Oil Recommendation for AC Shelby Cobra Roadster replica

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I have a co-worker who just acquired a 2006 Shelby AC Cobra Roadster replica made by Back Draft. While he's always admired performance Ford racers, he's relatively new to owning performance cars, his main hobby has been golf, and he might need some advice for what oils to run in this new-to-him magnificent beast.

It has a Ford Motorsports built 351 Windsor crate engine, stroked out to 393 cubic inches, +.030 bore (3.030 inch bore), +.350 stroker crank (3.850 inch stroke). 9.7:1 compression ratio, requires minimum 91 octane gas, was factory rated at 440 hp at the flywheel. The previous owner had it chassis dynoed at a performance shop in Michigan after some routine maintenance work about 3 years ago - I need to look at the dyno chart again to relay what those results were (but I think a little over 400hp on the wheels). It uses forged pistons, ported stock Windsor heads with 1.94 intake and 1.55 exhaust valves, true roller rockers, Victor Jr. intake manifold topped with a Holley square bore 750 cfm carburetor on a spacer, Crane hydraulic roller cam, headers, Laker pipes, and serpentine accessory drive. Fuel comes from a tank-mounted electric fuel pump. Emission controls are limited to PCV valve only. The factory manual states the main bearings are clearanced at +.025 to .030" and the connecting rods bearings are +.013 to .018".

The output drives through a Tremec close ratio 5 speed manual. I do not know the ratio in the differential (likely in the range of 3.3 to 4.1 but that doesn't pin it down), but will try to find out the engine rpms at a known speed in 4th gear, which I think is direct drive 1:1 - with the tire circumference I should be able to calculate it that way.

Maybe some of you folks with experience with high performance hot rods would like to offer your opinions about what oil and viscosity (range) that they would use in the engine, transmission, and differential. Like me, he lives in north Florida, absolutely will not drive in rain or cold weather - meaning it could get stored from December to February, and says he plans to mainly cruise around only in low traffic, with very limited numbers of "hard acceleration events". He thinks he'll put about 2,000 miles a year on it.
 
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Its simple answer........contact Back Draft Racing and they will look up the build information and give you what they recommend for their motor they built or had built for that "KIT" AC Cobra.


+1(561)752-3693



You might also suggest to your "golfer" buddy to join :

There are a few others I may belong to all of them ...hahaha, but you can get first hand AC Cobra replica information from them about many AC Cobra replica topic's.
 

CentAmDL650

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The full documentation that came with the car has an engine oil recommendation. Without prejudicing the responses, I was hoping some of our esteemed board members could use their knowledge and experience to use the specification data to formulate their own recommendations. And maybe debate the merits of their selections. My intention in asking this was not to skip the work and be served a simple answer on a silver platter.
 
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Its a roller cam, so you don't need sky high zinc, but we don't know the valve seat spring pressures or the valve lift. I'd use a syn 15w 40 at the minimum. 20w 50 to be safe.
 
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If it has a FRPP/Ford Motorsport/SVO 393 crate motor the recommendation is easy enough to find.

I agree with the SYN 15/40 recommendation, though anything from 10/30 to 0/40 be fine, not that complicated if it is properly screwed together.
 
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Ford Performance no longer has the 393 engine listed, they are all 427 unless a sealed race engine. That being said the newer ones recommend a 10W30 or 10W40 along with a FL-1A, or FL1HP if you still have any, filter. The FL1-HP was discontinued at some point in the past couple years.

I would be hard pressed not to use M1 0W40 if it were my car. Your co-worker is most likely out of any warranty since those only had a 2yr/24K mile warranty.
 
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Ford small blocks are not fussy about oil. You just need something that maintains enough oil pressure in all conditions with a good additive pack. If I was tracking this car, it would get something like 15w50 M1. If just tootling around, and good oil pressure on the gauge, any good synthetic xW30.
 
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LOL that's why I suggested to contact the builder.... look at all the guesses and assumptions.
Also the engine information is not detailed by any means. Look more like a general informational with sorta specifications about the engine.

:geek:
 
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LOL that's why I suggested to contact the builder.... look at all the guesses and assumptions.
Also the engine information is not detailed by any means. Look more like a general informational with sorta specifications about the engine.

