Ok guys, its been a while since I posted but I've been stacking parts pretty much all winter and I'm very close to ripping this thing apart and doing a bunch of work on it. Here's a list of what I'm doing mechanically: All new steering components and suspension all the way around including all control arms, bushings, bj's, etc. Lowering 2 inches all the way around. 1 1/8" front sway bar and adding a 7/8" bar in back. 18x10.5 rear and 9.5 fronts. 285/30 rear 255/35 fronts (yea I know they're a size smaller than typical) 4 wheel disk conversion 13.2" GT rotors in front 13" GT rotors in back. Wilwood master cylinder and proportioning valve. Stainless braided brake lines. New fuel tank and lines. 448/472 cam, lifters and valve springs. 1.7 roller rockers. Double roller timing set. Weiand Stealth Intake. Holley street avenger 570 4 barrell. Hooker headers. Champion Radiator w/ elec. fan. MSD style distributor and ignition box. There are some other small odds and ends but thats the jist of it. My question comes from the cam/heads department: Given my cam and roller rocker choice, will I need to worry about pushrod length/valve clearance? Also, I'm debating if I should have my heads ported, new valve seats and guides and what not? 72xxx miles on the original all stock 302... I will eventually (possibly 2 years away) switch to some aluminum heads so should I even worry about anything orher than the valve springs? Sorry for the essay of a post and thanks for any help ya'll might give me! I'm hoping to have all this done by late September so I can get some good seat time through the fall.
Can I get by with the cam I have and my stock heads with upgraded valve springs? I wont be doing aftermarket heads for a couple years... With the cam, intake, 4brl, and headers I have will my factory flowing heads hold a lot of power hostage?
you can find aftermarket heads for about what it cost to work a set of stock heads. and with them your headers will work a lot better. it just depends on your money and what you want out of the motor. with the stock heads the stock manifolds will be fine... again...JMO
I'm with Frank here. If you're going to pay for porting stock low compression iron heads?.. you're literally half cashed into a real set of higher compression aluminum heads. You may be ok on the ptv clearance(duration is often more an issue there than lift) since that doesn't seem like an overly large cam judging by the lift spec's alone. The stock pr length goes out the window with aftermarket roller rockers so needs to be checked for valve tip sweep pattern. Cast manifolds don't like added duration and extra overlap.. stick with headers but try to keep collector sizing on the smaller side at 2.5" rather than 3" if possible.
Yeah looks like I'm just going to bite the bullet early and pick up some aluminum heads in the next few weeks. Heard back from the machinist today and ya'll are right, damn near there on a pair of aftermarket heads so I might as well go for it. Finding the cash is going to be the hard part haha This is my first attempt at building a motor, let alone building/restoring a classic. I mean I've done all the simple bolt on stuff for years but never any internals and never really hunted gor big power gains, my main priority on my cars and trucks up til now has always been handling characteristics. In a nut shell, I might annoy the hell out of you guys with monotony over the coming months haha
I guess by big power I meant big power over stock output... I don't think 300-350hp/tq at the wheels is too much to ask for. I think that's kind of conservative based on the things I've read on this and other sbf forums. I'd like a reliable and fun weekend street car. Something like 3.55 or 3.88 gears but I'm thinking that the 25" tire will only exaggerate those gears and even the factory 3.00's. Is that correct?
don't know about conservative, that's about a "435 HP motor". more than a valve job, cam and headers... https://www.mk5cortinaestate.co.uk/calculator4.php
Frank is right, with just 302 ci a good set of aftermarket heads in addition to the cam, intake manifold and headers has the potential to make 350 - 300 HP/TQ respectively at the crank not at the wheels. My combination makes about 380HP. Members like groberts101 with great engine building knowledge can squeeze over 400 HP out of a street driven pump gas 302. But again, that is at the crank.
I feel like I'm getting schooled here lol I have no real world experience with this I'm simply going off of what I've read but I was under the impression that a mild cam, aluminum heads, nice intake, headers and a 4brl brings the car up around the 320ish hp range(at the wheels) but seems that might not be the case? When you say you're making 380, is that at the crank or wheels and whats your combination consist of?
