I'm in the midst of building up a 350 Olds using a Diesel block as a foundation. The goal of this engine is to be in a street/strip application with a hopefull 400+ hp final result. My question is: Does anyone have experience building a gas engine from a diesel block? How do you block off the hole cast in the front of the block for the diesel pump drive?

Joe Mondello is the one of the premier Olds gurus- he has an excellent Olds V8 Technical guide that has a section devoted to the conversion you are looking to do! Search for him on the web. Located in California

Mondello's website is <A HREF="http://www.mondello.com" TARGET=_blank>www.mondello.com</A> . For a very brief introduction to this swap, check out these pages: <P><A HREF="http://www.inil.com/users/dlbrown/ofedsl.htm#EDSL%20DieselEngineDetail" TARGET=_blank>Link 1</A><P><A HREF="http://www.442.com/oldsfaq/ofeng.htm#ENG%201964%20-%201990%20Small%20Block%20CIDs" TARGET=_blank>Link 2</A><P>For both of these links, scroll down until you get to info you need. The diesel block is one of the few olds engines that you can count on to be super sturdy on the bottom. It seems pretty simple: small block with tons of meat for boring + big block main journal sizes = bulletproof 411-451 small block. I am thinking of this route, but need to explore more. I've heard that the block is heavier than a big block, and yields fewer cubes, so a big block is a more logical choice. Even keeping the stock crank (which is nodular) will make a nice overbored engine. Given that it is a small block deck height with short rods (to accomodate the tall piston compression height) you may run into custom rods or pistons. Just putting a big block crank with stock rods will push the pistons way up out of the bore I would think... anyone? Also, I don't know rod journal sizes on the diesel.<P>Curtis

"One of the few Olds blocks you can count on to be super sturdy on the bottom end?" We're not talking about mushmetal Chevy blocks here. The 64-76 (and esp 64-67 when they were using forged cranks across the board) Olds bottom end is one of the strongest ever built. Once they started windowing the blocks for weight reduction in 1977, things changed a bit, but the earlier blocks are tough. They had good metal in them, strong alloys- Olds never built a production 4-bolt main engine, and rarely did it on the experimentals.<P>It was explained to me once that the reason Chevy put 4-bolt main caps on their heavy duty engines was not because it was a high performance advantage, it was just that four bolts in mush holds better than two bolts in mush. <P>Sorry. I have to disagree here. [img]images/icons/frown.gif" border="0[/img]

Sorry, didn't mean to offend... It was the later windowed blocks to which I was referring. I didn't say that [img]images/icons/cool.gif" border="0[/img] I should have, though! I totally agree with you on the chevy mush metal, though. Even the bowtie blocks are poopy. You're right...the chevy blocks didn't use four-bolts to make high performance, they used them to make them stay together in some STOCK applications. I think some of the highest nickel content can be found in really early Buick blocks and all Caddy blocks. I've torn apart a 300,000 mile caddy 500 that could have been re-honed and assembled...still had visible crosshatches on the bores!<P>I don't have any brand loyalties...heck I have a Hemi that's going to go in my 85 El Camino.<P>This thread has me thinking....I know where there is a 350 diesel just waiting for me to modify it. [img]images/icons/wink.gif" border="0[/img]

Thanks guys for the help. I'm still debating on whether to do the stroker idea right away or not. I have the 425 sitting in my shop right beside the 350 diesel now, but I might do a build-up with the 350 crank to start with and save the 425 for later. I've got a set of 68-69 heads for the 350 (#7's I think) that I've been working on as of late porting them and doing all the necessary valve work too. An adjustable valvetrain will make its way onto them in the future and so on. Just the short block I'm having trouble deciding what I should do. <P>With the 350 crank would you guys run the original connecting rods (shorter than gas ones) with a better-than-diesel piston (Probably a custom job). Or would you swap in a set of gas con rods and pistons? Rod journals are the same size as any other small block Olds, only the main journals match the big blocks. I don't even know if you can get a gas piston for the diesel rods.

