What can I do to squeeze a little more out of this combo?

[1KWIK72]

406 SBC, 6" rods, 13.6:1, 1/16 1/16 3/16 low tension rings, Brodix Track1s ported flow just over 305 int 225 ex @.700" , Lunati roller 276 284 @ .050" .683" intake (1.6 rocker) .645" ex(1.5 rocker) 106 LC, installed on 102 intake centerline, Ported super victor intake, holley HP 950, 1 7/8" hooker super comps, 3100lb 72 Nova stock suspension w cal tracks 29x11.50 Hoosier QTP, TH400 8" Coan converter flashes to 5300, 4.22 gear. The car runs great for what it is 10.20 @ 130 in decent air but I would like to run 10.0X consistantly and at least dip into the 9s occationally. The car right now is traction limited it seems to make a ton of low end and not much on top. I broke the rear gear last year and switched to a lightweight oneh(hence the weird 4.22 ratio). Prior to breaking I ran a 4.10 and a 28" tire, the .12 ratio change was enough to slow the car .1 in the 1/4 I then went to the 29" tire and it picked the tenth back up. I tried a similar cam (same duration @ .050 but 2 deg smaller advertized with a 110 Lc installed at 105) but it made the car a complete dog and it slowed over a tenth. A couple seasons ago I cracked a block and replaced it with another stock block that we did a partial fill on. This new block had an issue with the cam bearing bores being too small so the cam bearing outer diamiters were "polished" so they would fit. The new block has oil pressure issues, it is good when cold 40-50psi @ idle but drops to less than 15psi hot and only about 60 psi @ 7000. this is with Mobil 1 15w50 a high volume pump wich my machinist shimed the spring on to bump the pressure (made no difference over the unshimmed HV pump) All the bearings were fitted by the machine shop. I dont remember specifics but it does have .001" over bearings on both sides to tighten things up into spec. The lower end has about 400 passes on it now and is smoking a little so it will come down for a freshen up this winter. I want to fix the oil pressure issue and maybe make some changes to gain some power. Sorry about the long rambling post, thanks in advance for any suggestions.

Craig

[Jay Allen]

Cam-rocker arms-and springs.

Is this Craig from ET?

[1KWIK72]

Nope must be a different Craig. Were you asking what Cam-rocker arms-and springs I have now or were you suggesting a change in that area?

[Loudpedal]

Maybe you should ask this question on the next forum down? :wink:

[Chris Uratchko]

Well.... there's a lot of things we could do to pick up the engine.... the ring package, the camshaft, the rocker arms.... compression. Intake manifold...... I'm not a big fan of the 4150 Super Victor manifold for a big inch engine.... it's more of a small inch roundy round piece, hence all the low end.

But.... if it's traction limited right now, more power isn't going to help you any. Tell us what you're 'willing' to change first.

A new Dart block would be worth a good 20.

[94guy]

chris how would you change the ring package to make more power? thinner?

[Chris Uratchko]

Absolutely.... go with a pro-series type .043 top ring with a gas ported piston.... cut down the tension on the oil rings.... there's substantial horsepower in rings.... especially when coupled with crankcase vacuum.

If it were my deal, I would do the ring package, and a better block looking at his issues.... that would be a good start for a solid foundation for future power increases.... cuz you know you'll want more later....

[1KWIK72]

Chris I agree there may be some power in the ring deal. Back when I cracked my previous block the shop I use now for machine work figgured that block had been bored and honed without deck plates. The "new" block we filled to just below the waterpump holes. With no other changes other than new block fresh rings and bearings it picked up a tenth even though the block was a bit heavier due to being filled. That said a new block and pistons are a bit out of my buget at this time. If down the road I do go that route I will probably go to a different head as well. I have wondered about a vacuum pump on my current setup (it has low tension rings now) but with the oil pressure as low as it is I worried about pressure issues. Interesting thoughts on the intake. I switched from a Victor Jr to the full ported Super Victor it picked up a little mostly mid range the bottom end was the same if not a little better. That kind of goes along with what you are saying....wich intake would you recommend? I probably will have to keep any inprovements to under a grand I have to freshen the engine trans and send the converter back this winter and money is tight. A cam swap may be feasable. I dont think a small change in gear ratio (4.10 to 4.22) should have slowed the car as much as it did. the motor just dosent like to make power up top. I cant get too crazy on lift as my springs are only good till .680" To get any more I would need to go to much longer valves and new springs and I dont want to do that. I just put valves in a couple months ago and springs last yr. Any ideas on the oil pressure issue? I know when it was assembled all the bearing clearances were right. It holds good pressure until it comes up to temp I suspect the oil temps are pretty high with the filled block. Thanks for the input

