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  #16 (permalink)  
Old 12-31-2004, 02:33 PM
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dome pistons

I definately wouldnt run domes on the street, considering fuel availability, and the kind of compression those pistons would make.

Kind of hard to make a good judgement on your cam without knowing the effective duration @ .050".

.25X?

Are you meaning it has 250 degrees duration @ .050"?
Thats a pretty healthy cam

With your gearing and stall speed, You could use a cam with that kind of duration, and probably the 4.11 gears you mentioned earlier would be ideal with it, rather than the 3.73.

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Last edited by Max Keith; 12-31-2004 at 02:33 PM.
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  #17 (permalink)  
Old 12-31-2004, 04:09 PM
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yeah it was .250 @ .050, i just couldnt remember exactly what it was but i thought it was 250 something (25X). so do you think everything sounds good now?
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  #18 (permalink)  
Old 12-31-2004, 06:42 PM
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estimated hp

The cam will run there is no doubt about that. The big concerns that I have is that its just not very compatable with stock heads. The air flow that cam requires in its lower operating range is near the middle to top of what your stock heads can seriously flow. Consequintly, you arent going to have much bottom end, due to the duration of the cam, then when the cam comes into its power band, your stock heads are going to choke it off. You will be able to turn the type of rpm that cam is intended for, but you arent going to be anywhere near what the cam will be able to provide to make real power.
Your stock heads on a 302, generally are sufficient to provide adiquate flow up to about 5500 rpm, then it gets very anemic.
That is why I recommend going with a smaller cam that will enhance your lower and mid range power. With the intake, carburetion, and headers, you have sufficient breathing there to turn well over 6000 rpm, but with the cam you are using, you wont have a lot of good bottom end power below 3000 rpm. From my point, you will only have a serious power band of about 3000 RPM (3000-6000), and with the cam you will fall off below that and above it, your heads are going to choke you down.
I guess drag strip time slips will show where you are in your power output, with 60, 100 ft times etc.
I would recommend getting a good set of aftermarket heads, as soon as your budget will allow, then you will have one super combination, a real terror.
As for afermarket heads, again if you want steel, I would go with World Jrs or in aluminum, go with Trick Flow or AFR, on a SBF.

The World Jr heads list for $469.50, each, complete, Trick Flow "High Port", aluminum heads, for $1,255.95, a pair, complete, Trick Flow "Twisted Wedge", aluminum heads,$1,150.95, a pair, complete, from Summit.

I dont have any current prices on AFR heads but I do know that their flow numbers are compareable to the Trick Flows.
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Old 12-31-2004, 11:05 PM
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ok thanks for all the info, you have helped alot
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Old 01-01-2005, 05:41 AM
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f81, stop and think it thru again

so far you have told us:

A: you want to beat your brother
B: you want to drive it mostly on the street
C: you are poor

choose "A" or "B" and stick with it.

How much money will you spend on the motor to beat your brother?
How much money for gas (and probably another motor) do you want to spend to drive on the streets. With what you are building now with the 250@50 cam, your at maybe,,, 10mpg.

Best combo of cam/heads/intake/exhaust spec's to use for general guidance I know is the Edelbrock RPM package. Very very strong but OK for the streets and reliabilty.

You have already broken one motor, you need this one to last, do this one right

(But then "sons" never do listen to dad, right Max..)
.................................................. .................................................. ...
Re: the 250 @ 50 cam

ask again, is it a 250 grind (very mild) or 250@50 (full race)

if it is 250@50 intake AND... 250@50 exhaust, buy a different cam.

You are almost off the chart with 250/250 for exhaust with stock heads.

