Muscle Mustangs & Fast FordsHow To Engine
Short-Block Quality Test
Concerned about mail-order motor quality? Are they as good as the advertisers claim? We take a close look at what you get when buying a DSS Bullet Pro short block.
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I have long been a little leery about buying a mail-order motor unless it's factory stock and the intent is to use it as a basis for greater things. After some close friends had bought engine kits of substantially less-than-stellar quality from a large, well-known discount mail-order company, I became even more leery. This was all in the back of my mind when my 140,000 mile 5.0 started using oil at the rate of a quart for about every 10 runs on the chassis dyno. It was clear that, as a test vehicle, this machine's days were done.
With a backlog of several pairs of heads, half a dozen cams and three or four manifolds to test, I needed a rebuilt bottom end fast. To be honest, with a stack of articles to get out,I did not welcome the prospect of pulling and stripping the motor, getting all the reusable parts (such as the block, crank and rods) cleaned and hunting down pistons, bearings etc.
Seeing my dilemma, Dale Sciranko at Custom Performance in Charlotte suggested I get a DSS bottom end. His company has used a substantial number of them and has found going the crate short-block route with a company that builds reliability allows a fast turnaround. This greatly helps when required to meet the needs of customers wanting the next best thing to instant gratification. Of course, factors such as getting quality end results in terms of performance and reliability figure heavily in the equation. In Dales words, the deal is this: "They ship you a meticulously cleaned block equipped with moly ringed, forged flat tops, a reground crank, an ARP bolted and balanced rotating assembly, oil pump, and mains girdle. All you need to do is install the cam and heads of your choice and you are back in business."
Since Sciranko runs Custom Performance on a strict quality basis, I took his recommendation seriously. In fact it gave me an idea. Normally DSS ships short-blocks in assembled form. But how about if I got one of its short-blocks as a kit, checked every part for quality and accuracy and let MM&FF readers know what they might expect of DSS? Assuming they went for this deal, the intent was to have them ship the same day so there was not time to supply a "special" that would skew results.
I called Tom Naegele at DSS and pitched the part of the plot he needed to know to make a decision. I kept the "same day shipping" clause till last. What I needed was a stout bottom end to test everything a hot street fanatic might want to read about including nitrous, and Naegele was more than happy to oblige. It was then I said I needed it shipped right away. Naegele replied that this might be a problem. Due to being in the middle of a shop move to a huge new facility, they had run inventory low. A check revealed that what I needed was not in stock but could be done in a few days. After explaining why I wanted the motor kit right away, he assured me that they had no time to do a special in the middle of a move and what I would get would be just the same as all the other customers. Although disappointed, the full intent of my original plan proving unworkable, I still decided to go ahead. This was based mainly on the fact that I knew Sciranko at Custom Performance would not knowingly touch substandard parts.
About 10 days later the motor kit from DSS arrived and the first thing that impressed me was the meticulous packing involved. Right at that moment I got the feeling I was going to like working on this DSS unit.
DSS uses a very effective oven/ball- peen method of block cleaning and my example was spotless and better-than-new appearing. All the external surfaces were finished in gloss black. As for machining tolerances, I had intended to show all relevant dimensions but this would have meant pages of numbers. Also, Ford blocks, being of the lightweight thin-wall type, tend to be less dimensionally stable than say GM or Mopar blocks. This being the case it seemed best to look at the dimensional machining accuracy of the bores statistically.
To check the bores I used my 1/10 reading Mitatoyu bore gauge that has about double the scale definition of a Sunnen bore gauge. Before starting the bore check, aluminum deck plates were installed on the block. This replicated the situation on the DSS honing machine. However, I should point out that dimensional repeatability when reinstalling a deck plate on a 5.0 block is about two-tenths of a thou. This means the bores, at the time of honing, could be up to two- tenths of a thou more accurate than measured here.
With that in mind, the bores checked out well. The errors on 50 percent of the surfaces were contained within two- to three-tenths of a thou. Ninety-six percent was within four-tenths of a thou and four percent within six-tenths of a thou. This four percent was right at the bottom of one bore and would have no effect on ring seal or anything else of any consequence. So how good is this? Well you may hear race engine machinists talk of bore tolerances of two-tenths of a thou but the reality of the matter is these can only be attained in a closely controlled temperature environment. In practice, five-tenths of a thou is good and, as such, this DSS block would pass any production line bore inspection with flying colors.