The amount of money you are talking about spending would pay for a complete aluminum block and heads of the engine of your choice.<P>Although I appreciate the idea, reality would preclude you from investing in what would be a "bastard" engine that had no value in todays market.<P>If you are looking for an advantage in a racing situation, there are better ways of doing this. Have you priced a set of custom pistons lately? These alone might cost you $1500 U.S. and you would be reinventing the wheel.<P>I have been a part of many well meaning projects such as this and they always end the same-the money and the interest runs out.<P>If I were you I would drop that 350 Diesel and spend your resources on the 425, the bigger cubes will give you the torque you desire and be reliable and repairable and worth something in the end.<P>Also the chevy blocks are made of a malleable cast iron that are hardly "mushy", true they are softer than most Chrysler, Olds, Cadillac blocks. <P>Guess what, this alloy has proven to be superior in every respect to the old "hard" blocks and every new engine produced today has this alloy or a variation incorporated in it's design.<P>They dampen vibration better, are stronger, rings seal better and casting the material allows beter quality control with more accurate wall thickness. <P>These are some of the reasons why the chevy became so popular with racers to begin with, the chevy bowtie blocks are the gold standard by which other other engines are measured.<P>No, I am not a "chevy guy". Just one who has done enough machine work on all kinds of engines to know the difference, and four bolt mains are just an inexpensive way to stabilize the bottom end. How many broken mains caps have you seen, I've never seen one. <P>You want strength, cage the bottom end like Honda or the other import manufacturers have done<P>Just an opinion.<p>[ 02-07-2002: Message edited by: Chuck da Machinist ]

Chris... I don't know if you can swap in gas con rods. I don't know if the diesel crank's rod journals are big-block size, small-block size, or their own size. If it takes big block rods and you use those, you will need custom pistons (it its even possible) to keep them from poking way up above the deck. If they are small block size, yes I'd definately use the SB gas rods. They are longer than the diesel's and would possibly prevent the custom piston thing, not to mention maximize rod/stroke ratio. I'm personally a big fan of big bore/short stroke engines. The torque tends to peak higher, but all other factors considered, they increase MY fun factor. If you kept the diesel rods and used diesel pistons you are maximizing rotating weight and minimizing rod/stroke ratio. If you use custom pistons with D rods, you are just spending lots of money to minimize rod/stroke.<P>I guess the best scenario would be if the diesel crank had SB rod journals. Then you could use gas SB rods and gas SB pistons on a nodular, big-main, diesel crank. Anyone know diesel crank rod journal sizes?<P><BR>Chuck....<P>Your argument makes perfect sense. Its true that harder alloys (while preventing fast surface-to-surface wear) would be poorer at quelling harmonics. In addition to being a gearhead, my degree is in Music. I particularly had an interest in the physics behind harmonic series' and temperaments. <P>Thus a question (off the subject): I recently assembled a Caddy 500 that had been machined for me. I noticed when installing [what I thought was] the harmonic balancer that it was just a big heavy front pulley...sings like a tenor when you hit it with a wrench. This engine has no harmonic balancer. Caddy enthusiasts told me that it was because they were "such high quality and balanced so well that they didn't need them" which we know is BS. Every engine has torsional harmonics created by combustion. Why were there no dampers on these caddys?<P>Curtis<P>PS. You seem to know your s#!t. [img]images/icons/smile.gif" border="0[/img] I'm currently in Louisiana, soon to be in Evansville, IN. Where are you and do you want to build an engine for me? [img]images/icons/wink.gif" border="0[/img]

Ok, nevermind...just saw that you were from Winnipeg. The closest I get to you is probably when I summer in Ontario.<P>Curtis