Craig

[94guy]

who ported the super vic?

[1KWIK72]

Same guy who ported my heads Phil Massuch sp? did them when he worked for Pierce race engines in Lansing. He now works for Engine Machine Service in Potterville.

[Jay Allen]

Yes, I was saying a cam change, a rocker change, and a spring change.

I didn't dive into the S/B stuff like Chris did, but as usual, he's dead on.

[1KWIK72]

What were you thinking in terms of a spring/rocker change? I am assuming more lift is what you are shooting for. In order to get a spring in there that will handle more lift I would need more installed height. In order to gain any more installed height I would need to go to a longer valve or cheat with +050" locks (I have a set that were on before I replaced the valves recently) That would get me to 2" installed ht. What kind of lift are you thinking I would need? On a side note swapping from 1.5 to 1.6 rockers on the intake did nothing with the current cam.

[Chris Uratchko]

You might also gain some IH by machining the spring pockets deeper.... but you have to carefully check that there is ample material above the intake runner.

[1KWIK72]

Well according to brodix they say no deeper or larger than how they come out of the box. But I have never checked the thickness.

[Chris Uratchko]

Well... what they say and what is true is a different story. If checked with a height gauge as long as there is .080 at a point in the spring pocket you'll be safe.... .080 is minimum in my book.

[Jay Allen]

2.00 I/H is plenty. Do you have a Manley +.100" retainer? You get some more there too. Plus, used titanium valves off of Ebay kick ass. I use them a lot.

I know of a 1.550 spring that sets up at 260# @ 2.000" and 275# at 1.950". It C/B at 1.080". I usually run it .075" from C/B.

Thus:
1.950
-
1.080
_______
.870"
-
.075"
_______
.795" lift.

.795" with a 1.6 rocker is a .496" lobe and with a 1.5 that is .530" lobe. With a SBC that needs a small base circle, even *IF* this was a *magic* camshaft it ain't gonna work because it won't fit. On a small base circle that safest lobe lift I run is about .465". Now, take a shaft mount 1.7 and run a .465" lobe cam, now we're talking!

It doesn't surprise me that when you changed from 1.5 to 1.6 nothing happened. If cam timing is wrong, adding ratio generally makes it worse.

[1KWIK72]

Well Jay that sounds like quite a bit more cam than I have now. Just curious how you think it would change the way the car acts? I wouldnt mind calming the launch down if it would make up for it on the top end. Also depending on how much bigger the duration is will P-V clearance become an issue?

[Jay Allen]

Well Jay that sounds like quite a bit more cam than I have now. Just curious how you think it would change the way the car acts? I wouldnt mind calming the launch down if it would make up for it on the top end. Also depending on how much bigger the duration is will P-V clearance become an issue?
Common mistake.

Guys think that duration MUST be bigger to achieve more lobe lift. Nope. Not true. I'll bet that a cam like I would do will GIVE you MORE P-V clearance. The car rev up significantly faster. Have more power everywhere.

Right springs-cam-rockers. Match that with what Chris is saying. You'd swear that another engine had made its way under your hood.

