Getting into the 12's

What would it take to get a 69 Chevy Step Side into the 12's, thats where it started! I'm on a budget and a big block project seemed out of reach, but after some reasearch and parts scrounging I decided a 454 and a shot of NOS should do it. Pat, John and a couple others have all had some great input and I welcome more. I have made one mistake so far, and am in the process of correcting it (to little valve to piston clearance). I am still stuggling with the cam I choose!. Here is project 454. MarkIV 2-bolt .060 over, line honed O decked, 049 heads w/ 2.19 & 1.88 Manley Pro-Flo valves, pocket ported, opened throats and unshrouded chambers, shaped the short side radius and cleaned up the ports a little (did not polish intakes or get to crazy w/ the cutters), matched intakes, polished exhaust ports and chambers, 4 angle valve job etc. Stock rods polished and shot peened w/ wave lock bolts. Cast crank, Balanced rotating assembly, Speed Pro pistons and rings. Melling oil pump and Moroso steet stip pan. CC'd heads and calculated compression to be 9.4:1. Edlebrock RPM Air Gap and a Demon 850 w/ anular boosters to top it off. MDS distribtor and 6A box. 125-150 HP plate style NOS system and 2" headers w/ X pipe or crossover, 2 1/2" exhaust. Last the cam I picked was a Crane 226 236 duration @ .050, .534 .553 lift and 112 degree LSA (this wider separation seemed to be better suited to the NOS). The truck has a 12 Bolt w/ 3.73's and a locker. I will run MT 325/50 Drag radials and a Turbo 400 w/ 2800-3000 stall coverter. Will this truck run 12's?

:whacked: it should

lol theres a guy here with a 68 stepside with a 327 running 12.80's

Depending how much weight you're pulling (~3500#?) you should easily be in the 12's without the NOS on pump gas. I would cho0se 3" exhaust with high-flowing mufflers, though.

Weight is definately an issue. With the big block under the hood and a driver in the seat I'm guessing close to 4,000#'s. I have not had it on a scale. I agree 3" exhaust would be best, but I've got a 2 1/2" S/S system with Borla Turbos and mandrell bent tubing under it now that I was going to reuse when it swap out the small block for the big block. How much HP do you think I'll give up w/ the 2 1/2" system. Thanks for your input!

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Originally Posted by Step Side

Weight is definately an issue. With the big block under the hood and a driver in the seat I'm guessing close to 4,000#'s. I have not had it on a scale. I agree 3" exhaust would be best, but I've got a 2 1/2" S/S system with Borla Turbos and mandrell bent tubing under it now that I was going to reuse when it swap out the small block for the big block. How much HP do you think I'll give up w/ the 2 1/2" system. Thanks for your input!

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if you're not gonna turn it but 6000 rpm's, i'd leave the 2 1/2 on there. **)

Yeap, Mike, I agree. There a whole lot of studies made on exhaust flow and velocity against engine pumping made in the late nineties and early 2000's that indicated many people are actually going with too large of exhaust and killing the intake signal, etc. I still buy that arguement.

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Originally Posted by Oldf100fordman

Yeap, Mike, I agree. There a whole lot of studies made on exhaust flow and velocity against engine pumping made in the late nineties and early 2000's that indicated many people are actually going with too large of exhaust and killing the intake signal, etc. I still buy that arguement.

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never have had a 3 " pipes on nothing, but i've never run hi rpm's either, except on my mod. round track, but i ran small headers on that for the bottom end.

that is a very good question i think a 2 1/2inch ex to 3 will not see to much hp if yours is a true mandrell bent. i would think a Xcross mandrell bent 3 1/2 would be the best and you may see some tq with the x cross and some hp. the mufflers have a lot to do with any ex so if you had a 3 with bad mufflers i think you would not see any thing maybe 20 hp on the 3 with good mufflers? but do not forget the headers . you need big headers 2 to 2 1/8 to. a big ex work the best with all the right parts matched .so i think you will be ok .try running it with ex un plug that will tell you

Stepside....you should have NO problem getting into the 12's with your combo....getting it to hook is going to be the key. I know of many guys with similar combo's running low 12's, even into the 11's, and no NOS either. It's pretty easy with a big block. Getting the power to the ground is not so easy. You'll have to mess with suspension, and use sticky tires...but otherwise it should be and easy goal. I have to disagree with the exhaust question though...I would not go with 2 1/2"....more cubes like to breathe, and the 3" will help with that. If you're looking for 1/4 mile times, you will want the larger system eventually. If you're strictly talking street and short blasts light to light, the smaller one is fine. Im sure there will be differing opinions. John

