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I have a bare block and crank from a stock 1991 stang lx, I want to make a 306 for my 4000lb Mark VII LSC 1991.I also currently have 3.27 gears stock dual pipes and cats, i will upgrade to 3.73 gears, 2500 stall, shift kit, vb upgrade, 2.5 exhaust and 1 5/8 ueq headers, on stock e7 heads and e303 cam, a good port job on stock upper and lower. I think that tells what i got to work with, what I want is to do some weekend stip runs and be a daily driver, what parts do I need exactly to build the block for a 306. What size pistons, connecting rods, roller rockers,bore job and what about shaving the deck on the block and what does this do and how does it affect the connecting rods,stroke and pistons compression
. What kind of power and times and longivity can I expect on a buget build thanks.
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George-
Building a 306 is really no different than building a 302 except you have to overbore the cylinder by ".030 and pick pistons to fit the new bores (4.030"). Stock rods will work fine in a mild build up like yours. Just have them shot peened and cleaned up. Roller rockers are a matter of preference. Some people go with the 1.7 ratio rocker arms since it gives the cam a bit more lift and duration. Others prefer to stick with the factory ratio of 1.6. Unless your block's deck is warped there's really no need to have it milled. That's really only for blocks that have usually seen some sort of damage...usually associated with head gasket problems. As for power...with stock heads you're probably looking at something around 250-275hp. If you swapped over to some cheap GT-40 or GT-40P heads (the P heads require special headers, though) you'd probably be more in the 275-315hp range or so. Even with a cam, stock heads are incredibly restrictive. I'd suggest having the heads ported and polished along with a 5 angle or radius valve job. That is...if you're married to the idea of having stock heads. Hope this helps.
Steve
thanks, thats what I needed, next, what advantages if any, I am talking power or strenght is there between I beam or h-beam rods. Will any type of piston work, I mean ftat top domeed, I see so many out there and puch rods what is a good choice, sorry so many questions I have never done this.
Answer -
George-
For a mild performance engine build up or even a moderate performance engine build, H-beam rods are overkill. Unless you're making 1000hp+, a good set of I-beams is all you'll need. Plus, I-beam rods are lighter than comparable H-beam rods. Piston choise is a matter of preference, but I'd go with a flat top piston with good valve reliefs. D.S.S. Racing makes a great and relatively simple rebuild kit with some good I-beam rods and forged pistons (along with bearings, rings, etc.). Avoid hyperuetectic pistons (otherwise known as "hyper-you-cracked-it pistons) at all costs. They're cheaper for a reason. You can use the stock pushrods without problem with your motor. If you really want to upgrade them, Crane Cams or Comp Cams make very good replacements. Then again, stronger pushrods are generally only necessary when your valvetrain becomes a lot more advanced. Hope this helps.
Steve
Hello Steve, I just got a 331 crank so things have changed, I believe that I can still bore to a 306, but do I have to change the rods and pistons or just rods and piston rings. Will this get me above the 250 hpmark with stock e303 cam and heads, intake with 1.7rr, 3.73 gears and 2500 stall with proper exhaust. Also any pro's cons's on 331 vs 306 I want to go with speed pro pistons and useded rods 5140 i think and tmd cast crank. mostly daily driver, track maybe 2 times a month, launch at 2500 to 3000rpm, please give me the details and this is the combo I will stik with, going in Mark & LSC close to 4000lbs. It would help if you could name sizes of the crank rods pistons and all bearings.
AnswerGeorge-
The 331 crank is a good addition. That alone should give you somewhere in the neighborhood of an extra 20-40hp. Your biggest bottlenck will be the heads...but it should be too much of a problem for your power goals. A cast crank and 5140 rods should work just fine for lower power levels. With all of the other modifications as well as a 3.25" stroke crank (to make 331c.i. after an overbore of ".030), I'd say you'll be making around 275-300hp at the flywheel...maybe 275-250hp at the wheels. The gears and converter don't really add any horsepower...they simply help your engine get into it's powerband faster and move the car quicker. That'll be a big help to such a heavy car. As for the rod size....I *think* it's 5.090". I could be wrong there. It's been a while since I built a stroker motor (I've been busy doing class-specific over the top 306s and 308s). The bearings should remain stock sized. Hope this helps.
Steve
