Stock 1975 302 HP Increase Options

SamD · Aug 11, 2017

I'm about to install a new Vintage air AC system on my very stock / original 75 and and it is already severly under powered, so i would like to wake it up a little while maintaining the stock look. Would installing a new timing set, and cam while keeping the original heads, intake, carb, exhaust manafolds make a noticeable difference?

If so, is there a recomended Cam / timing set Kit that work well together?

This is a street only 75 with stock size wheels and tires with 3.50 rear end

Sam

Broncobowsher · Aug 11, 2017

Ford loved to put a retarded timing chain in during the 70's for emissions reasons. The 302 wasn't as bad, 4° retard. The big blocks got an 8° retard. Add in timing chain wear (and the nylon teeth falling off) and the cam gets really far behind. So if the engine is completely stock, just a new straight up timing chain will do wonders. And no need to get a new cam and do all the break in stuff to it.

If you are getting into a cam, expect to pull the engine. There is not enough room to the grill for the cam to come out. At that point you are going down the rabbit hole. The intake will already be off, and it won't breath as well as the new cam will. You can only fight low compression so much with cam timing, so how about a different set of heads? Some aluminum heads with a mild cam you can really bump the compression and wake up the engine. But now the bottom end is still original, you are so close you might as well freshen up the bottom end with some new bearings and rings. And a couple of bores just won't look good enough, bore it over and some new flat top pistons...

Just do a good roller timing chain and call it done.

englewoodcowboy · Aug 11, 2017

A new timing set would be a must. If you are going the vintage air AC route I would seriously consider stepping up to the explorer front dress. It gives you a much better mechanical fan that is clutched so it will free up some ponies when it disengages. I would also look at upgrading your radiator at the same time, if you didn't have cooling issues before, you most likely will now and WH sells a tight packed 4 core radiator and a full circle fan shroud. As far as power out of your motor, you won't get much until you address the anemic heads that they came with. You can find E7 heads off of a 5.0 HO fairly cheap and they will make a very noticeable difference. Adding to the upgrade you would also want to address the carb, a 4bbl will gain more power as well but if you go that route and are thinking one day you may want to go efi you will need to upgrade to a 4bbl intake. Your 2 bbl carb will be ok, maybe a little laking with head and cam improvement on the top end but should boost the torque (which is what you feel off the line etc.) on the bottom end. I would look at a decent RV type cam and if you care doing a cam swap, might as well spend a few extra and upgrade to a roller cam which will not be too much of a change in price from a new cam lifter set anyway.If you call comp cams and tell them what you are running, what heads etc. they have complete K kits which includes cam, lifters, timing set etc. I know this is a lot of info but you are on a very slippery slope when you are wanting to do upgrades fro power and performance. Bottom line if you are wanting to stay on the cheap side of things just do a timing set swap. I have not seen a set that was decent yet out of an original motor. Good luck resisting the temptation to make it run...

Timmy390 · Aug 11, 2017

SamD said:
Would installing a new timing set, and cam while keeping the original heads, intake, carb, exhaust manafolds make a noticeable difference?

Bad idea to change the cam and keep the stock carb/intake/heads. You might pick up a few horses with the cam and getting the timing advanced but the intake and head restrictions are going to hold you back so just not worth the effort.

You can get a set of E7 heads for cheap at the yard. They will look stock and preform much better than the 70's smog heads. GT-40's are around and GT40P's are all over the yards for cheap. Pull them off a running engine and go.

Intake, either go EFI or 4V intake and carb

Cam has lots of options....

Tim

englewoodcowboy · Aug 11, 2017

Tim is right with his info. Another avenue is to look at the packages Edelbrock sells which is a complete new top end kit, heads, cam intake etc all matched to work together.

blubuckaroo · Aug 12, 2017

I not going along with the pack on this...

If you were doing a complete engine rebuild, then things might be different, but I get the idea you're looking for more usable power rather than build a tire burner.

I don't think you need to go the route of heads with big valves.
If most of your driving is done in the lower RPM range, bigger valves, ports and carb won't help much.
The biggest problem with the factory small block Ford head is with the exhaust port. But even then you can get a great improvement with the proper cam, ignition timing, and a free flowing exhaust.

The heads you have aren't bad in that they have the smaller (more desirable) combustion chambers.

