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Post by crowdpleazer on Sept 10, 2014 12:30:28 GMT -6
This winter I plan to build a new engine for my Hotmod (similar to a b-mod or sport mod). I am asking for any advice on which parts to select. Any advice is greatly appreciated! The rules are pretty restrictive. 358 cubic inches max, Holley 4412 500 cfm 2 barrel with choke horns still on, 175 lbs compression per cylinder max, flat top pistons, flat tappet cam and lifters but no other cam or vacuum rules, stock rockers or roller tip allowed, no angle milled heads or angle plug heads, I recently bought a 350 block casting # 3970010 4 bolt main. Stock now but will need bored probably .030. I do not know what heads to go with. We are allowed screw in studs, guide plates, and poly locks. No stud girdles. Vortec style heads are allowed but with the research I have done about them paired with this 2 barrel I'm not sure. (what do you think?). Aerohead racing has sbc reconditioned heads assembled for $400 a pair, add $50 for 2.02 valves. They offer 58, 65, or 76 cc combustion chambers. Are they any good? A little research found out that they are similar performance to old school double hump 2.02 heads. We don't have to run Chevy heads as long as they are iron. My research on what intake runner size, combustion chamber size and valve size works best with this carb has been almost a dead end... Aftermarket aluminum intake is allowed but no high rise or air gap style. Most people run high test pump gas in this class (including me right now). My goal is to have a strong reliable engine that is competitive but 100% legal. I would like to do most of the work myself short of machine work. It would be a plus to buy heads that are ready to bolt on, but that's not necessary. Jegs offers just about any combo of heads which makes it confusing. I am thinking about this bottom end. www.speedwaymotors.com/Premium-Small-Block-Chevy-Rotating-Assembly-350-Flat-Top-57-Inch-Rods,3177.html Sounds like a good deal to me but I'm new to this. Let me know good or bad. Thank you in advance for any help! My main question is which heads work best with this carb. |
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Post by crowdpleazer on Sept 10, 2014 12:39:33 GMT -6
I forgot to mention track is 1/4 mile high banked red clay. Engine runs about 3500-4000 rpm in turns and about 7000 max on tell tale. Tires are American Racer G60 KK704 which have terrible traction...
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Post by flipflopoo1oo on Sept 10, 2014 14:14:59 GMT -6
.030 is a wasted build! .060 is the way to go if looking for horses! Check out my other post and run searches to get the ins and outs as to cooling and making horses! A lot of heads out there, ours had to be limited legal 1.5-194 valves! 147 pounds cranking but who knows running! Its kind of like transfer of left rear! Either you gain or you don't move quickly! You have to work on all the 4 of the corners and cycles of the tune to perfect any combo you have! It is more all the little things that gets you where you want to be! Its harder to tell if geared to low and running a locked dist. and a power valve!
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Post by flipflopoo1oo on Sept 10, 2014 17:36:19 GMT -6
What gears are you running now! You may be better off narrowing the band to peak the power by loading it heavier and raising the torque band to handle the load! It then should pick up speed faster without the rpms! We won more at 6400 on 1/4 mile with faster times in limited than most mods! Roller tips are fine but I fool around with geometry of most any cam to bring it alive and tips don't allow what I want to happen very often without getting off the top of the valve on 2 or 3 at best with 5 different lengths of push rods! Some cylinders naturally run hotter so they tote the load and should not have to if pre-tuned by theory to all be or not to be the same! It would seem by now cams would have that ground into them by design on a 350 engine! .060 may-be just needs more attention but not at 150 degrees it seems mostly tolerant of cylinder temps compared to .030! More the compression issue of control of burn timing against the heads to have heating problems it seems to me! I never leave things where they should be by most standards to achieve my own twist in power! TORQUE is the key unlocking horses!
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Post by crowdpleazer on Sept 10, 2014 18:19:12 GMT -6
Right now im running 5.83 rear end in a 9 inch floater. My friend tried 5.43 and it didnt hardly spin but he said the engine bogged a lot out of the turns. I may consider the 5.63 but im not sure.
I have a locked distributor. We have to run the hei style with the coil inside the cap.
358 inches is the max so that comes out to .040 over. I said .030 over because its common.
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Post by crowdpleazer on Sept 10, 2014 18:34:44 GMT -6
Also I have about 100 lbs of lead in the back plus a 22 gallon fuel cell that I keep full. it spun tires on the straights until I put the last 35 lb chunk in.
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Post by flipflopoo1oo on Sept 10, 2014 18:56:42 GMT -6
It may just be your corner speed is off but first things first! Get all the legal cubes you can! If no stroke rule,.015 stroke may help with a bit of off-set grinding! I have run .010 clearance on a stock type piston to get a bit more cubes! Some pistons come with clearance and others has to be over bored to fit!.006 is less friction! I bevel the outer skirts to let the oil hold it centered if not designed so! .001 rods and .002 mains! Most piston weight loss is in the pins! Polishing rods makes them stronger but 305 X rods work great! A NF crank is a good bit lighter than steel and should have no hole in ft. rod journal but a nipple there as not to break !
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Post by crowdpleazer on Sept 11, 2014 11:22:55 GMT -6
I bought the engine that I'm running now. I don't know very much about it other than it has surprised me this season. What heads would you recommend would be best with a 500 cfm 2 barrel?
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Post by flipflopoo1oo on Sept 11, 2014 22:03:33 GMT -6
Its not the carb that controls the flow so much as vacuum and temp drop under the carb with the other things doing their job also! We have won with stock heads! They really don't matter too much to me! I work on making any combo work! Every engine I see is different! You can spend any amount you want now days on most any idem! I can't help you here! I hope these other guys speak up about how theirs works!
