pparaska

Agreed. I found that I needed to run a larger than stock nozzle as well. I also played with the different pump cams, but the default one was close enough. Oh, get a hollow nozzle screw if you're upgrading the squirter nozzle. Just filling in a different value for accel enrichment in the Megasquirt computer is SO much easier!

I'm not sure what about the mechanical secondary carb made the difference that I noticed - but the effect was to cause the car to have IMMEDIATE response from having the throttle punched! Finally, the car felt like the beast it should have been all along! Maybe it was the instant opening of the throttle blades, but most likely it was that along with the immediate extra shot of fuel from the accelerator pump on the secondaries. Anyway, my 327 with a lumpy cam loved it, and an engine with even more cubes should love it more!

Glad you finally figured it out. But let me tell you my experience. I tried a 750 vac sec, then a 600 vac sec. The 750 made more power (I tuned both of them for the 327). The 600 would idle much better and had better low speed response. Then I got a like-new 650 DOUBLE PUMPER (12 dyno pulls only) very cheap and tried that. NIGHT AND DAY difference to both the vac sec cars. Lesson I learned: Most of the 'net knowledge and HOTROD mag articles say "DON'T USE A MECHANICAL SECONDARY CARB ON THE STREET". That's because they are talking about a big muscle car that weighs 5-700 lbs more than most V8 Z's. Sure, a mechanical secondary carb can cause bog, but only if you do something stupid like mash the pedal in top gear at 40 mph. The Lesson IS: GO AHEAD AND USE A MECHANICAL SECONDARY CARB ON ANY V8Z. Even an automatic car that has the kickdown setup correctly.

I wasn't going to say anything, but since it was brought up, I agree. With the nice 2-to-1 merges out there (flowmaster, etc.), that U-bend thing looks really silly on there. I'm not surprised that replacing something like that with a good merge would add hp. Probably not just peak power either.

Ahh, thanks for that clarification - I'm speaking "American," not "English," as my school teachers had told me. Now it all makes sense!

You two kill me!!!

Go for cubes with the longer stroke, unless you NEED to rev higher for some reason. My 406 is mild, 10.3:1 compression, Canfield 215 heads, 274/279 solid roller with .574/.577 lift. No it's not running yet, but with that seat timing, I'm betting it idles smooth. DD2000 says 520/520 hp/lbft. Sure, I won't rev past 6000rpm, but I won't HAVE TO.

A favorite article by a favorite engineer on Exhaust stuff. http://popularhotrodding.com/enginemasters/articles/hardcore/0505em_exh/index.html

Grumpy, I'm green in MD! That's awesome! The pics of the people standing inside and the truck out front really give away just how HUGE this thing is! I like the hip roof. Few people would go to that expense or care about what their garage looked like to do that...except you .

You guys are kidding, right? Say the word "Hybrid", then pronounce the letter "Z", as in ZEE!!! I never even thought anyone would pronounce it "hybrids" ??? I mean, it's about ZEEs, and they are Hybrids, meaning engine swaps! Not lame running HYBRIDS !!! So it shall be written, so it shall be pronounced! (Sorry Aussie's, Anglo's and Kanuck'ss - I just can't get over adding the letter "D" or the pronunciation of "Zah" with "ED" tacked on. I mean, do you pronounce the letter "S" like "Said" ? Makes no sense to this 'merican. ) (j/k)

Nice! Low/mid lift flow is up there with the similar AFR 190/195's. I also had similar good experience with flow testing Canfields. The exhaust didn't turn out so well out of the box (but the intakes were BETTER than advertised), but a minor cleanup on the exhaust bowl area fixed that: http://alteredz.com/data/canf215flow_1_data.htm Can't wait to see how your engine goes on the water pump - Have any computer simulations to compare that to? DD2000?, etc.?

I at first voted to ban the political/religious topics, but quickly changed my mind to let Johnc (who always thinks before he types, and I dare say never says anything he regrets) be the moderator in a politics and religion forum. But that was not a vote to the winning side, no big deal. I certainly am in agreement with katman: I too will miss johnc's research as well as the ability to see other's points of view on these topics.