The next important dimensional check on the block was the deck height. In final form, I wanted the pistons five-thousandths out of the bore at TDC so the block needed to be decked to achieve that. As near as I could measure the side-to-side deck heights were within 1.4-thousandths of each other and end-to-end within 1.2-thousandths. I did not check the stroke length, but after installing the rotating assembly, all the pistons came out of the block between 2.5 to just over four-thousandths. A tolerance stack up of slightly less than two-thousandths on piston-to-block deck height is very good.
The last major check done on the block was the dimensional accuracy of the main bearing housings. For the spec of motor I had, DSS does not normally touch the mains unless they uncover a problem during assembly. Although line honing the mains is an accepted race motor practice, it is a much overrated pastime for a street or production-based race motor. Rarely are the main bearings out of alignment or tolerance. If they are, this is evident at the time of teardown. If bearings show no signs of such block problems after high mileage, it just does not pay to remedy a non-existent problem.
Having said that, I did find that although housings #2-5 were right on the money, #1 did show an anomaly. It was correct side-to-side and from the crank center line up into the block. However, the cap itself was elongated by a little over a 1/2-thousandth, which took it out of spec. It is extremely unlikely that this would have caused any problems if not remedied, but as anyone who has worked around me will tell you, I am ultra-fussy when it comes to putting motors together. I effected a simple fix by rubbing the caps, mating face down some three-four- tenths of a thou, and was now left with a great block, ready to start putting in the rotating assembly.
Since the assembly process at DSS follows much the same procedure I used, i.e., checking fits and limits with dial bore gauges and tenth micrometers, they would also have found and effected a fix for this wayward cap.
Crank Rods & Pistons
All the crank journal dimensions were checked as were the clearances within the bearings (Federal Mogul brand). The journals were round and parallel to as close as I could measure with a tenth reading micrometer. As for sizes and bearing clearances, these were all within the specs that DSS use. These are different from the factory specs and DSS asked me not to reveal them. It seems they spent considerable time and effort to come up with an oil pump and bearing clearance combo that has less parasitic loss and better bearing life in a high output motor. As far as crank balance goes this was one aspect I was not in a position to check.
The next checks were on the rods and pistons. These were already assembled as received from DSS. The rods had ARP WaveLoc bolts installed and the big end bore resized. I checked the journal bores on a Sunnen rod-honing machine and found all were well within limits.
The forged pistons supplied by DSS were of their own manufacture so I did somewhat more than just a cursory dimensional check on them. Essentially I wanted to see if the machine-work was as at least as good as a well-known brand such as say Federal Mogal or Sealed Power. In a nutshell, the pistons met, where applicable, my expectations and SAE tolerances.
The Moly ring set supplied was of 5/64-5/64-3/16ths widths. These being used in preference, in this instance, to the thinner 1/16 compression rings for less wear when nitrous is used. The rings appeared to be the pre-gapped variety. As such, the ring end gaps within the bores were extremely consistent and I had no file-fitting to do to achieve the required figures.
With all the parts checking I had done, I did not expect any problems with the assembly of the principle parts and this proved to be the case. The only part that required me to do other than regular assembly work was the installation of the mains girdle and oil scraper. At first I thought that DSS had dropped one here, but it was a case of me not reading the instructions pertaining to the mains girdle installation. Basically it is a straightforward procedure involving the possibility of a little cuttering of the girdle to give it clearance with the oil pickup tube. Also, the pickup tube-locating tab has to be repositioned. This is simply done with the aid of a hammer and a stout piece of wood.
After the installation of each piston, I checked the turning torque required to rotate the assembly. This was my final test to see that all was in order. This particular short-block turned over at 22 lbs-ft. That's about five to as much as 10 less than a typical new factory short-block.
After this fine-tooth comb session with this DSS short-block, I can say that if the opportunity to work with DSS comes up again, I am ready. The quality is all that my friends at Custom Performance lead me to expect, and for the $2000 a ready built, Pro Bullet short-block assembly costs, you get your money's worth. My next step with this short-block is to complete the rest of the build with a good set of heads and a reasonably large cam, but that's a story for down the road.