How to properly mount pre-roller-heads (pre TPI Fuel Injection) on a roller-cam (OEM TPI) block: includes Chrysler Dodge and Plymouth 318 and 360 blocks and heads.
by Vince Spinelli and Jack Perkins
This is not a “340 friendly” modification… all the 340s were out of production by the 1980s, and several head changes occurred after that.
318 (1988 through and including 1990) Dodge Truck
318 (1985 through and including 1990) Chrysler Car
360 (1989 through and including 1990) Dodge Truck
318 heads (through and including 1987) Dodge Truck
318 heads (through and including 1984) Chrysler Car
360 heads (through and including 1988) Dodge Truck
The reason for two 318 listings is that roller-cams and lifters hit Chrysler sedans and such 3 years before hitting trucks. There was some “leftovers” though… the only way to really know if you need to deal with this whole issue is to look at your motor (regardless of whether it’s a 318 or 360) and follow the table below…
318 or 360
~ 6.78" x 0.3125"
318 or 360
* Roller = Roller cam and lifters? Needed = Do You Need This Modification?
This all came out of a mistake, a “almost-fatal” one. I purchased my beloved “first car”, or at least one that was a dead ringer for it, a 1988 Dodge Power Ram D100. I had previously owned a 1988 Dodge Ram D-150. A 4x4 to 2-wheel conversion and a tranny swap later (from a 727 Torqueflite with a NP-Transfer case over to a straight up 727 and a soon-to-be-built custom driveshaft), I was almost there.
And so, we’re brought to the motor.
The TPI (throttle point injection – the proverbial toilet bowl-predecessor to multi point fuel injection, using a single fuel injector) equipped 318 V8, the stock 1988 mill, was found to be cracked. The truck had sat upon 35” swamper tires with a total of 13” suspension+body lift. The previous owner had decided to drive it through one too many cold streams and swamps on his hunting trips. Coolant and oil were mixed throughout. The motor had to be scrapped (it was saved in the backyard as a reference, and still sits there at the time I am writing this article).
This motor had a few ‘innovations’ for its model year. First, Chrysler finally switched from standard hydraulic lifters (and matching camshaft) over to a roller hydraulic lifter (and thus a new matching camshaft). The roller design allowed for a steeper cam profile, and thus a more precise valve-train actuation. Second, no more carbureted intake – but that blasted 2 barrel TPI fuel injection intake. Third… the heads. Oh yes, the heads are oh so different. While the basic casting is the same, the fine points are not.
To make better use of the benefits of fuel injection, swirl intake ports were introduced. Also, to accommodate a slightly changed pushrod angle (the new roller lifters were taller than the previous standard hydraulics) the push rod guide holes in the cylinder heads were changed from roughly 0.5 inches to a published 0.66 inches (Dodge DW Series Truck Factory Service Manual 1988). Upon measurement, this was confirmed to within an accuracy of 0.01 inches. Push rod length changed from about 7.5” down to 6.78”, and diameter shrunk from 0.360” to 0.3125” (again to accommodate the changed push rod angle).
There are other changes and modifications for this model year, obviously, but that is not the purpose of this log.
I had thought that a “318 was a 318” so long as it was from the 1980s or early 1990s. I was, of course, wrong. Thanks to my former employer and long time friend, Carrie Sweeney, I was given a 1990 (not Magnum!) LA block… free of charge. Upon opening it up, it looked like a million bucks. Clean and clear throughout, only minimal wear. Pistons, rods, cam… everything was re-useable. And so we did re-use just about everything in doing this rebuild.
But, as my good friend, and engine-building-instructor, Jack would put it, “You try to re-engineer everything, and that’s your problem in life.”
I decided that TPI (Throttle Point/Body Injection) “stunk”, and I wanted to go to a simple 4 barrel carburetor and call it a day. But the swirl port heads and lower compression ratio of the heart shaped combustion chambers inside of the 1988 and older fuel injection heads (which were present on my 1990 boneyard motor) would not be “carb-friendly,” so I opted for 1983 police heads.