Oh OOhh, I can feel my head swelling.<P>Thanks Curt, you are absolutely right on the harmonics theory. Most people don't realize how much a cylinder wall flexes during the engines operation. It's also the #1 reason for cracked cylinder walls if the engine runs in preignition for any length of time under heavy load.<P>Softer cast iron quells the harmonics better and also allows for more deformation before cracking. The higher nickel content of the bowtie blocks provides a better wearing surface for the rings while also increasing tensile strength slightly.<P>As for your question of do I rebuild engines, this is what I would say.<P>Dissassemble the engine into it's component parts and send each part in for overhaul separately. Do not allow the machineshop/ engine rebuilder to assemble your motor.<P>Inspect each part, if it is a head being overhauled tell them to grind the seats/ valves etc. and test fit/blue each part to verify that you are getting quality work. If you do not have the tools, take the parts to another shop to have bores/valves etc. measured and dialed out. <P>Valves are such an important part that I do not regrind them unless replacements are impossible to find. <P>Engine blocks should be honed to size (not bored), with your new pistons available to custom fit each bore. Why not bored? because removing 0.030"-0.060" can be done on a Sunnen CK10 honing machine in a shorter amount of time and in the same machine setup. Boring should only be done if the bores have shifted or you are sleeving the bores. Either way, very unlikely scenarios.<P>A typical bore can be honed out 0.060" with coarse grit stones in about 5 minutes, some shops will tell you they "bored the block" and charge you extra. If you know better they will not pull this trick on you. Have the engine washed and bagged for you to pick up.<P>Once you have it home you can then check each bore for roundness and taper with tools you beg, borrow. Take it to a machine shop for measuring if you don't have the tools. This can be done without even removing it from the back of the truck/trunk if the owner is smart enough to realize he can make a few bucks from 10 minutes work with a micrometer and bore gauge.<P>Don't freak out if the bores are 0.0005" to 0.001" too large. Tapered bores are what kill an engine because the rings will constantly be flexing with every reciprocation. Take the engine back if you find a bore with more than 0.0002" taper. <P>I purposely build every engine loose just to eliminate the possibility of hot seizure. My wife once drove 30 highway miles in a Ford truck whose engine I had just rebuilt (like 2 days earlier!) with no coolant (the brand new water pump puked!). <P>The engine had twice the recommended piston clearance (0.0055"), after I was done freaking out on her (she deserved it, the coolant light was on!) I did a leak down test on the engine to make sure there was no serious damage, and leak downs were under 3 percent on all 6 cylinders.<P>If I had put only 0.0025" clearance in that engine, it would have seized for sure and I might have divorced her (maybe not, she does make a great spagetti sauce).<P>Anyway the moral of the story is that all interior engine dimensions are only recommendations and good careful inspection and assembly are more important than anything else.<P>This is why I have the machine work done elsewhere and then I play the role of anal-retentive inspector, it also gives me the right to [censored] when things are not done right.<P>One other thing before I quit ranting here, don't believe the notion of "non-retorquing" head gaskets. There is no such thing, I retorque every critical engine gasket after the break-in startup and guess what, they need to be retorqued to ensure adequate clamping. The only exception is cork gaskets like oil pan seals, they are like springs and don't need retorquing.<P>If you take the initiative and build your own engine you will gain the expierience and knowledge and satisfaction of saying "I did it myself".<P>If you have any questions or get stuck.<P>I and others like me will be here to cheer you on and assist you with any questions you might have. Remember, this is not rocket science.<P>Your friend, Chuck.

Doh, just realized i didn't answer your question.<P>Harmonic balancers help reduce crankshaft harmonics, not eliminate them. Those old Caddy engines were built heavy enough and were relatively low RPM motors so they could live without balancers. Some engines have external balance weights built into the balancer so they are extremely necessary to properly offset crankpin weight etc. <P>Those balancers with the heavy cast ring and rubber insulator between hub and ring are very poor harmonic dampers, but are better than nothing. The new aftermarket liquid dampeners are light years more advanced and effective. Also dont rely on the timing marks on the OD of these rings almost every one I've checked is off at least a little bit. <P>When I rebuild a motor I mark a spot on the hub and make a new pointer to reference TDC. When I time the engine I use my Snap-on timing light which has a dial in feature which allows you to input a timing value digitally. <P>This is more for a starting point than anything else, I then start bumping up the initial timing in 2 degree increments until the engine "pings" or I notice a torque drop off. Then I back off 2 degrees and note the timing figure for later tune ups. Most early engines could use more initial timing (particularly Fords).<P>But this is fast becoming a thread unto itself.

Wow, thanks for all the great info! Whew...absorbing it all. [img]images/icons/smile.gif" border="0[/img] Look out world, I am going to try my first short block assembly after the machine work!<P>Thanks<BR>Curtis