quote:

Originally posted by 1320racer:
I’ve been wrenching hot rods and rebuilt my first engine nearly 50 years ago as well I worked in an engine shop and I never have heard the phrase “touch off” must be a California thing.

That said, while qualifying a block has value, for this build, anything more than checking for cracks and maybe pressure checking is a waste of $. This is obviously a budget build otherwise it would start with a new aftermarket block and be built with at least a 4.560 bore.

Me, today, I would not waste my time today with a stock/gm block for any race engine.

Not Quite Ed. But I’m not surprised you don’t know of it. NC, the machine basically finds zero by touching off with a probe. Then plots block dimensions.

BTW if you assume all of your block dimensions are correct you are making a big mistake. Granted stock blocks are all over the place dimensionally but everyone makes mistakes even with Dart, World or anyone.

Not one engine builder I have spoken to over nearly 50 years, including our own SCDIV1 aka Rich has ever used the phrase “touch off”

Who really cares about the phrase I used? You! Why ? Because ya had no idea what I was referring to. BFD! Who cares and no it’s not a West Coast thing!

Rottler has them on every nc. It’s the point of zero! It touches off to find zero! At starting
point.
Have you learned something today??


Do you think I would come on here and poke fun at your “ phrases “ ?? F no I have better things to do.
It’s a “Term” by the way… Not a phrase..

It’s a bullshyt “term” either you made up or somebody else that you think knows made it up

This message has been edited. Last edited by: 1320racer,

I shouldn’t bother but here is some education for you.

https://www.manualslib.com/man...-Series.html?page=80

https://m.youtube.com/watch?v=SCPzcgQVGf4

You need more?

Look I have been using mark IV engine blocks for almost 40 yrs. I had 2 motors. Race one for 2 or 3 yrs and be rebuilding the other at the same time. I had 5K invested initially. Everyone wants to be the fastest guy on the track. NOT ME, Like I said before I just want a motor that has some longevity and with 40 yrs. with these blocks I think they are up to the task. Look I'm getting up there in age and so grateful to have the desire to still race. So going to the race track and going a few rounds and making new friends along the way makes me happy. Buying an aftermarket block does not guarantee anything over using an old tried true GM block. Like I said 40 years and finally one of them broke and it probably wasn't the blocks fault.

For your power level a stock GM block is fine and what I used for over 15 years making 500 to 700+ and used 2 bolt mains too.

Also I meant to say that my mark IV engine block will go through all the testing available to make sure it's usable.

quote:

Originally posted by 50fordsst:
Also I meant to say that my mark IV engine block will go through all the testing available to make sure it's usable.

Don’t forget to start with a “touch off”

Pay attention, there will be a quiz later.

quote:

I googled the block number and found of course pros and cons on this block. (Pros) One person said they made 1400hp using that block and the(Cons) they have thin wall castings. My plan is to make about 600hp+ with a 489 stroker.

Thick cylinder walls make more power and will hold hp longer between freshen ups. SONIC TESTING any GM block is a must !!!! "286" blocks are known for thin cylinder walls and need to be offset bored accordingly to what the sonic test tells you. I have two 286 blocks that didn't pass my machinest scrutiny for .030 over. The older 289 blocks are the thickest, 445's not bad either and it what they mostly used for the LS6/LS7 crate engines. I've heard "959" is a good casting so I hunted down 3 of them. One is really good, the other two are average good, much better than my "286" blocks.
I like to go 600-800 runs at a minimum between freshen ups and thick cylinder walls certainly help !!

For the record I hoard big blocks, currently have over a dozen

quote:

I wouldn't be afraid of a late model Gen IV block +030 at all.

Do you or your machine shop sonic test the blocks you use Mike ??
If so' Id like to see the numbers.

HS professor. Thanks for the heads up, I read that too about wall thickness. Do you think there was a bad batch or generally for the 2 years they were just not made well. So sonic test is a must, but with their reputation seems like it's money not well spent.

quote:

Originally posted by 50fordsst:
HS professor. Thanks for the heads up, I read that too about wall thickness. Do you think there was a bad batch or generally for the 2 years they were just not made well. So sonic test is a must, but with their reputation seems like it's money not well spent.

The machinist will know what is acceptable, the machinist is aware of core shift, thick & thin area's.

Like I said I paid for one I couldn't use, it's part of it when you're driving a hundred miles to pick up a block.

I've gotten blocks .350 thick to blocks I chose not to use.

I like my chances with a standard bore Big block Chevrolet, late or early model.

Bob, what exactly are you looking for? I'm assuming you'd like an early years 454 w/ 4bolt caps? Do you need a certain casting number?

quote:

Do you think there was a bad batch or generally for the 2 years they were just not made well. So sonic test is a must, but with their reputation seems like it's money not well spent.

Who really knows ??? Over the years I've just started paying attention to the little details and my stuff is a little faster and lasts a bit longer. A Dart block is the shyt, but comes with a 40lb penalty. I think for 600-800 hp a good reasonably thick block will last just fine, anything over that and aftermarket would be my choice.
In my experience a thinner block will run fine but lose ring seal quicker and ultimately slow and need a freshen sooner in a bracket combo.
I would think any good machinest/builder would sonic test an oem block before boring so they can offset bore the cylinders to maintain as muck thickness in the critical areas for a performance build.
I've seen people use "concrete" also, I've never done this but I would assume done correctly would stiffen things up too.

I've seen Ed's old Chevelle run for years, it ran real good. I'd really like to see how Mike Rietow's engines actually perform in a real car, his dyno numbers seem a bit unrealistic to me but aything is possible.
Our good 460" engine went 142 mph @ 3400lbs how much power does that take ??? I'm sure there's people making much more power but we went well over 600 runs with ease with that combo.

hey Dave- I have a mark IV 454 4 bolt #10069286 block that most here say its ok for my application at .030 over, but now someone mentioned maybe NOT. Sounds like you may have some blocks around your shop. Finding a older mark IV with standard bore is pretty difficult. The block I have is late model (90-91) standard bore but they seem to be the black sheep of the herd. So to answer your ?. If I send this block back I'm looking for a #3999289 or14015445