347 hp vs long rod 306 hp. Which way to go? (Edited) - Ford Muscle Forums : Ford Muscle Cars Tech Forum
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Old 08-27-2004, 07:26 PM   #1 (permalink)
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347 hp vs long rod 306 hp. Which way to go? (Edited)

I am at the point where I need to give the go ahead on building a long rod 306 or a 347 stroker shortblock for my 65 Comet. I have provided the std bore flat tappet 302 block. I have been quoted a $300.00 difference between the two with my choice of custom grind that Bullet Custom cams will cut. They will make a cam grind recommendation based on my modifications, but I was hoping someone may have a good proven flat tappet hydraulic cam for a weekend drag strip/ street car. Is there much of a difference in HP between the durable 306 and a built 347?

I turned 13.80s with a basically stock 302 block and heads, but would like to see some high 11s low 12s on motor.

Help me make a decision and cam selection please. Don't want to turn more than 6200 rpm if possible.


I have ported TFS twisted wedge heads
1.6 roller rockers
2800 Pro egde stall
3.55 Trac Loc with 23 inch tall drag radials
Hooker super comp headers
Edlebrock Air gap (port matched #1250)
Holley 650 DP

3100# car
track is at "0" elevation and Hooks almost all the time.

*** I had to reword that whole thing.LOL. I couldn't even figure out what I was asking. I was very tired when I wrote that. Sorry. It should be better now.



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[ This Message was edited by: 65cyclone on 8/29/04 5:27am ]
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Old 08-27-2004, 07:37 PM   #2 (permalink)
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347 hp vs long rod 306 hp. Which way to go? (Edited)

I guess I dont understand your question. 347hp or 306hp?
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Old 08-27-2004, 09:22 PM   #3 (permalink)
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347 hp vs long rod 306 hp. Which way to go? (Edited)

Should I go with the 347 or the 306 long rod motor? It's a somewhat daily driver. Is durability a concern for the 347? Over heating? Any cam recommendations for either to turn high 11s or low low 12s? I just don't want to make poor decisions since there are others here that can help guide me. I hope this makes since. The flat tappet cam in a 347 probably isn't all that common so cam selection is critical and difficult for me. Thanks!


James

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Old 08-27-2004, 09:37 PM   #4 (permalink)
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347 hp vs long rod 306 hp. Which way to go? (Edited)

Are you going to run a mech or hyd flat tappet.I would go with the long rod 306. Because that what i run and what i like..Its faster then a lot of roller strokers.my old 306 with DOOE 351w heads ran 11.70@113
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Old 08-27-2004, 09:51 PM   #5 (permalink)
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347 hp vs long rod 306 hp. Which way to go? (Edited)

347, you cant beat the extra cubes, if they were built the same.....good heads cam intake etc.. the 347 will make about40-50 more HP and TQ, you would have to really buld the 306 to match it and then you loose low end and drivabilty.

You have a rock solid foundation, just add a comp xe 274hr or even better get a cam custom ground.

Thats like asking a 302 or a 351 which will make more power?

You wont have to spin the 347 like you would the 302= longer engine life, even though the oil ring deal. If your concerned about that then do a 331.

Theres no replacement for displacement except a blower,turbo or nitrous.
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Old 08-28-2004, 12:42 AM   #6 (permalink)
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347 hp vs long rod 306 hp. Which way to go? (Edited)

It's going to be a hydraulic flat tappet cam set up for sure.

I would be very pleased with drivability and 11.70s @ 3100#s.

Thanks for the input from all. I'll post the results when I decide and get it all together. Thanks again.

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Old 08-28-2004, 12:57 AM   #7 (permalink)
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347 hp vs long rod 306 hp. Which way to go? (Edited)

Theres some good cams out there off the shelf BUT call Denny at Motor Machine in Tuscon AZ 520-792-1156 or cammasters@msn.com fill out the cam form and for about 40 bucks he will come up with the absolute best cam for your combo and if he grinds it he waives the 40 bucks.

It is so worth it you will gain about 30hp/tq over an off the shelf cam and it will usually be smaller, better idle and vaccuum. Theres alot of great cam guys out there but he is one of the best , alot of winning racers go to him for cams, Its absolutely worth it, spend the 40 and punch in the specs on a desktopdyno and pick any other cam, his will make more overall power and better low end too.
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Old 08-28-2004, 08:14 AM   #8 (permalink)
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347 hp vs long rod 306 hp. Which way to go? (Edited)

Its going to be hard to run 11.70's with a hyd flat cam. I would install a mild mech flat tappet cam. Give cam research a call or check there web out www.camresearchcorp.com
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Old 08-28-2004, 10:38 AM   #9 (permalink)
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347 hp vs long rod 306 hp. Which way to go? (Edited)

Tony,

How did you get you car to un so quick? Can you give a break down on your engines build? That's very empressive for a 306 and that weight. I'd appreciate all the help I can get.

Thanks guys!

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Old 08-28-2004, 04:36 PM   #10 (permalink)
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347 hp vs long rod 306 hp. Which way to go? (Edited)

Do you want to know about old 306 or the long rod 306

[ This Message was edited by: tonys10sec306 on 8/29/04 4:37am ]
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Old 08-28-2004, 04:42 PM   #11 (permalink)
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347 hp vs long rod 306 hp. Which way to go? (Edited)

I've had good luck with my 289 headed 306, but if I was starting over with a new shortblock, it would be a 331. I think 347 is just too big for the standard deck height 289/302 block... but that's just my opinion. They seem to be okay for lower rpm, torque engines.

Look into a 331.

Good Luck!
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Old 08-28-2004, 05:32 PM   #12 (permalink)
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347 hp vs long rod 306 hp. Which way to go? (Edited)

Thanks for the info and sorry for butchering the original question.LOL. I fixed that.

I did go ahead and get the Derale fan that was recommended as well as the Ebay aluminum radiator. Now if I ever get this thing back together and running it should run cool, but of course it will be winter by then.LOL.

I do want a low end torque set up, but I want it somewhat durable as we drag race pretty regular. Thanks again!

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Old 08-29-2004, 08:06 PM   #13 (permalink)
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347 hp vs long rod 306 hp. Which way to go? (Edited)

302 = cheaper, easier to repair/replace, you don't have to worry about blowing internals and spending a $$$ replacing the bottom end.

347 = much more power, lower RPM Powerband is beneficial for a street car, especially with your 2800 rpm stall converter.

Justin
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Old 08-30-2004, 04:05 AM   #14 (permalink)
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347 hp vs long rod 306 hp. Which way to go? (Edited)

Im no expert like alot of the guys you work with here on the boards but i will give u a bit of my experience. I used to run a 289 in my 67 stang. Single plane with a lunati cam and such headers and bla bla bla. Car ran 12.60s on slicks at the track. Probley would have ran 12.40s with a decent stall converter but anyways.

Later on i went to a 351w. I went with the same exact camshaft in the 351w as the 289 even used the old 289/302 firing order. Single plane intake headers and all. The difference was NIGHT AND DAY. My 351w will blows the tires off at a roll. Its a mid 12 second car without a doubt. Cant wait to get the news heads and such on which is in a different discussion posting right now guys Anyways though if i was you from what ive seen now. Go for the cubes. The torque will amaze you
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