Though this is not a subject often discussed on this board, it often brought up on other sites. Due to our new upgraded features, posting pics here is a breeze! Just limited to three pics per post.
Pics aren't perfect, but it gives a good idea of each block.
Here are a series of three posts showing three different 302 engine blocks:
The first series of three is a late model roller block, second series is early 289/302 block, third in the series is a Mexican block.
Areas to note on a late model roller is the size of the main cap and webbing area beneath the main (can be easily seen in two of the shots of the #2 main).
This is the 289/302 block
Mexican block. Difference between the early 289/302 are obviously the main caps. All these older blocks have more material in the main web area and have "blind" holes for the main bolts/studs and head bolt/studs (late model blocks have the holes drilled all the way through, this is where the block begins to split when you put a lot of power to them).
Cool. This should be a sticky.
Good info, I've seen the term Mexican block used a lot but never knew the difference.
I've heard the iron content of the Mex blocks wasn't as good as US which is the reason the caps are larger, could be a rumor I've never checked...
Unless it's a HI-Po 289 or Boss 302 which are desired by the restorers, I'd never consider anything but a roller block for a "modern build"...
If you keep the power level and/or the RPM low, a roller block is fine. Raise the power level and/or RPM, you often end up with a block in two pieces.
Due to the thicker main webbing and the blind main bolt holes, the early blocks have less tendency to split, offering the ability to take more power and RPM. Use of a roller cam in an early block requires link-bar lifters.
In all of my research, the quality of the Mexican blocks casting has not been a question. Rumors of higher nickel content in Mexican blocks in common, but is commonly dismissed by those in the know. The blocks are generally percieved as equal in quality and strength of the early 289/302 US made units. The advantage to a Mexican block is the extra support offered by the sturdier main caps.
A lot of people say that "500 hp is the most a roller block can take" which is not really true. It depends on the tune/rpm more than the power level. If you're going to build a 700 hp 302 with a blower spend the extra money and get a BOSS block with 4 bolt mains. Then you only have to build in once ;).
Absolutely right.
There is no one number which will break a roller block. Stress on engine blocks varies depending upon how the power produced.
A high HP 8.2 deck motor natually aspirated will typically take 7,000+ RPM to make that power.
Nitrous has instant and massive torque that can play havoc with any block, depending on the size of the shot.
Supercharging introduces the variable of pulling the nose of the crank with the belt, introducing side loading on the crank.
Turbos can be less demanding on a block, due to (potentially) lower RPM, smooth ramp up of boost and no side loading on the crank.
If the tune is off in any combination (N/A or power adder) and detonation takes place, things will break...
Putting a lot of power to stock block is never a problem. That is, unless it breaks and it's your's!:toilet:
There is no doubt an early or mexican block is sturdier than a roller. How much? Hard to say, lots of opinions out there. It's a step up.
There is, absolutely no comparison between an early or mexican block and an aftermarket block. Maybe someone has pics of an aftermarket block which could be added here.
If its high rpm and big hp you seek then:
http://www.dartheads.com/products/engine-blocks/ford-small-blocks/shp-ford-small-blocks.html
Hold on to your wallet though.
Darren
Darren, thanks for the link.
When folks ponder a powerful build up, cost considerations are always a factor.
The one most seem to miss though is the amount of money it takes to get a block properly machined for performance use.
Cleaning, checking, boring, decking, line honing all add considerably to the cost any stock block. Be it a roller, early or Mexican, the costs are the same. In my experience it may run $800 to $1,200. Kind of makes a free block (or $300 - the current going rate on a "raw" Mexican) less appealing.
Or course the Dart block will also require some machine work (the bores need to be finished), but when its all said & done, the cost differential may not be as great as it first appears.
That being said, all of blocks shown are mine and I still haven't sprung for aftermarket block! It's just so much harder to take the pain all at once.
Kind of like putting a frog in boiling water, he'll jump right out, but put him in a cool pan and gradually raise the heat, he'll be cooked!
FWIW the mexi 302's had rail mount rockers my cousin has a 60's fairlaine with a mexi 302 in it from what i hear the heads are very desireable.
I wouldn't waste time on a set of 60's factory Ford Windsor heads. Modern heads will beat the old stuff all the time no matter how much you port the stock 60's heads.
I would take 69-70 351 heads over E-6 or 7's any day. Not thrilled with the push in studs, but that can be fixed.
It sorta sucks more when you break it and it belongs to your buddy.
I had a set of 69-70 DOZZ heads on the first motor in my Coupe and what I put into them to make the work sort of good I should have just popped a set of Edelbrock Performer RPM's and have been done with it. Now if you can port them yourself then that might help but once you put valves, springs, keepers, retainers, and shims on them not to mention having them decked to make sure they are square you have spent a chunk of change and that is if you got them free. They still flow like until you open up the pockets behind the valves and get rid of the thermactor hump in the intake passage. The car put down 249 rwhp / 289 ft-lbs of torque but not worth it in my opinion. Same motor with stock Edelbrock Performer RPM's went 272 rwhp / 292 ft-lbs of torque. Bolted them on and did not touch them and the cost was the same and I got better performance. This was my experience though. If I had it to do over I would have bought bare castings and had the guy that does all my machine work port them and then dress them out with Manley valves, keepers, & retainers, Isky springs, and ARP studs that are the correct length for a Ford. This is what I had to do later down the road (minus the porting) so again I spent even more money. Sucked but the car is now 315 rwhp / 323 ft-lbs of torque and the little Coupe makes some bacon with that. I have an Ed Curtis custom cam for the car but I still need to port the heads so it will be later this Spring before I tear it down again...Tax Return money!!!
Darren
I should have said modern aftermarket aluminum heads ;).