What problems were you having with p/v clearance? You should have no problems there with most cams for this combo, and certainly not with the Crane you mentioned. You cam choice will make a huge difference in this engine. John

will your 2 .1/2 stop you from the 12. 00 NO. will you go faster with bigger YES but what do you want drag truck or street driver ?the bigger EX gets very loud have done many ex and think going to 3 1/2 with a x cross would be the best for the track.butwill be louder on street so keep that in mind .the crane cam will not fit? with the lsa at 112 and the low @ .050 it should but i would not be surprised if it did not o deck block less.020 cut heads ?.020 less big valves ? no valve drop you will see this no intake side i have seen them hit @ .050 240 on 110lsa 510 lift .i can not see ripping your EX out for the 3inch but would do it for the 3 1/2 if you use the NOS a lot. like i said if you have small tube headers than i would first loose them

Thanks for all the input guys, this is good stuff. The truck is definately a street truck going to the track once in a while so I think I'll stick with the existing 2 1/2" exhaust for now. I used stainless steel tubing and fittings salvaged from a cheese plant (true mandrell bends with a long radius and polished inside and out) It was all hand fit and welded with a heliarc (no miss matched connections or weld burn through). The X-pipe was also hand made the system turned out nice and the Borla mufflers sound pretty good, don't know how much they flow though. As for the VP clearance issue. We cut .028 off the decks for 0 deck, about .015 off the heads to reduce the chamber volume to 123cc (the valve unshouding enlarged them from there origional 118cc). Also the new 2.19 intake valves sit much higher on the seats than the old ones. After I got it together and degreed the cam I put the heads on with light check springs on No. 1. I was bummed when I found I only had .048 VP clearance @ 7.5 ATDC. The pistons are Speed Pro #2465F and gaskets are aprox. .040. Do you guys think I am bettter off to put some slicks on a set of spare wheels, rather than run the drag radials? The curent suspension setup is drop spindles and coils front, Truck Arm rear suspension with drop coils and gas shocks all around. I did fab and install a fuel tank in the rear and plan on relocating the battery and NOS to the bed. If you guys think the cam is a poor choice I'll swap it , but I can't afford a roller at this time (this thing could be a real beast with one of those). Thanks again everyone, look forward to more ideas and input!

Yep, the milling of both parts is what's causing you some problems. Nothing much you can do about that except change around pistons and cam to match. Wow, 123cc's still?? That's a pretty big chamber. Im not extremely familiar with those pistons...I know they're a popular one to use, they are a medium size dome, aren't they? Which valve did you have that clearance on, intake or exhaust? And what were your clearances from .020 BTDC to .020 ATDC? You can gain some clearance by advancing or retarding the cam...depending on where you need it. But when you gain on one valve, you lose a little on the other. I know on my engine, Im almost 0 decked (.005), and heads have been milled about .040, so I have the same problem. I have plenty of intake valve clearance cause the pistons have large valve cutouts, but Im tight on the exhaust. I advanced the cam to gain more on the exhaust, and the cam I just ordered was custom ground to help with this same problem. You can work around it.

The intake is the problem, plenty of clearance on the exhaust. Everything I have read says minumum of .080 clearance on the intake side. I don't think I can change the cam timing enough to resolve the issue, so I am going to pull the the motor down and flycut the pistons (looked at some other options but I think this will be best in the long run, engine is still on stand and this should only lighten them a gram or two). I don't need to make a deep cut but I definately want a little room for a bigger cam in the future, if this one gets boring or I go with a roller down the road. I was also suprised the chambers ended up so big, but I unshroaded both the intake and exhaust valves (hope it pays off they look real good). I was shooting for 9.5:1 and .040 quench, we came very close and every chamber is between 122.5 and 123cc. Like you said the pistons have a medium size dome and come to find out this is a more common problem than I realized, but thinking about it I have changed a quite a few things. I checked VP starting 20 degrees BTDC to 20 degress ATDC, I don't have all the numbers but 7.5 ATDC was the tightest clearance. If you can think of a better cam choice let me know, but I think a tighter LSA will increase overlap and make my problem worse won't it? Thanks for the help John, let me know what you think.

