LS5 454 two or four bolt main? or BOTH

[Marc S.]

I am hoping to see if I can clear up my confusion on whether or not LS5 454 blocks were ever built at the factory with 4 bolt mains?

I did obtain a reference which read the following:

In Colvin's "Corvette By The Numbers" in the Engine Block chapter, the breakdown on block #512 for 1971 says that the 365 hp came in 2 bolt main only. It says the 425 hp (LS6) is 4 bolt main.

The text does not address this further.

I have seen on other forums several owners claiming they have original 4 bolt mains on their blocks? I can provide those links if requested.

But I like to know if there is any information if GM at times used 4 bolt mains when producing 454 LS5 blocks at Tonawanda?

Thanks.

[Terry M.]

Re: LS5 454 two or four bolt main? or BOTH

Trial lawyers like to ask the question: "Is it possible .... ?" At least they do on TV and in the few court cases I have been involved in.

On the broad scale almost anything is possible, and I suppose that is why they learn to ask that question.

You want documentation? I have never seen any, but I have seen about the same percentage of GM's documentation as I have of the Corvettes they have built. No maybe I have seen less of their documentation.

Edit ad: This isn't about a bar bet, is it?

[Thomas H.]

Re: LS5 454 two or four bolt main? or BOTH

Well............ My 71 LS5 has a 4 bolt main block. Owner I bought car from said block had never been out of the car. He bought the car back in the late 70's.

My car is a very early 1971, Sept 70 build S/N 1632 and has many 70 "left overs" on it.






Tom

[Marc S.]

Re: LS5 454 two or four bolt main? or BOTH

Tom thank you so much for coming forward and presenting your block and associated stamp pad which is clearly correct.
This goes in line with the other reports of LS5's with 4 bolt mains scattered among the forums. I am beginning to see a pattern here.

If there are others that have a LS5 with a 4 bolt main please let me know or if you know someone who has. I would appreciate that.

Terry, not about a bar bet, but the idea is a great one. I am learning about these motors and reading and finding this discrepancy. These reports such as the one Tom presented, and the others reported on other forums, could suggest that 4 bolt mains were indeed a practice at the factory at times for LS5 blocks. Perhaps as tom stated, leftover parts from the previous year. There was a strike then so it makes good sense.

I think there may be others out there waiting to be discovered. Best regards.

[Marc S.]

Re: LS5 454 two or four bolt main? or BOTH

Well............ My 71 LS5 has a 4 bolt main block. Owner I bought car from said block had never been out of the car. He bought the car back in the late 70's.

My car is a very early 1971, Sept 70 build S/N 1632 and has many 70 "left overs" on it.






Tom

Tom would it be possible if you could provide a picture of the drivers side of your block where I could take a look at the 2 cap plugs indicating the
4 bolt main block? Thanks and best regards.

[Tim G.]

Re: LS5 454 two or four bolt main? or BOTH

Did these blocks also have the larger plug by the oil filter? That would help identify them externally.

[Dick W.]

Re: LS5 454 two or four bolt main? or BOTH

Did these blocks also have the larger plug by the oil filter? That would help identify them externally.

Real four bolt main blocks have the plugs.

[Phil W.]

Re: LS5 454 two or four bolt main? or BOTH

Check out the "4-bolt main oil cooler plugs" thread below in Similar Threads started by Jeff Morgan. John Hinckley posted a good picture of the plug holes by the oil filter on a 4-bolt main block.

[Joe L.]

Re: LS5 454 two or four bolt main? or BOTH

I am hoping to see if I can clear up my confusion on whether or not LS5 454 blocks were ever built at the factory with 4 bolt mains?

I did obtain a reference which read the following:

In Colvin's "Corvette By The Numbers" in the Engine Block chapter, the breakdown on block #512 for 1971 says that the 365 hp came in 2 bolt main only. It says the 425 hp (LS6) is 4 bolt main.

The text does not address this further.

I have seen on other forums several owners claiming they have original 4 bolt mains on their blocks? I can provide those links if requested.

But I like to know if there is any information if GM at times used 4 bolt mains when producing 454 LS5 blocks at Tonawanda?

Thanks.

