Hi all.
I wanted to post my combo to see if anybody had any input on any areas that might be lacking, or just plain mismatched. The reason I just did this is because I recently had a chance to write down the part #'s from the heads.
The only area I'm really not sure about is the compression ratio. I'm using open chambered (113 cc) heads, and the pistons have a fair amount of dome on them, but I can run 91 octane pump gas with no problem, so I doubt it's over 10:1 compression. Probably closer to 9.5:1.

Anyway, here it is:

427 cid + .030 = 433
#3999241 heads. 1972 oval port, OPEN chamber (113cc) - originally equipped on 402, 454. These have been gasket matched and had some bowl work done to them and are fitted with bigger than stock valves (2.19/1.88).
1.72 ratio billet roller rockers.
Forged pistons, not sure CR. cast rings.
Hydraulic cam, 228/238 dur @ .050", .540" lift.
Stock rods, steel crank.
Edelbrock Performer RPM intake
Cheap Holley performance mech fuel pump
Holley 830 cfm annular booster double pumper.
Stock HEI dist w/ Accel super coil, 300+ wires and NGK plugs.
Hooker Super Comp headers
3" exhaust with H-pipe and flowmasters
Behind all this is a 4200 RPM converter in a TH-400 transmission and a 12-bolt posi with 3.70 gears.
New multileaf springs, Crap tires (I'm working on these).
I think the car is fairly light for a big block, it has a fiberglass hood and front fenders, and no inner fenders.
Anybody have any input on the engine or drivetrain?
Maybe a desktop dyno run?

I've got a dyno run here. I guessed a few things (coolant temp, no windage devices, cam installed 4* advanced, stuff like that).

461HP @ 5500 (average: 305)
490LB-FT @ 4000 (average: 400)

Those figures are with no exhaust and no accessories. For your exhaust system, you're going to lose about 15 LB-FT and 17HP.

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Matt Jones
1969 Base Camaro
Vortec 355, Perf. RPM, Demon Carb., TH-400
All sheetmetal is NOS GM
See my UPDATED webpage at: http://www.geocities.com/compuboy007/ (Updated: 1/13/03)

On the whole the combo looks good. There is an area where you are lacking(the cam) and there is a mismatch (converter to cam).

If you really want the car to run harder you`ll need a bigger cam.
But one that will work with your converter.
4200 stall is on the high side of streetability IMO.
But a 3.76" stroke big block would be less inclined to blow off the tires than would a 4.00" stroke.

An Ultradyne custom grind like this would do well for a hyd F/T.
290 adv. 239@.050 .567 lift 108 sep single pattern.
It will rev to 6500 and will work with that converter too




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78 Camaro hyd cam 406
TH350-3.23 gear
11.86 ET
116.7 MPH

Thanks!
Matt, I really appreciate you running that through desktop dyno for me. Just curious - does that program assume optimum timing curve and optimum carb jetting, etc?
I'm just asking because the numbers are a little higher than my "seat of the pants" dyno tells me (although I haven't put it on my patented dyno since installing the new carb). By the way, your guesses were right on.
BigRed, thanks for the input! I agree totally. I'm torn as to whether I want to slap in a bigger cam or a smaller converter. I'd like to get more performance and go with the cam, but on the other hand, I'm a little suspicious my converter is trying to poop out on me, which makes me want to look in that direction.
Anybody have any input on the head castings?

Before you ditch on the converter consider this...You will NEVER see the true potential of that converter till you do the cam swap.

What does it do to make you feel as though the converter is going? What make is it? size?

If this were my call...go with the cam you NEED IT ANYWAY! then see how the converter works you might be pleasantly surprized.

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78 Camaro hyd cam 406
TH350-3.23 gear
11.86 ET
116.7 MPH

what are the port sizes in the heads? keep in mind that a longer duration exhaust lobe is for weaker, more restricted exhaust ports. usually, cams like these are bought when stock heads are used. i dont think it will hurt you. the .54 lift is very nice. if you have about 225-230 cc intake ports, it should run nice if it is for daily driving IMO(just a ballpark off of the top of my head.) the 4200 stall convertor is very high for the cam you have selected. if your dead sure you want this cam, get a smaller convertor. higher stall speeds tend to slip more at higher speeds therefore robbing you of true speed potential. if it is for street use only(which i doubt) the convertor is way too high. you will be driving under stall speed most of the time and heat will build up in the tranny. the performer rpm intake is a dual plane(to the best of my knowlege. see what a single plane manifold runs through on the desktop dyno again. i only use single planes for strip use. other than that, everything is nice.