Wow, just the opposite of my problem. Well, it happens. That's a pain that you have to pull it all apart again, but I guess it's the only logical thing to do. Yes, going with a tighter LSA will make it worse. If you're not running the thing at 7K, you can run the intake pretty tight...I know several guys who get away with .060, even a tad less...but it's taking a risk of course. Is your intake valve hitting the entire flat part of the piston dome, or is it just kissing the edge of the cutout?? Can you tell? This is a very common problem with those brand pistons. If you do the clay method, as well as the dial indicator, you can actually see what is hitting, sometimes that can be a help. Im going to send you a PM with some info on cam choices...Im working with a guy who is grinding my new cam (as we speak, hopefully) and seeing as how Im having basically the same problem as you, he asked me to take some measurements, and he knows by those measurements what the clearance will be at all times...we did the cam specs based on that. I think you will be interested to see what he has to say. John

what you have going on is very common with a big block have see this from 500 lift to 800 lift and had to fix many.this is not to big of a deal on the big cid engine the the rods will hit the cam to that is engine building the pistons on a big block will hit all of the time intake side i have used them pistons you have in 6 or so builds and they will not take much cam so they will hit if the valves are hanging down you may want to try moving the cam retard 4 and try that you will not see much but you would be better cutting the pistons .and put the cam where it should go i would not look at a custom cam for this problem if the intake valves are to low you will have a lot of promblems if the pistons do not have a big valve relief and them do not i have cut them .060to get 710 lift roller cams to fit with 268 @ .050 on 110 lsa you need to make sure you do not cut in the top ring land or get to close with the nos you will burn the piston where it has been fly cut so maybe both move the cam and cut the pistons you do not want to cut down to or past .060 if you are using nos if you do not have to cut that much say .030 with the cam where it should be you will be ok i have runned many down around .060 with roller cams with big springs BUT you need to check all the holes and would say on a hyd cam you could at by at to 080 but like i said you nee to know all the holes are that or more not all of the valve fly cut hits the piston sometimes you can tape the engine of and use a psa sanding disc and sand the deep part of the stock fly cut BUT you have to make srue no junk get in the bore or engine or you can rent a cutter from isky or make one from a old intake valve it will work you need to use a head like yours or you head to hold the valve with some tool steel welded on the face or have it cut in the valve face with teeth this is low tech but has been done many times with out taking down the bottom end do not ask me how i know:whacked:oh grind a hex where the keepers would go on the valve stem so the drill can hang on with out digging in the valve stem and screwing up the guildes in the heads

Thanks John and Pat for the advice and input! Before I pulled the heads I stuck a Q-tip with blue on it through the spark plug hole and applied it to the valve by spinning the valve with my fingers. Then I pushed the valve into the piston and spun it. When I pulled the head it left a half moon almost dead centered in the valve relief. I talked to a machinst that has a jig and fly cutter set up to make the process fairly cheap and all pistons will be the same. I was bummed thinking about tearing down the motor at first, but its been a fun project and the truck still runs strong with the Small Block in it, so I decided to take all the time neccessary to make the Big Bock right. I think I will also open up my ring gaps a little (installed speed pro moly rings with the top rings at .018) thinking about going .020 to .022 to be safe with the NOS. What do you guys think? This motor should make max HP around 5500 to 5750 don't think I should ever need to turn over 6000. Should I shoot for .080 intake clearance for a cam with .600 or so lift (a little room to grow in the future). One last thing that has bugged me is bearing clearances. I ended up with .0025 on my rods (just right) and a little over .003 (.0032 to .0034) on my mains. Do you think that is to loose on the mains? my machinist says no but what I've read says run big blocks on the tight side. I am running a Melling high volume pump and a Moroso pan with trap door and screen. Last question! Rod side clearance was .014 between a couple pairs, is this to tight? Thanks again guys for your help!

run them all the time at 002.5 on the rods to003+ on hi whinders on the mains 0.003 to 0.003.3 is ok you may see more on the rear main #5 this is ok but for a stock driver i would like to see the mains a bit smaller with a stock pump but this is not so you will be fine on the ring yes open them up .022 +or so cut the ring with the QT plate on the deck if it was honed this way you do not want them to butt and i hope you added at least .001 more on the big side of the piston to wall you do not want them to tight. the rods would be be nice to see abit more0.003 you could lap them with wet dry 320 on a very flat surface

You dont have to spin a BB very high to make great power...Nice, huh!!?? I would think the .080 is fine for clearance on the intake...and remember, the lift doesnt have as much to do with P/V clearance as does the duration and LSA. Im glad Pat agrees with the bearings too...Mine runs pretty much the same clearances, and I have a stock pump with the hi perf. spring in it, and I have no problems with oiling at all. You will be fine. Sounds like you're on your way with this big block. John

Thanks John, Thanks Pat for all the info, it sounds like were all on the same page with this motor build. I need to figure out how to post pictures and put together a few of the motor and the truck for you guys. I'd like to here your ideas for chassis set up and tires (refer to my previous post for my ideas and exisitng setup) PS loved the 505 Camaro video John, can hardly wait to get this big block done!