|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 12:01 PM|
Measure then primary tube diamter of your block hugger headers with a dial caliper.
if 1 5/8" they can be used for parts to build a custom header
4-2-1 4 into one long tube ,,,step header.
many of the block hugger are only 1 1/2" or 1 3/8" primarys,,,,don;t even bother.
Often a existing 1/5/8 1 3/4 SBC header is a good start point.
Sometimes a nice Real Deal Hooker competition race header ( super stock)
corvette, camaro , 55 chev etc can be bought used and cut up and refabbed.
if you want power you want a powerfull exhaust header and a full exhaust system to match..
SBC in a Celica you will need to fabricate.
its up to you to be creative.. The exhaust system makes or breaks the car. The key word is SYSTEM.
The Exhaust is your scavender/ supercharger on a Hi perf N/A motor. Works with the camshaft,,, valve timing and induction system... And it don;t need to be loud to make power.
1 5/8 o 1- 3/4 is good You can make a rocking header from either.
all the exhaust-header company sell components for fabrication and customization.
find or build a 750-800 DP.
|11-20-2012 11:21 AM|
You can build or adapt /modify a 1 5/8 header or a 1 3/4 header. Both will work very well
and be miles ahead of what you got.
Another way to build a effective powerfull header, when room is tight is a 4-2-1 design.
This is not a tri Y design. The 4-2-1 scavenger header w collector acts much like a 4 into 1 long tube w merge collector.
Usually where a block hugger header fits a C3 long tube corvette header will be very close.
center dump tubes.
may only need minor modification. thats nothing for a welder.
If routing he primarys back and down is better look at a 3rd gen camaro header. Or a S-10 header
Or a 2nd gen camaro/chevelle header as a base.
The typical little block hugger headers have very small primary tube diameter. No scavedging effect
poor flow. Often worse than a corvette ram horn exhaust manifold. They are for near stock motors.
Fit easy, cheap, no power. Great for 300hp street rods.
The car is a 72 celica with fabricated tube frame.
You got tons of room to work with.
Its very easy to make up excuses..... No buddy is suggesting a 25K budget.
By the way that simple roots street blower motor can be built complete for well under 5K
Its real simple. and you already have most of the components. The punny carb isn't once of them.
Ita a 330 to 360Hp carb for guys that do not want to go fast.
|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 12:43 AM|
Why are you asking? It will make 50+ HP and a ton of torque LESS than it could make.
Youa re fabricating the whole car/ chassis and cannot weld up a decent exhaust system for it?
Non of the head porting or the roller cams power will be reaized with a choked induction and exhaust system. The engine has to breath deep to make power.
You got both ends corked up.
Don;t ask epole how much power it will make Put the engine on a engine dyno and dyno test it wht your dunky carb and exhaust and then compare to the dyno headers and the 750HP carb that all dyno shops got on hand and you will see.
The engine cannot make power if you choke it. Why even ask. its not rocket science.
|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 12:23 AM|
If I was absolutely stuck with a shorty header I would get or build shorty headers with a 1 3/4" pri pipe
if I wanted to use that and the 3.55 gears I would have supercharged the motor.
850 950 carb Weiand 142 or 177 blower 3.55 gears , big exhaust big tube shortys.
Your roller cam is good. low engine compression ratio.
That would G L H.
|11-20-2012 12:13 AM|
You got a good engine that is choked on both ends
The air can't get in and the exhaust can't get out..
Don;t expect much from this motor.
|11-20-2012 12:04 AM|
|prostcelica||you really think im leaving 50HP on the table with the block huggers??|
|11-20-2012 12:01 AM|
Long tube headers from a C3 corvette or a third gen camaro may fit or only need minor modification.
Big difference from crappy block huggers. Don't waste time money and energy on X H pipe BS when you can build correct long tube headers. Why chop off 50hp and then start asking about how it will ET.
The exhaust system is a very critical part of the whole combo. If you want to get the benefit of all the money you spent
on a roller cam etc etc, don;t choke it with a bad exhaust system,, just cause its easy..
|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 11:25 PM|
|F-BIRD'88||Forget all that crap and get or build some long tube headers for it.|
|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 11:14 PM|
The tires are tall, I would use the 4.11's. Why shorty headers? what chassis is this.
i believe the drag strip on the island (outside Victoria) is 500ft. You want lots of gear on a 500ft drag strip.
The hiway cruise rpm will be just right wiht the 4.11's and 27.5" tires.
3000 rpm @ 100 klicks. This cammed engine does not want a slow cruise rpm.
crusing at 3000 rpm, @100Kph is just right for this motor.
rpm / gear ratio x tire diameter x 336 = speed in MPH
convert MPH to KPH x 1.613
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