Which block casting number to get?

[DrScientist]

I'm about to start my first engine build for my 94 GT. And I had some questions as to which junkyard block I should be looking for. From what I've read there seems to be several different 302 blocks over the years, with several different numbers and sets of attributes. I want to build a 306 cause I hear that if done right, they turn out pretty fast. So which block should I go with? There seems to be something called a "Mexican" block which has thicker sidewalls? I must admit I really have no idea where to start with all this block hunting. Perhaps someone could fill me in on the various blocks and their do's and don'ts.

 

[revhead347]

You want a late model roller block. The old "Mexican" blocks supposedly had a different nickel content and were a little stronger. They are all non roller block, and it's going to cost half as much to change it over to roller lifters as it costs for a strong aftermarket block. Also, they are going to be warn out as crap. Metal fatigues over time. I've never seen a "Mexican" block hold up any better than a late model one. Half the people that claim they have a Mexican block are just saying it to make themselves feel better, and in reality, probably don't even have a Mexican block. The reality is that all the stock blocks are about the same, and no one in particular is any more likely to be any stronger than another.

Kurt

 

[Rick 91GT]

The old 70's mexican block are stronger then the late models and we've put over 800hp through them with no issues, they are thicker and are stronger then the late model stuff, but are rare and extremely hard to find, and as mentioned they will require a linked bar lifter $450+. Expect to pay $700+ if you can find a block. The last one that came through my shop was $1200 off ebay and it was 95% machined and ready to be built.

As far as late model blocks the 86 blocks tend to be a little stronger from what we've seen, not sure why...The latemodel stuff is all about the same, the key is good machine work and keep the crank from moving or it will split right at the #2 main and lifter valley. I prefer to add a girdle on the bottom end to tie the caps together and help limit cap walk.

 

[DrScientist]

So basically, from beginning to end, the 302 block didn't change much? Save for the roller aspect, I mean.

 

[Rick 91GT]

Correct

 

[DrScientist]

Alright well thanks for the replies. Might as well ask another question then. Doesn't having linked bar lifters cost you some power? It just seems to me like that much more moving mass, would have to cost some power somewhere...

 

[revhead347]

Oh, and the rear main seal. The early blocks are designed to have a two piece rear main seal, which almost inevitably will leak oil on your clutch. The late model blocks have a one piece rear main seal.

Kurt

 

[DrScientist]

Yeah that's a nice upgrade. Anyone know about my linked bar lifter question? Has to be robbing power...

 

[revhead347]

Linked bar lifters don't rob power, they are just expensive.

Kurt

 

[DrScientist]

As far as late model blocks the 86 blocks tend to be a little stronger from what we've seen, not sure why...The latemodel stuff is all about the same, the key is good machine work and keep the crank from moving or it will split right at the #2 main and lifter valley. I prefer to add a girdle on the bottom end to tie the caps together and help limit cap walk.

Yes I was thinking that the girdle was a good idea. Have you seen that trick that people do where they run some new 1/4" (or maybe it was 1/8") tubing underneath the lower intake manifold to help oil the front of the motor? Would you say that is necessary? Some people say the they need a little help getting oil up there so its a good idea.

 

[Rick 91GT]

Ive done that on some of the 351W where it is more of an issue.....havent had to do it on a 302 yet. It all depends on the combo, some I restrict depending on valve train, etc...

 

[txstang84]

Oh, and the rear main seal. The early blocks are designed to have a two piece rear main seal, which almost inevitably will leak oil on your clutch. The late model blocks have a one piece rear main seal.

Kurt

Never had that problem with my Hecho en Mexico block, it was two piece...I never had a days trouble with the block itself. I just wish I'd kept it around. It was in good shape, 30 over and I sold it for like $150 to a friend who wound up trashing it...idiot.

 

[txstang84]

There's actually one on eBay...surprise surprise...

http://www.ebay.com/itm/FORD-302-BO...pt=Motors_Car_Truck_Parts_Accessories&vxp=mtr

 

[DrScientist]

Anyone know what vehicles they actually came in, from what years? Might find something at a junkyard still in the vehicle, with the owner still thinking that its just your typical 302.

 

[castine917]

Where are you located Dr. Scientist? I have a stock 95 gt long block and a 70's 306 with dart iron heads in my garage.

 

[DrScientist]

I am in Fort Worth TX.

 

[txstang84]

Anyone know what vehicles they actually came in, from what years? Might find something at a junkyard still in the vehicle, with the owner still thinking that its just your typical 302.

If the sources I read were correct, they came in late 60s-early 70s vans and I think it said sometimes broncos. I've never personally pulled one from the vehicle itself.

 

[castine917]

I am in Fort Worth TX.

That's a little to far of a drive.

 

[DrScientist]

Yeah. Well now I wonder if there is such a thing, as an aluminum 302 block. That'd be cool.

 

[Rick 91GT]

Yes, how many do you want?

DART PT# 31344175 $5450.00