raypratojr Posted October 11, 2011 Share Posted October 11, 2011 98 Cobra, stock long block. Long tube headers, non catted x-pipe, march under drive pulleys, IMRC delete, 1"intake spacer with Canton road race pan and windage tray. Replaced crank trigger wheel last year because the stock one let go. While replacing that I replaced the oil pump with a Melling high volume, steel geared pump. The engine only has 50k miles on it. While at The Glen two weekends ago, the motor seized. This was a very rainy weekend so i was very surprised because the engine wasnt being pushed very hard at all. In car video shows about 20psi of oil pressure just before it stopped. I took the engine apart to find the center 4 rods discolored from heat and the bearings for those rods completely gone. The front two and rear two rod bearings look close to perfect. Does anyone have any idea why just the center 4 rod bearings went? Cylinder walls , cams and all else seem to be fine. I called two engine shops and got two guesses as to what might have happened. Im also looking for an engine shop to put together the short block in the tri-state area. Preferably a shop that deals with modular engines. Any leads would be appreciated. Quote Link to comment Share on other sites More sharing options...
gbrown8439 Posted October 11, 2011 Share Posted October 11, 2011 I'm not sure I have a good guess but I would eliminate normal oil starvation at the pickup. EVERY mod motor we have seen with oil starvation issues ruined the cam journals first. Many times (especially in a Cobra) snapping timing chains and stopping the motor before the crank or rods were severely damaged. What did the oil pump look like after you disassembled the motor? Was the o-ring still in good shape at the pickup? Quote Link to comment Share on other sites More sharing options...
raypratojr Posted October 11, 2011 Author Share Posted October 11, 2011 The pump looked ok from the outside. Who knows what the gears inside look like. I do want to take it apart to see. I have heard of the cams seizing and creating havoc when there is a loss of oil pressure. The o-ring on the pick up looked fine. Quote Link to comment Share on other sites More sharing options...
99cobra2881 Posted November 2, 2011 Share Posted November 2, 2011 Any update to the cause of the failure? Quote Link to comment Share on other sites More sharing options...
raypratojr Posted November 12, 2011 Author Share Posted November 12, 2011 I took apart the short block. By the looks of it, the 2nd main bearing spun which blocked the oil port to the crank. Because of the blocked port, 4 rod bearings are completely disintagrated. I'm not sure why the main bearing spun. The crank is shot along with 4 connecting rods. I'm going to be sending the block out to JDM to have them build a fully forged 5.0 stroker with I beam rods and flat top pistons to bump up compression. Quote Link to comment Share on other sites More sharing options...
brkntrxn Posted November 12, 2011 Share Posted November 12, 2011 Thanks for the follow-up, Ray. Good information to know. -Kevin Quote Link to comment Share on other sites More sharing options...
Holster Maker Posted November 18, 2011 Share Posted November 18, 2011 Hi-vol oil pump is my guess. Okay for drag racing, however in road racing it sucks to much. Accusump is a must also w/4v. Everybody I know "that is in the know" agrees. 2 cents given! Quote Link to comment Share on other sites More sharing options...
raypratojr Posted January 20, 2012 Author Share Posted January 20, 2012 Just picked up a complete 99 Cobra motor with wiring harness for $200. The donor car was in a bad wreck which caused the AC compressor to punch a hole in the block. I'll be using the crank and rods out of it. I'm going to be buying a new set of pistons. Looking for forged flat top pistons for reliability and more compression, probably around 10.75-11:1. Im also going to use the C heads and intakes from the 99pics motor. Id like to swap over to coil on plug s and ditch the coil packs. I got a quote of $750 to check the heads. Im hoping that with the better heads and intake and upping compression will give me +340 hp at the wheels. Is this far fetched? I was running 302hp with the stock motor, long tubes, under drive pulleys and AL drive shaft. Quote Link to comment Share on other sites More sharing options...
Al Watson Posted January 21, 2012 Share Posted January 21, 2012 I dont think flat tops will be a good choice for the dohc 4.6l. Probe makes nice SRS pistons at decent prices, I'd look into them. They list 4 types, flat top which yield around 12:1, 4cc dish around 11:1, 10cc dish around 10:1 and 18cc dish around 9:1 all of which depends on the volume of the heads combustion chamber, gasket thickness, deck height etc. Bet you'll be looking at the 4cc or 10cc dish. Remember 11:1 is the limit for pump gas and alum heads, 10.5:1 would be a good target which leaves a little cushion to 11:1. One thing that needs to be done is to have the chamber on those heads cc to verify the volume, sure you can look up the OE specs but actual measurements is best especially when cutting things close. As for the heads and the $750, I hope that is fully rebuild price not just checking them. Heres some of the things the heads would need: cc the chambers to select piston, pressure test, visual inspection, verify deck is flat or do a cleanup cut, check guide/valve wear and/or replace the guides/valves, performance valve job, verify the springs have sufficient seat and open pressure or better yet replace the springs with nice beehives so you can rev the motor. As for the 340rwhp mark, not sure those parts will get you another 40rwhp, more like another 20rwhp. So look into more airflow or more rpm. Heres some things you could do: port the heads a little, nothing crazy, if you have a die grinder and tools to remove the valves springs you would just cleanup the casting, remove rough spots, blend around the guide and valve seat, and port match them to the geaskets. That be cheap and good. Normal a cam is an easy cheap hp getter but you got 4 of them so it gets real expensive. So i would do the 10.5:1 pistons, port the heads, gasket match to the intake and exhaust and that should get you close. Quote Link to comment Share on other sites More sharing options...
