I'm having an interesting email conversation with AED at the moment. I have to acknowledge their willing ness to help but I'm not convinced they understand that there are differences between these engines and a Chevy engine which are important to understand. AED are surprised this engine makes as much as it does with such a small cam and heads, and feel that around 240 of intake duration at 0.050" would make more power. I'm sure it would but that's starting to get into some seriously rough idling cams from what I can see. Not something I want on this engine. On the question of a larger carb there is probably nothing to be gained here. AED say the differences between the 850HO I have and the 1000HO Larry uses is only 30cfm. The 850 flowing 870cfm and the 1000 flowing 900cfm, I suppose that is only to be expected in the engine numbers game. So, I'll put the inner valve springs in and will think about re-timing the cam. The question that remains to be answered is, are the dips in the torque curve merely the missing inner springs or something else?
Just had one of those moments when your heart sinks. Decided to do a cold compression test so pulled the plugs and started with no4 cylinder. Worked around the block towards no7. Had very consistent results between 160 and 165 with no2 a little higher at 170. Then I got to no7.......80psi and it was dropping like a stone. Checked no7 spark plug and it was just like the rest, a lightish brown so decided to try a leakdown test. Put n07 valves on the back of the cam and plumbed in the adaptor I have for my airline. Fully expected to hear air rushing past the rings or coming back at me past a burnt valve. It held 140psi and dropped to 100psi in just under two minutes, so evidently nothing wrong there. Put the compression test on no1 and tried again with the resut that I had 80psi and it was dropping like a stone. Turns out my compression tester has developed a pin hole leak.
Ok, so I reinstalled the inner springs and we got it back on a dyno. Picked up a little at the top end but nothing to shout about, and not enough to be sure it was the springs or just the engine bedding in. For those that are following this build you will remember that I never resolved the issue of the cam lift not matching the cam card, 0.287" against a spec of 0.297". My thoughts are that the missing 0.010" of lift is having an effect so I've decided to pull the cam and fit a new one. Given the engine is at close to 10.5:1 and that I'll be running a switch pitch TH400 I'm going to go up a few knotches in respect of the cam. Last night (UK time) I rang TA Performance and placed the order for a set of roller rockers and the 288-98H cam. I know that with the power band between 2000 and 6000 this might not appear to be ideal for a Land Rover but I'm figuring with the switch pitch, full manual transmission control, and the transfer box I should have no issues always being in the sweet spot. Hopefully that will wake this engine up a bit. As always all comments are welcome.
Let's recap you are making 460hp and 510 ft lbs with a mild cam and you are putting it into a 4wd land rover. If you just want a cruiser with off road capability you are there. If you want a 500hp sleeper then I would change the cam.
@Brandon Cocola .... Yes I agree with everything you say, and 464hp is a chunk of power. At 464hp the engine is making less power than it could. I've gone round bouy on the carb and concluded my choice is a good one, the heads are capable of 500+, compression and leakdown tests show the rings and valves are good, the only thing that I know is not right is the lift on the cam. Even with standard rockers I'm losing 0.015" of lift and the dyno results show it's not making the power this engine should. The dyno operator commented that he felt the engine wasn't breathing enough. As Larry said, "I thought it was virtually impossible to make under 500 HP with TA aluminum heads, 10:1 compression and a decent cam". So did I, and it comes back to the cam lift. As you say it's making 464 with a mild cam, point is though that mild cam is even more mild because of the missing lift. I'm not a perfectionist, but like pretty much anyone on this forum knowing there's an issue, and suspecting the issue is costing power, I have to rectify it. My intial thought was to leave the cam in there and go with the 1.6 roller rockers which would put the lift back to where it should be. That developed and so if I'm putting rollers in there I may as well change the cam.
At this point since you are going to be changing cams & adding roller rockers MY choice would be a ROLLER cam. The cam & lifters you have now will be worth some $$$ to someone looking for an upgrade without breaking the bank. Just keep the lifters in order of cam lobes. I'm sure there are plenty here that can give the pros & cons of a full roller setup. Just my thoughts. Tom T.
