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.
318 Build
- Thread starter Davidrad
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Need more information.
Some quick questions:
- what gears?
- what stall converter?
- Is the bottom end (short block) stock?
- what exhaust, headers?
How many cc's in the 308 head?
What head gasket?
Actual cam specs or part number would help big time. Stating "I have a .480 cam" honestly doesn't help much.
Your issue could be (very) low compression which would leed to a doggy feel. A head killing to raise the compression ratio might be in order. "Over fueled" is a tuning issue.
What head gasket?
Actual cam specs or part number would help big time. Stating "I have a .480 cam" honestly doesn't help much.
Your issue could be (very) low compression which would leed to a doggy feel. A head killing to raise the compression ratio might be in order. "Over fueled" is a tuning issue.
j par
Well-hung Member
nm9stheham
Well-Known Member
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.
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.
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Davidrad
Well-Known Member
Davidrad
Well-Known Member
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.
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.
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.
Davidrad
Well-Known Member
Just had someone measure. 230 @ 050. Didn't measure LSA.
nm9stheham
Well-Known Member
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.
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.
Dartswinger70
Well-Known Member
Put the parts in and floor it, let us know what it does.....
Nm9, good post and yes to what 318WR & I were poking at. I normally don't go there because most new people and novice's will not understand and have problems getting it.
I generalize by stating the advertised ratio drops to low to be an effective ratio for the cam to operate at. Add in the converter and gear issues and heads start to spin. Never mind cam timing events that add to the problem of understanding it all.
Dartswinger70, good idea. But, maybe not the best move. Though I have done it and I'm sure I'll just do that again..... LOL!
Davidrad; Hyd. Flat tapper cam right?
Generally speaking that cam is in the 2000-5500 rpm range unless cylinder heads and other parts complement it for another 500rpm's.
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. (Try not to go for the max. It is unwarranted.)
Remember to include the gasket specs for n the calculations. (Bore and thickness.)
I suggest the rest of the drivetrain to be 3.55 gears (at a min.! 3.91's if there isn't going to be a lot of Hwy. driving.) and not more than a 26-1/2 diameter tire (approximately a 245/60/15 size)
A shift kit in the transmission. (Trans-Go) IMO, a general off the shelf torque converter should not be looked at. A call to a place like Dynamic will yield much better results. And there going to ask a lot of questions about the car. Just tell them everything you can so you can get the best result possible.
Also knowing your cars actual weight is a huge plus!
I generalize by stating the advertised ratio drops to low to be an effective ratio for the cam to operate at. Add in the converter and gear issues and heads start to spin. Never mind cam timing events that add to the problem of understanding it all.
Dartswinger70, good idea. But, maybe not the best move. Though I have done it and I'm sure I'll just do that again..... LOL!
Davidrad; Hyd. Flat tapper cam right?
Generally speaking that cam is in the 2000-5500 rpm range unless cylinder heads and other parts complement it for another 500rpm's.
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. (Try not to go for the max. It is unwarranted.)
Remember to include the gasket specs for n the calculations. (Bore and thickness.)
I suggest the rest of the drivetrain to be 3.55 gears (at a min.! 3.91's if there isn't going to be a lot of Hwy. driving.) and not more than a 26-1/2 diameter tire (approximately a 245/60/15 size)
A shift kit in the transmission. (Trans-Go) IMO, a general off the shelf torque converter should not be looked at. A call to a place like Dynamic will yield much better results. And there going to ask a lot of questions about the car. Just tell them everything you can so you can get the best result possible.
Also knowing your cars actual weight is a huge plus!
nm9stheham
Well-Known Member
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.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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OW!
You're gonna need to;
A) make some compression,or
B) forget about that cam, or
C) start over with a bigger engine, or
D) Start over with a new plan.
The biggest stumbling block is this;"just a cruiser but will want to break the tires loose at will".
Here is what your cam will do to this combo; I grossed the cam up to 272 advertised and selected a 62* ICA.
Static compression ratio of 8.0:1.
Effective stroke is 2.61 inches.
Your dynamic compression ratio is 6.51:1 .
Your dynamic cranking pressure is 121.91 PSI.