99cobra2881 Posted January 22, 2012 Share Posted January 22, 2012 11:1 c/r, .020" over teksid, ported C heads, FR500 intake/cams, Cobra R underdrive pullies and MAC LTs netted me 372 rwhp at only 6500 rpm. Engine/rings were brand new, is why didnt push rpm any higher. Now I have to go back to the dynp to restrict HP to AI specs. Quote Link to comment Share on other sites More sharing options...
Mystic_Cobra Posted February 15, 2012 Share Posted February 15, 2012 I had a similar failure (or series of failures) with my 96 4.6 DOHC. I lost the stock cast crank trigger wheel last year, too. v1 of my engine was 268/265 v2 was 305/300 v3 was 330/321 v4 was 365/330 v5 TBD... I can elaborate if you want. Quote Link to comment Share on other sites More sharing options...
AI Saleen Posted February 21, 2012 Share Posted February 21, 2012 Please elaborate. I have a 98 dohc cam and I'm about to rebuild it. Quote Link to comment Share on other sites More sharing options...
Mystic_Cobra Posted February 21, 2012 Share Posted February 21, 2012 98 Cobra, stock long block. Long tube headers, non catted x-pipe, march under drive pulleys, IMRC delete, 1"intake spacer with Canton road race pan and windage tray. Replaced crank trigger wheel last year because the stock one let go. While replacing that I replaced the oil pump with a Melling high volume, steel geared pump. The engine only has 50k miles on it. While at The Glen two weekends ago, the motor seized. This was a very rainy weekend so i was very surprised because the engine wasnt being pushed very hard at all. In car video shows about 20psi of oil pressure just before it stopped. I took the engine apart to find the center 4 rods discolored from heat and the bearings for those rods completely gone. The front two and rear two rod bearings look close to perfect. Does anyone have any idea why just the center 4 rod bearings went? Cylinder walls , cams and all else seem to be fine. I called two engine shops and got two guesses as to what might have happened. Im also looking for an engine shop to put together the short block in the tri-state area. Preferably a shop that deals with modular engines. Any leads would be appreciated. Which tri-state area are you in? Quote Link to comment Share on other sites More sharing options...
Mystic_Cobra Posted February 21, 2012 Share Posted February 21, 2012 Please elaborate. I have a 98 dohc cam and I'm about to rebuild it. There are a bunch of weak parts that Ford upgraded throughout the production of the 4.6 DOHC. One of those is the 2-pc crank drive gears for the primary timing chains. The rear one likes to rip the key out of the crank snout. Keep in mind my engine/parts had 150,000 miles on them (including 5 years of road racing and 5 years before that of HPDEs) and the engine had been rebuilt reusing the original timing components. Ford switched to a 1-pc gear that handles both chains and is twice as wide. I was running the old original design on mine and should not have beenfor road racing. The crank trigger/pulse wheel is another item that got upgraded from cast to stamped steel-mine broke. I ended up buying the new Ford Racing Timing kit that includes everything. Feel free to ask more specific questions if you want. What are your goals with your engine? how much power? what class? Quote Link to comment Share on other sites More sharing options...
gbrown8439 Posted February 22, 2012 Share Posted February 22, 2012 I assembled my 4V with the Accufab billet crank trigger wheel. Fits much tighter than stock and isn't as fragile. Quote Link to comment Share on other sites More sharing options...
99cobra2881 Posted February 23, 2012 Share Posted February 23, 2012 I used the accufab piece on mine also. Melling also makes a good oil pump with Billet gears for about $300. Quote Link to comment Share on other sites More sharing options...
Mystic_Cobra Posted February 23, 2012 Share Posted February 23, 2012 Good tips. When my crank gear failed and my chain started flapping around, it seriously damaged my Accufab trigger wheel. I also have been running billet gears in the oil pump. <--Gotta have those! Quote Link to comment Share on other sites More sharing options...
