Gonna' freshen up my motor, thinking of Nitrous... I've wanted to yank my motor and freshen it up a bit for quite some time, and since I have to pull the trans any way I figured I might as well do it at the same time. It's going to be a fairly simple build. Stock heads, Tom's roller rockers, right around a 10:1 compression ratio, modified factory intake (the doc special), headers, and a nice hydraulic cam (223* Intake Duration, 235* Exhaust Duration, .505" Intake Lift, .515" Exhaust Lift, 112* LSA, and 111.5* centerline). I've been looking around at what others have done and what their dyno results were, as well as playing around with some programs I have on my computer. I'm fairly confident that I should be able to achieve right around 325hp and 435ft/lbs tq with this setup (yes, they were WAY over-rated from the factory). This got me thinking about using a small (50 or 75hp) shot of NOS. Just a simple plate setup. The Nail seems like a tough old motor that would be able to take it. Yes or no? Also, any one want to critique my build? Having Gessler port the heads as well as using a TA Performance hydraulic roller cam might be an option, depending upon funds. The heads/cam would add approximately 71hp and 66ft/lbs, but would tack on about $3k. Nitrous is sounding mighty temping...
I'm very interested in where this goes. I think your a little short on the hp. I may be wrong but I don't think so. Also this is a 401 correct? Since I see Tom's rockers going in there. From what i've been told, a set up very similar to yours minus headers, manifolds ported, and a little pocket port will make 375 to 400.? Tom are you around?:spank:
When I first started crunching the numbers, that's what I thought too! I've looked back at a few threads, specifically the 2x4 intake comparision where ahhh65riv dynoed his 425. He had a 425, ported heads, a decent cam (very similar to mine), headers, Tom's rockers, and dual quads. He made 365.5hp and 468ft/lbs tq. I attribute a very large chuck of that to the heads, as the heads are where the Nail lacks. Since he also has a few more cubes that helped to. Also, I want to make it clear that I didn't just pull those numbers out of the air. I looked at a few builds, and what they made. I also have two dyno programs on my computer that are fairly close to real world numbers, one of them usually within 5-10hp! If you think my setup should make more power, I'm all for that! I was just trying to be realistic, and not expect over the top results for such a mild build.
Yeah, the recent builds didn't produce big hp numbers. Nailheads usually make peak hp by 4800 rpm, but they do make lots of torque over a wide rpm range, so they are great street engines. I'm just finishing up a build on a spare 401 I'll be putting into a 66 GS along with a Richmond 5 speed. My goal is a nice street and highway cruiser....much different than my big-cammed, 4.11 geared blue 66 GS. It got a 0.020" overbore, cast pistons, 3 angle valve job, and only minimal head mods....I blended and smoothed the valve seats into the ports, and did some gasket-matching. My goal was a good 'baseline' engine. I can always put better heads on later.:Brow: Cam is a relatively mild Poston NH400, spec'd at 272/282 duration and 0.486/ 0.495 lift, with 114 degree lobe separation. It's comparable to a TA 25, but has more lobe separation than TA's 110*. Oh yeah...and some of Tom's roller rockers!:TU: These babies will bump your max lift by about 0.050", and will increase off-the-seat duration, and 'area-under-the-curve' significantly!:grin: You have to watch valve-to-piston clearance on Nailheads. It's the tightest during overlap...about 10* BTDC on the exhaust, and 10*ATDC on the intakes are the closest points. Increasing duration, or tighter lobe separation could give you trouble! With my Poston NH400 cam, 0.015" head gaskets and .007" head cut, I'm 'snug' with about 0.090" on the intakes and exhausts. Adding the roller rockers didn't affect it by more than 0.020" or so.....the rollers' extra ratio has much more effect at max lift than they do at valve open/close points. My point is, if you are using cast pistons, you'll have to stay on the mild side when choosing cams. My machinist didn't feel there was enough thickness on the cast pistons to machine deeper valve pockets. I'm curious to know how others made out with this issue... Nitrous sounds like a good idea! You might want to run a bit more ring-end gap, and add some exhaust duration (as you did). Forged pistons would be good insurance, but are pricey at $800. When I have my next heads done, Gessler (or Mondello Mike)will get them. A stock rebuild cost me $650, and that's with doing the port work myself! Gessler will do them for $899, which includes new valves and some other items I didn't have done....good deal. I'm curious how varying the compression ratio from say 9.0 to 11.0 will affect the hp figures in your programs?
