Cam - which to choose

Mopar Big Block Talk
redy
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Cam - which to choose

Post by redy »

Hi

I need to replace my stock cam since it it worn...

I would like some help validation of the specs for stock one

the Information the I have been able to find is that the stock one is

Duration at 050 inch lift:
208 int/210 ext.

anybody have more info to validate?

I was recommended to go to 230/236 if I wanted a slide upgrade- any exercise on the

What er the values if you go for at “purple” cam

I would like to have a car with a smoothly running engine also at idle... and very close to stock...

Regards René
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NigelK
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Re: Cam - which to choose

Post by NigelK »

Hi René

If you can retrieve the Mopar part number from your existing worn cam it should be fairly easy to find the specs online (for example here http://victorylibrary.com/mopar/mpcam-tech-c.htm#b).

Cam selection is a bit of a minefield, especially for mechanical novices like me. So I asked Comp Cams in the US for advice, using their cam recommendation service (https://www.compcams.com/cam-recommendation-form). You tell them the specs of your car and what you want to use it for, and they recommend a cam. Based on their recommendation, I chose this cam for my 383/432 stroker in my Mk1 (https://www.compcams.com/xtreme-energy- ... 3-440.html). Can’t wait to drive the car to find out what it feels like!

I’m sure you’ll get plenty of recommendations on here too, but the more detail you can provide on your Interceptor (engine spec, final drive ratio) and what sort of driving you want to do, the closer the recommendations will be to what you need.

Best wishes,
Nigel
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Bradford on Avon, Wiltshire
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Roh
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Re: Cam - which to choose

Post by Roh »

What motor do you have? Which year?
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Steve Payne
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Re: Cam - which to choose

Post by Steve Payne »

I have seen a lot of Interceptors ruined with there owners choosing the the wrong cam. You have a Gentleman express not a hot rod.

Choose the cam for the rev range you use not the rev range you would like to use. I expect the majority of owners use the 1500 to 4500 rpm so there is no point in having a cam with a 2500 to 6000 range. A cam with such a high range will give you a bad idle, poor brakes and be a disaster in traffic.

If you have the budget a roller cam is a great upgrade but you will be spending at least £1000 on parts, an RV roller cam will give you loads of torque, power and with a set of adjustable rockers you are going to have more power than you have ever had. A Lunati cam does not even need a special dizzy drive.

Steve
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johnw
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Re: Cam - which to choose

Post by johnw »

Steve Payne wrote: Tue Jun 15, 2021 8:58 pm I have seen a lot of Interceptors ruined with there owners choosing the the wrong cam. You have a Gentleman express not a hot rod.

Choose the cam for the rev range you use not the rev range you would like to use. I expect the majority of owners use the 1500 to 4500 rpm so there is no point in having a cam with a 2500 to 6000 range. A cam with such a high range will give you a bad idle, poor brakes and be a disaster in traffic.

If you have the budget a roller cam is a great upgrade but you will be spending at least £1000 on parts, an RV roller cam will give you loads of torque, power and with a set of adjustable rockers you are going to have more power than you have ever had. A Lunati cam does not even need a special dizzy drive.

Steve
I bought an FF ruined by a bad cam. I met the owner at Bristol JOC International, and he told me what a great cam he had. I bought the car which he had restored, 5 years afte the International, it was amazing apart from the cam. Top end, due to a nice pair of stock manifolds and inlet, was not noticeably different to a normal FF, but low end was ruined. Living on the Isle of Dogs in London, I had Mk3 alloys and NOS period tyres on it which looked super cool and modern. Coming up to a Zebra, I smiles at the pedestrians well in advance and so they start walking, I am just rolling nicely, not at all fast. I braked, and nothing happened! Not enough vacuum for the Maxaret or anything else! At the last minute I nailed it with gritted teeth and screeched to a stop. In contrast Jensen Parts and Service did a resto on FF 73 that I had as well, and it had a great cam in it. No idea what it was but it was unbelievable. A V8 Vantage owner (as in quad Webers 1986, auto) whom I took to Dave Barnets JOC meeting, in a burn up from the lights, said "I wish my car could do that!". An RV roller cam presumably with solid lifters! Sounds like a great idea! Would that be a no name set of inexpensive roller lifters?
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Steve Payne
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Re: Cam - which to choose

Post by Steve Payne »

Hi John

No Hydraulic roller lifters ( comp cams in my case) and a set of adjustable roller rockers so probably nearer £1200 in parts ( these should be stainless not Aluminium)

The problem with hydraulic roller lifters is they can rattle a bit on start but will go silent within 30 seconds or less.

