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Discussion Starter · #1 ·
Hello! New here, though I give it a try as google searches have not given me what I was looking for :).
Thought I try one new thing in my search of hard facts for my 305 chevy that I have just bought. It's actually not in a car but an -73 Flatty v-drive I could not resist. As it turnes out, it seems that enigne package is a bit of a leftover kit I guess.
This is what I know of the package up to now:
305, (flat pistons?) block id 14088551, heads 333882 (yes, the ones with bad rep, but larger than std intake valves of 1,94 and sadly 76cc cambers), intake Edelbrok Street Eliminator, Edelbroke 600cfm carb, and Basset 4-1 headers, no silencers.
So as far as I can see the question for this case is how much can be had with the right cam?
And which is the right one?
Looking for an engine that's to give max power at about 5500-6500rpm. Don't need to have good torque or low ideal speed, ex below 1000rpm, so large overlap would be ok for me. This as a boat of this size don't need much to plane and is not to be used for drag racing, but I do like speed.
And a bit of that rump rump sweet sound of a hard camed v8! :)

I know that best thing to do would be to get a 350 vortec, but would like to run first summer with roughly what I got and cam change.
Ever so greatful for useful tips!
/Per in Sweden
 

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Race it, Don't rice it!
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Small bore and large valves....Small bore, small stroke and big chambers.....long cams....high rpm....all these add up a terrible combination. I'd save your money and start over.
 

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I like 882's for big, heavy, REAL everyday work truck 350+ builds. NOT garage queens or trailer queens:p. 882's don't breath well with high lift cams. I like to keep em under .450 lift. they don't like high rpm's. about 5200-5500 max. I have never put em on top of a 305. with 76cc chambers, they will make the CR way too low on a 305 to make any kind of decent power. more like 7.8:1- 8:1:nono:, and that would be a big MAYBE. call around your local machine shops and see if they got any good 305 heads with 58cc or less chambers, 1.84/1.5 valves. they probly got a set sitting on the floor that a customer changed his mind on:D. the 416 305 head would work good:thumbup:. get that CR up to 9:1-9.5:1 and you could run the good ole crane 10017 or the summit copy 1785, its got great sound, plenty of power up to 5500 with a 9.5:1 305. just my 2 cents;)
http://www.summitracing.com/search/...4294891071&SortBy=Default&SortOrder=Ascending
 

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Discussion Starter · #4 ·
I like 882's for big, heavy, REAL everyday work truck 350+ builds. NOT garage queens or trailer queens:p. 882's don't breath well with high lift cams. I like to keep em under .450 lift. they don't like high rpm's. about 5200-5500 max. I have never put em on top of a 305. with 76cc chambers, they will make the CR way too low on a 305 to make any kind of decent power. more like 7.8:1- 8:1:nono:, and that would be a big MAYBE. call around your local machine shops and see if they got any good 305 heads with 58cc or less chambers, 1.84/1.5 valves. they probly got a set sitting on the floor that a customer changed his mind on:D. the 416 305 head would work good:thumbup:. get that CR up to 9:1-9.5:1 and you could run the good ole crane 10017 or the summit copy 1785, its got great sound, plenty of power up to 5500 with a 9.5:1 305. just my 2 cents;)
http://www.summitracing.com/search/...4294891071&SortBy=Default&SortOrder=Ascending
Hello Jax_pap!
Thanks soo much, this is exactly what I was looking for, excelent feedback! I was afraid that the heads needed changing, as both the boat didn't make any speed and they are for 350. Did some calculation and comp ratio could actually be lower with about 7,4:1.
Best regards
/Per
 

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Discussion Starter · #6 ·
Or scour craigs list, find a used 4-71 blower and hang on....
Hehe, well that's a more agressive way, but please, tell more! How much one of stuff or special building is needed except charger? Does it mount on st intake? Does the carb I have fit? Guess you go suck through? It's for sure the coolest most hardcore solution. I had a XJR v8 jaguar a couple of years back and miss the howling...
And, what would be the approx power...
Will start looking... for 4-71... ;)
 

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Hehe, well that's a more agressive way, but please, tell more! How much one of stuff or special building is needed except charger? Does it mount on st intake? Does the carb I have fit? Guess you go suck through? It's for sure the coolest most hardcore solution. I had a XJR v8 jaguar a couple of years back and miss the howling...
And, what would be the approx power...
Will start looking... for 4-71... ;)
You can find a complete kit used that will include pulleys and belt, belt replacement should be done regardless. Then I would use a quality ignition, and an MSD BTM (boost timing master) which will allow you to dial in the timing correctly while in boost. Weiand says up to 5psi on stock cast junk, and keep RPM limited to 5000, for Carb choice a standard 750DP would suffice with limited boost like your 5psi Max, you will jet up the primaries to somewhere around 10% from stock sizing and secondaries can need up to a 20% increase. Quality free flowing exhaust, the best fuel you can find, a non restrictive air cleaner and enjoy. Power? Who knows, but at 5psi an additional 75-100 on your little 305 wouldn't surprise me. The table top flat torque curve is the big bonus....
 