Thanks for the info! As far as compression, with my setup changing from 9.0 to 11.0 results in an additional 36hp and 32ft/lbs tq. It also moves the HP slightly higher in the power band. I'm not saying it's 100% accurate, but I'm confident it's fairly close. As far as my setup, I'm leaning toward adding a TA Performance roller cam & using a plate setup with a 75 shot. That should yield around 366hp and 477ft/lbs tq without nitrous and 440hp with a CRAZY amount of torque on nitrous. Then if I so choose, I could add heads later on. Anyone else care to comment on the use of a 75 shot of nitrous on a mostly stock Nail?
Andy, ...Glad you are doing your homework! You are already a step ahead of me, as I was making pure hypothetical guestimations based on many Nailhead gurus here on the board and local race engine builders experience. I think you are on the right track about heads and porting. I have a sneaking suspicion you can outperform my resuts with further porting from an expert at nailheads like Greg Gessler or the like -Even with less cubes with a 401! Gary did a great job of porting mine, but was based on general porting principles for any engine... Dare I say "the Nail isn't just any 'ol engine". I did go with forged aluminum pistons, not only because they are lighter, but for the potential for playing around with exotic fuels or maybey Nitrous. It was a choice for a piece of mind, if you know what i'm saying? Having "custom" pistons allowed us to fly cut as needed, and not have to worry about V-P clearances. Walt- you are exactly right! The claimed HP gains due to higher compression I belive is exaggerated. Is this going to be a driver? Don't mess around with the risk of detonation if you plan on runnig pump gas. For the few HP gains I don't believe it is worth it unless you are planning on rebuilding the motor often. In my case I left the ability (in V-P clearance) to alter (increase) compression if I want at a later date just by changing head gaskets (and Toms adjustable rockers!:Brow: ) As for the cam... I think this selection is the closest to maximizing some of the breathing limitations of the small valves and still retain the low end torque. As a matter of fact with over .500 lift at the valve you are doing a lot what Toms rockers are doing because of the ratio. Tom and I had a discussion about why his rockers had less of an effect on my engine. I was surprised too, but I think our concensus was chalked up to the cam selection. With all the above, I believe you could get away with over 100 shot of Nitrous on the nail and will live! What intake and carb are you planning? Keep us posted! Erik
I'd like to have Gessler port my heads but it's not in the budget right now. At over $2k it's going to have to wait :ball: . I'd like to go with forged internals but again, it's not in the budget. It would be good insurance especially since I'm considering running nitrous, but I've got alot of stuff that needs to get done (trans, possibly rear end, etc). As far as the compression ratio, I ain't messin' with it. In your thread someone mentioned that all the Nailheads they had apart averaged about 9.9:1. That's plenty for a pump gas iron headed motor, especially since I'm thinking about running "juice". Cam wise, the Nailhead REALLY seemed to prefer a split profile cam with more exhaust duration. This makes sense since the Nail is a little challenged in the breathing department. It also makes sense that Tom's rockers would have less effect on a motor where the cam already has the extra lift. You should still pick up some power becuase of the roller configuration, but it surely wouldn't be as noticeable. I plan on running the Eelco single 4bbl, if it ever gets released. Otherwise I will probably run a stock intake modified into a dual plane, or possibly a stock intake modified into a single plane. I'll probably run either an Edelbrock or Holley 850cfm. And I'll definitely keep you posted :TU: !
My relatively stock 401 ended up at 9.8 with stock steel head gaskets. The thicker Fel-Pro composition gasket would drop it to 9.1. Heads got a 0.007" clean-up cut and averaged 126cc. Piston domes on the Zollners were 46.5cc. The stockers were about 1cc less. The excessive deck clearance on the stock blocks kills the compression ratio. Mine is 0.045", uncut. If I cut 0.020" off the decks, my CR would be near stock at 10.28. Compression ratio should be matched to the cam. Longer duration cams can tolerate more compression. Do a search for 'Dynamic Compression Ratio' when you have a few hours to spare. It's an interesting concept!
