I have a roller cam, 302 head 318 in an 89 dodge P.U.. I am doing a rebuild & want to upgrade & eliminate lean burn. Pistons are easy - KB167, Summit headers, Mopar electronic ignition w/ orange box. The problem is the cam. I think that I read, somewhere..... how to change the roller cam to a flat tappet cam, However I cannot find that info. I know that the push rods have to be changed, & i think it was either the Jeep, or the AMC lifters that had to be used. Any help would be appreciated. I need specifics not guesses. Thanks.

 

another possibilty?? What if instead, you shave the block .020", use a .027" head gasket, ( Net gain .013"), w/ stock pistons, yields about, (starting at 9.1:1 compression), 9.6:1. Because of shorter height from valley to rocker assy., there would be a slight increase in lift. which of course would be offset by hydraulics in lifter& cyl. to plumb difference. I don't know the calculations, but there would have to be some gain. Right?

 

OK, Welcome, here we go.

#1-Milling the block will not have any affect on the camshaft lift.

#2- Changing that block to a Flat Tappet needs no special parts or the AMC oil through lifters, that stuff is for putting Magnum heads on an LA block. LA (302) shaft rockers are oiled through the block.

#3-Your existing rockers with standard length 318 pushrods, LA hydraulic fat lifters and cam kit will drop right in, like we did to our same engine.

#4- Now the fun part is that piston with a 1.81" compression height will be .012" below deck and with no decking and a .030"something thick gasket will give you good Quench and higher compression.

I will do a couple of calculations and get back.

If you mill the block with a .040"- .045" gasket, or no mill and thinner gasket with 4.040"-4.180" gasket bore your compression will be...

9.6 - 9.8 to 1.

Any cam with lift over .420" and for sure .450" will need valve retainer to guide clearance checked, but can easily be cut down with a cutter from Comp Cams and hand drill.

 

On an LA decking the block is doable.. I did .050 on a 360 build once. Then you need to check valve to piston clearance... You do have to custom fit the intake...Shorter push rods may be required ??

 

Thanks. I am not sure about the compression height of the piston in the cyl., but it seems that it was much farther down than that. This engine OEM was a 9.1:1 & a piston compression height of 1.755". The KB piston w/ the 1.810" compression height is a 10:1 piston in a stock block, at least according to their advertisement. So if I use that piston I would use a OEM, ( .040 - .045" thick) head gasket. I read on Hughes engine builders site that they used the .027" gasket & decked the block, they claimed 9.7:1 compression w/ stock pistons. I am not trying to argue, just saying that this is what I found in searching. I have built about a dozen of these in the pre 1987 style w/ just bolt on improvements. Just haven't messed w/ the roller cam & the 302 heads prior to this.

 

No secret.


Block 9.6" - 6.123" (rod length)= 3.477".


3.477" - 1/2 stroke = 1.822"


!.822" is the number you will be working with. Whether you have 1.81" compression height or less, milled block with thin gasket, it all comes down to that one number for an LA block.


Do the math yourself to be sure before you start cutting your block based on some web site say so or forum discussion you have read, BE SURE!

 

Thanks Dan. The formula will be especially useful now & in the future. I would never cut a block without actual measurements having been made. I was only pointing out that , that was the info I had found in doing the research online. In the end, after measuring everything, I will be using the KB pistons in 10:1 & OE style gasket. Comp Cams grind # 252 flat tappet hyd.. I think this will make a nice streetable package.

 

We are running the 256 in our truck with the 901 spring. Fantastic cam!

http://www.compcams.com/Company/CC/c...?csid=625&sb=2

Is yours this: http://www.compcams.com/Company/CC/c...?csid=617&sb=2

 

Why do you need to screw with the roller setup? Send the present cam, or a core, off to Oregon cam regrinders and get a nice performance grind, and stay with the roller setup.

Call 'em on the phone. Easy to deal with

http://www.oregoncamshaft.com/

Be careful you don't get "too much" cam, especially in a heavy pickup

 

I checked w/ some local people concerning this & was told that the roller cam is a very mild profile & doesn't easily lend itself to a real performance regrind. A flat tappet hyd. offers as much variety as anyone could want at a much lower price. If you regrind the roller you have to have custom length pushrods. One of the advantages in the roller cam is the parasitic loss consideration, but Chrysler rated that at only 8% of total parasitic loss, which is easily made up for w/ a cam that meets your particular needs. Roller or flat tappet hyd. will need better valve springs if you get very far from stock figures.

 

The cam I bought is from a local vendor, rather than the Comp cams, it is: 204@.050; .422 lift on Intake; & 214@.050; .444 lift on Exh.. I know it isn't wild, but I didn't want a thumper & I wanted to keep the vacuum high. It is in a pick-up & w/ headers I think it will do just fine. I did consider something like the 256 grind you spoke of, but the heads are already assembled w/ stock valve springs.

 

Two quick questions? With the flat tappet hyd. cam & stock pushrods, can I use the factory rockers from the roller set-up, or do I need a set from a non-roller? They appear to be the standard stamped steel, shaft mount rockers, that they used forever. Also w/ all the engine stuff switched over, do I need the computer, ( ECU ) for anything? I would like to maintain the cruise, climate control, variable wipers, etc. but I don't think I need the ECU for any of that. Thanks again for all the info & suggestions. I am always willing to learn something new.

 

Stamped rockers are just fine. The lean burn control can go and I don't think it has any other function. There is a possibility it is involved with the cruise but I'd have to check my wiring diagram if I get a minute. Sounds like a good cam to me, our 256 has high vacuum and no thump if you ever go that way.

 

Woops! When you said lean burn I'd forgotten the truck year, 1989 is throttle body injection and has a bunch of stuff tied into it. You'll need a wiring diagram and some head scratching.

I did our '92 Multi Port Fuel Injection SBEC when we went carb LA, and cut out almost everything and reconfigured the relays. The dash lights and gauges were about all that was still used through the SBEC. It sucked but I got it.

 

I figured that there would be some things that would have to be traced & rerouted. But w/ all new engine sensors & gauges, new manifold & carb, & electronic ignition conversion, I just don't think that there is much else on that old 59 pin Nippo ECU. I could be wrong. The new ignition will not use any existing wiring. I am also using a fuel pick-up & lines from an '84 truck. The only other thing I am not really sure of is the Kelsey - Hayes anti-lock brake set-up for the rear brakes. I don't think that it uses the computer at all. But that is easily deleted, just need an adjustable distribution valve.