spring pressure

[dbusch]

how about some more info about this engine? what heads, manifold, header size, exhaust size, compression ratio, etc. that is a really big small block that is a big block in nature. peaking at 6500 rpm, you should be making 740 SAE corrected and about 680 uncorrected. your cam is only good to about 625 SAE corrected power. actually, using your bsfc and fuel flow lbs/hr you are only making 580 uncorrected. You have about 100 hp left to unlock with the right changes...

[70MC]

The heads are Brodix T1s. I included a picture of my flow sheet, where i have my dyno sheet listed in my earlier post. My intake is a brodix HV 1002. Compression is 12.0:1. My headers are 1 3/4 primary 3 1/2 collector, but they would not work on the dyno they hit the bell housing. The dyno headers were 1 7/8 x 3 1/2. I thought about going with a larger cam when i built this engine but since this is a 100% street car (never trailered), ATI did not want me to go any higher with the stall speed of the converter. I have an 8inch 4000-4200. So i did not want to get out of the range of my converter. There is more info on the car and a time slip from last year, before i made a few changes this year, also were my dyno sheet is.
If you still think this engine has more in it, i am all ears. Thank you for your help.

[dbusch]

you have an induction system sized more for a 355 or 383. you could pick up a ton of power with a head that has a 2.125-2.150 valve flowing 340-360 cfm. Seems like a fully ported super victor would be the best. headers should be 1 7/8 or even 2". you could keep the cam, but i would put some more rocker on there for about .700". if you keep the rockers you should go with a cam with more lobe lift to get .700". 12.0 compression is fine for street driver with low octane racegas. shifting at 7400 with what you have seems way too high to me. 7000 would be a better shift point.

you need to take advantage of all those cubes with new heads/manifold/headers!!!

[70MC]

My thoughts on the heads also, i used them since i had them from my previous engine, same for the headers. This engine is new so i can upgrade in the future. I my be getting a pair of 18deg heads new, for a very fair price here soon. Do you think the Super Victor is a much better intake, if they both have had work done to them? I am no expert but i did spend a good deal of time porting the HV 1002, from plenum to port opening.
My carb looks to me like it is getting fatter at high RPMs. What would be the best way of keeping the fuel metering even throughout the rpm range? 1- By making the high speed air bleeds larger, they are .035 now? Or 2- By making the intermediate air bleeds smaller, they are .070 now, and make a jet change? That is of course if i don't have all that backwards.
Thanks again.

[dbusch]

you could try a 36 and a 37 high speed bleed at the track. i am not familiar with the Brodix HVH manifold. maybe you could start a thread about the difference between that and a ported super vic and see what some of the other guys on here have to say. the 18 degree head would be killer. like i said, i would go with a 2.150" valve if you can, and probably some new pistons or rework the valve pockets to match the 18 degree head. you still need more cam too. going with more lift is the ticket with low(er) compression. add duration and the torque down low will suffer and your converter wont work anymore. more lift gives you more cam without the drawbacks that more duration gives. I would say .700" is the limit for a street driven car. an excellent source for a new cam would be Jay @ Camshaft Innovations 734-730-2574. Make sure you have the cam made for your new induction combo not the current one!!!

[SStrokerAce]

The BSFC on your motor should stay in the .39-.42 range, as you can see the HP droped to and the BSFC started to climb there as well. You have some little bumps in the curve as well (6200-6500) which could be the begining signs of valvetrain issues before they really get bad at 6800rpm Your A/F starts going rich there as well.

On the cam lift might help as well, but a tamer lobe profile would help the valvetrain issues. Something is going on if you have float at 6800rpm on a SBC with the parts you have, the Hi-Torque .406" Roller lobes are pretty aggresive, going to the RZ series would get you the .700" lift and tame the lobes down a ton. For example your .050 duration could stay the same but the .200 duration would drop 6degs with the same rated duration and more lift, that lobe would make controling the valve much easier. I don't get the 6degs of advance in the cam either.... you might have some low compression for the cam but dam I don't think you need to go that low.

Bret

[70MC]

The BSFC on your motor should stay in the .39-.42 range, as you can see the HP droped to and the BSFC started to climb there as well. You have some little bumps in the curve as well (6200-6500) which could be the begining signs of valvetrain issues before they really get bad at 6800rpm Your A/F starts going rich there as well.

On the cam lift might help as well, but a tamer lobe profile would help the valvetrain issues. Something is going on if you have float at 6800rpm on a SBC with the parts you have, the Hi-Torque .406" Roller lobes are pretty aggresive, going to the RZ series would get you the .700" lift and tame the lobes down a ton. For example your .050 duration could stay the same but the .200 duration would drop 6degs with the same rated duration and more lift, that lobe would make controling the valve much easier. I don't get the 6degs of advance in the cam either.... you might have some low compression for the cam but dam I don't think you need to go that low.

Bret

Thanks for the input. When i orderd my cam from Comp, i asked for a cam that was semiagressive since it was going to be used on the street, not sure how agressive this cam is. When you say the Hi-Torque .406 Roller lobes are pretty agresive do you mean mine, since i have a .420 lobe? How can i find out just how agressive this came is, without a tech at Comp simply saying it is mild, semimild, or agressive? If i asked for some specs, say like you said at .200 would that tell more? My cam is ground on a 110LSA, it is at 106ICL now. When you say that low, do you think the cam is to retarded? That is were i found the most power, which is the copy of the dyno sheet i show. But i must add that as i moved the cam around i also reset the ignition timing, but i was running out of time when i moved the cam to 106ICL and forgot to reset the ignition timing. I rememberd about the timing after the pull and it was 39 deg. That is more than i am comfortable with with pump gas. I was keeping it at 35-36deg.
I changed to Comps #944 spring installed at 1.900 w/240# and open at 1.250 655# but havent driven the car yet. Again thanks for everyones help. Any other thoughts?