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Post by flipflopoo1oo on Sept 17, 2014 13:01:53 GMT -6
Its easier for me to build less compression and use smaller runners to speed up velocity to get my colder fuel in the cylinder to expand and make compression than to loose the power trying and then have to buy racing fuel to try to repair this mistake in judge-ment in making horses! Burning twice the fuel and cleaner than most yields a time controlled burst of power stroke that requires control of variable ignition timing and not the widened range of octane to slow down or time the power stroke! We all light the fuse and run leaving the rest up to other factors in the mix but there are more adjustable factors than timing and most have blocked even this controllable factor of change! So many horses lost and found by a constant factor in timing and the compression of heating fuels too soon!
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Post by Krooser on Sept 27, 2014 14:07:43 GMT -6
The horsepower is in the heads and camshaft. Depending on your budget the Vortec 906 and 062 head work pretty good and you can buy them cheap in a salvage yard. They are about the best OEM head available. Dart and World also are good with the Dart's being a little better from what I'm told.They will out HP even the Vortecs. Don't go too big… 170 or 180 CC runners will do fine with 358 CI. Don't ever buy pre-assembled heads… buy them bare and your local engine guy do the head work, supply the valves, etc. He'll know what you need to do to run with the locals. Pre-assembled heads are know to be thrown together and do not have much quality control. I've seen them where the valves don't even touch the seats on several cylinders. I'd call Charles @ www.camcraftcams.com or Mike @ www.jonescams.com or Bullet for your cam. They can custom grind a cam just for your application. The fast guys don't run off the shalf cams and neither should you. Your best bet is to find a good engine shop in your area and give them your business. Throw away that Speedway catalog and buy local… in most cases you'll pay about the same, get better stuff and, most important, build a relationship with a good shop who will appreciate your business and do a good job for you. |
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Post by crowdpleazer on Oct 11, 2014 7:56:45 GMT -6
@ Krooser, I found a pair of double hump heads for sale in the newspaper with 1.94 valves and accessory bolt holes (which I need for my alternator and power steering pump as there is not enough room for block mounts). The seller wants $200 for complete used pair of heads....
My engine machinist will probably want to go that route instead of buying new heads but for the price, even some of the better heads from JEGS seem worth it to me. Used heads run the risk of being cracked or warped. If you honestly believe that most all pre-assembled heads are junk then I wont argue with you. I honestly don't know. I'm looking at trying to get the best value for my money the first time around.
I should note that last weekend overall I did pretty bad but learned that the secret to this class is in the crappy G60 tires. I ground the tires with a 36 grit sanding disc for the feature. In the first 2 laps I started up through the middle of the pack from the tail. Was gaining on the leader till I got spun out and the tired cooled down and glazed over again. I was able to hold onto 5th place but there was no traction at all front or back. The engine that I have now is not much other than a wild cam. So I think that the main thing that I need is reliability and just some power.
Thanks for the input!
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Post by flipflopoo1oo on Oct 11, 2014 9:00:07 GMT -6
Same track and tires for everyone! I would look at the traction transfer before adding more horses or drop the timing with weights in the turn for a car length as to getting it moving with out spinning! If wearing or heating the right rear, consider the fact there is not enough weight or thrust angle to keep it planted too! Planted and steering enough keeps it working with out side bind heating it up! If making air it needs some to have less flex if low to produce heat especially once planted with more load on it! Harder tires can tell you a lot about a setup!
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Post by Krooser on Oct 11, 2014 18:29:00 GMT -6
Vortec's will be the best GM casting… good valves, springs and retainers are important. You don't know what those double humps have in them… you will probably have to start from scratch might as well get the Vortec's. Buy the springs from the cam grinder or use what he recommends. I used limited travel hydraulic lifters this year but you can run a solid cam so that's a better choice. An EDM hole in the lifter may also be a good idea depending on your spring specs.
If you have the budget look at Dart heads… they are priced well and can give you some HP. They are the best head in the WISSOTA super stocks and those guys get 425-435 HP out of a 358 with a solid cam and no compression rule. 4412 with an iron intake. Headers.
Here's what I would build… .060 over lightweight pistons (380-420 grams or so) with a lite ring package (Mahle, Autotec or Racetec…there are others) rings should be .043/.043/3mm or, even better, Mahle has 1/1/2mm rings. You'll gain from 6-12 HP just with the light rings. Autotec will run you about $400.00 and they will build them with the light rings at your request.
Hyper pistons would also work if you have a tight budget but they are a lot heavier.
I used GM powdered metal rods in my son's MWM this season. I found cheap low time used ones from marine engines… 19 rods for $60.00. They mag'd fine and lots of guys around here use them. Otherwise Scat rods will work… many engine builders say they have to rework Eagle rods to make 'em right so I'd avoid those.
Use a steel GM crank or a lightweight aftermarket. Again your budget dictates what you can afford.
A stock SBC Melling oil pump is fine… no need for high pressure or volume.
I used a Champ 7 qt. pan on my son's mod.
I don't have an intake suggestion because we use cast iron here… maybe an Edelbrock RPM or a Weiand Stealth.
Just my ideas….
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Post by crowdpleazer on Oct 14, 2014 12:32:47 GMT -6
Thank you for the info. .06 over will make for 360 cubic inches, and im only allowed 358. Dumb rule...
I talked to me engine builder (he built a couple engines for my dad many many years ago but they were late model engines). He doesn't like hypertaunic pistons. Says they wear out too fast. Could it be there is something he is supposed to do differently with them? Again i'm not sold on them and plan to do more research as I get the time.
What do you mean by an EDM hole in the lifter? Referring to wire EDM used to precisely cut internal profiles in metals. I know of that but never heard of it being used in lifters.
Also I did not realize that rings can free up so much power. Will definitely look into that.
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