 Crown Vic LX SOLD!!

New Daily 2016 Dodge Charger R/T Road and track, purchase with 16K now 23K after 3 months. 5.7 Hemi, 8 speed ZF trans 3.06 open rear 13.98 @ 99.2 mph 4740 lbs with driver!!

R.I.P Photobucket 10 years of hosting down the drain

Project car 74 Chevy Laguna type S-3, # match 400 SBC

Previous rides
93 P-71 2001 P-73, 94 TC Exec, 96 TC Signature, 04 LX

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#1783931 - 06/06/09 10:21 AM Re: Engine swap advice for CNG model Crown Vic [Re: TheShadow]
CNGBiker Offline
Rookie

Registered: 04/02/08
Posts: 50
Loc: CA
 Originally Posted By: TheShadow
Regarding knowledge and research: I cheat. I have a Ford shop manual!!

I finally got my hands on one as well and couldn't believe what I read. In the specifications section, they broke it down between the 2 different engines. At the top, it said CNG engine 10:1 then listed all the specs you mention. Then it had GAS engine 9:1, then listed all the specs.

Then I checked all the part numbers of the pistons, head, block, crank, etc and they were all the same. Why does Ford list those different compression ratios?

Now I'm not about to put on my foil hat and yell conspiracy, but when I called 3 different Ford dealers, they all said the compression ratio was different and if I swapped in a regular gas motor, it would run horribly if at all.

Most of the aftermarket folks I spoke to said it's no problem to swap the in the regular gas engine.. weird!

Anyway, thanks for taking the time to look up those specs, TheShadow!

 Originally Posted By: Chevyguy

1999
Engine
Lincoln Towncar *(8-280, 4.6L, VIN W)-39K 39,000 A J487 $1000.28 All Auto Parts Co. -- Gold Seal USA-CA(Fontana) Request_Quote 1-800-797-4595 Request_Insurance_Quote

1999
Engine
Lincoln Towncar *-(8-280, 4.6L, VIN W)-49K TESTED GOOD 49,000 A V034 $975.28 All Auto Parts Co. -- Gold Seal USA-CA(Fontana) Request_Quote 1-800-797-4595 Request_Insurance_Quote


Wow! Those were the exact engines I was looking to have swapped! I had called that yard and lined up a garage 2 miles away that was willing to try to tackle the swap, even though they never worked on CNG cars before.

Then I was staring at my fridge and noticed the South Bay Yellow Cab magnet with the number on it and it hit me.. I've seen a bunch of their CNG Crown Vics running around. Someone's gotta be working on them, right? So I called them and got referred to a local garage.

When I got there, there was probably 30 Crown Vics there and 5-7 of them were CNG.. seems like I might be in good hands! Its a few more bucks than the plan I had lined up in Fontana, but he's local and seems to know what he's up to. He said the new motor will be in by Monday.. so we'll see!

Thanks for all the help, this place is great.

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#1784120 - 06/06/09 03:58 PM Re: Engine swap advice for CNG model Crown Vic [Re: CNGBiker]
GM_Guy Offline
Posting Addict

Registered: 12/17/00
Posts: 18653
Loc: London, Ontario Canada
 Quote:
Then I checked all the part numbers of the pistons, head, block, crank, etc and they were all the same. Why does Ford list those different compression ratios?


Any head gasket part numbers? A thick head gasket will reduce your compression ratio, a thin head gasket will increase it, (ie: steel shim vs composite gasket).

Alex.
_________________________
Box stuff in the Box forum!

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#1784410 - 06/07/09 12:58 AM Re: Engine swap advice for CNG model Crown Vic [Re: GM_Guy]
MrEvil Offline
Over the Hill

Registered: 10/06/07
Posts: 1763
Loc: Austin TX
If Rock Auto can be trusted, they list the same Fel-Pro Part Numbers for the head gaskets on CNG and gasoline engines for a 2000 Crown Vic.
_________________________
1998 Ford CVPI formerly an unmarked for the Potter County TX Sheriff's department
2012 Ford F150 XLT 2x4 with Ecoboost
1966 Ford Thunderbird
1961 Ford F100

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#1784414 - 06/07/09 01:04 AM Re: Engine swap advice for CNG model Crown Vic [Re: CNGBiker]
TheShadow Offline

Over the Hill

Registered: 05/01/07
Posts: 1781
Loc: SoCal High Desert
 Originally Posted By: CNGBiker
Then I was staring at my fridge and noticed the South Bay Yellow Cab magnet with the number on it and it hit me.. I've seen a bunch of their CNG Crown Vics running around. Someone's gotta be working on them, right? So I called them and got referred to a local garage.

When I got there, there was probably 30 Crown Vics there and 5-7 of them were CNG.. seems like I might be in good hands! Its a few more bucks than the plan I had lined up in Fontana, but he's local and seems to know what he's up to. He said the new motor will be in by Monday.. so we'll see!


Good job! You can usually trust mechanics who keep cab companies as clients. But I'm surprised they are a little pricier...a shop I have dealt with in downtown LA was usually less, and to compensate for their quick service, we would tip them $50-$100.

I think in your case, smile, shake hands, swap business cards, and DON'T DRINK AND DRIVE!!
_________________________
'95 P71, 5xx,xxx miles, Rebuilt tranny, 2.73. Lives as a cab, and will die as a cab. (Died-FrontEnder)
'96 P71, 640,xxx on original drivetrain. (Now parts car - T-bone & roll)(You should see the roof - A,B & C-pillars chopped on driver side)
New to list: '96 MGM (Nice! @ 35x,xxx), '97 CV P71, '98 CV P71, '00 CV P71, 01 P71 (2 of 'em) '03 CV P71 (Nice so far) (All Ford Zinc Yellow w/Black decals & trim) And the list is growing...........
Taxicab mechanic: I HATE DRIVERS!

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#1784433 - 06/07/09 01:46 AM Re: Engine swap advice for CNG model Crown Vic [Re: TheShadow]
OldPaint Offline
Member

Registered: 04/08/07
Posts: 491
Loc: California
CNGBiker, please followup on this when you're done; I'd like to see how it worked out.

And yes, CVN is a heckuva resource!
_________________________
2004 ex-Calif. Highway Patrol P71. Now with Cruise Control, electro-dimming mirror, courtesy lighting, headlight relay harness, and console.

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