SBF need more duration on the exhaust ( even with better heads check the recommended profiles for Edelbrock RPM, Twisted Wedge just as examples)

The new cam will definitely be the best "bang for the buck" and worth the $150

Re: porting stock heads = $$$, you need more exhaust flow, problem is the I/E valves almost touch in the head, no room for a bigger exhaust valve to go with a bigger port that eliminated the bend for better flow. Good aftermarket heads have almost no bend so 1.6 valves work great.
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Old 01-01-2005, 09:19 AM
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well this car will not be my every day driver so im not real worried about the guess mileage. i think with what im building i should be able to beat my brother, but the ls1's are stout, especially with nitrous(i dont trust the juice). as for the cam im pretty sure it was 250 @.050, but im not all that familiar with cam specs (still learning). and i would spend about whatever it takes, it may just take a little longer to get it built. the guy building this motor is the guy who had my last one, and he said he wouldnt change the cam for nothing. he may know more about the cam than i have posted here im not sure. ill try to find out more.

right now all i like having this motor built is machine work on the block, timing chain, gaskets, and bearings......... im getting there
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Old 01-01-2005, 09:47 AM
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You might try looking at Powerheads, they are factory ported heads. http://www.powerheads.com/products.html

One other thing, compression ratio can vary and saying a motor that has 150 PSI is 9:5 to 1 is not always true. Cam duration and valve overlap will effect your PSI reading. This is why engines like 289 HP's and Boss 302's only carried like 120 PSI, big cams cause alot of bleed of at cranking speed.

Last edited by onebadmerc; 01-01-2005 at 10:13 AM.
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  #23 (permalink)  
Old 01-01-2005, 10:32 AM
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estimated HP

red65, you are right on about "sons" listening to dear old Dad. Classic case is my Son with those Loser Brodix heads he bought for his 347.

red65 is completely right about your engine.

Were I building it, this is the way I would go.

302 buildup:

Twisted Wedge or AFR 165cc heads,

Performer RPM or Weiand Stealth intake,

9.5:1 compression

600 cfm vacuum secondary carb

Comp Cams XE268H, or equivalent grind cam,

1 5/8ths primary headers with 2 inch exhaust,with an X or H pipe between the exhaust pipes, BIG turbo mufflers, exiting in front of the rear tires, if thats legal where you come from; otherwise run them out the back. 2 1/4 inch exhaust from the mufflers on back.

Mallory, or Accel dual point or a Petronix conversion of stock distributor.
If using the Dual point would us a 60K volt coil.

8 MM wires

Shift kit in trans, with 2000 RPM stall. Probably could achieve that with the stock early C-4 converter. I did with a 302 in a 69 Mustang with C-4 and it wasnt hearly as hairy as this engine.

3.73- 4.11 gears with a posi unit.

Tie the sub frames together.
Good traction bars

BF Goodrich Comp T/A drag radials (street legal)

And go kick some serious butt all over the neighborhood.

This engine combo will produce well over 350 Hp, and have a serious torque curve below 4000 RPM as well.

I would also put some good after market (ARP) rod and main bolts in the engine as well.

You can easliy wind this engine past 7000 RPM and still make power but most likely, your peak HP would be around 6000-6500 RPM.

Quote:
One other thing, compression ratio can vary and saying a motor that has 150 PSI is 9:5 to 1 is not always true. Cam duration and valve overlap will effect your PSI reading. This is why engines like 289 HP's and Boss 302's only carried like 120 PSI, big cams cause alot of bleed of at cranking speed.
289/302 all ran 150 PSI compression or better, depending on version of engine, well up into the 70's, from the time they were developed.

Standard 289/302 cam had 184/189 degrees@ .050" duration, .368/.381" lift, 107 degree lobe separation cams.
Yes, lobe separation and duration do play a part in cylinder pressure, but with the cam I have recommended, and along with running aluminum heads, a 9.5:1 compression will be very safe and you will be able to run the engine easily on 89-91 octane gas.

As an after thought, I would also run an electric fan and a smaller crank accessory drive pulley, and a 160 Thermostat.