There are squad car heads, and there are interceptor heads. Don’t confuse them. Squad car (cruiser) heads are 360 heads with little to no modification depending on whom you talk to. Interceptor heads are high compression heads, identical in every way to standard 318 heads of the era, but with a smidge tighter combustion chamber. Compression works out to high 9s to 1, as opposed to the standard 318 head at about 8.5 to 1. Interceptor heads also have slightly large valve aperatures. It was not enough to make a huge difference, but combined with the added benefit of a roller cam and lifters, I felt I would be doing a grave injustice to not put those heads on my motor.
While many of you may not be doing this exact swap… this article is intended for anyone who wants to put use “pre-roller” heads on a “roller” block (as I've pseudo-nick-named them); note that “roller” heads on a “pre-roller” block will work without a problem. Just be sure that your cam+lifter+push rod combination does not change… you will use either a non-roller cam + a non-roller lifter + a 7.5” pushrod @ diameter 0.360” OR a roller-cam + roller-lifter + 6.78” pushrod @ diameter 0.3125”. (These are the STOCK parts. I cannot and will not make recommendations as to modified parts or aftermarket cams, etc… this of course excludes cams or lifters that are DIRECT OEM REPLACMENT and/or OEM parts refurbished or rebuilt by an aftermarket company to OEM SPECs!)
The only thing left to get ahold of was a 4 barrel 318 friendly intake. 318 and 360 intakes are generally swappable, just be sure that if you have an EGR “smogger” motor (and don’t get me wrong, EGR is good! – ensuring that the combustion chamber is cooled and reduces spark knock, adding to fuel economy as well) that you have an EGR cross through in the intake. Most Mopar 4 barrel intakes fall into this category, but some do not… Holley and Edelbrock both make intakes though; the Edelbrock 2176 and 21761 are NON-EGR, Edelbrock 3776 and 37761 are EGR-Friendly (the “1” simply stands for “polished finish” in the model number). I chose the Edelbrock 3776 (non polished) for my application. It would be mated with an Edelbrock 1403 500 CFM 4 barrel.
Well …I buried myself in a hole so unimaginably deep that I thought I could never get out of it.
After months of scraping and cleaning, learning, and fixing, the motor was done. I painted it beautifully, mounted all the accessories, and we dropped it in the truck.
Fired it up… TICK TICK TICK TICK TICK TICK… and it wasn't the lifters.
Shut it down, all 16 push rods bent. That’s when I realized what had happened.
This is also right about the time that I actually started to research what the heck I had gotten myself into. When I figured it out, I wanted to crawl into a hole and die. I had spent nearly $300 per cylinder head, just to get into trouble.
Time to get to work… I got all my ducks in a row, and this was the solution…
1 – Remove heads from block.
2- Take a 5/8” heavy duty (1/2 inch chuck) drill bit (preferably carbide tip or better), and mount it in a stand up drill press. DO NOT DRILL BY HAND. You will not get the holes straight; I know this because it’s the first thing I tried. Line up the holes “dead on balls” center with the drill bit… you want to make these 0.5” holes into 5/8” holes (0.625”), with the SAME center points. Remember, the stock roller-heads had 0.66” holes… well, you can’t buy a 0.66” drill bit unless you have a BlackHawk Tools dealer on the corner and are going to use a drill press with NO SLOP. That large of a bit, with the minor slop of the drill press (god forbid your cylinder head “wiggle” on the deck), and you'll go through an intake jacket or bust the mounting face/flange for the intake manifold. Keep in mind, when you drill something out, the drill press itself is going to shake, so your actual hole will be slightly larger than the drill bit – by only a tiny bit.
Follow the diagram above to line up the heads with the drill press… when you’re done drilling out the holes, you should double check with a micrometer. You should have 0.630” to 0.635” holes. It is absolutely CRITICAL that you keep the drill bit within the press absolutely vertical – no wobbling, no tilting. It is also critical that you do not “wiggle” or allow the cylinder head to move about when you are drilling. CLAMP IT DOWN or you will crack the head! A LIBERAL amount of cutting oil will be necessary. In lieu of cutting oil, standard gear oil (the heavy 80w90 differential stuff) will do the job. Do not force the drill bit. Nurse it slowly in, then out, then back in again. Excessive pressure will crack the drill bit and/or your cylinder head, at which time you will surely want to kill me, kill yourself, and set your truck or car on fire.
