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pacemaker vs HM headers 

 

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 Post subject: pacemaker vs HM headers
Posted: Thu Feb 16, 2006 10:28 am 
Getting Side Ways
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i currently have the pacemakers on my gt40p heads. Im getting some mixed opinions about the primaries being too large and only good for top end range. There's HM interference headers for 625 on ebay and i've heard these give better torque down low which is what im after. whats the interference mean?
any opinions?
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Posted: Thu Feb 16, 2006 11:25 am 
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Mate, I caled HM directly and had a chat. They say the 4-2-1 (try - y) make better down low power. I think the interference is to do with the 4-2-1 config.. I found them very helpfull.. Give em a call.
I am also trying to compare the 2 for my ED sprint

 

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Posted: Thu Feb 16, 2006 12:37 pm 
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What Pacemakers are you running? The PH4000 tri-y's are generally the ones used on e-series V8's and IMO are a very good design overall, a good match between low end power and high rpm flow.
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Posted: Thu Feb 16, 2006 2:56 pm 
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im running the ph4000 i think. but was wondering whether it would be better to get the HM ones for their better low down torque capabilities. just want to improve torque down low as the mid range/top end is fantastic atm.
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Posted: Thu Feb 16, 2006 3:06 pm 
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If you have the PH4000's then switchin to HM wouldn't give you anything IMO (in fact I thought HM used the same 1 5/8" primaries). The only ones I knew that ran smaller primaries were the hurricane headers which from memory run 1.5", but even then I don't think there would be a huge difference in low end performance. 1 5/8" primaries seem to be regarded as a good size for stock to fairly modified 5L's, then 1 3/4" for all out performance / high reving engines.
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Posted: Thu Feb 16, 2006 6:34 pm 
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off the topic... would 3.9's go well for my car being an auto for more get up and go off the line? or 3.7's maybe? just need that extra bit off the line, keeping in mind i have a bigger cam etc.
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Posted: Thu Feb 16, 2006 6:56 pm 
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3.9's are perfect for an auto IMO but if you do a bit of highway driving it may be a little steep. 3.7's would also be a good option.
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Posted: Thu Feb 16, 2006 7:01 pm 
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ok then, do a bit of highway driving so mite go for the 3.7's. should give the car some balls off the line now, coz the auto with 3.45 isn't that good off the line. cheers
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Posted: Sat Feb 18, 2006 3:57 pm 
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Pacmaker PH4000 are an interference (tri-y) header too, so I agree with the others that its doubtful you'd see an improvement.

 

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Posted: Tue Feb 28, 2006 12:29 am 
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Pacemakers are mandrel bent pipe where as the hm are press bent so technically pipe diameter on the bends would be probaly 1.5 or less on the press radius where as the pacys would be consitsant 1 5/8. hm argues that there are no need for mandrel bent pipes as the narrowing of the tube on bend radius creates a venturii effect in turn increasing the scavnging effect of the cylinders.... ( probaly not ideal. it is kind of like turning on the garden hose and letting run freely then put finger of a little on the hose you will get the water to shoot further and faster but would have greater pressure on the water trying to exit therefore greater back pressure. very basic theory) . on a stock car i would doubt that you would find any difference between the two. but personaly i would take the pacys if they are the same price as they are built a little better.
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Posted: Thu Mar 02, 2006 10:32 am 
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Just had a chat to the guys at Pacemaker re the PH4000 headers. I have a ED sprint and as they run the GT40 heads they say the plug angles are different and may cause issues. Does anyone have any experience with this? Pics etc?
Cant run the AU headers as the cross members are all different..

 

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Posted: Fri Mar 03, 2006 10:04 pm 
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Hi unsure but the au heads with plug angle make changing the plugs a little bit hard. fitted a set of genies recently to a au xr8 and the rear spark plug on the drivers side has very limited room can just be removed with socket an ring spanner not ratchet due to pipes. thank god that the only iridiums or platnuims are fitted so it is only a issue every 50-100k lol
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