396 LT1 clearance/rotating assy. questions
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From: Buffalo, New York
396 LT1 clearance/rotating assy. questions
I am thinking of a 3.875" vs. a 3.75" stroke on the "10 over" block I am going to build up over the winter. The starting point is a stock LT1 block. The block will be partially filled, so I am not worried about the water jackets, but are there additional clearance issues with a 3.875" stroke as compared to a 3.75" on an LT1 block? A small base circle cam isn't needed, is it?
When we did my current shortblock, the rods that gave the best clearance without grinding the big end were Lunati Pro Mods, so I went with them. They have given great service, and were reasonably priced. So, I could use a set of them again. But if any of you have experiences with this combo and a different brand of rod, I'd be curious to know of any that worked well or if you had problems. A set of high end rods like Carillo or Oliver are tempting, but the additional $$$ isn't so good and especially if there will be additional clearance issues, then I would just as soon stick with the Pro Mods.
The only thing about the rotating assy. I have decided for sure is JE "Extreme Duty" inverted dome pistons with HD pins. Other than that. I am open to suggestions.
Rich Krause
When we did my current shortblock, the rods that gave the best clearance without grinding the big end were Lunati Pro Mods, so I went with them. They have given great service, and were reasonably priced. So, I could use a set of them again. But if any of you have experiences with this combo and a different brand of rod, I'd be curious to know of any that worked well or if you had problems. A set of high end rods like Carillo or Oliver are tempting, but the additional $$$ isn't so good and especially if there will be additional clearance issues, then I would just as soon stick with the Pro Mods.
The only thing about the rotating assy. I have decided for sure is JE "Extreme Duty" inverted dome pistons with HD pins. Other than that. I am open to suggestions.
Rich Krause
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Joined: Jan 2001
Posts: 293
From: houston, Tx
You should be fine but you will probably need a slightly reduced base circle depending on the cam you will be running. The block is easy to clearance without hitting water even with H-beams. People just don't pay attention to what they are doing usually and want to get done fast. I've done several 396 LTxs with no problems.
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From: Buffalo, New York
Originally posted by racer7088
You should be fine but you will probably need a slightly reduced base circle depending on the cam you will be running. The block is easy to clearance without hitting water even with H-beams. People just don't pay attention to what they are doing usually and want to get done fast. I've done several 396 LTxs with no problems.
You should be fine but you will probably need a slightly reduced base circle depending on the cam you will be running. The block is easy to clearance without hitting water even with H-beams. People just don't pay attention to what they are doing usually and want to get done fast. I've done several 396 LTxs with no problems.
The cam will be a fairly small HR, not more than 0400" lobe lift.
Rich Krause
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Joined: Jan 2001
Posts: 293
From: houston, Tx
The H-beams and your Pro-Mods do have better clearance at the cam and if you need to you can clearance them there a little more. You could do a slightly reduced base circle or try a similar cam to see how much clearance it looks like you will have before you order your other cam.
Thread Starter
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Joined: Dec 1969
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From: Buffalo, New York
Originally posted by racer7088
The H-beams and your Pro-Mods do have better clearance at the cam and if you need to you can clearance them there a little more. You could do a slightly reduced base circle or try a similar cam to see how much clearance it looks like you will have before you order your other cam.
The H-beams and your Pro-Mods do have better clearance at the cam and if you need to you can clearance them there a little more. You could do a slightly reduced base circle or try a similar cam to see how much clearance it looks like you will have before you order your other cam.
Rich Krause
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Joined: Oct 2001
Posts: 144
From: overland park, ks usa
Rich,
I went with the Lunati Pro Mods and didn't have a clearance problem...either at the cam or the pan rail. My buddy (posts on here as "Hoostie") went with H-beam rods and had to take quite a bit of material out of the oil pan rail and then had to clearance the oil pan itself. Also, he had some clearance issues at the cam and he went with a small base circle cam. I think the Lunati rods are the best choice for the 396.
I went with the Lunati Pro Mods and didn't have a clearance problem...either at the cam or the pan rail. My buddy (posts on here as "Hoostie") went with H-beam rods and had to take quite a bit of material out of the oil pan rail and then had to clearance the oil pan itself. Also, he had some clearance issues at the cam and he went with a small base circle cam. I think the Lunati rods are the best choice for the 396.
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Joined: Jan 2001
Posts: 293
From: houston, Tx
Well the Eagle H-beams have always gone in easy for me and now they even have a smaller bolt head. This was the finished block for a 396 we did in Houston not long ago (make 465 at the wheels too!). Had no troubles with anything either and never have. I honestly don't know what most people do to get way into the pan rails? You shouldn't really have to much at all!