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Re: Cam - which to choose

Post by Roh »

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Re: Cam - which to choose

Post by Steve Payne »

Things have come a long way since then, higher ration rockers roller cams as I have already mentioned and profiles that will give you the torque you need and more HP.

Steve
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PeterHume
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Re: Cam - which to choose

Post by PeterHume »

Hi Rene
For what it's worth, I rebuilt my interceptor mk3 H series 440 using a Lunati hydraulic roller com and lifters, along with comp cams steel adjustable roller rockers. Also I used a bronze oil pump drive gear. It was necessary to determine the correct length pushrods after the rest of the engine was assembled but otherwise it was pretty straightforward to fit.
The cam and lifters were Lunati 20230711LK. The cam is 270 / 278 deg with lift 0.515 / 0.530. These durations are pretty close to the Chrysler performance cam (268 / 284 deg) with a bit more lift.
The rockers are Comp Cams sku1621-16. They bolt straight onto the heads, but, you do need to mill a few mm off the bosses on the inside of the rocker covers to raise the baffle to ensure clearance to the rockers.

Lunati advertise this cam as suitable for 1800 - 5800 rpm. Overall, I am really pleased with the way it goes, pulling really strongly until well beyond me getting scared. There is another Lunati cam ( 20230710) with slightly less duration, it would come in at slightly lower revs (might cost you more in tyres) and for road use you would not notice the slightly lesser top end.
I haven't really experienced other interceptors so I can't comment on how it goes compared to other cars / cams etc but am really pleased with it.
Regards Peter
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Steve Payne
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Re: Cam - which to choose

Post by Steve Payne »

PeterHume wrote: Thu Jun 17, 2021 9:36 am There is another Lunati cam ( 20230710) with slightly less duration, it would come in at slightly lower revs (might cost you more in tyres) and for road use you would not notice the slightly lesser top end.
This is the cam I have ( 20230710 ), as you say a little bit less top end but I have found it gives me all the power I will ever need. No need for a bronze drive gear for the distributor on these according to Lunati.

Steve
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Roh
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Re: Cam - which to choose

Post by Roh »

Those two cams look to be well matched to a stock motor.

Something to remember is that these motors already had a performance camshaft in them. If you had a two barrel engine then a bigger camshaft would really waken the engine up. The 2 barrel camshaft was p/n 3577181 and it was a much smaller camshaft.

.050" DURATION
206 degrees intake,
210 degrees exhaust, .

LIFT
431" gross intake lift
429" gross exhaust lift

LSA
113 degrees

My view has always been that big hydraulic camshafts don't make sense. If you have an engine that needs a bigger than OEM sized camshaft then either switch to a solid camshaft or a roller camshaft. Either option will give you faster ramp rates that allows more power for a given level of drivability.
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johnw
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Re: Cam - which to choose

Post by johnw »

redy wrote: Fri Jun 11, 2021 10:36 am What er the values if you go for at “purple” cam
FYI The Mopar purple shaft cam today is a copy of the old historic grind and has part numbers P4452783 (1 bolt sprocket) and P4529270(3 bolt sprocket). The first two lines in this Mopar table have the same cam parameter values. These are the purple shaft 1 bolt and purple shaft 3 bolt, otherwise identical apart from bolt patterns. These are the part numbers from the year 2005 table below, these "newer" part numbers have been around decades now, sometimes with an A or AE suffix added.
4727252-camshaftchart.jpg
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RockyUSA
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Re: Cam - which to choose

Post by RockyUSA »

Why is it called “The Purple Cam”?

Thanks...

Rocky
‘71 TVR Vixen 2500 - (M Series Prototype)
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Steve Payne
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Re: Cam - which to choose

Post by Steve Payne »

RockyUSA wrote: Fri Jun 18, 2021 2:32 pm Why is it called “The Purple Cam”?
The purple shaft was just a name for mopars after market brand cams. they were made by crane.

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Basil McKinley
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Re: Cam - which to choose

Post by Basil McKinley »

Hi Steve,

Some years ago I purchased the same Lunati hydraulic roller cam I as you. I recall thinking at the time that their information on whether a bronze oil pump/distributor drive gear was required was ambiguous so I rang their tech support to check and they advised me to use a bronze gear. It would be interesting if you have got more information on this,

Regards,
Basil
1970 Interceptor MkII 123/3798
1973 JH MkI 1141/12698
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