|11-20-2012 12:30 PM|
Thanks for the great info Fbirb. I really appreciate it. This is my first engine build so im kinda learning as i go. I had no idea block huggers were such a power killer but know i do That is a good plan. I think i will cut apart my exsisting headers to make long tube. I have measuered the primarys and they are deffinatly 1 5/8 od. I have a freind that will most likley have a 750 he will sell or trade me for.
Again, thank you for the very helpful info.
|11-20-2012 09:28 AM|
exact header tube size and length is hard to determine. similar formula as an intake manifold except the other end.
A 4 into 1 header is like a single plane intake,it will make more power at a higher rpm than tri Y headers.Try Ys act like a dual plane with the bottom end increases starting at a lower rpm and rolling off peak powers sooner.
Tube size,smaller tubes scavenge the head sooner but will not have enough volume at higher RPMs or on bigger displacement engines.
some engine builders will generalize and say you need 1 5/8 primaries for 375 hp or less and 1 3/4 primaries up to 500 hp,after 500 hp you might need 1 7/8 primary pipes.
this type of statement is ok at best,or a starting point. There are a lot of ponies left on the table because people buy a $200.00 set of headers that fit 5 different cars,then spend 10k on stroker engines with big cam/heads and wonder why there engine makes ok but not spectacular power
choosing perfect headers is very complicated and almost always over looked
|11-20-2012 01:03 AM|
|prostcelica||WOW!!!! Why dont you tell me what you really think. Im asking because I DONT KNOW. isnt that what this forum is all about?? I am jsut trying to figure out how much is to be lost. If I go by your theorys id be into this motor for 25k. If you asked me a question I thought was "not rocket science" I would never speak to you or anyone that way. I would answer and try and be as helpful and friendly as possible. Im embarrassed to call myself a canadian.|
|11-20-2012 12:34 AM|
With the way the motor is know what is your HP/TQ estimate
and what with a 750DP and longtube?? would you use 1 5/8 longtube?
|11-20-2012 12:04 AM|
|prostcelica||you really think im leaving 50HP on the table with the block huggers??|
|11-19-2012 11:48 PM|
|prostcelica||I am using shorty header as Im tight for space. I know i could build a set of long tube but when I originally built the car and wanted to get it on the road so I picked up a set of shortys for cheap. The car is a 72 celica with fabricated tube frame. You are correct about the 500' track outside vic but this is street that will occasionlly go to the track so Im wanting to get a gear that will still hit hard but wont be a total bear to drive on the street|
|11-19-2012 11:18 PM|
|prostcelica||LOL!! sounds good. Were do usually race?? Also....I hate to ask but im going to anyway What kind of HP/TQ #'S do you think that combo of mine will make? And any suggestions on things to improve?? What do you think about the 670 carb ? Also, I had a H pipe in my old exhaust system. I am going to re-route the exhaust and am torn between an X, H or no cross over pipe at all. Any thoughts on that??|
|11-19-2012 11:08 PM|
|vinniekq2||Ive only been to mission twice since about 2006. you can ask them if they know Rapid rory McNeil, the fat turnip Dan Madeloni,the Farmers of course. Dave Hall,Richard Johnson, We keep naming names and one will click.If you come over here,get a hold of me|
|11-19-2012 10:58 PM|
|prostcelica||Im in Nanaimo but Im just starting to get into racing but my family is into pretty huge. They are always over on the mainland racing. Mission, ashcrost, etc. if your into racing you may know them. My uncle had a burgandy chevy II with "MID LIFE CRISIS" on the side. My cousins have a Yellow S10 with a big block, Green Vega and a Beretta door slammer with a blown hemi. Ringing any bells??|
|11-19-2012 10:50 PM|
|vinniekq2||I live in port coquitlam.where do you race?|
|11-19-2012 10:41 PM|
|prostcelica||Thanks for the link Vin. Thats a long way to go at 4000rpm Hey Vin you live in Vancouver?? Im on the island.|
|11-19-2012 10:24 PM|
|vinniekq2||over 120 mph is a high 10 second car. Ive used gears from 2.73 -- 5.57 on the street.My big block Camaro had 3.36 gears and on the high way I felt the gearing was a little steep for long trips,and it destroys gas mileage. I drove my old 67 Camaro from Vancouver Canada to Bremerton raceway Washington state,,60 mph equalled 3.700 RPM on the highway for 2 hours, 3 hour trip took 4 hours|
|11-19-2012 10:21 PM|
Gear Ratio Speed Calculator
play with gears/tires trans ratios
|11-19-2012 10:19 PM|
Thanks for the feed back Vin. I think what ill do is run it with the 355's in it at first and see how it is. If its a total dog off the line I can go to the free bee 411's. I just wanted to ask you guys to see what everyone would say. If everyone came back and said "it will be a total slug off the line" I would do the gear change now but it seems like im in the ball park with the 355's.
On a side not any guesstamations on 1/4 mile ET's??
|11-19-2012 10:12 PM|
|prostcelica||I want to try and get the best of both worlds. I will say that with the old motor which was pretty well a bone stock sbc 350 with performer intake, that holley carb, humps, headers and an "RV" cam cruised at around 2500-3000rpm at 100KMH and hit pretty hard of the line. Any idea what the highway speed woud be with the 411's knowing that the 355's ran around 2500-3000??|
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