Well, 0.630-0.635” is far from 0.66”… so you still have some work to do.
3 – Time to get out the die grinder.
Use an air-powered 180 degree (straight, not a right angle / 90 degree) die grinder. Fasten a 1/4 to 5/16th inch straight (non-tapered) high grade die grinder bit into the grinder tool. You’re going to chamfer the holes out. Go have a cigarette and take a break first. A steady hand and patience are the key. It’s fairly easy; it took Jack all of 10 to 15 minutes to chamfer all of the holes in both heads, except one. It took me 20 minutes to try to do the remaining hole before I gave up. If you do not have a steady hand, have a friend help or make a jig to hold the grinder in place.
This is critical… YOU WILL CHAMFER THE “INTAKE” SIDE OF THE PUSH ROD HOLES ON THE TOP OF THE HEAD (THE TOP WHERE THE VALVE SPRINGS STAND) AND YOU WILL CHAMFER THE “EXHAUST” SIDE OF THE PUSH ROD HOLES ON THE BOTTOM OF THE HEAD (THE BOTTOM WHERE THE COMBUSTION CHAMBERS ARE).
Chamfering the “Top” half…
Chamfering the “Bottom” half…
Below is a cross sectional view of what your push rod holes will look like after you’re done with the die-grinder.
Notice how the push rod hole is now angled… it has a bit of “play” in there. Obviously, the drawing is not to scale and exaggerated. However, when you’re dealing with something of this nature, the smallest amount of clearance is all that’s necessary.
You want to remove enough metal on both the top and the bottom so that you put a micrometer on it and measure the oblong-ed hole diameter to be 0.66” or a little more (so long as you don’t start grinding into the valve cover mount.
Keep roughly a 20 degree angle, and go deep enough that the taper of each camfer will meet each other. This should give you the 0.66” mark that you’re looking for.
Clean off any burrs and vacuum, vacuum, vacuum, vacuum. Get a magnet and a paintbrush and clean the head out. Be thorough; one metal shaving can ruin your day later on. Polish it out, make sure everything is smooth. If it’s too sharp to put your finger in, then you need to polish it up some more. It should be baby-bottom smooth
Put your motor back together, put in the proper length push rods (6.78” @ diameter of 0.3125”, either oiling or non oiling depending on your lifters and rockers), prep, and fire it back up.
Do a quick timing and carburetor adjustment to make sure you’re at least in the ballpark… we’re just looking for basic functionality right now, not fine tuning or high performance.
Let the motor run in neutral or park at 1500-2000 rpm for about 20 to 30 minutes … or until the lifters pump up (whichever happens first).
After your lifter noise is all gone, or almost gone, start listening for rapping or an erratic ticking. If you don’t hear anything other than minor lifter noise, then move on to the next step. If you start hearing rapping or erratic ticking, pull the valve covers off… pull the ignition cable, have a friend turn the motor by hand, and check each rocker and push rod for proper range of motion and to see whether they’re sticking or not.
Your next step is to do a basic vacuum test. Tap into manifold vacuum with a reliable vacuum gauge. You should have no less than 17 inches of vacuum. Initially, I had only 15, and it was very erratic (bouncing).
What we want to see is a nice, rock steady, vacuum reading at idle. That needle may twitch, but it shouldn't bounce around at all. Dump the throttle, watch vacuum drop to virtually zero and then return to roughly 17 to 20 inches.
As I said, initially I had only 15 inches… I thought that one of the holes was not drilled properly, but in reality I had a collapsed lifter (from the jammed push rods previously used… the lifter was destroyed).
I replaced all 16 lifters with new Federal Mogul units (OEM direct replacement)… and tried again.
17.5 inches of vacuum, rock solid steady.