V/P (Volume to Pressure Index) is 92..............................................92VP
92VP is about as powerful as a 225 slanty.This will never get you the results you want, even if you pump the compression to the moon.
To run that 272cam you need;
Static compression ratio of 10:1.
Effective stroke is 2.61 inches.
Your dynamic compression ratio is 8.09:1
Your dynamic cranking pressure is 162.22 PSI.
V/P (Volume to Pressure Index) is 122...............................................122VP
This is about the max cylinder pressure that you can run with pumpgas and iron open-chambers..
Now 122VP is not bad, but this puts your powerpeak way up at about 5400rpm which with 2.76s is about 58 MPH at the top of 1st gear. You didn't say you wanted power at 58mph. No you want to lite it up at will.
To that end and interpreting that to mean from a dead stop,mostly, Here is what your combo would look like with the stock cam, and the compression boosted to the max,again;
Static compression ratio of 9.2:1.
Effective stroke is 2.86 inches.
Your dynamic compression ratio is 8.07:1 .
Your dynamic cranking pressure is 161.70 PSI.
V/P (Volume to Pressure Index) is 133..............................................133VP
Notice the VP is up to 133, which is 133/122=9% more powerful than that 230@050 cam, and a whopping 133/92=Plus 45% more powerful than the stocker. And the power peak is down at around 4500, or 50 mph with those 2.76s!, which is 8 mph sooner.
.
Now the torque peak of the 272 cam will be at maybe 4000, whereas the T-peak of the 240 cam will be at maybe 3300,700 rpm sooner. There is a slim chance that the 272 will make similar torque at 4000 to the 240 at 3300, but there is a waaaay bigger chance that at all rpms below 3300, the 240 cam will make more torque.
That means below 3300 or 37mph with 2.76s, the smaller cam has a better chance of busting the tires loose, and the slower you drive it the more advantage the smaller cam has.
But this is still a relatively poor way to spend your money!
The cheapest,easiest way to busting the tires loose is with torque multiplication (TM).
So the first thing to do is get rid of that 1750 stock TC (torque convertor), and get you at least a 2800 in there. Next, put the biggest rear gear in there that you can stand. If hiway cruising is not required, then I recommend something in or near the 4s, like 3.91s . These will put your Rs right close to 25mph at peak-torque. So when you go hammer down at 25mph, and it downshifts into first, hang on!
Now, you're gonna need this TC and the gears anyway if you cam it up, so you might as well start here; with the TC and gears.
Now don't go putting 295s on, cuz you know, it's only a teener.lol. But she will break 2.45s loose at will, to about 30mpg,guessing, with a 2800 and 3.91s. And it will all be cuz of the 3.91s cuz the TC will be "locked up" by about 22 mph.
Now, from here,you can put some power into the teener, but without a compression boost you will be trading away low rpm torque for high rpm power, that's just the way it works.
Now in case you're wondering, I used to have a winter engine and a summer engine. The winter one was a stone stock 1973-teener short block with a TQ and headers, that same 2800, and gears; sometimes as high as 4.30s and sometimes as low as 2.73s. My favorites were 3.55s, cuz there was very little tirespin with studded 235/75-14s,(28" tall) then she dug in and got to business,hitting about 40mph at 5000rpm with a 2.74 low-gear. I ran this combo many different ways, the 4.30s were with a stick, and therefore with an adjustable stall,lol, and it smoked 275/50-15s (25tall). shredded them.
I could tell you about the 2.73s and the manual-shift valve-body. This was also a favorite. I would floor that poor sucked out teener and jam it into 3rd as soon as she'd take it without detonating, and then sit back and listen to that TQ moan, and the dual 3" full-length pipes "roar", for what seemed like forever; but was really only maybe 3 minutes to 65mph,lol. Then stop and do it again,lol. What a blast that was. Yeah that was with the 2800,too.So pretty much 2800 from take-off to close to 80 mph,lol!
