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Pyro

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Everything posted by Pyro

  1. Always match the head gasket to the block. The ports in the heads are all about the same but the blocks are very different. You will also get over heating problems.
  2. The reason the valve train is quiet is because the wipe pattern is a little closer to the lash pad side of the rocker (thicker lash pad). When the wipe pattern is set up closer to the pivot ball or even centered, the valve train will sound like a diesel (thinner lash pad). All the noise is from slop at the rocker tip and lashpad. I prefer to set the wipe pattern closer to the lash pad side of the rocker like you did. If I want a diesel sound from my engine, I would buy a Ford Super Duty or use a centered wipe pattern on my Z.
  3. There are 9 bolts on the 240mm flywheel to mount the pressure plate. The 225mm has only 6. So, just count the number of pressure plate mounting holes to figure out which flywheel you have.
  4. Shimming the spring or using a stronger spring will not help idle pressure. The spring doesn't effect pressure until a high enough pressure is reached. And idle pressure is way under any relief pressure. The problem is that your engine has too big of a clearance in the bearings for your stock oil pump with the oil you are using. So, either use thicker oil (10-40W, 15-40W, or 20-50W) or use a turbo oil pump that pumps more oil per revolution due to longer pump rotors.
  5. I run a holley 750 on my 350, 454, 396. And they all needed 68 to 69's on the primarys and 72's to 74's in the secondary. So I think a set of jets ranging from 67 to 74 should cover it. A "bit of a cam" may require a 6.5 power valve Change the primarys jets based on the amount of soot around the metal base ring at the bottom of the threads. A soot ring that goes 1/2 way around the base ring is a good mixture. The "base ring" is the flat surface at the bottom of the threads that is perpendicular to the threads. Then if you see black smoke blowing out the tail pipe during WOT, then jet down the secondarys until the smoke stops. Use a vacuum gage on the ported vacuum source and if there is more than 1 or 2 inhg then the throttle blades are openned too far into the main idle circuit. This will make the idle mixture screws do almost nothing to correct the idle mixture. If you have this conditon, two 0.060" holes drilled in the front throttle plate will allow more air into the engine with the throttle blades in a more closed position. This will make the idle mixture screws work correctly, then adjust the idle mixture when the engine is hot to the highest idle vacuum. You may need to drill a 0.070, 0.080, or even a 0.090 to correct the problem. Do a web search on how to tune a holley. There is a lot of free information out there.
  6. My car only started to break stub axles when it got into the 11's at 120mph using slicks and 4000 rpm clutch drops. stay with street tires and you will not have a problem. You need a T5 from a V8 car. And do not shift it fast or hard. Slow easy shifts will make it live. And don't give it full power in 5th gear.
  7. I don't like the downshift cable on the TH350. It messes with the throttle feel. The TH400 is bigger and stronger. The size may be an issue when installing into a Z. I like the electronic downshift switch setup.
  8. Piston coating can also add thickness.
  9. All forged pistons have this problem. They are set-up loose when cold, so they can expland to the proper clearance when hot. If you have stock cast pistons then this could be a problem. This indicates engine was bored to big for cast pistons. The cold bore clearance on cast pistons is about 0.0015" and 0.0050" for forged. As the forged piston warms up, it will expand to the tighter tolerance. The cast piston doesn't change that much. As long as the noise goes away you should be OK. Continious piston slap will wear the bores and pistons out quickly. Yes, let it warm up before getting heavy on the throttle. Do you have cast or forged pistons?
  10. No, a Q-jet is not too big for a 350. GM put Q-jets on engines from 283 to 454. A stock 2.4L fuel pump is not good enough. A Q-jet needs 5 to 7 psi. A stock 240 runs 3 to 4 psi. Lean mixture pops out carb Retarded timing pops out carb Retarded timing makes the headers glow red Rich mixture makes the headers glow red Rich mixture pops out exhaust Re-check the firing order very closely, sounds like a 5/7 switch. What are your engine specs?