Thanks for that link. I ran some numbers on it, says I need 380hp at the crank to get 325 at the wheels. 325 seems pretty conservative to me... I'm running more than a valve job, cam, and headers. I am also going to be running aluminum heads (per suggestion over factory ported heads) a dual plane intake and a Holley 570 4brl. But honestly, even if I can up around 300 at the wheels I would be ok with that. This is my first time at all of this and I'm not trying to do it the biggest and the best. I just want a fun street warrior. What would be your suggestion to get near 325 at the wheels?
At the crank. Check out my Garage posting on this site for full details: http://mmb.maverick.to/garage/1972-mercury-comet-two-door-1-of-34.4/
If you just arbitrarily pick some peak power number then you will get what you get for average power under the peak torque rpm for which a street engine will primarily spend most of its life. With smaller CID(short stroke) engines, the sweet spot can only be so wide and fat.. purely physics and if you want more then you must build a bigger air pump. If you want more peak power then the powerband must be moved upwards and the affect becomes much more lightswitch like with poorer street manners the higher you go. Smaller motors promote this effect more quickly since the cams get more aggressive as you go towards higher peak power numbers. RPM also beats up parts quicker and they tend to get more expensive to cope with the added rpm capability Trick is to figure out WHERE YOU WANT the meatiest portion of that power to be located on the tachometer.. and that is generally based on driving style and personal preference. Tall gears, short gears, average all-around gearing?.. motor needs to be built around the intended rpm sweet spot and the gearing chosen to suit so you stay in that meatier portion of the powerband. One mans race motor is another mans street motor.. so "power" is a very very subjective subject. The other thing to keep in mind is that these cars are lighter than most other old cars of the era by about 300-500 lbs so it ends up feeling like you have a bit more power under the hood than is actually there. Power to weight ratio is better than a Camaro or Mustang or whatever yardstick comparison you use. Another important factor to consider, especially with smaller CID motors, is gear multiplication factor.. trans gearing multiplied by rear gear ratios. So in that respect a 302 backed by a 4r70 trans(whose internals can be swapped into and AOD case) with a 2.75 1st gear and 4.11 rear gear will feel like an absolute beast compared to another backed by C4 with 2.46 1st gear and 3.50 rear gear while still cruising down the freeway at more leisurely rpm's. Based on the little info so far(and this is where you'll get in trouble when asking for internet recommendations), here's what I would likely do if stage building a budget based engine. IE; building the motors top-end first and bottom-end last. Fresh set of budget heads with smaller 58cc chambers(be aware that the budget/entry level stuff's quality control is all over the place so plan on disassembling and inspecting all clearances and parts fitment). Keep intake port volume around 190cc MAX or you will begin to soften the torque peak a bit more as the intake port gets larger and will lose more power under its peak(average power).. where most street cars tend to live their lives. 165-180cc is a very well known sweet spot for smaller CID motors needing better off-idle/part throttle cruise torque. Smaller ports will give slightly snappier throttle response too. RPM style air-gap intake Good quality double roller chain, roller rockers in the 1.6-1.65 range, .080" wall pushrods Cam in the 210-220 duration range @.050" lift.. around .500" lift to help stay away from the pistons. Smaller tube header with 2.5" collector size into mandrel bent exhaust and straight thru mufflers(or chambered muffler if you want it quieter despite the slight power drop) Higher stall converter(note that you will need to choose higher than advertised to end up where you want to be due to this smaller CID). 2,800-3,000 advertised will get you around 2,400-2,600 actual. 3.50 or 3.80 rear gear(with posi) depending on what you can tolerate for highway cruise rpm's. Taller gearing is softer off the line but better cruise rpm.. or shorter accelerates quicker but rev's more on the highway. Between the two is not a huge difference and more about tuning towards the engines final powerband characteristics and how you like to drive it. Later on when time and cash permits.. build a 331 or 347 stroker.. freshen this top-end back up.. maybe add a bigger cam to match the bigger CID.. and go have fun! Bout all I have time for.. hope it helps! PS. don't forget the new back tires.. you'll definitely need em'!
That is what I was going to add......lol. I have found that the motor my car came with ('68 iron 2v heads, 71 block, mystery cam, Torker 289 intake, holley 1850-2, hooker long tubes, 3.25 gear) after electronic ignition and distributor re-curve, wants to rev more than I actually have the nerve to do. I never had a V-8 with such a short stroke, and 5K is where my ears say "shift". So, even my less than optimum set up is turning out to push my boundaries of what I would normally do. I would guess I am close to 300 HP at the crank, but it feels like a lot.