[This message has been edited by nate (edited 01-14-2003).]

BigRed: Regarding the converter - the car "shudders" pretty badly when under load. I don't notice it if it's in park or neutral, but I definitely notice it if it's in gear. Doesn't matter if I'm going down the road or stalling against the brake. I feel a vibration. It's an Alabama "Boss Hog" converter... 11" if I remember correctly. It was rated at around 2800 RPM stall, and when they sent the converter, they mistakenly sent the next model up. It flashed 3400 behind my no-torque 327, and like I said, 4200 behind this big block.

NATE: Unfortunately, I don't have any flowbench data, or any real specific info on the heads. They're a '72-era head, not particularly high performance, with a shadetree port job (not that there's anything wrong with that) and big valves. See my post above. You're very correct on the converter, it does slip a lot, particularly on the highway, but it doesn't spend an awful lot of time on the highway or anything. It's a non-daily driven dual purpose car: street/strip.

By the way: if I do decide to step up in the cam, am I going to be OK with my relatively low compression? I'm thinking I'll be alright, because it looks like the cam you're suggesting adds more lift than duration. And on that note, will I need to pay attention to any other areas of the valvetrain in order to use that cam?

Yes, the program does optimize for timing and fuel.

The program does, however, tell me what the optimum timing should be, and the brake specific fuel consumption. Wish I remembered what those numbers were, but I don't...

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Matt Jones
1969 Base Camaro
Vortec 355, Perf. RPM, Demon Carb., TH-400
All sheetmetal is NOS GM
See my UPDATED webpage at: http://www.geocities.com/compuboy007/ (Updated: 1/13/03)

If your static compression is really 9.5:1 your dynamic compression ratio would be pretty weak at 7.3:1 with a 290* cam. We definately need to figure out what your compression ratio is before picking a cam IMO. I agree that more cam would match the converter, but if your are guessing at your CR then you are guessing with the cam.

Any idea at all which dome pistons you are running? That's the only variable we still need to get a pretty good idea what your CR is. BTW I thought most open chamber pistons had bigger domes - like 45cc. Not 100% sure though.

<BLOCKQUOTE>quote:</font><HR>Originally posted by 69 Rat:
By the way: if I do decide to step up in the cam, am I going to be OK with my relatively low compression? I'm thinking I'll be alright, because it looks like the cam you're suggesting adds more lift than duration. And on that note, will I need to pay attention to any other areas of the valvetrain in order to use that cam?<HR></BLOCKQUOTE>

What pistons do you have? TRW/SPEED PRO have very little for selection in a 427 motor.
9.5-10-1 comp .should be ok.
If you find that you`re alittle higher in compression than you thought say 10.5-1 then this cam would work too with a loose converter:

Ultradyne 296 adv 239@.050 .575 lift 108 sep single pattern.
Always make sure that the springs are right.
Do you know what the springs are ?
A cam like that would need say 130 lbs seat and 320 lbs +-
Piston to valve clearance should be fine. But always make sure


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78 Camaro hyd cam 406
TH350-3.23 gear
11.86 ET
116.7 MPH

I think you're right, Eric. All the open-chambered pistons I've seen have a good-sized dome on them.
The cam I have in there now is 286/296 advertised, if I remember right. All I can recall for sure is the @ .050 duration.
Is there any way to get a fair idea at what the ballpark CR would be without removing the heads? I've done a compression test on it quite a while back, and it was pretty high, but I don't think the rings were quite seated yet, etc, so I'm not sure how useful that figure would be (I think it was upper 100's/low 200's).
Matt, I had no idea that program would tell optimum timing and fuel figures! That sounds like really useful software.
Based on my combo, can anyone give me an educated guess as to where they would set the timing? I think mine currently is around 35 degrees advanced, all in by about 2800 or so.
I have no idea how to figure brake specific fuel consumption, though.