  11. The Q-jet is most likely a 750cfm. They did make a few 850's but 95% were 750cfm. And since the secondarys only open as needed, GM put those on 283's to 454's. The very small primarys give it very good throttle response, very good mpg with light throttle input, and the very big secondarys sound great when they start to open up (very cool sounding!). Plus the carb is very reliable and is made out of the right material (not aluminum). I hate edlebrock carbs! Throttle sticking, vapor locking, cheaply built carbs. Pure junk! I threw two of those in the trash a few years back. Edelbrock makes great intakes but they should be ashamed of their carb. I perfer the Holley 750cfm, 3310 vacuum secondary carb. It is easy to tune and looks good. The Q-jet sounds better, gets better mpg, and makes great power but doesn't "look as high performace" as the Holley. If it wasn't for the way the Q-jet looks, I would use it on all my V8's. I guess I'm a little vain when it comes to my engine looks. I just like the way Holleys look.
  12. A lopy idle will reduce vacuum at idle which would warrant the use of a bigger diameter brake booster. The more overlap a cam has, the lower the vacuum. Plus the use of a larger diameter brake cylinder will require more pedal force to make enough line pressure. Looks like the larger diameter booster would be a good idea for your set-up.
  13. I had the larger diameter booster on my 76 with 5spd trans and I hated it. The bigger booster made my brakes hard to modulate. The pedel was very easy to push and the brakes hit very hard. I went back to the smaller booster and love it. However, if you are running a big cam with low manifold vacuum, it could be a good thing.
  14. A stock cam will not pull to 7200rpm and seem like it wants to do more. A stock cam will fall on its face at 5500 rpm. The idle sounds a little lopey. But a header and a carb with a rich mixture could make it sound like that. Kind of hard to hear off a computer.
  15. I still would recommend using stock turbo pistons with a N42 head and a stock NA cam. 8:1 cr versus 8.3:1 cr is not a huge difference. A few degrees of ignition timing reduction in 4000 rpm range and maybe a little more fuel will be the only tuning difference. A stock NA cam has 8 more degrees of intake duration as compared to a turbo cam which will bleed off some cylinder pressure and give another 500 rpms of power band You don't need a wide band to boost at 8.3:1 cr. Spend your money on a good efi system with ignition timing control. Ignition timing control is the key to prevent detonation and make great power with good mpg and drivability. Just the price of custom pistons will be 1/2 the price of a bad-A efi system. If the engine has detonation problems then turn down the timing with the EFI system or lower cylinder pressure with a little more cam. Don't spend a bunch of money on engine components if you don't have a good efi system in place first. Forget the Z31 efi. You need ignition control and easy tune changability. You could make 300hp with a completety stock L28et with T3, 15 psi of boost, a NA cam, N42 head, bar & plate IC, and a good efi system. I don't like walbro pumps. Very noisy, expensive, and are over-kill. Look at the MSD efi pump (MSD-2225) from summit racing. You can get it for only 90.00. 2500.00 will go fast, so keep the engine simple and spend the money where it counts, in the EFI system. You will also need a better clutch if you plan on using a manual transmission. Check out nipponpower.com and take a look at the stage 2 SPEC clutch.
  16. A L28 with dished pistons and a P90 head makes 7.4:1 cr. You need to make the combustion chamber smaller or the engine larger to make more compression. Adding a thicker head gasket is NOT how to decrease the combution chamber size. Why would you want to use a thicker head gasket then slave the head? The net effect is the same combustion chamber size. Like taking two step forward and two steps back. A L28 with dished pistons and a N47 or N42 head will make 8.3:1 cr with a stock 1mm head gasket. This is the easiest to make close to 8.0:1 cr.
