Ok, I'm an idiot but here goes... First off, I want to end up with 427 cubic inches. I like the figure, it's got some historic Chevy significance, so I'm not interested in any other bore/stroke combo than what will achieve 427ci. That being said, here's my question:


4.060" bore with 4.125" stroke (resleeved aluminum)
or
4.125" bore with 4.000" stroke (resleeved aluminum)
or
one of the above, with an iron block



I want opinions on the pros and cons of using more BORE to get 427 cubic inches, or more STROKE to get 427 cubic inches. This is assuming of course that you percieve some value in a "square bore" motor. Also, this is going to be a pretty high-effort setup, so it will see some high RPM.

 

If you go with the big bore 427 it would rev faster and produce more on the top end, but with the stroker 427, I honesly think that youll have more torque than you could use. With the stroker 427 you would have one bad *** TQ curve, and thats nice and all, but it would be way to easy to break the tires loose when you dont entend to do so. And its no way that I would drive a 427 stroker in the rain regaurdless of what tires are on the car.

 

Well both of them can be considered strokers.

 

I know they are both strokers, I'm not asking that. I'm talking about increasing stroke to either 4.00" or 4.125" from the stock 3.622" so of course I've "stroked" the engine. What I'm asking is for opinions on whether it would be better to go bigger bore, shorter stroke 427, or smaller bore, longer stroke 427.

I was thinking that it might be better to keep the stroke short and go bigger bore for the sake of RPM. 7000+ RPM is up there for a long stroke engine. Anyway, I was just hoping some engine builders would have some experience/thoughts about this..

 

Seems to be the general consensus that you are better off making your cubes by using the biggest bore that you can and less stroke. The 427 C5R motor is the perfect example using a 4.125 bore and 4.00 strok. That is the combo i recommend for you but just make sure you get the best proven engine resleever b/c you certainly don't want to drop sleeves. If you can afford it the C5r block is the BEST WAY to go. The bigger bore will rev faster and higher than the big stroker motor and that seems to be one of you goals.

My motor is a MTI 427 ironblock using 4.060 bore and 4.125 crank. I went this route b/c i personally don't trust resleeved motor and felt the ironblock would be more durable and relialbe and i wasan't going to spend 6K for a C5r block (even though that's my dream engine).

See my sig. for my power numbers through my A4. My car is a complete BEAST and just today i enjoyed smoking my et streets on the street from a standstill for about 75 yards. The torque is outrageous as i'm making about 500rwtq.

Best of luck.

MTI 427 Roadster

 

So, would you consider a re-sleeved block from MTI, or ARE unreliable? I was leaning this way as a foundation for this build. I was thinking that a MTI block prepped with a 4.125" bore, a lunati 4.00" stroke crank, and some lunati rods would be a good start on my new bottom end.

Anyone have thoughts about this?

 

I think as long as you go with a proven engine builder like MTI or ARE you will be fine with the resleeved alum. block but i personally have more confidence in the strength of an ironblock as i wanted to eliminate the possibility of sleeves dropping.

However, as long as you go with a reputatble builder as metnioned above(backed by a warranty), then you should be good to go and i agree that your bore size and stroke selected is the best way to get your 427 cubes.


Best of luck.

 

Thanks.

The only reason I don't just buy a 6.0L iron block and be done with it is for the sake of the extra weight. I mean, $600 is a lot better than $2000+. I just didn't want to double the weight on such a high dollar build!

 

You won't drop sleeves if they are Darton.

 

With the tons of power made by those big bore/stroker 427s ironblock the 90lb weight penalty is negligible in my honest opinion.

I'd rather save the $ and have the durability and that's exactly why i did it.

 

How much would one of these setup's cost? seems like any one of them would cost a fortune.

 

With the bigger stroke, you're gonna' have a heavier piston, shorter rod, high piston speed, not good. So, this is not a real good choice for a street motor, that you just want to have fun and annihilate with. A drag racer wouldn't care much about that, because he only runs for a few seconds. I would go the "bigger bore" route.

 

Sawedoff:

Before building my MTI 427 motor with 4.060 overbore and large 4.125 crank i research the issues your raise with top SBC engine builders and found out that what you raise as issues are really non-issues at all and i can assure you that my motor makes for an INCREDIBLE STREET MACHINE.

 

On a C5 I can see why the 90lbs would not be a problem, but on a F-body with no weight reduction and already tipping the scales at 3800lbs. I would think that 90lbs would make a difference.. I am talking about with me as the 280lb driver as well..

 

Be that as it may, it is afterall your money, and your boat to sail in. Building an engine, can be done in many different ways and techniques, depending on the desired goal. There's little point in negating one's approach over another.

 

Sawed off:

I do agree with you that ideally it is always more optimal to get the desired cubes by going with the biggest bore size possible. In my car i don't trust resleeved alum. motors and didn't want to spend the huge $ for a C5r block, but in a perfect world i would have opted to get my 427 cubes just like the C5R does with bore size of 4.125 and 4.00 crank.

I had to make my final decision while balancing my goals of performance, reliability, peace of minid (objective confidence level regarding durability) and cost and came up with the 427 LQ4 option which i am very happy with so far.

 

The terms 'high rpm' and '4.125 stroke' do not fit in the same sentence.

4.000 stroke is in fact about optimum.

You can do 4.125 stroke if you only buzz the car up to like 6500 rpms or less.

 

so which is the preferred set up? which will have the better chance of survivability up to 7-8K rpm? i was thinking of doing a VERy similary build but going with a 6.0L Iron block for stability issues and i cant afford a C5R race block..somebody already got this built with a *recipe* maby? part #'s etc..? thanks

 

This thread is over 4 years old!

Preferred is bigger bore, cheapest is bigger stroke.

 

For that many RPM darton sleves knocked out to 4.185 with the stock crank. 398 cubes, but dont forget the dry sump.