Ford 302 engine flow: Matching parts for street engine

Not sure where to go with the engine in the Molvo. It runs fine but feels a bit lazy. Scoots the best when I really put my foot into it. Gets about 14 mpg.

9.5/1 compression 

Holley 670 carb

Torquer air gap dual plane intake

Chinese alloy heads with 2.02 intake valves ( forgot what size exhaust)

Stock Ford Explorer cam

MSD ignition

I think, or at least I want to think ,that the Explorer cam is the  weak point. I have a line on an F303 cam and it is easy enough to swap in.  My expectations are that it will wake up the engine. At what cost to fuel economy I can't predict.

What I am looking for insight into is the large VS small intake valve theory when it comes to an engine that spends 99% of it time doing legal street driving stuff.  It may come to pass that I would be better off with stock iron heads than the blingy alloy bits.

Pete

The explorer cam is probably pretty well suited for low rpm street duty. If you do upgrade cams, I'd skip the alphabet cams all together, there's much better options out there. Have you done any carb tuning? What's the timing advance and curve like?

Carefully remove the Torker intake and smash it to bits with the largest sledge hammer you have.  That thing was awful in the 60s when they made it.  It was designed for weekend racers who needed a little edge at the drag strip, but the RPM range where it comes alive is so ridiculously narrow... like 4500-5000.  It sucks everywhere else, and even in that narrow range where it works better, it still kinda sucks.

Also, don't use any thing with an "air gap" for the street.  All manifolds will eventually get hot.  Air gaps are great for drag races where you can get that last 2 hp because you're only running 12 seconds at a time and the runners don't have time to soak up the heat.  On the street you want that intake hot and you want it to get hot fast.  Air gaps on the street can mean choke tuning issues and having to set things too rich to compensate for the 20 minutes it takes for the runners to get up to operating temperature.  If an engine has an exhaust crossover in the manifold, I leave it open.  I don't block it.  I want that intake HOT.  Do I lose 3 hp?  Yup.  Gladly.  Does it make my morning commute easier?  Yup.  Does it translate to 3 more MPG?  Yup.  A good dual plane will serve you well.  If you want to shift the torque up a bit and make those 3 hp back, cut out a 3" section of the plenum divider to trick it into thinking the plenum is bigger.

I will assume that the chinese heads are fair, but without knowing intake runner volume I can't make any recommendations.  If they're huge, you're mismatching the rpm range that you want for the street.  Any more info on them?

Cam opinions are like shiny happy people.  With the 9.5:1, I would pick something in the mid-200s or low 210s duration.  Anything more than that and you're looking at converter stall, gears, and other supporting mods.

Look up Melling 24110.  210/211, 115LSA.  I'm not a big fan of the 115 LSA but it will really make midrange shine and keep the idle smooth.  You could have them grid it on a 112 or 113 LSA to make a bit more top end and broaden the torque down low.

In reply to Curtis73 (Forum Supporter) :

Funny you mention getting the intake manifold hot quickly.  I have been told it's because a warm manifold will keep the air/fuel mixture from condensing in the passages.  Triumph (and many others) runs coolant through the manifold for this reason.  Instead, I end up in arguments with guys who want the manifold to be as cool as possible. Because racecar. Despite the fact they don't have a race engine nor are they racing. 

Subscribed to see how this turns out. I'm running the smaller of the chinese heads with a 180 intake runner and 1.96 valve. Trick flow stage 2 cam, 289 performer (hood clearance constraint), and 500cfm carb. I'm currently focused on the air cleaner and exhaust setup to try to pick up some power.

ross2004 said:

Have you done any carb tuning? What's the timing advance and curve like?

This is what I was wondering. OP mentioned various parts but not a word on an effort toward tuning.

In reply to NOHOME :

A Holly 670? Ain't that pretty big for that engine?

Like, not to bow and prostrate myself before the Altar of Curtis, but wouldn't a 2-barrel increase your air velocity?

I'll disagree with the "you want the manifold hot" brigade.  Plenty of modern engines do not plumb hot air or water through their intakes.  On SBC it was done for the carb choke.  Literally plumbed exhaust to the carb choke tubing to get the choke off.  I'm sure it helped the cars "warm up sooner" on cold winter days.  Modern electronics and fuel injection have made that thinking obsolete.

Now on a carbed 302, if you live where it's cold, OK, but if you live where it's never cold, forget it.

Edelbrock Torker Air Gap?  Don't think that's a real model.  Wondering what the intake actually is.

This sounds like a tuning issue to me; jetting a little off, perhaps, and I'm wondering about the ignition advance curve.  

I think the 670cfm carb is probably fine for this; slightly large maybe but not badly off.   This thing sounds like it's running rich to me.  Are the exhaust tips sooty?  

Been up and down and all around with the carb tuning to get it running as well as it does. Fires up and runs fine from cold with the choke doing what a choke does.

