Temporary cam?

[scgamecock]

Can anyone offer suggestions on a nice lumpy flat tappet cam preferably solid for my 72 351cj? This is a stop gap mod while I build the 460.  I dont want to put much money in it.  I am looking for nice rough idle and some performance.  I know heads will be a limitation but there is no point in changing them.  I just want to do a simple cam and lifter swap and rockers if needed.  The 460 will be the real burner but I am a couple of years before finishing that

It is a 72 model Mach with 4 speed and posi. It had a stock rebuild around 2 years ago.  

I already have a used edelbrock RPM air gap and 650 dbl pumper to use. The carb will have to be rebuilt and I assume detuned with smaller jets and probably squirter's. The rockers are stock pedestal mount. I guess I will need to change to either full roller rocker, rocker tip or long slot arms for the added lift and stress on the stock pedestals??

So what are the cam recommendations?

 

[MeZapU]

Most lumpy cams might require adjustable rocker arms and heavier valve springs so it might make things more complicated and expensive than you think. If you know it's temporary, stick with something stockish or things might snowball. If you are willing to take the plunge, then I'd just try a solid flat tappet cam. I'm partial to custom cams and cant really recommend anything off the shelf.

 

[c9zx]

Why would the heads be a limitation? They are 4Vs, right? Are you retaining the exhaust manifolds and the rest of the stock 72 CJ drivetrain? Chuck

 

[scgamecock]

Yes they are the 4v heads. Someone put headers on it but they are rusted out so will be replaced. Every thing else is stock 351 cj.

 

[73pony]

My suggestion. If it is merely a stop gap, stick with the hydraulic flat tappet. Get a new cam to your liking and new lifters and prob push rods. If stock rockers are in good condition and you do not go crazy with the cam specs you should be able to reuse them. If you are upgrading the cam and with the airgap intake on a 4V you might want to consider a larger carb, something like a 750.

 

[c9zx]

Assuming the stock springs are not dead, a cam similar to this would work. http://www.lunatipower.com/Product.aspx?id=1608&gid=340 However, the lump factor is moderate.  Since you have headers, it has a bit more exhaust duration than I would use and the 114 LSA tames the idle even more. Search the Elgin cams site to see what they have to offer in a hydraulic flat tappet cam. Something like 218/224 duration @ .050, .505/.515 lift, 112 LSA should work well with stock valve train and drivetrain IF all the components are serviceable. The stock pushrods are a known weak point. If the budget allows, get something with a much thicker wall. Just my opinion. Chuck

 

[scgamecock]

So with the stock heads I need to stay away from solid flat tappet?

218/224 duration @ .050, .505/.515 lift, 112 LSA is max for stock Springs?

There's not really a budget. I can add pushrods and even roller, roller tip or long slot arms if recommended. I will have this original motor in for at least 2 more years. I am trying to resist the urge of putting a lot into this motor but I can see it spiraling if I let it.

 

[sicndhed]

If you want a lumpy choppy idle you want more overlap. Two variables give you overlap, duration and lobe separation. A medium size cam with 112-114 LSA will tame the idle. Tightening the LSA to 108 will reduce idle quality but it will sound much meaner and typically have better mid range power. Usually with a stick things work OK. With an auto you can create a car that needs a higher stall to do anything off the line with the added overlap.

I've never built a 351 so I don't know what fits and what has valve train or P to V issues. I did a 383 scb with mechanical roller mid 240s @ .050 and a 108 LSA. People noticed its idle.

 

[c9zx]

So with the stock heads I need to stay away from solid flat tappet?

218/224 duration @ .050, .505/.515 lift, 112 LSA is max for stock Springs?

There's not really a budget.  I can add pushrods and even roller, roller tip or long slot arms if recommended.  I will have this original motor in for at least 2 more years.  I am trying to resist the urge of putting a lot into this motor but I can see it spiraling if I let it.

   The stock heads don't have adjustable rocker arms so, there is no way to set the lash required for a solid flat tappet (SFT) cam. The SFT will make more power than a HFT but, the heads would need to be machined and adjustable rocker arms would need to be purchased. I looked at the Elgin site and didn't see anything I'd use. 

