67 GTX cam selection

Hi everyone the time has finally come after 20 years in the garage and my 3 yr resto almost complete I dropped the block at the machine shop and now selecting the cam I was interested in the Hughes solid lifter cam the smallest they make i will be using the 915 heads.Unfortunately I have power disc brakes hughes said that cam will be at 11in of vacuum has anyone tried to run their power brakes this low everything will be stock intake and exhaust manifolds as well but it seems I will have to buy and hide a vacuum pump what have you guys been doing out there thanks

may be iffy. the stock intakes don't flow any air and the exhaust manifolds don't like a bunch of overlap. that's more cam than i'd consider for a stock build. iron heads quit flowing air around .450" lift.

lewtot184 said:

may be iffy. the stock intakes don't flow any air and the exhaust manifolds don't like a bunch of overlap. that's more cam than i'd consider for a stock build. iron heads quit flowing air around .450" lift.

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Also from everything I have read, if you are going to run manifolds you need to stay with a cam in the 112 to 114 LSA to help the engine breath. Usually a custom cam is required. I would suggest calling them if you haven't already.

I have called Racer Brown but from all the research I may be using the 528 purple shaft mechanical it seems to work well with the manifolds

i use the summit 6401 in my power brake car. a howards 720141-12 might be ok. you'll need about 13" of vacuum in gear to make the booster work.

gtxno1 said:

I have called Racer Brown but from all the research I may be using the 528 purple shaft mechanical it seems to work well with the manifolds

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The 528 would be a good choice in my opinion.

BLK 68 R/T said:

The 528 would be a good choice in my opinion.

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The 528 is a small sold grind and after lash I don't think the valve see's 500lift not a great cam for someone that doesn't want too set the or check lash 2x a year.

Pretty good hydraulic cams that work with PB, and if you like the old Purple Shaft's. The old Six Pack cam or a step up the .474 also works well with magnum manifolds. Yea, there dated and there are other NEWER grinds out there but the old Purple Shafts are still pretty hard too beat for the money.

Biggest cam really recommended with a choppy idle, street machine,
stockish type converter, with a dual plane intake & a 750cfm carb
& stock style hp iron manifold & a solid lifter, like 10.5:1 compression 440ci

for example;
Rough idle power range 2200-6200 rpm, most at 4500rpm
Grind 21-231-4(single bolt) XS274S

Comp says int/exh
with those heads basically stock port "might" flow like 223cfm/Intake &
@ 0.500" gross valve lift {best case scenario}

274/280 advert. duration
236/242 @ 0.050 w- 0.016/0.018 lash
0.502"/0.511" gross lift net would be/less lash
Lobe centerline 110*
Intake centerline 106*

Iron HP exhaust manifolds kills the power 364hp @ 4500rpm
& 393hp @ 4500 even with a small tube headers & thru the mufflers

try going to Comp Cams & download the Camquest6 software
you don't need to use their cams, you can change variable too,
it's just to get an idea what small changes "can/could possibly theoretically make"
"BALLPARK #'s" it's not all encompassing/for every combo but it will help some...

you can do custom heads flow rates, change compression, exhaust types/sizes,
solid/mechanical, solid roller, hydr. flat tappet, hydr. roller, carb size,
intake manifold types, etc. etc. etc.

good luck

Thanks I will try that

Whatever you decide to do for a cam whether it be a solid, hyd, or a roller type. I would strongly suggest that you talk to reputable cam company and go over your engine/car specs. You will want a minimum LSA of 112* if you are going to run stock iron manifolds in order to get the most out of the engine. Also the wider the LSA the more vacuum it will make.

Good luck.


Wes