Davidrad
Well-Known Member
So I've decided to build the top end of my 318. I have a 480 cam, an ldb4 intake, 308 heads, and a holley 750 available. Thoughts and tips? I don't want to build an over fueled dog.
Need more information.So I've decided to build the top end of my 318. I have a 480 cam, an ldb4 intake, 308 heads, and a holley 750 available. Thoughts and tips? I don't want to build an over fueled dog.
So I've decided to build the top end of my 318. I have a 480 cam, an ldb4 intake, 308 heads, and a holley 750 available. Thoughts and tips? I don't want to build an over fueled dog.
Need more information.
Some quick questions:
- what gears? 3.55
- what stall converter? None
- Is the bottom end (short block) stock? Stock
- what exhaust, headers? Stock duals
Need more information.
Some quick questions:
- what gears?
- what stall converter?
- Is the bottom end (short block) stock?
- what exhaust, headers?
As said, we all need a cam manufacturer and part number, not just ".480 cam"; there are several different duration cams with .480" lift, and some will be much better than others at not damaging the low end torque too much. (I.e., not making it doggy...)
Are you racing this car on the strip? Or just cruising? Or??? That will say how the engine torque band should be set up.
And I'd be preparing to do some milling and chamber volume measuring on those heads.
Just had someone measure. 230 @ 050. Didn't measure LSA.Well, considering the lift, it is more than likely around the [email protected] mark. Different manufacturers will have similar cams. Even if the duration numbers are a match, (Advertised and to a smaller degree, the .050 numbers) the intended purpose of the cam can be different.
I only ask because a general blanket type answer may not be a very good one. Would the answer fit? Yes. But how well?
Is it a MP, Comp cam, etc.... ?
If you know who made it, we could zeronin on it a little better.
That is where everyone would love for stock 318 LA block/piston owners to be able to go on static CR. But I have worked that challenge out multiple times and the answer is always the the same.I generalize by stating the advertised ratio drops to low to be an effective ratio for the cam to operate at.
My advice for getting the best you can out of it from where *I think* you stand is to start with removing the 318 heads and measure how far down the piston is exactly. Then cc the 360 heads. Report backnor have a friend/machinist do the math and the required amount to mill the 360 heads down for a 9.0-1 ratio with a 9.5-1 being the max.
So I've decided to build the top end of my 318. I have a 480 cam, an ldb4 intake, 308 heads, and a holley 750 available. Thoughts and tips? I don't want to build an over fueled dog.
My info on the cam is really shotty. I'll have to get it in my hands to get more and that won't happen for a while. It's just a cruiser but will want to break the tires loss at will. Might take it to a race night or something just to see what happens.
Just had someone measure. 230 @ 050. Didn't measure LSA.
Got any idea on the brand by any chance?
Are you familiar with the term DCR (dynamic compression ratio)? If not, it would be useful for upcoming discussions to read up on that a bit.
Just as a sneak preview of where this is likely to go (and what I think RF360 and willrun318 are poking at), the 318 is a fairly low compression engine. If you put a big cam in it (long advertised duration), then the DCR drops too much and the low RPM torque falls apart. You can make up for it a bit with head milling, but you only get so far.
Then you put in a higher stall torque converter so that when you take off, the RPM's jump way up and you just bypass that low torque problem at low RPM. And you put in higher rear gears to help in the same way.
But that all effects fuel mileage (if you care), and the usable RPM range is narrower; that's not too much an issue on the strip, but it can effect driveability on the street (doggy at low RPM's is a popular term for it). So that is where a too big of a cam plus low compression will give you what you may not like or want. It normally does not line up so well with a cruiser only application. And 'breaking tires at will' means you will first have to rev it up to 2500-3000 RPM; it won't do that just giving it half throttle from idle like a high compression engine will.