Of course, you will be cruising up to Laurel this weekend to give me a ride, correct? HINT HINT Great news, David - I can't wait to enjoy it in person!

Actually, I expected it to come in at around $15-17k I'm surprised it's that low. Those engines are a lot different than the LS1/6. Many changes and upgrades. For a GM crate (really a racing engine) built by hand in a special facility like they are, with a 12 month, 12,000 mile warranty, I think you may want to reconsider just how inexpensive that engine is.

Vinh, did you try the power straight to the +bat connector on the distributor cap, and the ground straight to the coil housing (with the dust cover off)? What you've related to me sounds like a wiring issue in the car or a slightly defective ignition switch. That switch may not be allowing enough current to the coil. Good Luck!

Awesome! That's a truly radical mixture of body and engine parts! So how does it feel to drive it?

Great replies all! I've learned a lot lately about piston design, pushrod length methods, etc. I understood the barrel shape of the piston design for material growth due to heating, but the numbers seemed like they showed more variance when I was measuring them at 230AM . I was surprised they were cone shaped top to bottom, instead of barrel shaped. But I guess with such a short skirt, that's to be expected. These are Probe SRS forged pistons. Oh, I was wrong. The builder included a build book. Here are the side clearances he measured: rod side clearance #1 .023 #2 .021 #3 .020 #4 .021 (the crank end play is 0.004") They are Cat Power I-beam rods, with ARP bolts. I've heard some bad things about Cat stuff lately, but the builder was reasonably impressed with them. They certainly look plenty hefty, but who knows about what the void content, treatment, etc. Next time I build an engine for myself, it will have US material and machined rods from Callies, Manley, Carillo, etc. I'm tired of making the Chicoms rich.

No worries on the pin-to-piston clearance. I pulled one of the pistons that rocked quite a bit for/aft and the pin is tight - I can't feel any play in the vertical direction, it slides smoothly, so that's probably in the less than .001" range. Certainly no more than that! The piston diameter is quite a bit smaller at the top and between the 1st and 2nd ring than at the pin CL and at the bottom of the SHORT (around 2") skirt. I can't remember the numbers, but it was enough to make it difficult to install the piston, since the diameter goes down so quick going from below the oil ring to the top of the piston that you need to tighten the ring compressor to get it to not catch the top ring on the deck. Minimum difference between the piston and bore measured at 0.003". The piston is largest at the bottom of the skirt. This seems like an uncommon piston shape, and I remember the builder commenting that way as well. The piston pin is RIGHT below the 1/8" oil ring. The ring package is pretty tight and high. The pin height is 1.125", and all the rings are just above that. Below the oil ring, just next to the piston pin, there's only about 1/4" height of piston that can touch the wall, and it measures a good bit less in diameter (can't recall the numbers) than perpendicular to the pin at that height. But perpendicular to the pin just at that height (just below the oil ring), the dimeter is about .003" less than at the pin CL, just ~0.4" below. In other words the piston is a good bit smaller than the largest piston diameter in the entire area that it can touch the wall if measured in the front/aft direction (along the pin.). Factor in the 6" rod and .0025" bearing clearance, and the piston rocking isn't hard to imagine. The rod side clearance isn't excessive, 0.004". Surprising this all is to me, since I'm used to dealing with 327 pistons with a 5.7" rod, which is A LOT longer piston. The short piston, of an unconventional shape, is the cause of the rock. Terry, any idea what the the height of the piston in you engine is in the for/aft direction (parallel to the pin)? I'm betting it's a good bit taller than these pistons and maybe the piston shape is more conventional (and tighter to the wall in this area). I'm through worrying about the for/aft rock. I am wondering if it'll knock at idle when cold though, but mostly due to the rock in the other direction, where there's a forcing function involved.