Your cranking compression (high 100's / low 200's) seems to match for an engine with 8.0:1 dynamic compression. That's 10.0 - 10.5:1 static compression with a 286* cam. This is BALL PARK and is based on a few data points I have where I KNOW static CR, dynamic CR, AND cranking pressure. Emphasis on BALL PARK. http://www.camaros.net/forum/wink.gif You could always confirm that cranking compression again and double check your memory. I think if you swap cams you want to keep your cranking pressure in the 190 - 200 psi range for iron heads and premium gas.

You would need a dome with about +33cc to achieve 10.3:1 static using 118cc combustion chambers and a .045" deck height. I'm not aware of a 427 piston with 30-35cc domes, maybe someone else that REALLY knows BBC's can tell if I'm all wet or not. http://www.camaros.net/forum/wink.gif

IMO if you KNOW cranking compression AND advertised cam duration stick with a cam that has the same advertised duration. IMO high 100's (like 190's) is about perfect for running pump premium gas. More agressive lobes (for example: 286* avertised with 245* duration @ 050) will extend your power band upward without sacrificing much (if any) low end cylinder pressure.

ALSO, If you run a tighter LSA you can run more duration and maintain a similar cranking pressure. For example: going from a 286* cam on a 110 LSA to a 294* cam on a 106 LSA will maintain exactly the same cranking compression / dynamic compression. This assumes both cams are installed 4* advanced.

ps. On the timing thing --- the bigger domes are, the more timing (in general) the engine might want. Big domes slow flame travel so you want more spark lead to make max power. I've seen some BBC guys that run big compression (and big domes) run 38-40* total timing to make best power.

This helps a TON.
I didn't realize two cams with the same advertised duration could be so far apart at .050!
Anyway, the motor was timed about 40 degrees advanced (by seat of the pants), and it scared me when I put a light on it, so I backed it off. It never seemed to ping or be hard to start, though, so I may bump it back up.
It's a 113 cc head, not 118. Not that it makes much difference.
I'll have to dig out my cam card, but it seems like my cam had a pretty wide LSA... I'm thinking around 114. I'll doublecheck that, though.

since its for all out racing, some will argue but i would change manifolds to a single plane. wieand team g's are about my favorite. as for the cam, go with about a .52 -.53 inch lift and select a relatively long duration. this will increase flow through the intake ports so when your piston is after bottom dead center you will still be drawing in air. mine closes about 61 degrees after BDC and with my .478 lift it keeps my manifold vacum higher so my brakes wont suffer and i can get crisp throttle response. but its in a 350 so i would'nt think about doing it to a big block. if you decide to put a blower on it, select a long duration. you will have to run their 101 octane at the track. lift wont need to be a worry since its forced induction. if you decide to go with the dome pistons this will increase the comp. ratio so i would'nt travel out too far of the neighborhood you're in with the cam.

Well, it's not really ALL out racing, I still drive it, too. But the motor makes peak power somewhere around 5500 RPM, so I'm not sure what a single plane will gain me.
No plans to add forced induction of any kind.
Let me ask everyone's opinion on this: would it gain me much to run a pair of close chambered oval-port heads? Like the ones that came on the 325 horse 396's or something? Sorry, don't know much about casting numbers... Maybe 049's or 063's?
If this would gain me anything, would it be worth the cost to go through the heads and port them, add big valves, etc?

69 Rat.. The heads you have now will be just fine.You say they are oval ports and they ALREADY have the bigger valves then you have it covered.
The performance diff between those and close chambered versions would not be worth the time/money/hassle. No way.

A dual plane will work to help move the car off the line, i wouldn`t put a single plane on it if it were my call.

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78 Camaro hyd cam 406
TH350-3.23 gear
11.86 ET
116.7 MPH

I agree totally.
It's nice to get opinions from people with more experience than me.
Well, it looks like sooner or later I'm in for two big performance increases: slicks and a cam. Both of those I've been planning on, so no surprises. Now if I ever get this distributor situation figured out, I'll be all set!
Thanks guys.

Actually, now I have a totally new question relative to my combo.
Why start a new thread?
http://www.camaros.net/forum/biggrin.gif
I'm kicking around the idea of buying a built 700R4. Supposedly, it's good to around 550 horsepower. Anybody have any input in this case? I'm thinking with the lower first gear I probably would need to use less stall than what I currently have (obviously I'd be getting a new converter anyway). But I wanted to know any input y'all may have.