If hiway cruising is required, then I highly recommend the 2.74 low gear in the trans. This will let you run 3.55s with the same first gear performance as the 2.45 and 3.91s. Ut will be well worth the hunt to get that trans. It will allow you to hit 37mph at about 5000rpm, but the shift into second will kindof spoil things as the Rs drop to 2800ish again. But first gear will be a blast, with a 2.74 x 3.55 =9.73 starter gear. Add the TC TM on the start line, which can be as high as maybe 1.8, so the starter gear could be as high,momentarily as 9.73 x 1.8 = 17.50 to 1. That is tire-frying territory with a teener spinning 2800. This TM rapidly diminishes tho, so don't wet yourself. By the end of the 60 ft it has all evaporated, but the engine Rs are up and into the torque, and you will hardly notice that TC trick.
In your best interest tho, do not install that [email protected] cam into an 8/1 teener. A 223*fast-rate would be way better for you, and and for torque a fast-rate 216* even better.And if you really wanna burn rubber, pump up the compression. A very nice side-effect of this is the way better fuel-efficiency.
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nm9stheham
Well-Known Member
And just running some combinations for SCR/DCR all with the pistons .077" in the hole, 6 cc eyebrows total and .028" head gasket:
1. Stock cammed 318 as above with 675 type 318 heads: SCR/DCR = 7.8/6.8
2. Put on 308 heads milled to 62 cc chambers and assume a 284 cam is what the OP has with 110 LSA and advance it a small gob of degrees to 102 ICL :
SCR/DCR = 8.3/6.6.... so not too awfully bad a DCR drop from stock but still a bit less low RPM torque than a stock 318
3. Put in a 268 cam in (somewhere around 215 to 220 duration @ .050") and 110 LSA and installed a 104 ICL:
SCR/DCR = 8.3/6.9..... hey, now we are back to stock 318 low RPM torque-land and of course the top end is gonna be lightyears better.
4. If we COULD mill those 308's to 53 cc chambers, and stick with the 268 cam as above.
SCR/DCR = 9.1/7.6.... hey, now things are better all over low and high end.
5. For laughs, let's compute my overcammed low compression Opel 1.9L from when I was coming up this learning curve 30+ years ago, with the 300 advertised Isky cam and 7.6 SCR:
SCR/DCR = 7.55/5.32.... WHOA, the Wright Brothers had better DCR at Kitty Hawk in 1903 LOL.
No wonder that thing was totally DEAD below 3800 RPM! It was kinda usable for racing since that engine could stand revving to 8k all day long, but you can't get away with that on a stock 318 bottom end. I woulda had a much wider usable torque band (larger ratio of good low to high end torque RPM's), and thus I'da been a lot better off racing-wise, by dropping the cam duration 20 degrees or a bit more.
1. Stock cammed 318 as above with 675 type 318 heads: SCR/DCR = 7.8/6.8
2. Put on 308 heads milled to 62 cc chambers and assume a 284 cam is what the OP has with 110 LSA and advance it a small gob of degrees to 102 ICL :
SCR/DCR = 8.3/6.6.... so not too awfully bad a DCR drop from stock but still a bit less low RPM torque than a stock 318
3. Put in a 268 cam in (somewhere around 215 to 220 duration @ .050") and 110 LSA and installed a 104 ICL:
SCR/DCR = 8.3/6.9..... hey, now we are back to stock 318 low RPM torque-land and of course the top end is gonna be lightyears better.
4. If we COULD mill those 308's to 53 cc chambers, and stick with the 268 cam as above.
SCR/DCR = 9.1/7.6.... hey, now things are better all over low and high end.
5. For laughs, let's compute my overcammed low compression Opel 1.9L from when I was coming up this learning curve 30+ years ago, with the 300 advertised Isky cam and 7.6 SCR:
SCR/DCR = 7.55/5.32.... WHOA, the Wright Brothers had better DCR at Kitty Hawk in 1903 LOL.
No wonder that thing was totally DEAD below 3800 RPM! It was kinda usable for racing since that engine could stand revving to 8k all day long, but you can't get away with that on a stock 318 bottom end. I woulda had a much wider usable torque band (larger ratio of good low to high end torque RPM's), and thus I'da been a lot better off racing-wise, by dropping the cam duration 20 degrees or a bit more.
Davidrad
Well-Known Member
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.
AJ/FormS
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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.