AI Saleen Posted February 23, 2012 Share Posted February 23, 2012 Mystic_Cobra What was done to your motor to get v4 was 365/330? Quote Link to comment Share on other sites More sharing options...
Mystic_Cobra Posted February 23, 2012 Share Posted February 23, 2012 I won't list everything here but the change that we made to go from 330 to 365 was upgrading from B-heads to 04 Cobra C-heads, ported 01 Cobra intake, and custom cams. I hope to have v5 installed and dyno tuned within the next week or two. Quote Link to comment Share on other sites More sharing options...
99cobra2881 Posted February 24, 2012 Share Posted February 24, 2012 What's V5 going to be? Quote Link to comment Share on other sites More sharing options...
raypratojr Posted February 26, 2012 Author Share Posted February 26, 2012 Sorry, I've been away for a while. Jimmy, we met a coule years ago at hyperfest. Any way, I live in northern NJ. Basically, I bought a complete 99 Cobra motor for $200. the car had been in a really bad wreck and the A/C compressor punched a hole in the block. My crank and rods were shot when the motor seized, so I'm using the crank and rods from the 99 motor with new flat top forged pistons in my old block. The short block should be put together in the next couple of weeks. BTW, the shop is charging me $2100 to build the short block and supply new rings, bearings and pistons. Sounds pricey What's interesting is that I bought 03 Mach heads (c. Heads), intake valve covers and computer from a fellow racer. I plan on converting to coil on plug and Am ditching the plug wires. Im sick of the Valve cover seals leaking every time i pull a plug wire out of the motor. I've heard that if I swap my 98 cams in the C heads, it should be good for some decent power increases as the 98 cam's are more agressive than the stock C head cams. I'm hoping that with the new heads and increased compression that I will make at least 335hp to the wheels. The new 9.25:1 rule allows me to go to 339hp I'm going to have JDM reprogram the Mach 1 computer to elimiate all emissions bull sh*t and anything else that isn't imperative to the engine running at WOT. I'll also be installing an Accusump and an idiot light to warn me of low oil press. To make a long story short, I'm giving this motor 1 last chance before I ditch it and go with push rods. This car was towed off track too many times in the past 2 years. This engine is not only heavy, but it's really expensive to fix and time consuming to work on. Ray Prato Quote Link to comment Share on other sites More sharing options...
99cobra2881 Posted February 26, 2012 Share Posted February 26, 2012 Ray, Find a new shop. ASAP. Go in there get your block/rotating assembly and walk out the door. I built my DOHC with $800 worth of custom pistons. The shop '0' balanced the rotating assembly. Then when I asked them how much they would charge me to assemble to rotating assembly, they quoted me $150 labor. My engine didnt even have an hour on it and it made 362 to the wheels at 6500 rpm. $2100 is robbery, ask for an itemized bill and see how they justify charging you that. Quote Link to comment Share on other sites More sharing options...
Mystic_Cobra Posted February 26, 2012 Share Posted February 26, 2012 Ray, thanks for the recap, my memory sucks. I've been too stubborn to ditch my mod motor after all these years and having my first one (two, really) last so long has kept me in it. I keep telling my myself that the new technology is better. You plan and your goal seems reasonable. Yes, the early cams will help with the C heads. There are dozens of threads on svtperformance (in case you haven't seen them) that discuss these changes. I decided to go with custom cams when I switched to C heads but it hasn't been tuned properly with the new setup yet. 2100 does sound a little high, I'd ask for an itemized list, too. I got disassemble, clean, hone, all new bearings, reassemble for 1000. I also got a crank and some head work done that was extra. A good tuner should be able to do all that you need. We mod motor guys need to stick together. Quote Link to comment Share on other sites More sharing options...
raypratojr Posted February 26, 2012 Author Share Posted February 26, 2012 Shop #1 told me they get $1200 for cleaning, machining and assembly. They were charging me an additional $300 for rings and bearings. If i wanted pistons it was another $500. Shop #2 wanted $750 for cleaning, machining and assembly. They wanted the same $300 for rings and bearings. However, i have to supply the rod and main capcap bolts which came to $195. Shop #1 specializes in mod motors according to their website. Btw, can i deck this block? I heard there were timing cover alignment issues if blocks wee decked. If anyone has any leads to a better/cheaper shop anywhere in NJ or DE, let me know. Thanks Ray Quote Link to comment Share on other sites More sharing options...
Mystic_Cobra Posted February 27, 2012 Share Posted February 27, 2012 I would definitely recommend my guy but he's in Springfield, VA about ten minutes south of DC. As for decking the block, I think you can if you keep it to a minimum. One of my heads was decked just to clean it up and it went together fine. I could tell when I bolted the head studs/nuts on. The cam covers would be the only issue and if it's a small amount the gasket will handle it. Quote Link to comment Share on other sites More sharing options...
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