Last edited by Max Keith; 01-01-2005 at 10:31 AM.
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  #24 (permalink)  
Old 01-01-2005, 10:48 AM
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If that is true about all 289's and 302 carrying 150 PSI then why does my 66 289 with 9:3 to 1 compression ratio only carry 120 psi. I measured everything and went over this with the machinist before this motor was built. The motor run well and is not weak in any respect, cams will affect cranking psi. I also have a friend who has a HP 289 all original out of a 64 or 65 Falcon and it only cranks 125 psi. The 289 HP he has was rebuilt to original specs and when he checked the compression, it only cranked out 125 psi. This motor is not a turd either, it is strong and would shame me on the strip. Maybe on stock non hp engines a general rule of 150 psi is ok, but on modified engines compression psi can vary quite a bit.
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Old 01-01-2005, 11:03 AM
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estimated HP

The book specs for 260/289/ 302, from 62 on up to the mid 70's all give figures of 150 psi in standard engines.

Yes, changing cams can change the psi. IF you are only running 125 psi, then its something other than a stock engine. As for your friends HP 289 running only 125 psi, I have no explanation for that nor do I need one. Factory spec for a Hi Po 289 n 65-66, calls for 200 PSI. It could well be that the replacement pistons dont pump as high of compression as advertised, and they often dont, thicker head gaskets, who knows.

The issue is moot in this case.
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Old 01-01-2005, 11:33 AM
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duration

I checked over your postings and all you specify is .575 lift. The edlelbrock performer rpm .488 cam has 308 deg of duration. The Crane h06 .500 has 302 deg of duration. Both these cams are very large in duration for flat tappet cams. Anything larger would be going into a roller. Your problem is going to be valve to piston clearance.
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Old 01-01-2005, 11:41 AM
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When I a checked my compression I told him I was only getting 120 psi with no less than a .05 variation per cylinder. I was kind of pissed off but he told me he was only getting 125 out of his HP 289. He pulled the motor and put a 302 in its place, was too worried he would blow it up at the track, too expensive of a engine to replace. I know for a fact my motor is 9:3 to 1 but it only pulls 120 psi. Like you said its just a moot point, my 289 runs strong I really don't care about the psi. Maybe its the elevation I live at that is effecting cranking psi, its almost 5300 ft where I live.
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  #28 (permalink)  
Old 01-01-2005, 12:22 PM
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estimated HP

Living a mile high can well explain your loss in PSI. I didnt notice til I looked at your avatar that you are in Colorado. That is probably the reason you dont see many 91-93 octane gas pumps out that way, as in Montana, Wyoming, etc.

Book spec numbers are all taken in controlled environments at controlled temps. with relative atmospheric pressure of sealevel.

As an annicdote, in 64 or 65, Parnelli Jones went to Pikes Peak for the Climbing race there. The 427 he had in his Mercury, was special built just for that race. I dont recall the exact compression ratio of the engine, but there was a notice on the car saying not to start the car below something like 6000 ft.

I used to live in Montana (3 yrs), and I did notice considerable differences in cranking compressions between there, living at 5000 ft.+, and down here at 750 ft. above sea level, along the banks of the Mississippi River, in Missouri and Iowa.
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Old 01-01-2005, 03:03 PM
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f81,

Max's suggestion for a cam choice/268cam grind I agree is a very good choice.
IF you are sure you are going to buy aluminum after market heads.

Intake 224@50, exhaust 230@ 50, .509" intake lift, .512 exhaust.
Excellent off the line torque because it has more exhaust timing, very strong mid range for "street wars" with your gears.
(Edelbrock rpm #'s 224/234, 496/512 for comparison)

This cam is so strong it REQUIRES screw in rocker studs to keep the rockers on the motor!

Compare those numbers to what your motor guy "won't change for nothing".

If you decide to keep the stock heads, you want a approx. max of 214/224 .500/.500 with good hedders
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Old 01-01-2005, 03:55 PM
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well the heads have had all that done to them, poly locks and screw in rocker studs. like i said im not good with the cam specs yet. all i know is this cam was in the car, and it run good, he said they had three different cams in the motor and this cam was 3 tenths faster than any other. he owned the motor before i had it and ran 7.69 @ 90 in the 1/8th. i had it and ran 8.17 @ 83. when we stripped the heads he took them to be checked and found out that every valve was leaking , machine shop cut the valve seats wrong. i think im gonna keep the cam and eventually buy some windsor jr.'s
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