I understand. I'll be pulling a piston tonight and checking the clearance, as best I can without disassembling the rod/piston. If it looks suspect, I can see the shortblock coming apart and the rods changed over to something with floating pins (they aren't very good rods anyway, according to the internet wisdom). If the clearance is out of spec, I'll be pissed. I always do my own engine building. Except this time I didn't. Decks cut way too far, a distributor gear-munged front cam bearing (the cam was difficult to remove due to it), and then loose piston to pin clearance to boot!? Any money I saved on having this engine built somewhere where machine costs and labor are cheaper has already been lost due to the expensive head gaskets I've bought. I'll be going negative if the rods need to be worked/changed. This is the LAST time I have anyone build me an engine! Damn, I may call off my Z convention trip due to this.

Terry, nice analysis, but the I have pressed pin. The play must be in the pin bore of the piston. Yes, I'm afraid to take it apart to see what's up!

Terry, Thanks for that data. How did you get them to rock? I was using light taps with a rubber mallet at the piston edge, watching progress on the dial indicator at the opposite side of the piston, making sure that the piston didn't "unrock" away from the furthest reading. John, I agree. Instead of using the copper gaskets that grumpyvette suggested, I found that Cometic has .051 and .060 (instead of .050 and .062 that SCE Pro Copper come in). So I ordered one of each from an online outfit. That'll give low .040's clearance on each deck. Oh, with those gaskets, I'm at about 10.3:1. 8.3:1 DCR with the cam in at 4 degrees advanced. I've yet to take the time to pull a piston but will do that this evening. I've spent the last two evenings doing cam degreeing and lobe surveys, and finding the pushrod length that will minimize the travel of the roller rocker's roller tip across the valve stem. (about .025" to .030"). I just ordered some Smith Brothers pushrods (damned expensive) in a custom length - I should have them early next week. Flatlanderacing has pretty good prices on them and just has Smith Brothers drop ship to you.

Grumpyvette is moderator on the "Performance Related" forum on Chevytalk.org: http://www.chevytalk.org/threads/postlist.php?Cat=0&Board=UBB64 (and I think a few Vette forums), as well as being a stellar citizen on other tech related boards like ours. I'm guessing his "home" is Chevytalk's forum (meaning he probably checks those forums more often, not sure) and that might be a more appropriate place to point people to find his wealth of tech posts. But we are very lucky to have him come here and answer questions, and just post nice long, detailed threads about performance related stuff, without anyone asking a question!!!

Brad, You're correct about 2bbl carbs. I'd forgotten that (CRS syndrome): http://www.225.ca/tech/jstk001.htm: "They use a 1.5" of Hg (mercury) pressure drop for 4 bbl, while 2 bbl carburetor flow numbers are generated at 3" of Hg." Thanks for keeping me straight!

http://www.thirdgen.org/techbb2/showthread.php?threadid=199786 Tell me that DLT504's LONG post in that thread doesn't look REALLY familiar. Check the length, great info, language, use of capitals, etc. Seem like someone we know? Jeesh, giving great info is noble, but to do it and not attribute the TRUE author is pretty lame. Last time I checked, G_____V____ lived in Florida, not Illinois. Since GV has posted that same info numerous times here on HybridZ and on Chevytalk, and he adds to it very thoughtfully to fit the particular question in a thread, I'm just guessing here that HE is the original author, not DLT504. Thanks again GV for all the great advice - I DO listen, I just don't always use my brain and follow it all-unfortunately!!! Pete

Thanks, Grumpyvette! I think you're advocating I use the AVERAGE deck height, not the maximum above-the-deck one. Cool. I'll order the SCE gaskets then. 0.043" thick for the deck with that deck height. The other one has the pistons even farther above the deck, the tallest average deck height at the quench area being 0.019", so I'll have to settle for a 0.062" one (to give an 0.041" piston-to-head clearance), since the next thinner is 0.050" which would give me a 0.031" clearance. I'll call to see if they can do something custom in between - they list a 0.055" thick copper gasket Titan series, so they may be able to make the Pro series in that thickness also. Thanks again! Yes, if I were to do it over, I'd order H-beam rods and use a piston with a D-shaped dish. Coulda, Woulda. .