Duster360

I am getting a 91 360 From a Van to go into my duster and i am wantin to put a 280/280 Duration .474/.474 lift Mopar Purple Cam in it but i am wondering it this cam is to big for stock valve springs or is it a good fit? I am looking for a great cam to help me get to 350hp i have the everything else written down just not the cam. And i am doing cam, exhaust, intake, and carb first. If anyone has a better idea for a cam let me know i love to have a aggressive lope in my cars even when i owned a 4 banger Crysler Conquest i had it cammed out the butt, but it was also built. Also I dont know much about classic V-8s as i am on my first project.

TVLynn

You need to d a lot more than just change the cam. Save your money and get a set of edlelbrock heads, 2500 stall converter, 4bbl 650CFM carb, headers, 3.55 gears

Archer

Duster -

The stock heads (valve springs), if in good condition, will handle that cam. Whether you'll get 350 HP from it, is another story. The things that TV mentioned, and the compression ratio all factor in.

Archer

Duster360

Im towing car to a tranny shop to get a stall built along with a 727 tranny, Car already has 8 3/4 with 3.73 going in it. Already got carb, intake, and exhaust picked out and ready to order. It used to be a drag car im just reviving it for street/strip. the engine im getting has 8:1 as of now but i am going to bump it up sometime at the end of the year. and within a month or 2 i am ordering edlebrock heads for it. Its getting ready but i just needed to know if this cam will work on the stock valve springs for a short time.

PK1

Too big? Thats up to you. I think the purple profile and technology is out dated. They work but are pricey. If you want noise and function look at Comps ***** Thumpa lines. They keep mid range nicely and sound nasty. Dave Hughes has some too.

You are doing it correctly but here is a suggestion.

Measure the piston height for us and tell us how far in the hole it is. Machining tolerances suck so they will all vary. We'll take the average. Then pay 65 bucks and have a machine shop flow the exhaust and intake port on a single head. Mark your springs and valves and take them out and label them. They will give you a sheet with numbers.

Get us the basic flow numbers so the cam / springs can be picked to get you your numbers.

Get a large full size header. 1.75 inch
Use an Airgap if you want to use this daily. If strip only use a single plane.

You are looking for 1hp per cube. Its not difficult but you need to pay close attention to the parts and how they work.

I have a old flow sheet numbers somewhere around here for the heads stock. Let me look and I'll pull them up.

Duster360

I was looking into an Airgap onr from Edlebrok its going to be street/strip but i am also going to go look into those Comp cams


Here is one i found how would this one fair vs the Purple cam http://www.summitracing.com/parts/CCA-CL20-600-4/

PK1

Ah, Street AND strip. Now we have info..

Yes. That cam will work. And you can keep it with Eddy heads later and it will make good power too. You need springs.

AirGap is great power piece for splitting the difference.

Duster360

Ok cool ill order some springs and retainers also when I order cam, I also got an awsome deal for a Holley 750 carb for $100 from a friend that took it off her 406 camaro and switch to a double pumper. So I will be set as soon as I get everything together.

bremereric

The heads that came on that motor are probably the cast 308 heads and the pistons are probably a half inch down in the hole. Comp Cam usually lists what compression ratio is recommended with each of their cams so watch out for that. Your stock motor was probably 8.5:1 with the stock heads.

Duster360

I just looked it up and it is saying its pretty much a drop in and go cam doesnt require vavle spings but i am going to put new ones in to make sure they are good til i get the edelbrock heads

Archer

Duster -

I ran a 318 with a similar cam and stock 340 (HP) heads for about 3 years, before dropping in the 440. You can certainly do the springs, but unless you live in the high rpm range, I wouldn't worry too much about valve float.

Archer

PK1

Archer, glad the stock springs met your needs and this is NOT a correction on your post. Just another perspective on today's cams and lobe ramp speeds in case someone reads this thread in the future..