Hope that all helps.[/QUOTE
Intsall that cam into your low compression engine, against all better judgement. If it's a super slow rate of lift as that, this is what it will like;The motor is stock 76 with the crappy smog 318 heads (63cc) I think factory specs have it at 8.5 Static Compression Ratio. I'm having trouble finding the actual size of the 308s chamber. (If you know or know where I can find out LMK) I've seen numbers in the 50s and 70s. I'm hoping it's smaller than the existing 63cc but I'm guessing not. I understand the Dynamic vs. Static. I'll need to find a calculator for that. Math and I never got along. Cam looks to be 480 lift 230 duration @ .050, advertised at 280. From that I can probably figure out who makes it. Either way it sounds like without basically making a closed chamber head I'm going to need a decent stall converter and a heavier foot. I'd rather not change the gears if I can help it. I would like to drive on the free way at under 4K RPM and keep my 8 1/4 in one piece. Thanks for the help, keep it com'n. Open to cam suggestions.
Which cam spec, intake, head, and carb combo would you recommend for a just a hot rodded small block with a ldb4. Having power around 35-5500 and a lopey idle. I'd put the 4 barrel on the stock but I don't think it can use it.Intsall that cam into your low compression engine, against all better judgement. If it's a super slow rate of lift as that, this is what it will like;
Static compression ratio of 8.0:1.
Effective stroke is 2.52 inches.
Your dynamic compression ratio is 6.32:1 .
Your dynamic cranking pressure is 117.18 PSI.
V/P (Volume to Pressure Index) is 85........................................................85
A VP of 85 is absolutely miserably sucked out.
This is a "race cam". And it will forever be a race cam in a teener. This cam requires
Static compression ratio of 10.3:1.
Effective stroke is 2.52 inches.
Your dynamic compression ratio is 8.07:1 .
Your dynamic cranking pressure is 161.70 PSI.
V/P (Volume to Pressure Index) is 117.................................................117VP
Notice the VP, a measure of low-rpm performance is still way less than the stock cammed 318 with pumped up compression, which was 122.
nm9 has the right idea. If you want a tire fryer, AND comfortable hiway cruising, AND some midrange, And some top-end, from a 318; then you are gonna have to pump it up.
Or get a bigger engine,lol. You're trying to cover too many bases with too much of a weight penalty in the chassis. Kick 400 pounds out of that chassis, then the teener has a fighting chance of covering all the bases.
I see a big decision on your horizon.
If it was me I'd leave the stock heads and then add the bolt ons. If you want to use the 308s, use the thinnest head gaskets you can find, and a camshaft in the 215-220 @ .050. Smaller would be better IMO. If you know nothing about that cam, get one new that you do know about. Then make sure you degree the new camshaft and that you replace the valve springs with Comp Cams 901-16s.
Well since you asked the guys gave you some good ideas. But if it was me. And pumping the compression up was not on the table;Which cam spec, intake, head, and carb combo would you recommend for a just a hot rodded small block with a ldb4. Having power around 35-5500 and a lopey idle. I'd put the 4 barrel on the stock but I don't think it can use it.
That is where everyone would love for stock 318 LA block/piston owners to be able to go on static CR. But I have worked that challenge out multiple times and the answer is always the the same.
With:
- stock 3.91" bore
- the best stock 318 piston height of about .077" below the LA deck
- .028" thick head gaskets
you come up needing 53 cc chambers to reach 9:1 Static CR. That'll take a mill of somewhere around .100" +/-off of the typical open chambered 360 head of this type. That basically takes all of the 'open area out and leaves the closed chamber shaped part only. That much off seems tough (but I have never tried to have it done). I know /6 heads can take that amount of milling but I am not sure on these. And you would still need to see if the valves would clear the smaller 318 eyebrows. (They may....)
So, I would lean towards keeping the cam smaller and doing the best you can with a not-so-complex mill job (like maybe .050"?).
Or accept the low end dogginess and gear up (like to that 3.91 ratio) and push up the TC stall and work the gas pedal to get around it. Works for the strip; but may not be what is actually desired.
well, a couple of things.I haven't read through this whole thread yet but aren't the open chambered 360 heads going backwards? Wouldn't #302 or a closed chamber 273 head be easier to build compression and quench? I think porting small chamber heads is a better idea than milling open chamber heads to get your 9-1 ratio. You mill the heads and the intake won't fit without milling and the two will always have to be used together.