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Davidrad
Well-Known Member
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.
Gotta agree with the guys here.
[email protected] intake duration, good power and cruisabilty. 1200 - 5500 rpm power band with cruise rpm of approximately 28/3200 with 3.55's.
I did a similar build on a '79-318.
It was a Crane split duration cam, LD4B, 600 Holley and later a Carter (same performance) Hooker headers into a 2-1/2 Jegs exhaust & 3.21 gears.
1st time out was a 15.14 in the 1/4. Pretty crummy on a lot of fronts that did get worked out a little bit. Timing jetting & cooling were the beginning issues. Traction at the track was non existing with the stock size tires. Stock converter.
It needed gears and wider rubber. The car left my possession before I could return to the track. But I know I made noticeable improvements. I think
I could have ran in the mid/high 14's easy.
[email protected] intake duration, good power and cruisabilty. 1200 - 5500 rpm power band with cruise rpm of approximately 28/3200 with 3.55's.
I did a similar build on a '79-318.
It was a Crane split duration cam, LD4B, 600 Holley and later a Carter (same performance) Hooker headers into a 2-1/2 Jegs exhaust & 3.21 gears.
1st time out was a 15.14 in the 1/4. Pretty crummy on a lot of fronts that did get worked out a little bit. Timing jetting & cooling were the beginning issues. Traction at the track was non existing with the stock size tires. Stock converter.
It needed gears and wider rubber. The car left my possession before I could return to the track. But I know I made noticeable improvements. I think
I could have ran in the mid/high 14's easy.
moper
Well-Known Member
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.
Davidrad
Well-Known Member
I spoke with Comp Cams this morning. They're thinking I'll be ok with this cam 20-223-3 - Xtreme Energy™ Hydraulic Flat Tappet Camshafts
I would end this discussion in a heartbeat. How? I would simply cut the 308 heads .040, and put your pieces together. Time, tune, and see if your happy. If not, your only out a few gaskets and a few hours of your time swapping in another cam.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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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;
Wait, hang on,
when it comes to pricing this out, I can tell you that a rebore with hiC pistons and a refresh, is ,in the big picture, the best almost cheapest part of the equation. Once you have decent compression, the rest gets so much easier. For example, with decent Compression comes a strong bottom end.Back in post #14, we saw a vp of 133 with still the stock engine.
If you don't know what 133 feels like,consider this;
The stock low-C 360 2bbl engine.
Static compression ratio of 8.0:1.
Effective stroke is 3.02 inches.
Your dynamic compression ratio is 6.91:1 .
Your dynamic cranking pressure is 131.95 PSI.
V/P (Volume to Pressure Index) is 120..........................................120
and
the stock 1969 low-C 440-2bbl
Static compression ratio of 8.0:1.
Effective stroke is 3.06 inches.
Your dynamic compression ratio is 6.71:1 .
Your dynamic cranking pressure is 126.92 PSI.
V/P (Volume to Pressure Index) is 137...........................................137
You see that 440 with the 137VP? A 440 has no trouble spinning the tires on a 2.76 equipped 1969 New Yorker.
Also going back to #14, notice that 133/111= plus 20% more bottom end.
Plus 20% if you don't know it, is like bolting on a supercharger, at least from idle to maybe 3000rpm,lol
Plus 20% can be thought of as upsizing the TC to an rpm where the engine is making 20% more torque, like slipping out the clutch on a manual trans.
Plus 20% can sort of be compared to upsizing the rear gear 20% as well; say going to 3.23s from 2.69s, or to 3.73s from 3.10s.
So as you can see compression is a really big deal to low-rpm useage. Ask anybody who ever put a 268* into an 8.0 teener. The first thing you gotta do is get a big TC to restore the bottom end performance. Usually followed by some hi-perf rear gears. And what was the purpose of said 268*?, Mostly everybody does it for the lumpy idle.
Ok so where was I?
Oh yeah, if I was forced to not pump up the compression;
In this case I would combine all the ideas presented so far, with the express purpose of keeping the Dcr as high as possible.
This means a small very fast-rate cam. In fact I would order up a custom cam with the fastest lobes ever built, and follow the grinders instructions to the letter.