[SStrokerAce]

Thanks for the input. When i orderd my cam from Comp, i asked for a cam that was semiagressive since it was going to be used on the street, not sure how agressive this cam is. When you say the Hi-Torque .406 Roller lobes are pretty agresive do you mean mine, since i have a .420 lobe? How can i find out just how agressive this came is, without a tech at Comp simply saying it is mild, semimild, or agressive? If i asked for some specs, say like you said at .200 would that tell more? My cam is ground on a 110LSA, it is at 106ICL now. When you say that low, do you think the cam is to retarded? That is were i found the most power, which is the copy of the dyno sheet i show. But i must add that as i moved the cam around i also reset the ignition timing, but i was running out of time when i moved the cam to 106ICL and forgot to reset the ignition timing. I rememberd about the timing after the pull and it was 39 deg. That is more than i am comfortable with with pump gas. I was keeping it at 35-36deg.
I changed to Comps #944 spring installed at 1.900 w/240# and open at 1.250 655# but havent driven the car yet. Again thanks for everyones help. Any other thoughts?

I was going off of this info....

http://www.knights-rule.com/albums/album04/scan0010.jpg

268/278 @ .050 with .650/.650 lift with 1.6 rockers.

That's .406 lobe lift. That is a Hi Torque .406 lobe then, which is aggressive like I said above. The lobe specs cam be found in the Comp Lobe Catalog online. I figured that the 106ICL would be the best for the motor, but you stated that it was installed at 104ICL.

I wouldn't be scared of the timing going to 39degs at max RPM since it makes the best power if you don't have any knock. No point of pulling timing out if the motor doesn't need you to do it. Might need a different timing curve down low to keep the detonation away but probably not up high.

Bret

[70MC]

Bret i see where you got the lobe lift. My lift i have listed is subtracting valve lash, the lobe lift is .420. The cam is a custom grind, will the online catalog still apply to this cam?

[SStrokerAce]

Yeah... It's a Hi Tech .420 lobe then.

Bret

[zeronine]

Just wondering about that rev kit part, earlier on in this post. I'm wondering why Comp would have said not to run a rev kit? What are the drawbacks of rev kits?

From what I understand, they do nothing but good: pre-load the lifter to the lobe, thereby helping the valve spring, extending the life of the lifter & rollers & lobes, and in the case of a broken rocker arm pushrod or other, maintain oil pressure, which could create a lot of havoc......

[dbusch]

i dont know...i ran a .440 high torque lobe all the way to 8200 without any problems. that was with stud mt. 1.6 rocker, titanium retainers, SS valves and the 943 spring. but, then again my base circle was about 1.1 not .900!!!

[b73]

--If this engine is truly in a streetdriven car then I'd think the cam bearings would be not liking all that spring pressure.
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Bill,
What max spring pressures would you suggest for a 'limited street' setup with respect to cam bearing life?? I'm talking about something that does maybe 2500miles/yr

[bill jones]

-I don't know for sure.
-Depending on the type of engine---for instance---I feel that a BBC will have less problem than a SBC because of the annular groove behind the cam bearings on the SBC always seem to show more wear than a BBC---probably because of not having that metal support on the OD of the bearings.
-Start up and idle time is where the problem would be the worst---low oil pressure and all that spring and rocker ratio energy working the hardest against the cam bearings.
-Coated cam bearings might be the key but I haven't been building street type race engines enough to really know.
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-I typically modify all BBC cam bearings where we're using 300# or more on the seat and 800 to over 1000# open---because of the wear patterns I see on the bearings.
-The oil hole thru the cambearing is always at the bottom so the wear pattern always shows some stress on the leading edge starting at about the 4 o-clock position and wipes to the 7 o-clock area.
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-So what I do is I drill a new hole (3/32") thru all the cam bearings at about the 4 o-clock position---then I made a mandral for my lathe to hold the cam bearings and I use my lathe tool and cut a narrow groove (about 1/16" wide x .030" deep) on the OD of the bearing that only connects the new oil holes to the original holes.,
-This is like a short interconnecting slot that requires you turn the lathe chuck that short distance by hand and feed the cutter in there a few thou at a time.
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-This has significantly reduced the wear in that wear pattern area in the Big Chief engines and I feel good about the extra small holes.
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-Another thing is oil.
-These big chief engines are running real thin synthetic oils and all the bearings always look absolutely excellent to me including the cam bearings which always show the most wear.
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-There are different grades of cam bearing hardnesses and I would NOT use a stock soft bearing.
-Durabond bearings have served the big chief engines excellently but I have seen some guys have problems with spinning cam bearing upon start up when using a variety of bearings and they don't care for the hard SBC SH1090S cambearings that I used to used 20 years ago.
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-Another deal that could help would be an oil accumalater where you can prelube the engine just as you go to start it---and if the engine is to be run in any cold weather I'd run oil and water heaters to help with oil FLOW at startup.
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-The valve spring pressure is probably going to have more to do with how high you rev the engine as you need that much spring in there---so all you can do is work on the details that cause the cambearings wear---and that is 90% at startup and idle.
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-And if you happen to be running methanol that's another story for another day.

[SStrokerAce]

Another thought I had rereading this thread with the springs, lift and pushrods....

If you had .100 more to go to coil bind, I'd throw more rocker arm at it and get you a lot closer to coil bind. Another .050 lift would help the power and the 240 seated is more than enough. Only thing is the motor would need a ton more pushrod, the 5/16 ones aren't close a 3/8 would still be a little thin in my book.

Bret