2 questions about cylinders and piston on a engine?

Question

okay im building my first muscle motor a 351 windsor. 1-im wondering how many horses will boring the cylinders 30 over 2- is it worth it to buying aluminium pistons when I can buy the cast ones a lot cheaper? and what is the best shape to get them? dome, flat head, etc... Im wanting to get about 350-400 horses so I need to do something to the bottom end will this be enough

Answer 1

There isn't a formula for HP gains for machining your block .030 over. That is done out of necessity, the standard bore is 4.000", on a used engine (if needed) they will make all of the cylinders larger to eliminate any imperfections in the walls of the cylinders. After they remove some material the cylinders would measure 4.030" (also called 30 over) or if necessary 4.040" 4.060" (40 or 60 over). This will also determine your piston size. H beam or I beam rods are likely fine for a 350-400HP engine and cast pistons will not be an issue. If you have extra money or might add forced induction in the future then look into forged pistons. Do not skimp on pistons



If you have a used 351 block then you need to take it to a machine shop and have it magnafluxed which will check for cracks in the block. Start there. A good machine shop can be a wealth of knowledge and an awesome learning experience



You can look into a main girdle if it will be a higher RPM engine. Where did 350-400HP come from? You will want some nice disk brakes on the front of this thing, save some $ for that

Answer 2

Some people believe there is no replacement for displacement, but there's a lot more to an engine than its size. I like the 5.0/302 dimensions better: it has the same bore as the 5.8/351, but a shorter stroke, so it can rev up faster. The real key to making big power is air flow in and out of the engine. If you stick a 351 in Mustang, you'll be limiting yourself to a smaller pool of exhaust manifolds that are available. You won't have this problem if you're putting the engine in a truck, or doing a Mustang-II IFS conversion. One of the advantages of multi-port EFI is that each cylinder gets the proper amount of fuel, so you don't have one cylinder running excessively rich in order to prevent another cylinder from running excessively lean. Also, you'll definitely want to use a roller cam, and if you're planning on using a 1984 or earlier block, you can have that modified to accept a roller cam. Gear ratios have a big effect on the performance of a car too.



Nearly all pistons, with the exception of antique cars, are made of aluminum. The difference is how they're formed. Forged pistons are formed under pressure, and result in a stronger structure than cast pistons. The question you have is "can cast pistons support up to 400 hp?" You'll have to ask an experienced engine builder, enthusiast/racer, or the manufacturer. The shape of the piston will depend on the type of cylinder head you're using.



You also wondered how many horses can you gain by boring the cylinders larger. That's impossible to answer because I don't know what you're starting with, but I am sure that increasing the bore won't gain you much if airflow is still restricted through the intake or exhaust system. Boring out the cylinders might even have a negative effect, because now you're trying to more more air through the same size intake/exhaust ports. You're more likely to make much bigger gains by improving airflow rather than displacement.

Answer 3

Your best bet is having the block machined so your cylinders, and crank bores are true and correct with a better tolerance level, and from there going to somewhere like Summitracing.com or Jegs.com with all your measurements and getting a full bottom end kit, along with a decent streetable camshaft, somewhere in the 282-292 duration area, but nothing higher than the 292 number, as you'll lose a lot of the vacuum that you'll need to run the carb and brakes correctly. Your heads can be the stock heads but have them reworked with new springs, guides, seals, 3 angle valve seats, and depending on what the combustion chamber of your heads measures along with what size valves you have would give you what type of piston face to use, but going with a flat top with valve relief like the Keith Jackson models will get you close to a 8.5 to 10.0 to one compression range, Your intake needs to be a Edelbrock performer or Weiland low-rise with a 650 cfm ( vacuum secondaries) or a 680 cfm Quad jet and use an MSD ignition like the MS6 set up along with full length headers (preferably) or short tuned headers if available. and that set up should overall get you somewhere between 300-370 horses depending on exactly what parts you choose... However since it is your first build get someone to help you who has built several so that it is a learning experience without haveing to tear down and start over which will cost a lot more when you are constantly replacing gaskets and time lost.

And all Pistons are aluminum even when they are cast, forged, or cnc made... but cast is stock or oem grade, forged is much better, and cnc is what you would see on a nascar or super drag carcause they are to costly to run in a daily driver or weekend ride.

Answer 4

Boring the cylinders is really not going to increase horsepower. You only need to bore if there is wear and it needs to be done. you need to know what heads you are running before you can figure out what pistons to use. A smaller chamber head is going to have higher compression and will need a flat or dished piston to be able to run on pump gas, A larger port may require a domed piston to get the compression up to where you need it. Why not by a stroker kit that will come with the proper crankshaft, rods and pistons and then top it off with a set of good aluminum heads. 400 horsepower is not hard to get, but you want it to be reliable enough to drive. It is not cost effective to blow it up every 100 miles, so don't skimp on quality of parts or assembly.