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Joined: May 2000
Posts: 799
From: Redmond, WA
Here are some pictures of the clearance work done on my 397* for Crower Maxi-Light rods. I don't believe that any changes were necessary to the cam (a pretty standard LT1 solid roller grind, as far as I know, with the exception of the duration), but my cam card doesn't specify the base circle diameter. Maximum lift at the lobes is 0.430" for both intake and exhaust (112° separation).
http://home.gci.net/~jimlab/images/Rods/PB140047.jpg
http://home.gci.net/~jimlab/images/B...d/PB160063.jpg
http://home.gci.net/~jimlab/images/B...d/PB160044.jpg
http://home.gci.net/~jimlab/images/B...d/PB160028.jpg
http://home.gci.net/~jimlab/images/B...d/PB160043.jpg
*Surprise, surprise. My build sheet says I have a 4.040" overbore with 4.037" JEs.
http://home.gci.net/~jimlab/images/Rods/PB140047.jpg
http://home.gci.net/~jimlab/images/B...d/PB160063.jpg
http://home.gci.net/~jimlab/images/B...d/PB160044.jpg
http://home.gci.net/~jimlab/images/B...d/PB160028.jpg
http://home.gci.net/~jimlab/images/B...d/PB160043.jpg
*Surprise, surprise. My build sheet says I have a 4.040" overbore with 4.037" JEs.
Registered User
Joined: May 2000
Posts: 799
From: Redmond, WA
Originally posted by rskrause
Jim: dang, those are nice lookin' rods!
Jim: dang, those are nice lookin' rods!
http://www.rx7club.com/forum/attachm...postid=2206713
LOL re: the JE's 
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Joined: Jun 2002
Posts: 2,456
From: sarasota, fl
Originally posted by racer7088
The H-beams and your Pro-Mods do have better clearance at the cam and if you need to you can clearance them there a little more. You could do a slightly reduced base circle or try a similar cam to see how much clearance it looks like you will have before you order your other cam.
The H-beams and your Pro-Mods do have better clearance at the cam and if you need to you can clearance them there a little more. You could do a slightly reduced base circle or try a similar cam to see how much clearance it looks like you will have before you order your other cam.
damn eric, that is one wicked looking rod at the bottom of your engine building page!!
and that shot with the gun rocks! what is that, looks like an ingram mac11?
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Joined: Oct 2002
Posts: 6,518
Originally posted by jimlab
Here are some pictures of the clearance work done on my 397* for Crower Maxi-Light rods. Maximum lift at the lobes is 0.430" for both intake and exhaust (112° separation).
Here are some pictures of the clearance work done on my 397* for Crower Maxi-Light rods. Maximum lift at the lobes is 0.430" for both intake and exhaust (112° separation).
So if you had a .320" lift lobe in a 396 you would be more likely to run into problems vs the .430" lobe because the base circle size is larger on the smaller lift camshaft.
The math works like this:
Journal Size: D=1.868 r=.934
Cam lobe lift: .375
Max Base Circle = (r Journal Size - Cam Lobe Lift)2 = base circle diameter.
So on a .375" lift lobe you would have a max base circle diameter of 1.118"
You could have it cut down to a .900 base circle or run a lobe with .484" lift either one will get you a .900 base cirlce.
Rich,
In your case the rod selection has more to do with it than anything. A wide big end or one that's not clearanced for a stroker is going to make the cam/rod clearance closer. I would imagine that high lift lobes are where you will be going now so a standard base circle cam is going to be o.k. but as Eric said try your current cam out just to check the clearances.
BTW I didn't forget about your e-mail. I'll zip one off to you today.
Bret
Last edited by SStrokerAce; Nov 11, 2003 at 08:55 AM.
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Joined: Apr 2000
Posts: 555
From: Yakima WA
Rich,
I have your same combination, w/ a 3.875" Lunati Pro Crank, and Carrillo Rods. All said and done , once the clearancing was done and engine was put together we inspected the bottom end, and we'll just say I felt the clearancing needed was "excessive" due to the massive big ends of the Carrillos 5.85" rods. If I had known it would have been needed, I would have opted for a different combination.
I'm skeptical about block integrity already for my aniticipated power levels (on nitrous @ 7500-8k rpms no less), and on top of that I now have an even weaker LT1 Block albeit a filled w/ hardblock. To this point I have just gone with it, and taken the "If it blows up oh well" attitude, in which case I will be doing a Donovan Block anyways.
Given your combination, I would think a 3.75, 3.6 or 3.5, or stock stroke crank could be used to alleviate all these possible issues. The slight lack of cubes has never seemed to hurt a Forced Air Combinations ability to make power, and given you stick to the LTx platform, the cubes are a minor concern when weighed against longevity and structural integrity.
JM $.02 from a similar combination.
I have your same combination, w/ a 3.875" Lunati Pro Crank, and Carrillo Rods. All said and done , once the clearancing was done and engine was put together we inspected the bottom end, and we'll just say I felt the clearancing needed was "excessive" due to the massive big ends of the Carrillos 5.85" rods. If I had known it would have been needed, I would have opted for a different combination.
I'm skeptical about block integrity already for my aniticipated power levels (on nitrous @ 7500-8k rpms no less), and on top of that I now have an even weaker LT1 Block albeit a filled w/ hardblock. To this point I have just gone with it, and taken the "If it blows up oh well" attitude, in which case I will be doing a Donovan Block anyways.
Given your combination, I would think a 3.75, 3.6 or 3.5, or stock stroke crank could be used to alleviate all these possible issues. The slight lack of cubes has never seemed to hurt a Forced Air Combinations ability to make power, and given you stick to the LTx platform, the cubes are a minor concern when weighed against longevity and structural integrity.
JM $.02 from a similar combination.