I'd rebuild a 750 or 850 dp holley or Qjet and save the expense of the FI. Other than temp or altitude extremes there's little performance potential added. It's definitely tough to justify an extra $850 for a better slug. That takes it out of a low buck cheap fun deal.
To keep it cheap just feed it a 100 shot of juice, those pistons should handle an entry level shot of N02 that low if 100 HP more is all you need for your goal. Derek
I want something all the time any time. im not a n20 fan at all. and the fi tech isn't anymore expensive than the carb really plus I just really love efi. im not above the carb though but rather have efi. what am I looking at na to make 350 rwhp?
Another thought here: leave the stock static compression alone if it truly measures out at 9.75:1. Focus on reducing the dynamic compression through a larger duration cam with a wider lobe separation (combining to close the intake later and control overlap). This can allow a cooler and larger charge into the chamber to be squeezed at a pump gas friendly (detonation resistant) dynamic compression ratio. It also helps avoid reversion at idle and part throttle applications. Under boost, a positive displacement blower will erase any deficient in torque normally associated with these cam settings. Our factory supercharged Cobra is an example of this thinking. The stock static compression was 8.5:1 with small duration cams on a somewhat wide lobe separation producing a dynamic compression of 7.75:1. We rebuilt the engine with 9.8:1 static compression, CNC head porting, and cams with more duration and an even wider lobe separation producing the same dynamic compression of 7.75:1. Other then a slight lope at idle, there is no difference in performance or manners under part and light throttle applications. On the dyno, the the added compression, larger cams and head porting give us 100 RWHP more then the stock engine with the same blower using the same fuel. Pump gas (93 octane) is used in this engine, but there is a ignition timing knock retard system in place and octane booster is added for the computer tunes with more aggressive boost and ignition timing. So, maybe the cake is already sitting right in front of you. Do you have a knife and fork? Cheryl
^^^^^ sounds like a plan! A thicker composition head gasket will further reduce the stock 9.75-ish compression into the lower 9's. The biggest concern is to prevent detonation. Water injection or modern methanol injection will help. Add the electronic boost-retard timing controls or even a knock sensor and you should be good.
^^ detracts from the already limited quench in this engine, but you may be able to get away with another .015" or so depending ............. Cheryl
Don't waste your time or $$$ on a Paxton anything(or most Vortec's for that matter), even if you got it for free. For big power with a Nailhead, turbo is the way to go. Easy to get 200hp gain with even a smaller turbo and no parasitic loss. Packaging is easier, in my opinion, and the fuel system is all the same $$$ anyway no matter which way you add boost. Regular crap cast pistons will hold up with decent boost with a turbo, just don't detonate and, if you want to go to the trouble, pull the pistons and open up the ring gap, usually detonation will cause the rings to butt together and that causes the piston to break(LS trick). Forged is still better and if you go forged, thinner rings are better(more hp, less wear, less heat, no negatives)-I have done a couple 401's with them and I am sure Tom has, also. Polish the chambers in the heads and drop every $$$ you have on port work, it will pay off in every way, boost or no boost. ARP head bolts are necessary. I would just do heads/cam before you go boost, it's the best thing you can do on any Nailhead. PM me if you have any questions.
Plan on an MSD 6AL-2 programmable ignition box. With it you can really dial in a safe timing curve with accuracy. Get your MAP sensor from a 3.8 supercharged Buick motor. I had all sorts of problems with the new MAP sensor, went to the junkyard and got one off of a Buick that worked perfect. Best way to do the fuel system is a new tank with fuel pump in tank. TanksInc is what I used. Buick experimented with a 401 nailhead and got 700 ft/pounds of torque with a tiny little turbo. Does not matter to me which way you go to get boost. I like the linear feel of my Procharger. I have a buddy that has a 1000hp LSX with a Vortec. Don't know anyone using Paxton. They have been around a long time. What really kills you on any boost project is the cost of the parts to support the boost. I you think ahead you can build up to it in stages. Get the ignition and fuel system. Then you can go to FI. Last step will be the boost and you will be ready for it.
True... Knock resistance is more of a heat sensitive thing than a high cylinder pressure one. It's an 'every engine' problem and solution. Very true... Skip the chamber polishing, just take down sharp edges that can affect flow or hold incandescence.
Agreed. But typical production engines already have pistons 0.045" or more below the deck and with a 0.015" steel gasket produces a quench around 0.060"..... already much more than optimum. Would 0.080" quench be that much worse? Again, the ideal solution is getting proper pistons made. What wound be the preferred head gasket construction to hold up to a little boost, stock steel shim, or Felpro/Best composition?
Exhaust valve contact width pattern set wider will greatly increase margin of safety over a minor loss in compression, esp. when a 'recently rebuilt' engine might have the usual rebuilder tactic of an interference angle valve job that contacts on a razor's edge. The head gasket composition question and many of the other aspects brought up in the thread raise concerns of the bigger picture, which is "what do you need to keep in mind when getting away with something unintended by a platform not played with much for the last 40 years?". Nailhead has aspects and characteristics that don't always hold with certain generally accepted beliefs associated with other engines. The physics are still the same, the methods and trade offs are not.
Walt, i think the 427-454 pistons pin height is only 1.275. think the only way to do it right would be a custom made piston. Cheryl the venolia pistons are now 900.00 . auto/rac tech. 650.00
Holy crap Joe. They quoted me $6xx for a set the last time I asked. Must have been longer ago then I thought. I should have bought them then. Cheryl Sent from my iPhone using Tapatalk
650.00 plus 250 for the pins. they only make the better pistons, 5-7 thousand clearance.forgot the the number 4310 or something
454 pistons are 1.645" or so, 1.7xx for 427. 6.535" rod + 1.645" piston = 8.180". Lots of ways to solve things.
that will work. the 1.645 would put the piston about .030 in the hole. then deck the block about .025. the 1.7 wouldnt work. you could off set ground the rod and get a 3.69 stroke instead of the stock 3.64. the would give you about zero deck height on a non deck block.
There's numerous length rods that are usable for various pistons, I was illustrating just one example that I've done. Makes sense if you have to grind the crank or if it's already ground down a few sizes. Being a cheap SOB myself, I wouldn't leave a piston in the hole and then deck...it's faster for me to trim the piston using a longer rod. There's various heights of 454 pistons, even the often found to be shorter-than-listed-in-the-catalog Speed Pro's that can hang on a 455 rod with a very light cut across the quench pad area. Tall domes are hollow, low ones are solid...no issues with any I've tried. One surplus piston for study is much less than a set. It could be done at home with a router or die grinder with some guide rails, maybe in a block. You can easily machine .125" from portions of BBC piston tops. Obviously these options aren't for people completely reliant upon paying shops full price for piece work ops., but with some thrifty purchasing...much can be saved over an $800 piston, lol. [1.820 + 8.180 = 10.00 ] "that will work. the 1.645 would put the piston about .030 in the hole. then deck the block about .025. the 1.7 wouldnt work. you could off set ground the rod and get a 3.69 stroke instead of the stock 3.64. the would give you about zero deck height on a non deck block." See above...no need to be as complicated.
am doing a 401 as we speak. going with the 6.535 chevy rod 2.20 journal, need to turn the buick main to 2.20 from stock 2.25. so might as well off set grind it to 3.69 stroke. with the over bore going to have 412 cubic inches. going with the race tech pistons. 150.00 to turn the crank, 650.00 pistons. now i can have the zero deck height.
