304 engine help - Page 2 - JeepForum.com

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post #16 of 24 Old 01-03-2014, 03:05 PM
swatson454
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You know, it always comes down to velocity through the ports at the desired peak torque rpm. If you have good velocity, you've got some things in your favor and it makes sense to hang those valves open a little longer. If you don't have it, and these engines in a 4x4 application don't, it makes much more sense to hold the valve closed as long as possible, take as big a gulp of air as possible and shut the valve quickly before any reversion can take place.

Here's an interesting bit of trivia that was presented at Vizard's seminar. Do you know how heavy a 100 foot by 100 foot by 100 foot cube of air weighs? 38 tons! He also said there's enough energy (weight of the air and its velocity) in the port of a Pro Stock engine to run a pellet clear through a 2x4. I know that's racing stuff but I'm using it to illustrate the point that velocity is king and the valve events need to be timed around it.

Ugh, I had a whole train of thought going and as soon as I sat down, it vaporized. Don't you hate that


Shawn


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post #17 of 24 Old 01-08-2014, 08:20 AM Thread Starter
matt1980
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Ok, based on recommendations I have ordered all of my parts, machine work is almost done and I should be able to pick everything up today. New bearings, pistons, rings, cam, lifters, push rods, valve springs, timing set, and gaskets. Block had to be bored 60 over. My question is when I removed my old pistons it appeared that they had a front and back, if that makes sense, there were two lower spots on top of all pistons that were to the front of the motor. Do the new ones need to go back that way? I was taught that the tangs in the bearings were suppose to always go to the outside of the block. Just want to make sure I am not putting this poor thing together wrong. I would hate to spent $1500 in parts and machine labor to have it come apart. I am sure I will have more questions in the near future, thank you all for your replies.
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post #18 of 24 Old 01-08-2014, 08:49 AM
Matt1981CJ7
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Most pistons will have a notation that indicates forward, or front. The numbered side of the rods face outward.

If the pistons have valve reliefs, it's critical to get them correct. Here's a pic that shows a typical orientation on one side.

Matt
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post #19 of 24 Old 01-08-2014, 11:40 AM Thread Starter
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Thank you for the info, I do remember the stamped numbers being to the outside and did not think of using the rod for reference rather than the piston.
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post #20 of 24 Old 01-11-2014, 09:14 AM
swatson454
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Well, after all of that typing, I've gotta ask what cam you went with?


Shawn

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post #21 of 24 Old 01-11-2014, 06:33 PM Thread Starter
matt1980
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spent the extra money on a comp cam, it is an rv cam, can not recall the number. It is suppose to have smooth idle in 304 and up motors, we will see once I get everything together. I still have the body off the frame, undercoating the body so I am probably a few weeks from turning the key to see if I put everything together right. This is a little off topic but do you if I can put mobil synthetic 75 90 weight gear oil in my transmission, transfer case, and differentials. The reason I ask is I have a one ton dodge 4x4 that requires I change the diff oil quite frequently so I keep it on hand and it would be easier if I could use the same stuff. I know that it is gl5 but not sure if it will harm anything being synthetic. Any input would be appreciated, thank you.
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post #22 of 24 Old 02-07-2014, 05:00 PM
roboto65
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I will answer that yeah should not hurt a thing using the synthetic lube.

And on the engine note I am rebuilding my 304 soon also Shawn and I have been conversing also so we went with a custom grind I am having Comp grind the numbers that Shawn described earlier. I cannot wait to get the engine together mine has been bored out to .060 over did not want to go that far but thats where it needed to go.

I may try and find a Dyno around Houston thats not to much $$$$ and run the Cam combo with stock manifold and 2100 and manifolds and then run it again with edelbrock manifold and maybe headers and see what the results are. I have no doubts about the cam just wanted to give real results and show them to you all.

They say money can't buy happiness but it can buy Jeep parts...and Jeep parts make me really Happy.
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post #23 of 24 Old 02-07-2014, 06:29 PM
swatson454
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You're a sick bast*rd, robo. Sick, I say! That would be a sweet test, though. Yeah, I'm pretty twisted too


Shawn

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post #24 of 24 Old 02-08-2014, 12:48 AM
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