[1KWIK72]

LOL well between what you and Chris are suggesting I would be closer to another motor. Seriously though I did realize that you do not need more duration to gain lift. I assumed (probably incorrectly) that you would recommend more duration. Somthing else I would be concerned with would be durabillity. I race alot usually about 300+ passes a season how long will springs etc. live with what I assume (probably wrong again) would be a pretty agressive lobe? Also I occationally take a drive down to the local cruise spot, out for ice cream or to a car show. I am guessing street driving somthing like that would be a no-no. I may be able to do a cam, spring, shaft rocker setup depending on how much I can sell my rockers for I got a pretty sweet deal on them and they were new in June. That would put somwhat close to my $1000 buget for upgrades.The block, custom piston and ring deal will have to wait for another time.

[Chris Uratchko]

Well, I would seriously consider another camshaft. If you could talk Jay into a .485" lobe with a .950 base circle you could get some more lift out of it, and maybe tighten up the duration some on the intake....

You might also consider getting the compression up some if you can cut the heads....

lots of avenues to gain hp.

[1KWIK72]

Yeah I thought about bumping the compression I even asked about cutting the heads when I had the new valves installed last July. The guy who does my heads didnt really want to cut em to gain compression he seemed to think the benifit would be minamal I dunno. I think I still have .005 of deck ht, if piston to head clearance is ok I may be able to deck the block to pick up some too. I am not up on what base circle is std size. I do know that the one I have is supposedly "small base circle" to clear the rods. I see Jay likes a smaller lobe and more rocker ratio. Is that so it can be on a larger base circle for less cam flex or is it a ramp dynamics issue?

[Jay Allen]

Be careful here......I like less duration at .020" and at .050". I like more lobe lift and a rocker to match.

[1KWIK72]

Well Jay I think you guys both seem to agree a cam swap (with all required accessories) would pick the car up. If I do decide to go that route I would let you decide what specifics would work for my application. That said what kind of durabillity could I expect on springs, lifters etc? My current lifters have about 1500 passes on em with a few thousand street miles to boot. I knocked the pin out of the one set that was damaged when I broke the rocker (the body was cracked no roller damage) and it is in sweet shape all the needles are smooth and round no wear on the pin at all. I am guessing I probably would need to change stuff a little more frequently with near .800" lift and less duration.

[Chris Uratchko]

Valve lift does not kill springs. RPM and unintended harmonics are what kill springs. .800 lift is relatively low lift in my world so I guess I'm a little desensitized.... but either way I think it would be the smart move.

Also, get that piston about .005 OUT of the hole if that is a steel rod.

[Jay Allen]

Valve lift does not kill springs. RPM and unintended harmonics are what kill springs
Yep, yep, and yep.

[1KWIK72]

Well seems how I am gonna be buying a block now due to finding 3 of the main caps broken :x . How much more could I expect to gain changing pistons and maybe the ring package? It currently has 4.155" Wiseco Pro Tru (similar to SRP) pistons with a 1/16,1/16,3/16 low tension ring pkg. Would bumping the compression benifit much? Its at 13.6:1 currently with an 10cc dome. Is there a big benifit on dome shape? I see most "good" pistons have a left and right dome the Pro Tru's like the SRPs have symectrical domes so they can go in either side. I am looking to pick up a solid 3 tenths. With the extra weight of the aftermarket block I figure I need at least 50+ hp over what I have now. Do you think with I decent block, pistons, ring package and a cam swap I can get there? What about bore size? The dart blocks can go 4.200" should I start std size 4.125" or punch it out or leave some room to grow and wear?

[ROB]

Big benefit on dome shape is to remove the dome entirely. If you can get the heads angle milled, the dome can probably go away or at least be reduced to an inconsequential height (.125" or so) and still achieve good compression ratio.

Aftermarket block isn't much heavier than production so no need to fret about loosing performance.

Definitely start with a larger bore. I'd go with 4.185" and hone .002" per rebuild until the block's all gone.

You didn't mention what you have for connecting rods but there's opportunity there by switching to a Lunati Pro Mod rod. This will allow at least a standard base circle cam with the 3.750" stroke for a big lobe lift cam.

Your carb & headers are both a tad small. If possible change headers to 2" primary and try to get the carb bigger (boosters from 1000 HP or whatever).

Are you running any spacer above the carb? It should be a 2" open on that intake.