14 degrees initial timing with vac disconnected and 33  degrees all in by 3500 rpm or so. The actual ploted curve from one point to the other I do not have.

The alphabet cams are affordable in Canada and I am not sold on the self promoting features of the 302 cam gurus; no way to vet their almost evangelical proselytizing of their products. 

Mostly I think it is a flow velocity thing. Trying to understand how the larger valves might help or hinder the cause, but also realize that it might be the runner volume that is more important; both intake and manifold volume might  add up to a lot of air mass to react quickly.

Lots to ponder parts and budget wise. The good news is that it is working reliably and other than gas at over 6 dollars a gallon fun to drive. I just feel that there is more on the table.

I also don't see a reason to turn on one's nose, given the application and such, at a cam like the B303.  They made good power over stock when they were new and I don't see that cam suddenly being not worth dealing with.

That said, if you think you have a port velocity issue now, I don't think "more cam" is going to fix the situation.  

GIRTHQUAKE said:

In reply to NOHOME :

A Holly 670? Ain't that pretty big for that engine?

Like, not to bow and prostrate myself before the Altar of Curtis, but wouldn't a 2-barrel increase your air velocity?

I agree with part of this statement on the 670 being too much.    Can't agree with the 2bbl suggestion unless you want to sacrifice upper end power and get better fuel milage for lower rpm street commuting.

The standard formula for carb rating is {engine cubic inch x rpm x engine efficiency}/3456. (an internet search will find this.)   A 302 at 6000 rpm works out to 524 cfm at 100% efficiency.  80% is more like it.  That's 419 cfm.  For street driving I am thinking you should be in the 450 cfm range.

  A too big carburetor will cause bogging, high fuel usage, and velocities too slow for good atomization of the fuel.

In reply to jharry3 :

That has been on the back of my mind.

Still trying to wrap my head around how the large valve size plays into the velocity parameter. I dont really see it as a negative since it does not add air mass that needs to be moved. 

Quick internet searching (grains of salt required of course) says that the 1985 Mustang 5.0 used a 600cfm Holley carb from the factory.  Is this really that different from the 670 that's on there now?  

I don't think the carb itself (outside of tuning which is sounds like has been well attacked already) is the issue.  I'm happy to be wrong and I'm just some dude on the internet saying that and not some dude that will actually fix the issue(s).  So take this as such.

Curtis73 (Forum Supporter) said:

Carefully remove the Torker intake and smash it to bits with the largest sledge hammer you have.  That thing was awful in the 60s when they made it.  It was designed for weekend racers who needed a little edge at the drag strip, but the RPM range where it comes alive is so ridiculously narrow... like 4500-5000.  It sucks everywhere else, and even in that narrow range where it works better, it still kinda sucks.

Also, don't use any thing with an "air gap" for the street.  All manifolds will eventually get hot.  Air gaps are great for drag races where you can get that last 2 hp because you're only running 12 seconds at a time and the runners don't have time to soak up the heat.  On the street you want that intake hot and you want it to get hot fast.  Air gaps on the street can mean choke tuning issues and having to set things too rich to compensate for the 20 minutes it takes for the runners to get up to operating temperature.  If an engine has an exhaust crossover in the manifold, I leave it open.  I don't block it.  I want that intake HOT.  Do I lose 3 hp?  Yup.  Gladly.  Does it make my morning commute easier?  Yup.  Does it translate to 3 more MPG?  Yup.  A good dual plane will serve you well.  If you want to shift the torque up a bit and make those 3 hp back, cut out a 3" section of the plenum divider to trick it into thinking the plenum is bigger.

I will assume that the chinese heads are fair, but without knowing intake runner volume I can't make any recommendations.  If they're huge, you're mismatching the rpm range that you want for the street.  Any more info on them?

Cam opinions are like shiny happy people.  With the 9.5:1, I would pick something in the mid-200s or low 210s duration.  Anything more than that and you're looking at converter stall, gears, and other supporting mods.

Well said Curtis.  I typically go right past these types of questions because the person has a hodgepodge of parts and isn't really sure what he wants.  
 There are computer programs  that will tell you exactly what you have and how to get more of what you want.  But you have to do the work.  
         Guessing because someone said or you think, is sure to result in less than good. 
        That makes me sound like a curmudgeon.  I don't mean to be but it's impossible to help people like that. High lift long duration cams make more power but they do so at high rpm places you never go 99.9% of the time on the street. ( and if you do you should be arrested) 

 Same with big carbs, trick heads etc. basically you're trading practical for ego. 

NOHOME said:

14 degrees initial timing with vac disconnected and 33  degrees all in by 3500 rpm or so. The actual ploted curve from one point to the other I do not have.

