Would like to know if any one has bored one of these blocks out to 4.500?
The two that I have are currently at 4.430.
Thanks for any input.
Dave
The two that I have are currently at 4.430.
Thanks for any input.
Dave
-
-
Re: 1969 ZL-1 engine
Dave-----
Are you talking about the original, PRODUCTION-type blocks with cast iron sleeves or are you talking about the later "Can-Am" type big block cylinder cases which used no cylinder liners? For a PRODUCTION-type block, I think that your current overbore might already be too much. For the later ("1970-ish") Can Am blocks, I'm not sure what the allowable overbore is. These blocks were large bore to begin with.In Appreciation of John Hinckley -
Re: 1969 ZL-1 engine
Dave - GM part number P/N 12480035 cylinder liner is used in the aluminum ZL1 cylinder case. This is a stepped sleeve, the top step is 4.635" OD, which is the apparent thickness of the sleeve you view from the deck surface. However, this step is short, and approximately .25" down the sleeve, it necks down to the parent sleeve OD of 4.555" OD. I was considering this sleeve for usage in my cast iron 1966 942 block. This sleeve has an overall length of 6.250" long. The bore you are after would result in a wall thickness of the remaining cast iron liner of only 0.0275"....WAY TO THIN for a liner and nearing the peel out thickness. I ended up working with Darton Sleeves, a division of Darton International, a supplier of most of the high performance step sleeves used in the industry, with most top fuel engines using their products. They can custom build sleeves for any application, and may have a blank ready for your application. The question is, can the parent aluminum wall thickenss supporting the sleeve be overbored far enough to retain the sleeve effectively, given the expansion/contraction of the two dissimilar metals. I am guessing it can, but knowing the core structure of the block would help. By the way, Darton indicated that keeping at least a 0.060 wall or more thickness is required. Here is their website.....
Darton SleevesComment
-
Re: 1969 ZL-1 engine
Joe - I posted below my analysis of the sleeve currently available for the ZL1 block which you gave me the dimensions a couple months ago. Based on working with Darton Sleeves, and the required wall thickness of the liner, this overbore will not work without boring the parent aluminum out, and installing a larger diameter sleeve. This may be possible, based on the core construction of the block, but I don't know for sure. It seems that the cores are a siamese construction in the ZL1 core, similar to the old small block 400 block, which probably means there is sufficient meat in the aluminum wall to support an overbore for a larger step sleeve from Darton...CraigComment
-
Re: 1969 ZL-1 engine
It looks like Darton does not have an appropriate top step sleeve for your application, but they do have a straight sleeve P/N 100-3140 that has the correct bore OD and ID to meet your desired final bore. This sleeve has a 4.47" raw bore, and a 4.754" OD of the parent sleeve. However, you can't use a non step sleeve in your block given it has been machined for a step sleeve already. You can have Darton build you a correct sleeve. They charge $100 for CNC setup for a special build, and go from there. This will get costly since you are talking about 8 liners in the range of $100 each plus CNC setup costs....I know this from been there, and done (evaluated) that......In my case, I could use their standard step flange blank 100-3139 for my application which was $56.00 for the sleeve, and I only needed one for repair.....CraigComment
-
Re: 1969 ZL-1 engine
Dave -
The original production ZL-1 (iron liner) blocks were 4.25" bore, and the Chevrolet Power Book calls for a max .060" overbore with a normal block, or an absolute max of .125" (to 4.375") on a perfect block with NO core shift at all. The iron-linered aluminum 430/465/495 and all-alloy 495 over-the-counter blocks had 4.440" bores, and Chevrolet doesn't recommmend going more than .060"-over on these blocks. Sounds like you have the service blocks, not production ZL-1 blocks. There was also an over-the-counter all-alloy 510 block with 4.500" bores, but there aren't many of those around.Comment
-
Re: 1969 ZL-1 engine
Joe, Craig,
These blocks have casting # 3946052 on them and they have cast iron sleeves.
Both must have been resleeved at some point as they have stepped sleeves that measure 4.812 at the top and 4.635 at the bottom.
Based on Craig's info of at least .060 min wall, I might be able to go out to 4.500.
Maybe they were can-am blocks with sleeves added?
Thank you both for the information.
DaveComment
-
Re: 1969 ZL-1 engine
John,
After your post I checked the bores with a dial bore gage and it looks like you are right on the money. 4.440 bores. Must be the over the counter blocks.
Thanks
DaveComment
-
Re: 1969 ZL-1 engine
I remember that the Black Shadow racing team on the Can-Am circuit for UOP had a whole passel of these over-sized blocks in the back of their shop. I wonder what-ever happened to all those blocks? Hmmmmmmmmmm
GeezerComment
-
Re: 1969 ZL-1 engine
Dave - sounds like they were Can-Am blocks based on John's post. Adding the 60 over gets you to exactly 4.500 and you should be good to go. Apparently, the current sleeve I mentioned is only for the original ZL-1 blocks, not the over the counter Can-Ams. Much better proposition that resleeving! CraigComment
Comment