Many owners have eliminated the EGR on these cars. If you have the factory cam in the car, and it came with EGR, those things were made to work together. If you defeat the EGR function, your engine will have a tendency to ping. So now you have to retard the timing, and now have a poopy motor.

Best thing is to contact a good cam manufacturer for a recommendation. I've had good experience with Comp Cams. They will ask you questions about your motor, gear ratio, tranny, and vehicle weight/use, then make a recommendation.

And let's not forget the distributor. No matter if you have points or electronic, your distributor curve needs to be set up to work with your particular cam. The factory advance curve was just too slow and didn't get you full advance until you were way past your normal RPM range. Kits are sold with springs and weights to correct this. It takes a bit of fiddling but it's worth it.

Actually, for torque, one of the strongest 302 I've seen had E7 heads, small dual exhaust with manifolds, and a two barrel Autolite carb. I don't have the cam info, but damn could that thing pull! And it idled with a slight lope.

SamD · Aug 12, 2017

blubuckaroo said:
I not going along with the pack on this...

If you were doing a complete engine rebuild, then things might be different, but I get the idea you're looking for more usable power rather than build a tire burner.

I don't think you need to go the route of heads with big valves.
If most of your driving is done in the lower RPM range, bigger valves, ports and carb won't help much.
The biggest problem with the factory small block Ford head is with the exhaust port. But even then you can get a great improvement with the proper cam, ignition timing, and a free flowing exhaust.

The heads you have aren't bad in that they have the smaller (more desirable) combustion chambers.

Many owners have eliminated the EGR on these cars. If you have the factory cam in the car, and it came with EGR, those things were made to work together. If you defeat the EGR function, your engine will have a tendency to ping. So now you have to retard the timing, and now have a poopy motor.

Best thing is to contact a good cam manufacturer for a recommendation. I've had good experience with Comp Cams. They will ask you questions about your motor, gear ratio, tranny, and vehicle weight/use, then make a recommendation.

And let's not forget the distributor. No matter if you have points or electronic, your distributor curve needs to be set up to work with your particular cam. The factory advance curve was just too slow and didn't get you full advance until you were way past your normal RPM range. Kits are sold with springs and weights to correct this. It takes a bit of fiddling but it's worth it.

Actually, for torque, one of the strongest 302 I've seen had E7 heads, small dual exhaust with manifolds, and a two barrel Autolite carb. I don't have the cam info, but damn could that thing pull! And it idled with a slight lope.

Yes, I'm not trying to turn this into a tire burner, just trying to wake it up a bit, while keeping it as stock as possible.

The Thermactor has already been removed by the PO, as well as all the head plugs installed.

I will have the grill, alternator, PS Pump and the associated brackets off for the AC install, so I thought while I'm in there, it would be a good time to replace the timing set. And while I'm in there, it would be a good time to replace the cam if it would help. This 75 only has 30k miles on it, and it is very reliable so I'm assuming I would just replace the cam with a flat tappet cam. If I do that, what else should be replaced at the same time? Lifters and pushrods?

Sam

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jckkys · Aug 12, 2017

The cam timing is a big deal. The pre '72 289s and 302s were far better in part throttle low RPM than the later engines. The cam is the same, only the crank sprocket was changed. Ford screwed with the ignition timing too. A good distributor timing curve is by far the most cost effective improvement. See this article;http://www.fordmuscle.com/archives/2000/03/timing/index.shtml. These are more about tuning than modification so stock appearance is maintained. Race car parts are for race cars ie. full throttle high RPM, and not what a truck needs.

blubuckaroo · Aug 12, 2017

SamD said:
Yes, I'm not trying to turn this into a tire burner, just trying to wake it up a bit, while keeping it as stock as possible.

The Thermactor has already been removed by the PO, as well as all the head plugs installed.

I will have the grill, alternator, PS Pump and the associated brackets off for the AC install, so I thought while I'm in there, it would be a good time to replace the timing set. And while I'm in there, it would be a good time to replace the cam if it would help. This 75 only has 30k miles on it, and it is very reliable so I'm assuming I would just replace the cam with a flat tappet cam. If I do that, what else should be replaced at the same time? Lifters and pushrods?