Adjusted idle and timing… (not even fine tuned, just “by ear” adjustments) and achieved 18 inches of vacuum at roughly 800 RPM (my idle setting) and just over 20 inches at around 2,500 rpm after a throttle dump.
Now, you’re not done just yet.
In God and Jack we trust… everybody else pays cash. Remember this.
Peg the throttle at about 650 to 700 rpm ( a little below the 750 OEM recommended idle ) because we want to hear it stumble… we almost want to encourage a stumble… we’re looking for problems still.
Perform a cylinder balance test. With the motor running at 650-700 rpm you’re going to pull each spark plug wire, one by one, off of the distributor cap tower. Start anywhere you like, just make sure you know which plug wire is which (if you notice a problem cylinder, you'll want to be able to figure out actually which one it is – numbering your plug wires on both ends with a Sharpie marker never hurt – especially when you've had the motor apart about 20 times inside the vehicle within the course of a 2 month period, and I'm not exaggerating). As you pop off a plug wire, listen very carefully… it also helps to have a tachometer hooked up. Watch the tach and listen.
You SHOULD hear the motor stumble, and you SHOULD see a dip in the tach when you pull a plug wire. As long as you do, you can replace the plug wire and move onto the next plug wire. If after pulling any given plug wire you do NOT hear a stumble or see the tach dip, then you know that particular cylinder is not firing (it may be getting spark, but the valves are probably hung open or closed due to the push rods for that cylinder being locked up in the modified holes). The vacuum test will also tell us this, but it will not tell us WHICH cylinder is having the problem… the cylinder balance test determine exactly where that problem is.
If you've got a problem cylinder… pull the valve cover off and investigate. You may have to “massage” the push rod hole out a little more, or you may have a collapsed lifter like I did. You may have a bad or bent valve stem too… don’t rule anything out – be smart, be observant. And DON’T PANIC. you'll figure it out.
Now, if you passed both the vacuum and cylinder balance test, then guess what?
Let that mill run for about half an hour at 1500 rpm, sit down, have a couple cigarettes, hug everybody you know, and pop open a beer. It’s a job well done. You just accomplished something.
After chamfering out those holes, you’re going to have a hell of a time getting a hard rubber or paper valve cover gasket to seat very well. Get a cork one, the “el-cheapo,” non-resuable, $3 cork ones. I recommend Mr. Gasket or Fel Pro Blue Stripe. The cork is an EXCELLENT material to form to the head and get the job done right. Little bit of Hi-Tac never hurt either.
While I have spent more hours then I can tally looking at reference books and webpages and old casting logs, my determination and confirmation of the problem would have been for nothing had I not had the many years of experience and wealth of knowledge that is Mr. Jack Perkins.
I've learned to trust his word and his ideas, if only because he never asked me to trust him. Every single question I've ever asked or ever had, he answered by teaching me exactly how the particular part functions, re-measuring, re-torque-ing, and performing each operation by the book. I cannot put a value on what he’s taught me.
I've also got to thank my grandparents, Vince and Theresa Spinelli, my only “sponsors,” and my mother, Marie. You can’t put a value on the faith that your family has in you. I remember sitting inside the engine compartment itself, with my head hung and a cigarette in hand… wondering how many more times I was going to have to take it apart before it would just plain work. I ran plumb out of funds, but I never ran out of parts. They kept pouring in by the boatload as I needed them. I think my family kind of picked up the flag of my mission somewhere along the way, because, hell or high water, that thing was going to run by winter. I've gone through enough rods, enough oil, and enough gaskets to attest to that. Keep in mind, every time I tested a hole pattern or a rod setup, I had to yank the intake, drain the oil and coolant, and get new rods (if the previous set was bent). It adds up after a while. But we finally got it done.
So, now I'm going to go break some more bolts…
— Vince Spinelli, www.spinellicreations.com, and Jack Perkins
Main LA engines page | 318 and 360 specifications for squad car use, 1967-1976
(Click here for repair tips | click here for performance tips)
All Mopar Car and Truck News