Originally Posted by Kennedys Dynotune

Cylinder block fill should be considered if a large overbore must be used or very heavy nitrous use is contemplated. A complete fill makes the block unsuited to anything other than drag strip use. But a 1/2 fill or less provides some added support for the cylinders and can be used on the street. A partially filled block will run hot though. Overheating may occur and an upgraded cooling system using parts such as an electric water pump, high capacity radiator, and a better fan may be needed. Agents that promote heat transfer such as "Water Wetter" are also helpful.

Before starting any expensive block modification, the block should be checked by a competent machine shop for cracks and casting defects such as core shift. Ultimately, if extra displacement is wanted, it should be attained by installing a stroker crank and not by excessive use of the boring bar.



Besides keeping the cylinders as thick as possible, the main cap area also needs attention in the building of a nitrous/SC engine. Stock SBC with 2-bolt caps are adequate for basically stock motors with small amounts of nitrous or boost (in the 100-150hp range). As noted above, block filler will help here also, keeping in mind the potential for overheating that relates to using fill. Block filler will stabilize the crankcase webs and help prevent main cap "movement" under load. The term "movement" refers to a consequence of block flexing and if excessive this will quickly destroy the main bearings and then the crank. Highly modified small blocks will need 4-bolt main bearing caps. The stock iron 4-bolt main caps are a significant upgrade compared to stock 2-bolt caps. They are all that will be needed for typical street or street/strip use. Very highly stressed engines (>250+hp nitrous/>20psi of boost) will benefit from 4-bolt steel caps. Caps with splayed outer bolts offer only a small advantage on stock blocks. Aftermarket blocks, with reinforced webs, will benefit most from the 4-bolt splayed outer bolt steel caps.



An analogous situation exists with respect to the SB Ford. This is an excellent motor in many respects, but the stock Ford small block has significant weaknesses, even more so than the SB Chevy. Most hot rodders consider these blocks as good to only ~500-575hp range depending on the exact combo before the strength of the basic block becomes problematic. Aftermarket main caps, main stud girdles, and block fill are all options for strengthening these motors.

The deficiencies of the stock small blocks have been addressed by both GM, Ford and the aftermarket. For both Fords and Chevys, the factory and the aftermarket produce a variety of heavy duty "race" blocks. These typically are made of stronger alloys, offer thicker cylinder walls, strengthened crankcase webs, upgraded main caps, and thicker deck surfaces. All are quite advantageous when a max-effort motor is being built. In addition to accommodating larger bores, these blocks are often designed to also allow use of longer stroke cranks than their OEM counterparts. The primary downside is cost. Typically, from $1,500 and up depending upon the model chosen. However, these blocks are stronger than even a maximally prepped OEM case. And compared to the cost of fully prepping a production block, the total cost may actually be less if a factory machined race block is selected. Having a stock block fully "blueprinted" is not cheap by any means and no amount of machine work can compensate for the basic deficiencies of the OEM design.

The "new generation" of small block motors are the future of the domestic performance market. Both the Gen III Chevy and the Ford "modular" motor offer significant advances over their traditional predecessors. While most of the advancement has been in the cylinder head area, the "bottom end" and cylinder blocks of these motors also have been improved. These stronger blocks have increased potential for handling high power without resorting to extensive modifications compared to the earlier models. Cylinder wall thickness is still an issue though, so overbore should be kept to a minimum if high boost is contemplated.

Originally Posted by AKlowriderZ71

Are there different block fill products for cast iron blocks vs aluminum blocks? Or do they use the same stuff?

Originally Posted by budhayes3

After reading this thread and thinking back, I now remember seeing blocks at my dad's shop that have been filled...I should ask him about this also. Guess that I should start making a list and writing down the questions that I have for him lol, I'm starting to lose track

Originally Posted by AKlowriderZ71

Get him to sign up and participate here on PT.net! Then we can just ask him!

Originally Posted by budhayes3

That's a good question...I tried to do some searching, and it seems like all of the block fillers, as well as some shadetree techniques, work well in cast iron blocks, but there has been some difficulty getting stuff to work in aluminum blocks. The Hardblock stuff claims that "Its coefficient of thermal expansion is identical to cast iron engine blocks. Product has been tested and proven effective in aluminum blocks." Which to me translates as "Works in iron blocks, may or may not work in aluminum blocks"...but that's just the way I read it

Top Fuel dragsters have aluminum blocks, wonder what they use? (and how much is costs!)

I did find that some ricers are fond of a product called "Devcon" for their aluminum blocks...

Found some more info, nothing too technical, and it seems like everything in this article has been addressed in this thread, but it's a quick read (shorter than some of my posts )

http://www.carcraft.com/techarticles..._question.html

After reading this thread and thinking back, I now remember seeing blocks at my dad's shop that have been filled...I should ask him about this also. Guess that I should start making a list and writing down the questions that I have for him lol, I'm starting to lose track