[slowbird]

I have few question about how to figure rod length. The Pontiac block is 10.25" tall (right?) so everything has to fit in that. I have talked to Ross Pistons and they said that the shortest compression height that can be use is 1.183 and is with the oil ring in the pin hole and I would have to use plugs to run that ring package, has anyone done this and is it ok to do it for a street engine. Back that the rod length, if I were to use a stroke of 4.13 you have to half of that and subtract that from the block height and subtract the compression height and leaves 7.002 left. Now that would be that longest possible rod that can be use (right?). Also when using the block height should I use the 10.25 or should I use a shorter height and mill the block for 0 deck. I have a block that has been mill once so how do I find out what the deck height of that block is? I am planning out a new engine combo and all this is new to me so I do not want to order part and then find out the the piston is above the deck! THANKS

One other thing if were to use a .927 pin instead of the stock .980 pin can I shorten the compression height more.

[This message has been edited by slowbird (edited 03-20-2001).]

[slowbird]

I have few question about how to figure rod length. The Pontiac block is 10.25" tall (right?) so everything has to fit in that. I have talked to Ross Pistons and they said that the shortest compression height that can be use is 1.183 and is with the oil ring in the pin hole and I would have to use plugs to run that ring package, has anyone done this and is it ok to do it for a street engine. Back that the rod length, if I were to use a stroke of 4.13 you have to half of that and subtract that from the block height and subtract the compression height and leaves 7.002 left. Now that would be that longest possible rod that can be use (right?). Also when using the block height should I use the 10.25 or should I use a shorter height and mill the block for 0 deck. I have a block that has been mill once so how do I find out what the deck height of that block is? I am planning out a new engine combo and all this is new to me so I do not want to order part and then find out the the piston is above the deck! THANKS

One other thing if were to use a .927 pin instead of the stock .980 pin can I shorten the compression height more.

[This message has been edited by slowbird (edited 03-20-2001).]

[Steve C.]

Forgot to add.... In MY opinion, and there are other ways to do it, use a standard rod length and use custom pistons to make up the differance rather than have a custom length rod made.

[This message has been edited by Steve Coombes (edited 03-20-2001).]

[Steve C.]

You cannot rely on the block being 10.25" tall. They will vary. After clean-up it might be around 10.215-10.22"
Before we go any further what crank are you going to use? Or is this a custom made crank?
In my opinion your best bet would be to use 6.800" BBC rods for the sake of ease and cost.
Yes... for a serious application you can bush the rod eye down to a .927" pin (small block chevy) to reduce the weight, however for street/strip I would stay with the .990" size on the 6.8 rods.

[slowbird]

I am going to use a SBC rod end and either use a 428 crank and stroke it or use a 455 crank and destroke it. I am looking to build something a little different and still make good power. It will be most race engine. Like I said this is just the planning stage for it.

[Bigred455]

how are you getting 4.13" for stroke? 428=4", and 455=4.21". So if you used a 4" theoretically it seems to be possible.

[slowbird]

I am going to take a 428 crank and stoke it .130. Since a SBC rod end measures 2.1 compared to 2.25 for a Pontiac it should be possible. Or I will destroke a 455 crank .080 to get the 4.13. I don't know how this will all work since the rods look like they will cost a bundle!

[Steve C.]

Slow- I saw the wording "street engine" in the post. Sounds more full race with the SBC rods. I looked into using them awhile back, some opinions suggested cutting a factory crank for SBC journals was not the way to go. Instead I went to a billet crank with 4.125" stroke, 6.8 BBC rods and JE pistons. The compression distance on the pistons ended up at 1.353". (I wanted a good r/s ratio yet keep the motor "over-square", thus the combo)

[Bigred455]

Why would you want to use SBC rods what are the advantages of them over Pontiac, or BBC rods?

[slowbird]

Steve how does your combo run? That is basically the reason I am doing it and to be a little different. How much did the crank cost? The reason I thought about doing this way is I have 2 possible cranks that can be made to work, a 428 or 455. As far as the street part of it, its not really, just enough so that I can go out on weekends and raise some hell with it but its main purpose is to run at the track.

[Steve C.]

Slow- I forgot to mention the motor is based on a 400 block, I wanted 3" mains for less bearing surface and better oiling.
It's done but waiting on getting it scheduled on the dyno... so I don't know how it runs yet [img]/infopop/emoticons/icon_smile.gif[/img] Computer profiles indicate about 725 hp.
The crank is a Crower lightweight billet, cost was about $2200. If your interested in a custom crank talk with KRE, they offer one for $2000... forgot the brand, but it's a quality piece. As for using a large journal factory crank it's no problem having them offset ground for the journal size you want.