Sam

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Did this engine have an EGR system? Is it still in operation?

jckkys · Aug 12, 2017

Ford put the same cam in 289-302 engines from 1963 t0 1975. It's a perfectly good cam for the EB application. In '72 the timing was retarded 4 degrees with a different crank sprocket. No change was made to facilitate EGR when it was introduced in '73. The 2100 carburetors may have been calibrated slightly leaner for EGR but the jets were the same size. My '77 simply ran better with more MPGs when the EGR was disconnected. A new timing chain and sprockets further improved performance. Finally, a good ignition timing curve got the '77 302 to run a little better than my '68 289. All this was cheap and easy. No visual difference from original. If you need to pass an emissions equipment inspection, just reattach the vacuum hose to the EGR valve.

blubuckaroo · Aug 12, 2017

jckkys said:
Ford put the same cam in 289-302 engines from 1963 t0 1975. It's a perfectly good cam for the EB application. In '72 the timing was retarded 4 degrees with a different crank sprocket. No change was made to facilitate EGR when it was introduced in '73. The 2100 carburetors may have been calibrated slightly leaner for EGR but the jets were the same size. My '77 simply ran better with more MPGs when the EGR was disconnected. A new timing chain and sprockets further improved performance. Finally, a good ignition timing curve got the '77 302 to run a little better than my '68 289. All this was cheap and easy. No visual difference from original. If you need to pass an emissions equipment inspection, just reattach the vacuum hose to the EGR valve.

Most of the cars I've worked on suffered greatly from disabling the EGR. Usually lots of pinging. The normal response is to retard the timing. Then the next complaint is poopy performance.
I really doubt that Ford used the same cam for all those tumultuous years.
Why would they change everything else to meet emission requirements and not change the cheapest item?

jckkys · Aug 12, 2017

I can't say why they did what they did. I do know, they did it. The cam part numbers are available if you need to confirm this. The part # was C3AZ-6250-V. The '76 cam with a little more lift than the C3 part stayed until it was replaced in '85. A perusal of my '72-'78 Motor Manual reveals endless schemes by all the automotive manufacturers to meet emission laws. None were up to it in any consistent way. Ford was no exception. Most if not all of the crap to make cars run poorly can be easily reversed. The inspections can only see if the emissions equipment is there. They do check to determine if the EGR is functioning. Simply reattaching the vacuum hose for the inspection covers that problem. My '77 never suffered from pre-ignition, even after advancing the initial timing to 18 degrees. I had curved the centrifugal and vacuum advances so the '77 factory set up may have caused pre-ignition if I'd kept it. I'll never know. Pre-ignition is usually caused by heat, too much compression, or overly advanced timing. The removal of EGR shouldn't change any of those things. I've run 2150 and 2100 carburetors on the same engine. They both work well and 2100s are simpler so I prefer them. Emissions inspectors don't know how to tell them apart.

SamD · Aug 13, 2017

jckkys said:
I can't say why they did what they did. I do know, they did it. The cam part numbers are available if you need to confirm this. The part # was C3AZ-6250-V. The '76 cam with a little more lift than the C3 part stayed until it was replaced in '85. A perusal of my '72-'78 Motor Manual reveals endless schemes by all the automotive manufacturers to meet emission laws. None were up to it in any consistent way. Ford was no exception. Most if not all of the crap to make cars run poorly can be easily reversed. The inspections can only see if the emissions equipment is there. They do check to determine if the EGR is functioning. Simply reattaching the vacuum hose for the inspection covers that problem. My '77 never suffered from pre-ignition, even after advancing the initial timing to 18 degrees. I had curved the centrifugal and vacuum advances so the '77 factory set up may have caused pre-ignition if I'd kept it. I'll never know. Pre-ignition is usually caused by heat, too much compression, or overly advanced timing. The removal of EGR shouldn't change any of those things. I've run 2150 and 2100 carburetors on the same engine. They both work well and 2100s are simpler so I prefer them. Emissions inspectors don't know how to tell them apart.

The good news is that here in Texas there are no emission tests for my 75.

My current timing is set it 12 degrees at idle, and @ 2500 rpm it is all in at about 34-36 degrees. I can't tell exactly because I don't have timing marks after 30 degrees. No sign of pinging on 86 octane at this timing setting.