   The specs I gave may not be "max" specs. but, they are safe specs. If you want more you will need to spend more for valve train upgrades. That intake valve is big, heavy, and hard to control at high RPM. As you increase cam lift and acceleration rates you need to increase spring pressure to control the movement of everything. This is a pretty good article on valve trains. http://www.sbintl.com/tech_library/articles/understanding_high_performance_valvetrain_technology.pdf

   As another warning, the stock, multi groove valves are notorious for breaking and destroying the engine. Chuck

 

[Don C]

Plus, the multi-groove valve keepers are prone to slipping out of the retainer if the valves are floated. This happened to the PO of my car and is one of the reasons I got a good price on it. My machinist said he had seen this several times before.

It happened to me on a '65 with a 289. I didn't float the valves but was driving at 120+ at the time (Nevada pre-speed limits in 1966).

 

[scgamecock]

Ok here we go!!! lollerz

Can I put valves, retainers, springs in on my own or do the springs have to be shimmed?

Can I buy a set of the proform bare heads or whatever they are called now, wash them and install my own parts into the castings.  Yes I know the proform heads have a bad reputation in some circles but they "may" fit iinto the budget that I didn't have until now... ::thumb::

 

[73pony]

Does your engine run now and was a fresh rebuild 2 yrs ago. You are building a 460 that will be ready to go about 2 years from now. Why waste money on new heads and the like? If you want some more power than the stock Q code in the meantime I would just do new cam, hydraulic flat tappet, with lifters pushrods and prob a 750cfm carb and run it like that until the 460 is done. Just my opinion but makes no sense to go through all the work and expense of swapping heads and such just to pull it in two years for the 460. Especially if it was a rebuild 2 years ago.

 

[Don C]

I agree with Jason. Why spend money heads that may be worthless?

Shimming weak valve springs and installing a bigger cam spells disaster. Shimming reduces the spring coil clearance, possibly enough to cause coil bind and breaking something. Minimum desired coil clearance is 0.060".

 

[scgamecock]

No I meant buying a cam and a cam kit which has the matching springs retainers lifters and locks. Most kits I have looked at are around $500 including cam. I was wondering if I had to shim "new" Springs. I have never done that before but I have pulled Springs off with the heads still on. I was thinking that sense I did not do the rebuild I have no idea what condition the springs are in to handle a bigger cam. I have all of the receipts from the rebuild. The springs were not replaced.

As for the proform heads I was just throwing that out there. I don't actually want to do that.

 

[Don C]

Springs that are correct for your engine, and that are good quality, should not need shims.

 

[c9zx]

Do you have a list of parts used to do the rebuild? What cam was used? Did they get rid of the 4 degrees of cam retard put there by Ford? As others have said, if it runs OK just drive it until you can build the engine you want. What kind of 460 build are you planning?  Chuck

 

[scgamecock]

The rebuild was a crank Polish, new rod and main bearings, oil pump and gaskets. I don't have have any receipts on block work so. Not sure what if anything was done to heads and block. Looks like original cam and lifters were reused.

Ok here is my solution based on every ones advice. Please tell me if I go off track.

1 look for a cam imilar to 218/224 duration @ .050, .505/.515 lift, 112 LSA. ***probably going to call comp cams tech line. Agree???

2. get matching spring, retainer and lock kit just to be safe. I can install these myself since no shims would be required for spring height.

3. New lifters and pushrods.

4. Roller tip or long slot rockers worth even if just for engine safety????

Thanks for all of the advice! I have rebuilt/built both BB and SB Chevy's so I have a better understanding of what will and will not work.

Wade

 

[Don C]

If you want a lumpy cam you'll probably have to go lower with the LSA, 108° to 110° and add about 6° to 10° to the duration. The lift should be OK, keeping it relatively low is a good safety factor for piston/valve interference.

I would not reuse the stock rockers.

Talking to Comp Cams is a good idea.

 

[c9zx]

OK, you are willing to spend some money for the temporary cam. If you are upgrading the whole valve train I would go bigger on the cam. With stock drive train and headers something like this should work. http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=847&sb=2 The 110 LSA may give it a bit of the lumpy you are looking for. Pay close attention to the installed spring heights and the resulting on the seat pressures. If at all possible, degree the cam at installation. Use a proper break in oil (Gibbs, Optima, etc.). Use a proper high ZDDP oil after break in. Let us know how it turns out. Chuck