You do loose compression with a big full chambered J head but you make up for it with flow. (as long as you build for a lower compression).
Steve Dulcich on building a budget 318
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Yeah you probably end up losing nothing because if the added flow from the better heads and bigger valves. Chrysler made police package 318s with 360 heads on them so compression wasn't all too important to them and those motors would haul the mail.
Yep. THat has been the old hot rod trick for ages. A 283 Chevy with double hump heads. A 318 with 340 heads.
Nope never popped a motor with it wasnt using it when i blew it
I popped the engine it was in after a couple of cocktails on the way to the drive in for the movie stripes teasing a 280z turbo on the way there he had shifted 3 times i was still in 1st gear woudnt let him pass me @7k the valves and piston said your night took a turn for the worst lol
Jim Laroy proved you could build a low compression engine that makes power on here more than once. As long as the flow's there, you'll make power. Evidently, Chrysler knew it, too.
Street Performance engines generally make 1.5 to 1.9 hp per cfm, 175 cfm head that's 263 to 333 hp, for a 200 cfm head that's 300-380 hp, going up 25 cfm should gain 30-50 hp, a drop of 1 cr point should be around 10 hp loss, so a 20-40 hp gain. Obviously this ain't meant to be exact.
Less air flow is less air to compress in the first place.
Easier to make power through large amounts inefficient fuel and air than highly efficient but very little fuel and air, the efficiency range for our type of engines aren't that huge. 1.4-1.67 lbs-ft per cid is an efficiency most of us won't see that's 445-530 lbs-ft for a 318, no one here would say 318 is the engine you need if looking to make 500 lbs-ft they build an inefficient 408 (1.23 lbs-ft per cid) instead
I believe you got my point. lolLess air flow is less air to compress in the first place.
Easier to make power through large amounts inefficient fuel and air than highly efficient but very little fuel and air, the efficiency range for our type of engines aren't that huge. 1.4-1.67 lbs-ft per cid is an efficiency most of us won't see that's 445-530 lbs-ft for a 318, no one here would say 318 is the engine you need if looking to make 500 lbs-ft they build an inefficient 408 (1.23 lbs-ft per cid) instead
junkyardhero
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define performance.
300hp? 400hp? 450hp?
i think the vast majority of people would consider 1hp per cube to somewhat be a performance motor. and you can absolutely make 318hp on a beer budget.
if the qualifier is 400hp, then no. you can't build a cheap 400hp 318 starting from zero.
if your goal is 400hp, and the budget is limited then it makes sense to start with bigger cubes. that's just plain *** common sense.
however... the advent of affordable aluminum heads has the benefit of making it much easier to attain lofty HP goals. there is also now the availability of less expensive pistons for better compression and these together spread across all displacements. so, technically it is now cheaper to build a more powerful engine than it once was because of the availability of parts to do so.
300 hp in a-body set up right 13.0
400 hp =12.0
450hp= 11.60s
everything setup on kill
Even if you take about an 1/2 second off those times your still doing good.
I think the trickiest power to make from a 318 is 300-399 hp, below 300 hp it’s just a cam 4bbl and exhaust above 400 hp your basically gonna replace everything but the block and crank, in between you need to do something about heads and cr and if it’s not a full rebuild or pistons are off the table it’s a bit of a mess.
RAMM
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This is about as far as you can go--cam/compression wise with a 318 and still have reasonable power and driveability. J.Rob
P.S. Forgot to add--IMO
318 Wolf in Sheep's Clothing
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Oldie but goody! Magnum I see. I saved that one. It's a good recipe.
then you spray it 460 hp 500 lbft
I haven’t built a street motor in 45 years, I’ve had some good 318 and 360’s and some dogs of both also. In my early years I built some real dogs putting a bigger cam and such on a stock shortblock, you sure don’t forget those ones! Not everyone agrees with ol’ Aj but he is spot on if you want to get somewhere with a little bit of thinking. A little compression makes things work a lot better, within reasoning of fuel. I really think a stockish 318 can and will run well with a smaller cam and the stock heads. 5.2 really shines if can get one and you are wanting that cubic inch, if you are patient ther are loads of 5.2 and 5.9 magnums around in my neck of the woods and can be built pretty well with minimum machine work. I’m definitely not a 318 hater, just more of a bang for the buck guy.
I raced a class where we had to run 9 to 1 compression, had a motor with cp pistons that mirrored a eq chamber, the pistons pins and rings cost more than I put in one of my basically stock 5.9 motors complete, was the good motor better, I sure hope it was, I didn’t dyno them but the butt dyno couldn’t tell the difference.
Lotta ways to skin this cat and I think most guys on here mean well, but of coarse someone’s gonna get all bent out of shape.
I raced a class where we had to run 9 to 1 compression, had a motor with cp pistons that mirrored a eq chamber, the pistons pins and rings cost more than I put in one of my basically stock 5.9 motors complete, was the good motor better, I sure hope it was, I didn’t dyno them but the butt dyno couldn’t tell the difference.
Lotta ways to skin this cat and I think most guys on here mean well, but of coarse someone’s gonna get all bent out of shape.
It's called stuffing the cylinder with air and fuel with a better flowing head and intake
Yeah, kinda what it's all about, really.
I wanting to say Jim made 787 Hp with 9.5 comp 451
I think that was the one Comp forgot to turn the water on and over heated it. It had 56% leakdown on the worst cylinder and all the rest had a good bit. They were expecting over 800 and that was through 906 iron heads.
Richard Holdener does a 8.5:1 vs 10:1 Chev 800 hp vs 850 hp there practically the same engine there’s a couple slight differences. That’s a 6% power difference. Down low the difference shrunk a bit.
Maximum pressure before detonation zone with pump gas.
I can argue that with a been there/done that & still doing it today.
Oh I know. With some good tuning, heads with quench, etc you can go further. There has to be a guideline for those guys that are beginners.
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