what is big bore????????

[josh0092002]

hello again, what is big bore? :dunno: iam guessing its boring the cylinders out as far as possible, more info is greatly needed, but ive only heard it done on cobra engines, if iam correct about it. Can it be done on a 96 gt engine. once again any an all info would be nice. thanks again everyone.

 

[Magic]

you have the concept correct. larger cylinder bores....and yes mostly done with teksid aluminum blocks (re-sleeved, big $$ process) or the ford racing 5.0 cammer block....
stock bore is 3.552 (?) and they end up having a 3.70 bore (which with the stock stroke crank = 5.0L) something like this would be more beneficial IMO, with a hi-po 4v motor....

the maximum overbore I would recommend for a regular block would be no more than .030

 

[DropTopPony]

We had a pretty good thread about this in the SVT section before...might even be a sticky.

 

[Boomer!]

Actually the larger 3.70" bore will help the semi restricted 2valve head breath, unshrouding of the valves increases the general flow chartacteristics of the head. It will increase torque and horsepower a ton and is a better option that stroking IMHO. There have been results of 40+ rwhp on a basically stock engine...

 

[phil_the_thrill]

sounds like a pretty price operation. what would be a ball park figure for a 4.6?

 

[Jrgunn5150]

sounds like a pretty price operation. what would be a ball park figure for a 4.6?

4 or 5k

 

[Magic]

Actually the larger 3.70" bore will help the semi restricted 2valve head breath, unshrouding of the valves increases the general flow chartacteristics of the head. It will increase torque and horsepower a ton and is a better option that stroking IMHO.

yup truth to that as well.....

 

[phil_the_thrill]

doesnt seem worth it for 4 or 5 thousand dollars though

 

[jfor441]

doesnt seem worth it for 4 or 5 thousand dollars though

Factor in the cost of sleeves. FRPP sleeves are 50 bucks a piece. Thats 400 right there. Then the cost of machine work to bore out the block insert the sleeves, and then bore the sleeves out. Another 1k minimum. Basically to go big bore is another 1-2k more than a straight forged short block unless you got the hook up!

 

[Jrgunn5150]

PLus your uncommon pistons you will need, and rods, crank, and bearing's. Which is why I have a stroker kit myself

 

[Boomer!]

My first big bore was $3098 that was not including assembly, you don't need special rods, bearings or crank . All you need are the pistons and the block machined. I want to see someone spin a stroker beyond 8000 rpm multiple times, I know my bigbore will handle it time and time again.

 

[Jrgunn5150]

My first big bore was $3098 that was not including assembly, you don't need special rods, bearings or crank . All you need are the pistons and the block machined. I want to see someone spin a stroker beyond 8000 rpm multiple times, I know my bigbore will handle it time and time again.

Maybe I should have phrased that differently, but I didn't say he needed special rods, bearings, or a cranks. Just that he needed to add the cost of custom pistons to the normal rotating assembly cost.

As for spinning 8k plus, I dunno if mine will or not, and I don't care. I'm not after all out max strip power, just an enjoyable driver, and that's what I have.

 

[phil_the_thrill]

i could see how going big bore would be useful if you were trying to squeeze every last hp out of a 4.6 block. but it just seems like the money could be spent more efficiently elsewhere

 

[josh0092002]

so what iam gathering is that big bore is expensive for little hp an tq gain. so i guess its better to just go with forged internals? i mean what is the gains from the big bore, other than opening the cylinders up and helping the engine breath in better? i know more displacement normaly means more power. but does that hold true to the big bore process?

 

[Jrgunn5150]

In a nutshell, yes.

It's also better to gain displacement from bore as opposed to stroke if you want to spend alot of time near the top of the tach.

Bigger displacement with same mods will always make more power, and can support even more radical mods in the future.

For instance a big bore with radical cams, will be more streetable than the same cams in a stock displacement block.

 

[Dalamar]

What is big bore? It's kinda like lining the cylinders with $500.00 bills.

 

[tooslow]

big bore is worth it. on a stock engine, maybe not. but if you are planning for the most, than big bore is a very good investment.

lets not forget here, there is at least one 450+ n/a rwhp 4v cobra with other in the lower 400rwhp range.

good luck getting that out of standard bore mod.

 

[DropTopPony]

You can get a Big Bore shortblock from www.modularperformance.com for $4300 and you supply the aluminum block...thats just $300 more then their Stroker shortblock in your supplied aluminum block. That is who i will use if i decide to send my Teksid out.