I'm in a similar boat as you as far as cam selection goes. My 462 has the T/A aluminum heads with additional porting, 10.5 to 1 compression and stock valvetrain. I wanted a smooth idle so designed a cam with only .499 lift and .050 duration of 228 & 237. And very little overlap. I got a great torque motor with HP at 468 @ only 4800 RPM and torque 554 @ 4100 RPM. That is with ported stock exhaust manifolds, by the way. If I had it to do all over again, I'd up the specs on the cam to peak at about 5500 but, this car is a beast on the street and I'm not crying too much.
I don't understand this. Are you not using a leakdown tester? Just pressurizing the cylinder from a compressed-air supply? If so, that works for checking valves, head gaskets/cracked castings; but is no good for verifying rings. Or maybe you have some other procedure I'm not aware of.
@Schurkey I'm sorry, and without wishing to sound blunt, but you are wrong at a fundamental level. Neither a compression tester, a leakdown tester, or just pushing an airline into a cylinder will tell you if the issue is valves, rings, head gasket, a combo of all three, or infact the hole in your piston caused by running 30psi of boost at an AFR of 17. As far as any of the methods described below they cant differentiate between one type of leak and another, effectively as far as any of these 'dumb' testers are concerned a hole that is leaking air is just a hole that is leaking air. If I run a compression test, which I did, that will only tell me what the cranking pressure is in each cylinder. Low cranking pressure is caused mainly by bad rings or valves, and sometimes to a lesser degree by head gasket issues. I can of course add oil to the cylinder which will help me narrow the issue down but again is not conclusive. In fact I did that on no7 and got a worse result which is why my attention then turned to the compression tester itself, and why I found the pinhole leak in the hose. If I run a leakdown test using a leakdown tester all I'm doing is applying a constant flow of air at a low pressure (circa 20psi). Basically the leakdown tester measures the pressure drop due to any flow, the flow being directly proportional to the size of the leak in the cylinder. The gauge on the leakdown tester that usually shows red, amber, green (or %) is in effect similar to the flow gauge on a MIG welder, it tells you what the flow rate is and from that it extrapolates if the leak in the cylinder is within the expected range or not, i.e. red, amber, green. Again it can't tell you if the leak is valves, rings or head gasket which is why most leakdown tester kits tell you to use a mechanics stethoscope, or something similar, to locate the source of the leak. So what is happening if I just attach an airline to the cylinder via the spark plug hole and apply lets say 140psi and then measure the pressure drop over a set period of time, lets say until the gauge measures 100psi? Pretty simple really, not only am I measuring pressure drop over time but I'm also measuring flow, the flow being proprtional to the size of the leak in the cylinder. The bigger the leak the faster the flow, the faster the flow the greater the pressure will drop over a set period of time. Admitedly, stuffing an airline into a cylinder is far from ideal but by doing the same across all cylinders it will act as a comparison and will help to identify a bad cylinder. It does this despite any additional leaks in the system caused by pinholes in the airline, or a leaking gauge, all of which can be discounted as the errors should be the same for each test if the same initial pressure is applied and they dont develop into bigger leaks. So in my example having stuffed an airline into 7 know good cylinders, and having applied the same intial pressure, and having observed the pressure drop over time to be the same within an acceptable tolerance across all 7 cylinders, I can conclude that if the unknown good/bad cylinder shows the same result it is no better/worse than the other 7 cylinders. I could have pulled my leakdown tester off the shelf but for some strange reason the M14 adaptor is M14 x 1mm which wont fit the Buick heads. In any event whichever method you chose none of them can differentiate between one cause of the leak and another, that's where experience comes in and/or the use of additional testing/tools. I could of course have used a fluid like water and filled each cylinder with it. Given the known density of water and a set value for gravity I could time how long it took each cylinder to drain down and thereby extrapolated a comparative figure for the