Marc------


"Officially" according to GM, L-36, LS-5 and LS-4 had 2 bolt main bearing caps. However, there have been numerous examples of apparently original engines with 4 bolt mains. Just why this occurred I do not know. One possible explanation, though: for 1969 and 1970 Chevrolet advertised that all engines with 4 barrel carburetors had 4 bolt mains. So, it might be that 4 bolt mains were included to meet the advertising. If so, though, they didn't comply with the advertising for a lot of L-36 and LS-5 because most of these do not have 4 bolt mains.

[Marc S.]

Re: LS5 454 two or four bolt main? or BOTH

Marc------


"Officially" according to GM, L-36, LS-5 and LS-4 had 2 bolt main bearing caps. However, there have been numerous examples of apparently original engines with 4 bolt mains. Just why this occurred I do not know. One possible explanation, though: for 1969 and 1970 Chevrolet advertised that all engines with 4 barrel carburetors had 4 bolt mains. So, it might be that 4 bolt mains were included to meet the advertising. If so, though, they didn't comply with the advertising for a lot of L-36 and LS-5 because most of these do not have 4 bolt mains.

Joe thank you for you response and confirming that there are other examples of 4 bolt main LS-5 motors out there with what appear to be original engines. Very interesting about the advertising that all engines with 4 barrel carburetor had 4 bolt mains. Could very well be one possible explanation for the examples out there. Would you happen to know if there are copies of said advertising? That is something I would like to see. Thank you so much.

[Thomas H.]

Re: LS5 454 two or four bolt main? or BOTH

Here are some more pics of my block






Tom

[Thomas H.]

Re: LS5 454 two or four bolt main? or BOTH

Here are some more pics of my block





Tom

[Joe L.]

Re: LS5 454 two or four bolt main? or BOTH

Joe thank you for you response and confirming that there are other examples of 4 bolt main LS-5 motors out there with what appear to be original engines. Very interesting about the advertising that all engines with 4 barrel carburetor had 4 bolt mains. Could very well be one possible explanation for the examples out there. Would you happen to know if there are copies of said advertising? That is something I would like to see. Thank you so much.

Marc------


I'm sure there are copies of the advertising around. However, I don't think I have any. I definitely recall that advertising from the period. However, what I don't recall, for sure, is whether it applied to all engines with 4 barrel carburetors or just small blocks with 4 barrel carburetors. For some reason, though, it just sticks in my mind that it just said all engines with 4 barrel carburetors.

In any event, this was only for the 1969 and 1970 model years. It definitely did not apply to 1971 and beyond.

[Marc S.]

Re: LS5 454 two or four bolt main? or BOTH

Marc------ I'm sure there are copies of the advertising around. However, I don't think I have any. I definitely recall that advertising from the period. However, what I don't recall, for sure, is whether it applied to all engines with 4 barrel carburetors or just small blocks with 4 barrel carburetors. For some reason, though, it just sticks in my mind that it just said all engines with 4 barrel carburetors. In any event, this was only for the 1969 and 1970 model years. It definitely did not apply to 1971 and beyond.

Thanks Joe for the clarification. Another thing I like to know is if you personally seen the examples of the LS5s with the four bolt mains, or have you read the reports like I have been on the internet. I especially like to know if you seen any 1971 LS5 4 bolt mains at any events you particiapated in? Or is this something that isn't even addressed? Also, for Joe or anyone, how would this play out during judging on a LS5 that appears to be a four bolt main? Is this something that would not even be evaluated as four bolt mains were built at Tonawanda. Assuming of course the stamp pad for the car in question is typical factory production and all casting numbers and dates are appropriate for the build date of the car.

[Patrick H.]

Re: LS5 454 two or four bolt main? or BOTH

Or is this something that isn't even addressed? Also, for Joe or anyone, how would this play out during judging on a LS5 that appears to be a four bolt main? Is this something that would not even be evaluated as four bolt mains were built at Tonawanda. Assuming of course the stamp pad for the car in question is typical factory production and all casting numbers and dates are appropriate for the build date of the car.

I don't think that anyone even looks at the oil plugs - or their absence - on the motor to determine if it has 4 bolt mains, at least on low horsepower cars. On an LS-6 that is suspect it may get attention.
As you already note the odds are that the external appearance wouldn't even be evaluated.