Suppose you could ditch 8cc on the 308s by milling .040. and suppose you could install the .028 gasket gaining 1.1cc back for a net loss of 6.9cc. This will get your compression up to about 8.5. Then I'm with the guys and about [email protected]. So if you could get one ground with say 38* ramps, making a 256* advertised cam, this is what you might get;
With a 252/260/108 cam in at 104
Static compression ratio of 8.5:1.
Effective stroke is 2.89 inches.
Your dynamic compression ratio is 7.54:1 .
Your dynamic cranking pressure is 148.00 PSI.
V/P (Volume to Pressure Index) is 123.....................................123
Now while that is not nearly optimum,it doesn't look that bad. Your Dcr is only down a half a point and the cylinder pressure is nearly 90% of what it could be. I tightened up the LSA to 108 for two reasons, well three actually.
1) it's a streeter so by tightening it up, you get a bit more specific power, at the expense of powerband. Since this is a zero to 65mph car, and this is gonna be a 1-gear run with 2.76s or even 2.94s, or even 3.23s with 28" tires we don't care about powerband, nor rpm drop into second.
2) this makes 40* of overlap so maybe if you idle it slow enough you might get a bit of lope.
3) but mostly the 108 will keep the compression up
4) the 40* of overlap means that with headers you might get a little bit of "supercharging " at around peak torque.
This 256 might make peak power at 4800/5000 in the teener, so the shift rpm into second will want be about 6200, so make sure you get the right springs for that, and follow the grinders instructions religiously as to installed height and what oil to run. 38* ramps are pretty fast for a FTH, but get the most lift he will let you have, and then follow the break-in instructions to the T.
123 is a reasonable amount of VP for a teener, but might still want a bit of a TC to launch hard. You can make that decision after the combo is up and running and you have run it for a few hours and have got to know it.
With a power peak at say 4800, the torque peak will come in at about 3600. So for best results gear the car to be doing a little under 3600 at whatever speed you want to bust the hides loose at. For instance, 3.23s will get you 30mph at 3300 with 80" (25.5s)tires and 5% slip. If you have 245s start with those,lol. And work your way up as you burn them off,lol.
So that's what I would do if compression was out.
But here's what you're missing by not bumping the compression to what the cam wants.
Static compression ratio of 9.3:1.
Effective stroke is 2.82 inches.
Your dynamic compression ratio is 8.06:1 .
Your dynamic cranking pressure is 161.44 PSI.
V/P (Volume to Pressure Index) is 131.........................................131
131/123= plus 6.5% more bottom end. But in this case, the boost also translates to more power everywhere in the powerband, not a whole lot but still, more.
compare the above to this, copied from #14
To that end and interpreting that to mean from a dead stop,mostly, Here is what your combo would look like with the stock cam, and the compression boosted to the max,again;
Static compression ratio of 9.2:1.
Effective stroke is 2.86 inches.
Your dynamic compression ratio is 8.07:1 .
Your dynamic cranking pressure is 161.70 PSI.
V/P (Volume to Pressure Index) is 133..............................................133VP
Notice the VP is up to 133, which is 133/122=9% more powerful than that 230@050 cam, and a whopping 133/92=Plus 45% more powerful than the stocker. And the power peak is down at around 4500, or 50 mph with those 2.76s!, which is 8 mph sooner.
So now you are just 2 points of VP down from the best the stock cammed teener has to offer. I'd say hallelujah!
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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.
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well, a couple of things.
- on the heads: You wouldn't mill heads to get 9-1 compression ratio. You would mill to get some of what your loosing back. If the op wants 9-1, better do all the measurements and math or you won't know.
- Next, and I am saying by experience, I've never, ever put cut 360 heads on a 318 and lost performance. Flow trumps compression any day of the week and twice on Sundays
. Bigger valves and ports would be a sure win. - Also, from my personal experience, I've never cut an intake when cutting heads .040 or less. Never. And, I've never had an issue or leak.
- 302 heads will do compression justice only because they are closed chambers. Never, in stock form, will they have a chance with flow vs. 308. Yes, you can fully port the 302's and add bigger valves and get some good flow.
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