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Author Topic: 4v headers on 2v heads?  (Read 11025 times)
aussiewinza
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« on: February 01, 2012, 10:50:13 pm »

i have acess to some free 4v 4 into one headers. i believe they are 1 7/8 into 3.5 (will have to check)

I currently have an aussie 302ci 2v headed celavo that has some mild head work and a nice cam. and a set of try-y 1 5/8 primary into 2.5 headers
first question will the 4v headers fit and seal on 2v heads (yes they fit the car)
and will it kill the small 302.

i have a 351 crank and rods i will be swapping out when it needs a freshen up....
thanks in advance
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SteveL
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« Reply #1 on: February 02, 2012, 12:45:34 am »

According to this...

http://www.spdexhaust.com/pdfs/HeadFlanges/351C-M-400.pdf

The bolt up is the same, so the 4V headers (extractors) should bolt up to the 2V heads...

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aussiewinza
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« Reply #2 on: February 02, 2012, 01:12:56 am »

ok cool, next thing is will going that big of a primary or even the 3.5 collector kill it as its only 302ci....or should i wait till i put the 351 crank in it.

thanks for the fast replies.
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turbo2256
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« Reply #3 on: February 02, 2012, 08:27:09 am »

I used 4V headers on a 2V head once (swapped 2V and 4V heads back and forth) was a 351C though. Was years ago think I had to use both 2V and 4V gaskets to seal properly. The big tubes on the 302 ,depending on how built the engine, could cause some reversion into the intake.
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aussiewinza
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« Reply #4 on: February 02, 2012, 04:20:18 pm »

wouldnt the step on the head (smaller exhaust port dia compared to primary tube dia) actualy slightly prevent reversion?

the only issue i can see is that the pull from the exhaust signal would lose some strength?
or have i go this ass backwards?
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turbo2256
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« Reply #5 on: February 02, 2012, 04:28:49 pm »

Yes reversion might be stopped or lessoned. Dont remember if some of the edges matched. I was going to make some real revision plates to place between the heads and headers. Short tube matching the 2V heads protruding into the headers a small bit. Never finished the stuff. Still have the reversion plates half built. Think that was back in 78 or so. Headers were like 2 1/8 ID.
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aussiewinza
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« Reply #6 on: February 02, 2012, 04:38:35 pm »

just for info my combo is
.030 over bore
10.7-1 comp
3 inch stroke
ported and flowed closed chamber 302c 2v heads- slightly bigger valves (have to find build sheet for sizes)
yella terra 1.73 stud mount roller rockers
holley 750 hp mech sec
torque power high rise dual plane (basicaly a taller rpm airgap with more plenum volume)
ice ignition 6 amp kit with billet dizzy

cam specs = hyd flat tappet (any input on better options would be cool)

duration in 282             duration at .050 = in 234         lobe centerline = 108    valve lift = int .525
              ex 295                                          ex 244                                                                ex .525

3500rpm stall converter, 3.9 rear gear car weights approx 3600-3700 at a guess

probably more but thats all i can remember off top of my head.
  i drove this every day until recently
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302ute
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« Reply #7 on: February 03, 2012, 06:53:05 am »

Aussie,
Sounds like it should work alright. You've got enough compression and camshaft. That torquepower dual plane I tried on a mates basicly stock 351 clevo(had a little 218@050" hyd cam)  with a small (2500rpm) convertor and 3.0 diff gears. It replaced a stock cast iron 4bbl manifold. The difference it made on his car was like taking the 3.0 gears out and putting 3.7s in there. It picked up a heap.

Can't say for sure on the pipes, try both and see. I reckon the tri-ys will probably work ok with what you have. Just put a 351 crank and rods in there and be done with it. There seems to be a few lying around now that stroker kits are so easy to get.

It will be interesting to see how well it works on your combo.Good luck mate , hope it works out good for ya.
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BirdMan
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« Reply #8 on: February 03, 2012, 10:33:06 pm »

The mismatch of bigger header tubes to the 2V head casting may leave an area of 'nothing' to seal to on the sparkplug side of port.
On my homemade headers of 1 7/8" as wide as the 4V port I had a gap.  I added welding on the inside of tube and ground/filed it flat to seal on the 2V head and using a 2V gasket as aftermarket 4V gasket was larger than the 2V casting.
On my friends Mustang using 2V ported heads and 4V 1 7/8" headers I made 'adapter plates' of flat 3/16 or 1/4" plates using 2V on engine side and 4V on header side sandwiching the plate between the gaskets.
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clevelandpwr
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« Reply #9 on: March 18, 2012, 02:57:16 pm »

I cut flanges off the 4v and used 2v flanges bought off ebay.Welded new ones on,worked great
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Brian S
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« Reply #10 on: March 18, 2012, 06:32:17 pm »

I cut flanges off the 4v and used 2v flanges bought off ebay.Welded new ones on,worked great

The Australian 2V heads have a bigger surface area where the exhaust bolts up so this isn't necessary for 4V headers to seal properly. This thread is also 6+ weeks old.
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clevelandpwr
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« Reply #11 on: March 25, 2012, 09:52:58 am »

whats it matter how old thread is?Just letting gentleman know what I did pissy pants
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aussiewinza
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« Reply #12 on: March 25, 2012, 07:17:34 pm »

lol, its all good.

i look at all threads on here........i found myself getting caught up in a thread thatwas YEARS old couple of weeeks ago. This site got some great info on it, dont matter how old it is.

I think im goint to go ahead and pick up a set of big tube 4v 4 into 1s if i can get em cheap...that way i can grow into them later on and they will look pretty nice on the garage wall till i need em!

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