  17. Could be a regrind already. Stock marking mean nothing after a regrind. How tall is the back of the cam lobe off the cam shaft? A reduced height indicates a regrind. The lift is the widest part of the lobe minus the narrowest part of the lobe times 1.5 then minus the 1.5 times the lash. You can measure this "expected cam lift" with a caliper. What is the idle like? What is the engine vacuum at 800 rpm? What does the valve train sound like? When does the engine quit making power? If there is a doubt what cam you have, you should check the lift and duration before doing anything. You will need a degree wheel and a dial indicator to make a cam profile measurement.
  18. 300 hp to the wheels is about 360 at the crank. 360hp only requires 180cfm at max lift, in your case, 0.477 inches. That isn't a lot of flow. 220+ cfm is what most good aftermarket heads flow at that lift. Install some better heads and the power will go up. Those heads are most likely maxed out. Sometimes people use 305 heads just because they have a set laying around.
  19. I don't use a damper on both my efi cars for the last 3 or 4 years without any problems. And I run about 95psi of fuel pressure on my turbo engine while on boost.
  20. You need to be figuring out dynamic compression ratio vs. octane. There are a lot of free dynamic compression ratio calculators on the web to choose from. 8 to 8.5:1 dynamic compression ratio (DCR) would be a good range to try for with 87 octane. An engine with 11:1 static compression ratio can have 8.5:1 DCR if the cam is big enough (late intake valve closing point). So, pick a cam that you what to run. Then run the calculator to figure out how much static compression you can run. Low speed torque can be made with gears or low a rpm torque engine or a combo of both. A 3.90 gear with a early 5 spd and flat top 2.8L with a P79 head and a 260/260 advertized duration cam should make for a nice runner with 87 octane. When you use the DCR calculator, input the pistion sticks out of the block 0.010", the head gasket is 6cc volume, and no valve reliefs.
  21. 8.5:1 DC is easily in the 93 octane range. Since you have a light car with fast burn heads than don't require that much total ignition timing, I'm sure you could get by with 9.0:1 DC and 93 octane.
  22. Drive 10 miles down a mile marked highway. If the odometer shows 10.0 miles then your speedo is correct. If the odometer shows 11.0 miles then your speedo is reading 10% fast, So 77 on the speedo is really 70 and 99 is really 90. If the odometer reads 9.0 miles then the speedo is reading 10% slow. So 70 on the speedo is really 77 and 90 is really 99. This works pretty well to figure out how accuate your speedo is. You could also drive a 5 mile run to figure it out. Get the odometer reading divided by the distance driven to get the percentage off. I hope you did your homework in math.
  23. Man, there must be over a million Corvetts out there with no engines, since everyone has one or is putting one in their car. Poor motorless corvettes.
  24. Pull the head. If it has dished pistons then use a stock head gasket. Don't get hung up on the compression gage reading. Those things can be off by a lot. I have two gages and one always reads 30 psi higher than the other one. Which one is right, who knows? If the timing chain is advanced, it will rise cranking pressure. So, you can reduce cranking pressure by retarding the cam. The chain could be on the third postion which will make the pressure higher. There could also be a lot of carbon build-up in the cylinders. With the cylinder head removed, this can all be seen and corrected. If you pull the head and there are flat top pistons in there, then install a P79 head and run only 8 psi of boost. No problem.
  25. 4 psi is too low for a holley. Run 6 or 7 psi. How do your plugs look? Does it smell rich at idle? Have you adjusted the idle mixture screws for best idle (highest vacuum)? You need to pull the front fuel bowl off to see what jets you have. Then you can order smaller or larger jets as you need them. But get a set of gaskets for the fuel bowl before taking the old ones off. Typically, holleys come jeted rich from the factory. This makes their carbs safe to just bolt on and go. You can gain 2 or 3 mpg and much better throttle responce with the right air/fuel ratio. I have found in most cases, 2 or 3 jet sizes smaller than the factory installed jets do the job. Every engine is different, so you must figure out the jet size for yourself, but 68's or 69's in the primaries is a good place to start.
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