I'd be running more total timing and in sooner especially since it's in a lightish car. Probably about 36 total, all in by about 2500rpm. That's based off experience with Mopars and Chevys mostly though, only had one small block Ford but would imagine they would respond similarly. 
670 carb should be fine, my friend's Falcon wagon with a mild 302, T5 and 3.70 gears ran great with a 650 double pumper and got nearly 20 mpg at cruise once we took a couple of jet numbers out of it. 
Would be interested to see the intake - the only Torker intakes I'm familiar with are single plane.

I'll trade you a nice set of iron GT40s for the Chinese aluminum heads. I've got essentially the same engine (torker 289 intake, e cam) I want more top end out of it and I'm happy to trade low rpm performance to get there.

maj75 (Forum Supporter) said:

I'll disagree with the "you want the manifold hot" brigade.  Plenty of modern engines do not plumb hot air or water through their intakes.  On SBC it was done for the carb choke.  Literally plumbed exhaust to the carb choke tubing to get the choke off.  I'm sure it helped the cars "warm up sooner" on cold winter days.  Modern electronics and fuel injection have made that thinking obsolete.

Now on a carbed 302, if you live where it's cold, OK, but if you live where it's never cold, forget it.

Which is exactly the point.  Why do you think carbs need a choke?  Because the amount of atomized fuel that actually makes it to the cylinders is far lower when they're cold.

And newer engines have EFI, so the intake isn't carrying the mass of the fuel and it has less effect.  The fuel is atomized by high pressure and laser-drilled holes.

And no, GM didn't plumb exhaust gasses to the choke.  Some of them used a tube that had a loop in the exhaust crossover to heat the choke, but they didn't use engine heat to "get the choke off."  They used engine heat as a reference for when the choke should start opening.  It wasn't done "for the choke," it was done to get the runners hot so it could signal the choke to open for normal operation.  Engines like to be hot. Drivers like them to be cool.

This was my job for decades.  Worked as a driveline engineer for some of the biggest names like Jesse James, Troy Ladd, Wil Sakowski and consulted on one of Carroll Shelby's BBFs.  Not tooting my own horn, just putting some gravity to my claims.  Can't tune EFI to save my life, but I can build a custom Qjet using a drill bit and some epoxy.

Ian F (Forum Supporter) said:

In reply to Curtis73 (Forum Supporter) :

Funny you mention getting the intake manifold hot quickly.  I have been told it's because a warm manifold will keep the air/fuel mixture from condensing in the passages.  Triumph (and many others) runs coolant through the manifold for this reason.  Instead, I end up in arguments with guys who want the manifold to be as cool as possible. Because racecar. Despite the fact they don't have a race engine nor are they racing. 

Exactly.  People do all sorts of wacko things to chase down the last 2 hp only to end up creating a nightmare tuning situation and long warmups.

Part of the reason for OEMs getting the manifold hot is for emissions, but for me, I want it as hot as possible and will gladly give up that 2 hp to get a driveable car and 2 more MPG.

The standard recommendation for a street manifold on the 302 is the Edelbrock Performer RPM.

670 carb should be fine. Holley generally require more tweaking out of the box. Are we sure AFR is good?

I don't know that an F cam will fit with the bigger valves of the China heads. I know they are pretty close on a stock headed 302.

My first though would be to change the cam and make sure the tune is good and see where that lands you.

What heads are they? People have made good power on the NBKs, I'm not as familiar with the other Chinese castings.

The stock explorer cam is like a 176/197 IIRC. The 5.0 HO cam is a 210/210, quite a few people have good experience throwing them in a mild build. Summit has recently updated some of the Ford 303 cams and they are very intriguing to me. I found a summit guy talking about specific valve events they wouldn't change and ones they would. He claims they will make more power all over than their equivalent Ford version, will tuning very similar. I think they redid the e b and f. They are 8900 8901 and 8902 I think. I can find almost no real world results on them, but they have caught my eye. My current favorites for my similar build are the XE274, and the summit or ford versions of the b and e cam.

In reply to Opti :

Had not considered that valve clearance might be an issue. 

Need to go verify the manifold model, I know it is a dual plane and I know it is an air gap because of all the parts I have had to retrieve from under the runners, but been a few years since I stuck it on the engine and old memories are not to be trusted.

Starting to hear the siren song of a stock ls1 with a powerglide as a way out of this. 

The Explorer cam is less aggressive than a stock Mustang GT cam. Seriously, any of the Alphabet cams will be a huge bump. 

In reply to NOHOME :

NOOOO. No LS Swap, youve already got a sweet engine, cam it up and it will be a completely different animal.

In reply to Opti :

I guess that comment comes out of frustration and a realization that OEM solutions are always going to be the best solution.  I started this project with a pretty solid base in fabrication and bodywork, but little practical experience in drivetrain design. The 302 was picked as a well traveled road that would be easy to follow, but has proven to be anything but due to my inexperience and a lot of conflicting advice.