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Discussion Starter · #1 ·
Any first hand experience ........ ported 670 well clutched /140hp how does it compare to say, a stock F7 or SRX in 660' ?Chassis used = "98 MXZX 440.
My guess is that the 670 would get the hole shot with the green and blue reeling it in on the long haul. Anyone seen this first hand?
 

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Any first hand experience ........ ported 670 well clutched /140hp how does it compare to say, a stock F7 or SRX in 660' ?Chassis used = "98 MXZX 440.
My guess is that the 670 would get the hole shot with the green and blue reeling it in on the long haul. Anyone seen this first hand?
The F 7 is the fastest the 670 will be next and the SRX will be the slowest, in a 1/4 mile the Srx will be second and the 670 would be third ! the F7 is in a category of its own!
 

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Discussion Starter · #3 ·
So even a 140hp 670 lacks compared to a stock F7? I take it the F7 gets the power to the track more efficiently?
 

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The F 7 is the fastest the 670 will be next and the SRX will be the slowest, in a 1/4 mile the Srx will be second and the 670 would be third ! the F7 is in a category of its own!
From everything I have heard and read, an SRX 700 would stick with you until 80 to 90mph and then pull past you on the very top end. It sure sounds like they are geared for higher top speed. The F7 would probably slowly pull away from you at the start and you would never reel it in. I have watched F7s at drag races and they are very fast.

I could be wrong but porting alone would not get a 670 to 140hp.

Obviously tracks and studding have a great deal to do with this.
 

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just food for thought, in 1999 magazine tested an 670 HO (129hp) i believe it was 1000 ft or maybe it was 660 ft, stock for stock it will outrun the F7 but the F7 at the traps had a higher mph, so it will freight train it if it had some more room. so a 140 hp 670 should be able to run if not keep up to an F7, but the 7 is hard one to beat, just everyhing about it screams speed, narrow track lighter. if you were able to get more hp to the ground you might have a fighting chance (p-85 primary with a roller cat secondary) and properly tuned. just don't open up your hood when there around. don't have to share all of your secrets.
 

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just food for thought, in 1999 magazine tested an 670 HO (129hp) i believe it was 1000 ft or maybe it was 660 ft, stock for stock it will outrun the F7 but the F7 at the traps had a higher mph, so it will freight train it if it had some more room. so a 140 hp 670 should be able to run if not keep up to an F7, but the 7 is hard one to beat, just everyhing about it screams speed, narrow track lighter. if you were able to get more hp to the ground you might have a fighting chance (p-85 primary with a roller cat secondary) and properly tuned. just don't open up your hood when there around. don't have to share all of your secrets.
Just go to the snowmobile drags and in stock class the F7 wins, ib the mod class the F 7 dominates! The 3 cylinder was top dog before the F 7 was built but the F7 gets out quick and makes big top end power !

A good 670 may beat a poor F7 but the guys at the drags don't show up with a poor running sled!
 

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An '03 F7 was 73 lbs less dry than a 99 670HO, iirc,and had about 15 more HP. And the right things to go fast, like said
 

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Discussion Starter · #8 ·
Thanks to all who responded. We are finally seeing snowmobile drag racing come back to our area. They by no means a "pro series" but there are some fast sleds there. Being that I have all the goods to build up a strong 670, and a decent chassis, I wondered if it would be competitive. I really have a hard time going green!
 

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Thanks to all who responded. We are finally seeing snowmobile drag racing come back to our area. They by no means a "pro series" but there are some fast sleds there. Being that I have all the goods to build up a strong 670, and a decent chassis, I wondered if it would be competitive. I really have a hard time going green!
It really depends on who is serious about the class My son raced his 670 Mach I twin pipe from 1995 to 2004 with real good results then the F7 cat came along, it ended the road for my son's wins as well as any body that was running a Mach I triple! Thr guys that raced the Cats in our area were dealer sponsored and were real fast!
 

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If your pushing 140 hp then you would be right in the mix if your talking about a comparison against stock sleds. It will come down to set-up and clutching you'll get some wins. If they are also modified or it's a sanctioned competitive event you have some trouble.
 

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If your pushing 140 hp then you would be right in the mix if your talking about a comparison against stock sleds. It will come down to set-up and clutching you'll get some wins. If they are also modified or it's a sanctioned competitive event you have some trouble.
The F7 Cats are lite and they have less rolling resistance They have a 3 " pitch track that is only 13 inches wide! even if you can match there power it is hard to win!
 

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Discussion Starter · #12 ·
I've watched a lot of videos on races with the F7 there's no doubt, they are the one to look out for. That and the SRX. My thought was that with a professionally ported 670 making 140hp as per Big Johns specs, that if would be competitive against the green and the blue in the 660'.i could just sell my beloved Rotax mills and buy an F7, but I've got morals LOL
 

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hey, I've heard the most power you can get out of a 670 is by using a 670HO bottom end and a 1996 mach 1 top end. I heard something around 136 HP with that set up stock. i would highly recommend using an H.O as your base motor at that came with the electronic timing advance. I've had a lightly ported and polished 670 dropped 4 teeth on the top gear and a stock 670 H.O with stock gearing in a beat chassis still had a lot more go on the bottom end. I bet you could run that H.O bottom end and mach 1 top end and still be able to run in the stock class
 

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The f7 will walk away from you they are hard to beat an can make 160 hp with a few bolt on's.they are known to beat mach z 1000s to.but theres allways that chance the 670 will shine on threw.

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By a few "bolt on's" you mean, a complete pipe, ported cylinders, probably a head, and fuel controller than yes the F7 would make 160hp and also set you back $2500. He was talking about his 140hp 670 vs a stock engine F7 or SRX. He'll do just fine set-up is key.
 

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My old 97 670 with quite a few mods was embarrassed by my all stock 03 F7. Mods included porting, 169° RV, twin pipes, and high comp domes. It never stood a chance. Same outcome with me or my buddy driving it.
 

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Discussion Starter · #18 ·
Engine packages for the 670 from reputable performance shops (Sled head Racing, Ian Tammasi, etc) are stating "usable"140hp. Facts are whether the it be a 140hp F7 or a 140 hp 670.....it's still 140hp. Getting the hp to the track is where the F7 prevails as far as I can tell. Whether a '98 mxzx chassis can be set up to compare is really the question.
 

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What kind of clutching did you have in it because that would be one sick running 670 if it got embarrassed with those mods need to do a little homework.

454 your right 140hp is 140hp comes down to who's turning the wrenches. There is more upside to the F7 that why they own a lot of records but not everyone is unbeatable. I've beaten 70 percent of the ones I ever raced.
 
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