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I like the idea of a 4-71 blower, but let's see what we can find naturally-aspirated first. Forget that rump-rump cam crap, that's just the sound of the motor being inefficient. We need efficient power to get the boat up on plane and that will take a different cam from a fosdick rump-rump cam. I like to hear a lumpy cam as much as the next guy, but this ain't the place for it. You will need mid-range torque to get the boat up on plane and keep it there. Let's just suppose a little bit here....
If the pistons are 8cc's in the crown, the bore is standard, the block deck height is standard and you used steel shim head gaskets with 416 heads (58cc chambers), you'd be at about 9.35:1 static compression ratio.
I'll do a DynoSim for you, with 1 5/8" long tube headers, up over the transom. No big deal, make 'em yourself with a kit from Headers by Ed and using a high-rise, dual-plane intake manifold such as an Edelbrock 7101, Weiand 8150 or the discontinued but available in the used market, Holley 300-36 or Weiand 8016. We'll use your 600 carb.
http://www.cromerexhaust.com/html/gallery/Ski Boat Headers Mufflers 4inch Stainless Tips.jpg
We'll use these flow numbers for the heads.....
0.200" 99 90
0.300" 144 118
0.400" 175 132
0.500" 185 137
0.600" 185 137

Tried 4 different cams with at least 4 different phasings for each, here's the winner....
Crane Z-268-2, 113522, operating range 1800-5800, 218/230, 268/280, valve lift 0.459"/0.486".
Install retarded 4 degrees on these numbers.....
Intake opens (-2)
Intake closes 40
Exhaust opens 48
Exhaust closes 2
Intake centerline 111
Exhaust centerline 113
Lobe separation angle 112

RPM.....HP....TQ
1500....89....312
2000...126...331
2500...162...340
3000...206...360
3500...252...378
4000...295...387
4500...331...387
5000...362...380
5500...371...354
6000...362...317

Max volumetric efficiency 93.9% @5000 (better heads would increase this).
Max BMEP psi 191.1 @4000

Try to rig up a large air cleaner assembly so the motor can breathe, I like 14" x 4" if you don't have to use a flame arrestor arrangement. I would lock out the timing at 34-36 degrees and use a switch to interrupt the juice to the coil so you can turn the motor over to start it without breaking the starter. I would not use vacuum advance on a boat motor, just set the timing at the crank to 34-36 and enjoy. The motor should be docile enough to idle up to the fuel pumps at the marina.

Read and heed this tutorial concerning flat tappet cams......
http://www.crankshaftcoalition.com/wiki/Camshaft_install_tips_and_tricks

Use this tutorial for setting the valves....
http://www.crankshaftcoalition.com/wiki/Valve_adjustment_SBC/BBC

Use this tutorial for arriving at top dead center on your damper, so you can time the motor properly.....
http://www.crankshaftcoalition.com/wiki/Determining_top_dead_center

.
 

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Discussion Starter · #9 ·
I like the idea of a 4-71 blower, but let's see what we can find naturally-aspirated first. Forget that rump-rump cam crap, that's just the sound of the motor being inefficient. We need efficient power to get the boat up on plane and that will take a different cam from a fosdick rump-rump cam. I like to hear a lumpy cam as much as the next guy, but this ain't the place for it. You will need mid-range torque to get the boat up on plane and keep it there. Let's just suppose a little bit here....
If the pistons are 8cc's in the crown, the bore is standard, the block deck height is standard and you used steel shim head gaskets with 416 heads (58cc chambers), you'd be at about 9.35:1 static compression ratio.
I'll do a DynoSim for you, with 1 5/8" long tube headers, up over the transom. No big deal, make 'em yourself with a kit from Headers by Ed and using a high-rise, dual-plane intake manifold such as an Edelbrock 7101, Weiand 8150 or the discontinued but available in the used market, Holley 300-36 or Weiand 8016. We'll use your 600 carb.
http://www.cromerexhaust.com/html/gallery/Ski Boat Headers Mufflers 4inch Stainless Tips.jpg
We'll use these flow numbers for the heads.....
0.200" 99 90
0.300" 144 118
0.400" 175 132
0.500" 185 137
0.600" 185 137

Tried 4 different cams with at least 4 different phasings for each, here's the winner....
Crane Z-268-2, 113522, operating range 1800-5800, 218/230, 268/280, valve lift 0.459"/0.486".
Install retarded 4 degrees on these numbers.....
Intake opens (-2)
Intake closes 40
Exhaust opens 48
Exhaust closes 2
Intake centerline 111
Exhaust centerline 113
Lobe separation angle 112

RPM.....HP....TQ
1500....89....312
2000...126...331
2500...162...340
3000...206...360
3500...252...378
4000...295...387
4500...331...387
5000...362...380
5500...371...354
6000...362...317

Max volumetric efficiency 93.9% @5000 (better heads would increase this).
Max BMEP psi 191.1 @4000

Try to rig up a large air cleaner assembly so the motor can breathe, I like 14" x 4" if you don't have to use a flame arrestor arrangement. I would lock out the timing at 34-36 degrees and use a switch to interrupt the juice to the coil so you can turn the motor over to start it without breaking the starter. I would not use vacuum advance on a boat motor, just set the timing at the crank to 34-36 and enjoy. The motor should be docile enough to idle up to the fuel pumps at the marina.

Read and heed this tutorial concerning flat tappet cams......
http://www.crankshaftcoalition.com/wiki/Camshaft_install_tips_and_tricks

Use this tutorial for setting the valves....
http://www.crankshaftcoalition.com/wiki/Valve_adjustment_SBC/BBC

Use this tutorial for arriving at top dead center on your damper, so you can time the motor properly.....
http://www.crankshaftcoalition.com/wiki/Determining_top_dead_center

.

Wow, thanks alot. That was quite alot of work you helped me with. Thanks so much. Haven't used the dynosim program, but was actually working with engine development towards Volvo cars/Trucks back in 2004. Did you borrow flow values from a tested 416 head with std runners and 1,84/1,5 valves? Haven't been around long enough to recognise flow values in Imperical units... :)

Anyhow, yes, it's important that boat does plane easy enough, but as said, it's quite a light flat bottom package, will probably only need 30-50hp to reach 15kn. And yes, would also prefer to go natural aspirated, feels like there is so much to be had in terms of power before stepping into supercharging. I am 100% sure that 300-350hp will give all the speed I need in the 16' boat :). BR /Per
 
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