:geek:

LOL did you miss the part where he says he has that? LOL :geek:
 

CentAmDL650

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NitroM3, what more detailed engine information would be needed? Cam lift, duration @ .050? Rocker ratio? Crank end play clearance? Camshaft bearing clearance? Weight of the engine? How about mass of the flywheel or harmonic balancer? Number of angles ground into the valve seats? Whether the valve stems are sodium filled? The point I'm trying to make is all of those things are esoteric distractions, not really contributing factors to what oil to use.

Some key information was contained in the general information that I called "specs." The fact that the cam is a hydraulic roller cam, for instance should tell us that the engine is limited to 7,000 rpm. And that, as spasm3 pointed out, the zinc in the oil doesn't need to be sky high. If I had the dyno results to post, you'd see the horsepower peak occurred at 6,100 rpm (I remember that much clearly). And I threw in the two major bearing clearance numbers that should allow those with experience to be able to compare to what average bearing clearances are to get a higher or lower viscosity reading.

You have the the kind of engine it is, the main & rod bearing clearances, the power output, the kind of cam and lifters, the general climate it will be used in, the way it will be driven, when and how much it will be driven and the assumption that owner would hope that it to last many more years based on how he drives it. All of those things should inform someone with hot rod V8 building/ tuning background (especially Ford) what lubricant would be appropriate for the application.
 
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Looks like a job for delvac extreme. around 1300 zinc 1200 phosphorous and a lil 50ppm crumb of moly ;)
 
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You have the the kind of engine it is, the main & rod bearing clearances, the power output, the kind of cam and lifters, the general climate it will be used in, the way it will be driven, when and how much it will be driven and the assumption that owner would hope that it to last many more years based on how he drives it. All of those things should inform someone with hot rod V8 building/ tuning background (especially Ford) what lubricant would be appropriate for the application.
Yep. The bearings clearances on his build are a little on the loose side compared with factory specs, so I would base my choice off what the hot idle oil pressure was. Chances are high that the builder used a high volume oil pump so 30 weight oil will likely give all the pressure it needs (20-25 psi hot idle is great).
 
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NitroM3, what more detailed engine information would be needed? Cam lift, duration @ .050? Rocker ratio? Crank end play clearance? Camshaft bearing clearance? Weight of the engine? How about mass of the flywheel or harmonic balancer? Number of angles ground into the valve seats? Whether the valve stems are sodium filled? The point I'm trying to make is all of those things are esoteric distractions, not really contributing factors to what oil to use.

Some key information was contained in the general information that I called "specs." The fact that the cam is a hydraulic roller cam, for instance should tell us that the engine is limited to 7,000 rpm. And that, as spasm3 pointed out, the zinc in the oil doesn't need to be sky high. If I had the dyno results to post, you'd see the horsepower peak occurred at 6,100 rpm (I remember that much clearly). And I threw in the two major bearing clearance numbers that should allow those with experience to be able to compare to what average bearing clearances are to get a higher or lower viscosity reading.

You have the the kind of engine it is, the main & rod bearing clearances, the power output, the kind of cam and lifters, the general climate it will be used in, the way it will be driven, when and how much it will be driven and the assumption that owner would hope that it to last many more years based on how he drives it. All of those things should inform someone with hot rod V8 building/ tuning background (especially Ford) what lubricant would be appropriate for the application.
Ok its your buddies engine. LOL My point is why ask DIY HOT RODDERS they are not engine builder maybe "re-builders" those are the guys that use to come to me for advise. LOL
Because the company that built the Cobra is not only still in business but in your state. Why ask them when you have all the answer here ???

OH and you engine info I would love to see all that specification you claim you have? The cam card you need to understand how to interpret and do the math specifically when setting the cam up in that engine not just what you are reading the cam card. BTW most cam card post the advertised number to make cams look more then what they are. ;) If the engine was actually BLUE PRINT BUILT then maybe you would have information on a spec sheet about end play, maybe? Sarcasm about weight of the engine but if the AC Cobra builder was trying to alter the weight ration by locating the engine differently sure! And why would you think the engines limit is 7000 rpm? Funny I have engineered valve train component's that easily could support a properly built V8 with hydraulic "type" lifter to run over your 7k limitation? Next valve seat angle , you realize that there are few depending on the type of vale and the use of the engine right? Bering clearance and oil viscosity in a well performance built engine.... no it goes back to what to use for viscosity based on engine use and the recommend viscosity by the engine builder. The DYNO sheets are likely only the final retail with SAE smoothing without the important information that some of us know about DYNO results and how they are achieved. ;)
Last wt(f)heck does a DIY Ford enthusiast with a American V-8 different from a Mopar or Chevy V-8 pre 90's have to do with knowledge on V-8s only specific to FORD?