size of the leak in each cylinder. This would have only tested the rings as last time I checked water had a tendency not to run uphill. So at best all I know after my testing is one of the following: All cylinders have the same leak All cylinders have bad valves All cylinders have bad rings All cylinders have a blown head gasket All cylinders have a hole in them All cylinders are as good/bad as each other All cylinders have good valves, good rings, good head gaskets as defined within the parameters and accuracy of my testing. My experience tells me that with the compression test on 7 out of 8 cylinders being good, and the pressure drop/time test giving me the same results (+/-) across all 8 cylinders then, ergo, all 8 cylinders are good to go...........and I did stuff a boroscope in there just for good measure. The point of such a long post is to show that it is not necessary to have all the equipment in order to do a particular test the way 'the book' says it must be done. If you can establish a known good baseline then the use of comparative tests is valid. Stating "Just pressurizing the cylinder from a compressed-air supply? If so, that works for checking valves, head gaskets/cracked castings; but is no good for verifying rings." is wildly innacurate. Some tests may be more useful than others in determining what the issue is, but fundamentally as far as any tester is concered a leak is a leak is a leak, and it always takes further testing/investigations to determine what is the root cause of the issue.
If you pressurized the cylinder and air leaked out of it. If there was air comming out of the intake that is intake valve, if it is exhaust it is exhaust valve and if it's the breather or valve cover its piston or rings. If it's comming out of the radiator then it's cylinder wall or head gasket. If you just plug in the compression tester and turn it over a couple of times you should get the compression of that cylinder and they should be within 10 or better. If the compression is good across all cylinders then pressurizing the cylinders isn't going to show much.
Depends on what you consider to be a "proper" leakdown test. Or low cranking speed, a closed throttle, worn cam lobes, etc. Fundamentally, you're correct. I gave up on the "add oil and re-test" decades ago. I could never understand how the added oil would make it's way "up" the cylinder to the intake-manifold side of a V-type engine to seal the ring 360-degrees around. OTOH, adding oil which is essentially non-compressible, is like removing cubic centimeters from the chamber. Sure, the compression goes up. Good catch. Not everyone would "get" that. I have heard of--but never seen--a Hazzard Fraught "leakdown tester" that "tests" at ~15 psi, with instructions to have the piston at BDC. This is TOTALLY CRAZY. Must have been "designed" by a lawyer, not an engineer or mechanic. I don't know what equipment you're using. I have two leakdown testers. One is an elderly Snap-On MT324, single-gauge calibrated in percentage of leakage not PSI. I believe it tests at 60 psi, but I've never verified that. The other is an Federal Aviation Administration (FAA) and Teledyne/Continental-spec unit. I test at 100 psi to make the mathematics easy, but FAA regulations say to test at 90 psi. Essentially true. The details vary based on what equipment you'd use. My Snappy tester is calibrated directly in percent. My Aviation leakdown tester is calibrated in PSI, so I have to divide the indicated psi on the second gauge by the input pressure, which is why testing at 100 psi makes the calculation easier. I don't have color-codes. The pressure reading on the gauge does not tell you where the leak is. HOWEVER, merely looking at the gauge(s) is not a PROPER leakdown test. I listen at the carb or throttle-body; if I hear hissing, I know the intake valve is leaking. I listen at the tailpipe, if I hear hissing, I know the exhaust valve is leaking I look/listen at the radiator cap, if I hear hissing or see bubbles, I know that I have a popped head gasket or a cracked casting. I don't need a "leakdown tester" to verify valves or headgasket/castings. But there's ALWAYS some leakage past the rings, I KNOW I'm going to hear hissing at the PCV grommet, or oil-fill cap. The issue is "HOW MUCH" leakage, and for that I need gauges. THAT is why I said your system can't determine ring problems, but would be adequate to verify valves and head gasket. THIS is the part that leaves me baffled. Indicated pressure drop? That's going to depend on how capable your air supply is. You have a small compressor, and a big leak, the air in the tank