In 1991 Dodge used the spring needed to control the low lift low duration van stick. Prob something like 196/202 with under .400 lift at 118LSA. The spring was spec'd to that stick. Prob has a little cushion to use the heads in mulitple applications but not much.

They probably have 70 pounds on the nose and 200 open. MAX! But that was 21 yrs ago.. They are toast! Your new cam calls for a Comp 995 spring. (use any manufacturer you want) I run these on my mule. They spec at 402lbs and are a triple spring. 100bucks for a set and they take a 50 dollar retainer or a 100 dollar titanium from comp products.

You CAN NOT use the stock springs on Hughes or Comps XE, XE HL, Thumpa or XFI cams. The ramp speeds for Mopar products are all kicked up for the .904 tappet. We no longer are stuck with Chevy lobes on Mopars..

If you skimp on springs you MAY avoid catastrophic failure but you will have new posts soon and these will be some of the symptoms folks will post with improperly spec'd springs:

1. Do I need a better carb? Wont rev past 5000 rpm but plugs read fat?
2. Why is this motor falling off early in the rpm range.
3. I bent a valve? Can I replace 1 and does it need a new guide? How did it bend?
4. I dynoed my ride and am off 50 HP?

They may be light enough to use at break in so they are good for something...

bremereric

On your Cam spec card it will tell you the recommended springs you should use. I always match the cam to the springs. If I buy Comp I use their springs.

Duster360

Yea that's what I always do the springs ain't that expensive.

TVLynn

Don't forget to get the Holly Mopar linkage for the carb. Think about what you are trying to do ?? Use it stock for now !!! Maybe do your parts shopping. cam, pistons, rings, bearings, heads, gaskets. Then have it rebuilt later do all the work at the same time.. Job goes better and is cheaper in the long run...

78doubleR

i believe in 91 they used a la short black with magnum heads and intake. i know the 91 dakotas with the 318 are that way, not sure about the 360s though.

Archer

PK -

You probably know more about current cams than I do, but the cam the OP is describing isn't that aggressive. I seriously doubt he's going to be limited to 5K rpm with stock springs, if they are in decent shape. Since this is reportedly a temporary fix, I'd just wait until he gets the new heads and then have a whole new valve train. If the problems you described appears, it will just hasten the head swap.

Sometimes it's better to do the whole job at once and sometimes piecemeal works better.

Archer

Duster360

The engine I was looking at is a no go got a great deal on a 360 and 904 transmission.

PK1

Arch-

Post 1 has a little purple mopar camshaft. For that, good to with stock if I you choose. I have NEVER run a performance cam with a stock spring.. So you have more info on that combination than I do for sure..

At Post 6 he switches to Comp Cams Thumpa Series.. That specific cam on my spec sheet in the shop rates a 400lb triple spring... Hence my post about the stock springs.

It dont matter anyway Totally different build now.... I kind of wanted to see the numbers... o well..

Duster360

Lol I may still build it not surr yet but im going to grab the new one I found because its low miles, and already has a mild build on it so will save me money to get the car on the road lol.

duster sweden

why dont go for a comp cam 275deh..it's a fun cam for low comp ratio..good mid range..i have that cam in my first 360 engine..stock stall and a litle nice lope.. 4 bbl carb and no headers if you want..i like that cam..you can stay whit stock springs..

PK1

O yeah, you got run the low cost one! Id do same thing... It always cuts down on the tears and alcohol when a rod jumps out the pan...

Duster360

Exactly don't wanna put it in then blow it up after the first start up.

TVLynn

Just noticed your gears ?/ Is it a typo They didn't make a 3.73 gear. 3.23, 3.55, 3.91,4.10 Probably 3.23 big difference..
Unless it is a ford rearend

duster sweden

how do you mean about that, "blow up"..??

Duster360

As in a rod going through the pan lol, and as for the gears its a mopar 8 3/4 rear just someone told me you can buy 3.73 for em