Really my response on your thread were to help you and your friend. So it is clear you want to read the consensus advise instead of get the best information from the actual builder for oil recommendation? Why is that?
Maybe you contact them and post up exactly what they recommend?

Lastly NONE of the other that have posted have built an AC COBRA kit car nor are professional performance engine builders( meaning they not only bought and assembled the engine but also all the machine work) that I am aware of....
Now I am sure that are a couple that own AC Cobra kit cars and maybe they should post what they use in their AC Cobra kit car engines?
 
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Sigh...

It is a FRPP crate motor and a Windsor at that... as long as it is not filled up with some off brand snake oil swill it will be totally fine..

There is no point in calling Backdraft, as backdraft is "one of the industry leaders in producing turn key minus cars." (emphasis added)

Further:

All chassis are sold minus engine and transmission. Backdraft Racing is not affiliated with Shelby® Cobra®. Shelby®, Carroll Shelby® are registered trademarks and/or the trade dress of Carroll Shelby Licensing, Inc. (Shelby).

I find is somewhat humorous that someone who is a Professional Cobra and Engine Guru doesn't know that.

@bdcardinal has already told us what the "builder" recommends.
 

CentAmDL650

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Nitro M3,

Why are you getting so worked up? We do not need to ask the original builder what the spec was, because it came in the folder with the car's documentation. My buddy has also seen the engine oil recommendation, and being a total newb to the performance car/ engine world, he is more afraid than you are to do anything differently. I can understand that.

On the Crane cam, I don't think he has the card that comes with it. While degreeing in the cam and getting the lash set correctly is one thing, it does not affect the oil recommendation outside of what rpm range and power output it makes the engine operate in, which will give us some idea of the temperatures and pressures involved. Which is given in my first post.

By the way there was a spec on crank end play, I think it was .040". And engine weight is 540 lb (all cast iron except the Victor Jr intake manifold and the tubular headers).

Why do I think there is a limit on hydraulic lifter engines at 7000 rpm? Because the hydraulic lifters in all of these cam in block V8 engines typically can't bleed out the oil fast enough thru the pushrods which causes the valves to float. It's a self-rev-limiting feature if the valves don't strike the pistons, and if they do, then it's a self-terminating feature. As someone with your level of engine building would surely know, most performance and racing OHV V8 engines that need to go over 7000 rpm use some form of solid lifters. I know, you were just testing me.

Look, the whole car came to him in an auto transporter fully assembled with 6000+ miles on it. Other than a fault in illuminating the brake lights, the car came with oil in it and runs very nicely (other than some roughness below 1500 rpm which is typical with this kind of performance engine because of reversion in the intake ports). No need to doubt the dyno results from the previous owner who had some work done at a performance shop who he also paid to put the car on a chassis dyno to get their best tuning result. Also no need to dispute the claims made by the manufacturer and builder, Ford Motorsports SVO.

I was hoping we could have a friendly discussion about what oils people would select and why based on what it was going into, how it was built, and where and how it would be used. I did not want to prejudice anyone's recommendations by giving out the Back Draft's recommendations, which he has in the documentation. In all likelyhood, he will not listen to any recommendations that come from here, he will go with the recommendation that came in the documentation because in his imagination using something even slightly different would cause catastrophic results. Which would give a ton of ammo to his household budget director, and a "I told you that was a complete waste of money" that he would never live down.
 
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Sheesh. This thread has gotten silly. Anything from 0w30 to 20w50 is going to work fine unless bearing clearances are totally messed up. The Ford small block was in production for 41 years and has an excellent oiling system that is well understood. There's no voodoo or crazy oil requirements for a warmed over crate engine that's not getting tracked.
 
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