I read up on it and yes, it's definitely interesting! My dynamic compression ratio would be between 8.3 and 8.5. From what I've read, that's almost ideal for an all iron pump gas motor. Not too shabby...
A 75 shot is good. Get some NGK plugs that match your engine. The "J" strap is wider on these plugs as compared to stock plugs they will take the nitrous better. You will probably just have to take out one or two degrees of timing on the engine so it won't affect your driving on the street. Just don't ever let your bottle pressure get over 1050 lbs. it just creates problems. If you run the pressure at 1000 lbs it will run perfect. This is where you need the bottle heater, to keep the pressure up on the bottle . You just can't leave it on tooo long like I did and had a nice nitrous explosion when I hit the gas at the starting line racing one weekend. Don't forget the safety device that cuts out the nitrous if the fuel pressure gets too low. Nitrous is fun.
How about this. Bring it by our shop. We're having a Refresh Special right now. I'll show you some DYNO FIGURES and we can go from there. Hell, I've even got a fabricated DUAL QUAD air inlet for our dyno so we can make corrections. In my personal opinion. Turbocharging is the most cost effective way to build big power with these things. Mike
Mike I agree with you on turbocharging if you're looking for all out power. I wonder if a 364 would be the better option if you went that route. When you go turbo you don't need as many cubes and the heads are a little better matched for the cubes on that engine.
I'm a little up the road doc in Crossville. I would LOVE to turbo a 322 or a 364. Preferably the 322. The bore to stroke ratio is good. the heads are similar to the bigger nails. all in all, It's just a 327 with factory forged goodies inside. I don't wholly agree with the result being high RPM/Horsepower though. I think by design of these things you're going to have a bucket full of torque regardless. A little 'pressure' should help it a little more. Mike PS> did some dyno work this week. Found swapping a carb on a 455 Olds was more COST effective for HP and torque than any shot of N2O!
I would still worry about the stock pistons with using NOS. I've heard of piston failures on Nailheads, but I don't have many details. One of the 66's I bought had 5 cracked piston domes. I'd say it was related to the bald tires on the rear! Teenage driver took mom's car out for some fun and killed it.:spank: Probably detonated it too death. I bought the car anyway for $200:bglasses: Jim Blackwood made an interesting comment on sbb pistons....basically, the extra heat produced by turbocharging (or NOS), was absorbed by the pistons and caused the alum to soften....resulting in collapsed piston domes. Mike, you work with specialty engine coatings....would coating the stock piston tops be beneficial for NOS use? Anyone else have info on Nailhead piston failures?
I knew the pistons were cast but I didn't think they were THAT weak. That kinda makes me a little worried. Why couldn't Buick have just made ALL the internals forged - is that too much to ask? Also, on a side note, with a 9.8-9.9 compression ratio how much boost could you run safely? 5psi? 6psi?
Here is good information source on Nitrous and using forged vs cast pistons and other good guidlines on how much you can get away with on a stock motor: http://www.nitroussupply.com/faq.php Looking at all the options of the different systems types and brands that are our there (there are so many!) I would be interested if there could be an advantage to use the dual stage system in conjuction witht the switch pitch activation?:idea2: Erik
i dont have any personal experience with nitrous, but I have seen three nailheads that had grenaded because the factory cast pistons failed.... all three were high milage engines that had crudded up radiators... that tell you something????? When they do this it usually busts the cast in oil galley that runs down the center of the engine, destroying the block..... I do think that the forged pistons that are available for nails are over priced... one could get custom pistons made for just a little more.... However, as usual, if one uses their brain, a man could run a small shot of nitrus on cast pistons if he did not get crazy with it.... any more would require forged pistons......
Uh, becuase the whole point of this was to FRESHEN up the motor and do it on a budget. If I had enough cash for forged pistons I'd turbo/super-charge it :TU: . Well, I'm at a cross roads. Now it sounds like I shouldn't go with nitrous or forced induction w/o forged pistons? I'd REALLY like to not be the guinea pig ...