will be depleted, the compressor will kick on and try to keep up. Maybe the compressor is big enough to "stay ahead" of the leakage. Maybe not. Because the results depend on the capacity of the air compressor, you're learning nothing about the engine, and everything about your particular air compressor. The only way this makes sense to me is if you're pressurizing the cylinder, shutting off the air supply so as to "trap" pressure in the cylinder, then seeing how long it takes to bleed-off. I've never tried this. I wouldn't expect it would take "minutes" to bleed-down, I'd expect it to take "seconds" for the pressure to bleed off. So your procedure has me VERY confused, and I don't think you've explained it very well. I agree that all cylinders should test the same if they're all in good condition. An outlier indicates a problem. Yeah, you'd be looking for M14 x 1.25. As said, a proper leakdown test will identify intake valve leakage, exhaust valve leakage, and head gasket/cracked casting leakage. Given some experience with the leakdown tester, it can identify excessive leakage past the rings. I suppose it would mistake a pinholed piston for ring leakage, but how likely is it that you'd have a pinhole in the piston so small as to masquerade as a ring problem? But you have to understand what you're testing. As I see it, your leakdown procedure is testing the capacity of your air compressor, NOT the leakage of the cylinders per se. However, we agree that the cylinders should all react the same way to the same test. As said--a proper leakdown test involves listening and looking at the engine, NOT JUST READING THE GAUGE(S). Which then verifies everything except ring seal. Of course, a given cylinder could have more than one leak. In that case, you'd be hard-pressed to determine what percentage is going out the exhaust valve, for example, versus the rings. Much more concise than I was. For the record, I acknowledge the Three Sisters of cylinder diagnosis. They can be used individually, or in combination to examine and diagnose problems. 1. Cranking compression test. 2. Cylinder leakdown test 3. Cylinder balance test This is by no means comprehensive; a person could do a running compression test, install a vacuum gauge on the intake manifold, install a pressure gauge on the exhaust system...there's a nearly-infinite number of procedures that can be done. I'm REALLY fond of slapping an igniton oscilloscope on the primary and secondary sides of the ignition system, you can see the voltage required to fire a spark plug, watch the "burn time", and so much more. But the "Three Sisters" finds MOST problems REASONABLY efficiently.
Well looks like we agree on somethings and maybe not others. That's what I like about forums, always good for an open and honest debate. On a lighter note:- Roller rockers and the new cam/lifters arrived this morning, that's less than 36 hours from Arizona to East Yorkshire, not too shabby in my estimation and indicative of the excellent service I always get from Sherri and all at TA. If I have time this weekend I'll get the new cam/lifters fitted and broken in.
As usual work has intervened in my plans and so I've only just got around to starting this one back up after the new cam and roller rockers. I've also purchased a distributor from Progression Ignition. Saw them some time ago and decided to give it a go. It may not do much but I like the idea of being able to map the ignition. I'm sure someone will tell me its a waste of money but I like experimenting. The map below is the one the App has generated as a first guess at timing. Idle at 850, 12 degrees static timing, 32 total, all in by 2800 and a max of 8 degrees vacuum advance. Does anyone have any comments?
Without reviewing the entire thread, if this timing curve is for a Land Rover, I'd say it's likely too aggressive. What might be suitable for a lighter vehicle with deeper gearing could be too quick for a chunkier vehicle. I'd say that "all in by 2800" is too fast. I'd delay that to 3200 rpm and potentially higher, test it, and see how well it works. 8 degrees of "vacuum advance" may or may not be enough--again, start conservative and experiment from there.
Thanks Schurkey, I suppose the advantage is that it only takes seconds to put another map together and load it.
If your 850 idle makes it too hard to tune the carb I would slide that 17 timing over from 650 to the 850 table and that'll help you adjust your idle system for a nice crisp idle and off idle Rev. I did this with a 310 hydraulic and I've never ever had an engine with this kind of tune ability and throttle response