Sam

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blubuckaroo · Aug 13, 2017

jckkys said:
I can't say why they did what they did. I do know, they did it. The cam part numbers are available if you need to confirm this. The part # was C3AZ-6250-V. The '76 cam with a little more lift than the C3 part stayed until it was replaced in '85. A perusal of my '72-'78 Motor Manual reveals endless schemes by all the automotive manufacturers to meet emission laws. None were up to it in any consistent way. Ford was no exception. Most if not all of the crap to make cars run poorly can be easily reversed. The inspections can only see if the emissions equipment is there. They do check to determine if the EGR is functioning. Simply reattaching the vacuum hose for the inspection covers that problem. My '77 never suffered from pre-ignition, even after advancing the initial timing to 18 degrees. I had curved the centrifugal and vacuum advances so the '77 factory set up may have caused pre-ignition if I'd kept it. I'll never know. Pre-ignition is usually caused by heat, too much compression, or overly advanced timing. The removal of EGR shouldn't change any of those things. I've run 2150 and 2100 carburetors on the same engine. They both work well and 2100s are simpler so I prefer them. Emissions inspectors don't know how to tell them apart.

There is a misconception that the EGR was meant to re-burn the exhaust to make it cleaner.

The EGR effectively slows combustion and lowers the compression by adding hot exhaust. That slower burn reduces hydrocarbons.
Believe it or not, that hot gas reduces pinging.
The hotter volume in the cylinder is more compressible than cold volume.

jckkys · Aug 13, 2017

I don't doubt that introducing a contaminate in the A/F mixture cools combustion temperatures. The problem is all the power produced in am internal combustion engine is the result of converting heat energy into mechanical kinetic energy. So with less combustion heat there's less mechanical energy or HP. EGR hurts fuel economy and efficiency. If pre-ignition becomes a problem, look at timing, compression ratio, octane, or engine heat. The reduction of hydrocarbons was the priority for political reasons. Nobody who drove vehicles made in the '70s thinks they ran better than '60s vehicles. Politics ruled the industry not consumer preference. EFI and forced induction have allowed us to have new vehicles that run well and meet the political mandates. This has made vehicles a lot more expensive and complex. I prefer the '60s style simplicity, but to each their own.

Broncobowsher · Aug 13, 2017

EGR actually helps economy, when working correctly. It increases cylinder pressure by filling the cylinder with inert exhaust. You are still running a small amount of air and fuel and will still make small amounts of power (this is part throttle stuff). But with the extra pressures, you get a little more work out of the combustion process. With a carb the tuning gets really funky but EFI it is simple programming. The inert gasses mixed in also soak up some of the thermal spike and reduce NOx (burning the nitrogen into the oxygen).

EGR is a great feature. But it is typically implemented so crudly and poorly in carbureted applictions it really suck most of the time. But let it go with EFI and good tuning, and half an MPG gain are known.

needabronco · Aug 15, 2017

For what your looking to do (stay as stock as possible), I would add an simple RV type cam like an Edelbrock Performer cam and timing set. When you change cams you must change the lifters as well. This particular cam usually comes with new lifters already. Don't forget to add a simple carburetor rebuild to the list, it's cheap and your going to re-tune it anyway. I would imagine a cam and a more efficient ignition would make your driving experience a little nicer.

SamD · Aug 18, 2017

needabronco said:
For what your looking to do (stay as stock as possible), I would add an simple RV type cam like an Edelbrock Performer cam and timing set. When you change cams you must change the lifters as well. This particular cam usually comes with new lifters already. Don't forget to add a simple carburetor rebuild to the list, it's cheap and your going to re-tune it anyway. I would imagine a cam and a more efficient ignition would make your driving experience a little nicer.

Sounds like a good plan. Any difference in timing sets. Any recommendations?

Sam

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nvrstuk · Aug 19, 2017

Here's the slippery slope and I'm the worst one for it as my two month fix is now nine months that I'm currently working on. If you are replacing the cam and the lifters check out the torque curve on dyno sheets showing the increase with the roller cam at lower RPMs right where you want your power I would go with a roller retrofit kit also and you will feel the noticeable difference with the roller cam over a flat tappet cam and you won't have any worries about oil that doesn't have zinc in it to protect your flat tapper cam for the rest of the days you own it.

Very easy they just drop right in to replace what you have

T-Stack · Aug 20, 2017

Working on a stock '74 302 currently. I have replaced the original timing chain with a double roller and used the 4 deg. advanced setting mark to make up for the factory retard. Is this a recommended thing to do for increased low end performance?

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