Fox Trick Flow 170’s on a 331 Stroker

[General karthief]

It can be very relevant to someone building their engine for a specific use. Most street driven hot rods that people build are not driven to the engines full potential or are over built with peak hp numbers higher in the rpm range where it is rarely driven.
since I drive on the street I want good torque down low so I can get away from traffic at a light,
I've read a fair amount of dyno tests on heads and intake comparisons and when using the same ci engine the difference in heads mostly comes down to just a few hp/torque numbers at different rpm ranges, same with intakes.
There are so many factors that need to be addressed when building an engine for a car driven in a particular venue (drag, autocross, top speed ect) but in a street car not so much. Yes you do need to plan the build so it works well with the rest of the car but to agonize over whether this particular head is better for a given cubic inch not so much. If he already has the heads then build the engine to fit the head, I think he would find a 306 with those heads and a cam that is matched to them it will be really fun to drive as long as the other factors are considered.
I am not a drag racer, I drive my crap in the real world where I know what I want it to do and it does it pretty good.

 

[from6to8]

It can be very relevant to someone building their engine for a specific use. Most street driven hot rods that people build are not driven to the engines full potential or are over built with peak hp numbers higher in the rpm range where it is rarely driven.
since I drive on the street I want good torque down low so I can get away from traffic at a light,
I've read a fair amount of dyno tests on heads and intake comparisons and when using the same ci engine the difference in heads mostly comes down to just a few hp/torque numbers at different rpm ranges, same with intakes.
There are so many factors that need to be addressed when building an engine for a car driven in a particular venue (drag, autocross, top speed ect) but in a street car not so much. Yes you do need to plan the build so it works well with the rest of the car but to agonize over whether this particular head is better for a given cubic inch not so much. If he already has the heads then build the engine to fit the head, I think he would find a 306 with those heads and a cam that is matched to them it will be really fun to drive as long as the other factors are considered.
I am not a drag racer, I drive my crap in the real world where I know what I want it to do and it does it pretty good.

Well said. Yeah and I'm like that to matter fact my cars are not daily driven but they are driven on the street on the weekends and a few times a week maybe. So in that regard it's not about trying to maximize the combination I need a lot of thought and some horsepower. So and the case well Kirk Kirk's opinion was too pretty much you know it depends on the budget as far as building a 3:31 or just doing a 3 or 6 if you are going to rebuild a stock block. And so I guess if you have the money then if you want the extra cubes it's going to help in torque and horsepower so if you can afford it I guess the best thing to do would take the 331 over the 306

 

[revhead347]

When talking about the heads by themselves, yes they can only flow one max amount of air on a flow bench. But saying the difference between said heads on a 306 cubic inch engine versus a 347 cubic inch engine is 0 horsepower, that literally makes no sense. Slap a Trickflow top end kit (stage 1 cam for discussion sake) on a 306, and you will net 280-290 at the wheels (most cases I’ve read). Put that same Trickflow kit on a 347 and you will net 330-340 at the wheels... How can you say all things being equal the extra 41 cubes nets a zero power gain? I’m lost here man.

I think the difference between the 347 and the 306 in that case is not necessarily the displacement. There are a few good dyno tests published over the years where it was done scientifically. That is to say that the exact same HCI was taken off a 306 and put on a 347, and the power difference was negligible. I don't think you will ever see 330 rwhp out of a TF stage 1 cam. Back to the argument I made earlier, when most people do an HCI combo on a 302, they want it to be all bolt on. That means, they aren't taking apart the short block to 0 deck for 10:1 compression, They aren't fly cutting the pistons to put an optimum cam in there, and that is why the engine only makes 280-290 wheel hp. Of course, if you are doing a stroker engine, the engine has been apart already, the compression ratio is going to be higher, and you are going to have a better cam.

So after year's of experience, we put a new engine in my friend's Cobra a few years ago. The goals were a little different than most, for one, we wanted all Ford parts. So we used Ford heads, even though the TFs are better. We also wanted to keep the Cobra intake, so that is a bit of a restriction. However, we did do all the other stuff. The engine has pistons with good valve relief, and 10:1 compression ratio, etc. The experiment did work, and the car put 302hp to the wheels. It makes really good low end torque, good power across the band, peak around 5300rpms, so perfect shift points, etc. We saved a few thousand over going to a stroker rotating assembly, and I don't think we lost anything by sticking with a 306.

Kurt

 

[General karthief]

Well said. Yeah and I'm like that to matter fact my cars are not daily driven but they are driven on the street on the weekends and a few times a week maybe. So in that regard it's not about trying to maximize the combination I need a lot of thought and some horsepower. So and the case well Kirk Kirk's opinion was too pretty much you know it depends on the budget as far as building a 3:31 or just doing a 3 or 6 if you are going to rebuild a stock block. And so I guess if you have the money then if you want the extra cubes it's going to help in torque and horsepower so if you can afford it I guess the best thing to do would take the 331 over the 306

Spending money on more cubes just because you can is not always money well spent. I don't know the rest of the cars combination like gears, trans, cam and the like.
Kirk makes a good point on that cobra build.

 

[from6to8]

I think the difference between the 347 and the 306 in that case is not necessarily the displacement. There are a few good dyno tests published over the years where it was done scientifically. That is to say that the exact same HCI was taken off a 306 and put on a 347, and the power difference was negligible. I don't think you will ever see 330 rwhp out of a TF stage 1 cam. Back to the argument I made earlier, when most people do an HCI combo on a 302, they want it to be all bolt on. That means, they aren't taking apart the short block to 0 deck for 10:1 compression, They aren't fly cutting the pistons to put an optimum cam in there, and that is why the engine only makes 280-290 wheel hp. Of course, if you are doing a stroker engine, the engine has been apart already, the compression ratio is going to be higher, and you are going to have a better cam.

So after year's of experience, we put a new engine in my friend's Cobra a few years ago. The goals were a little different than most, for one, we wanted all Ford parts. So we used Ford heads, even though the TFs are better. We also wanted to keep the Cobra intake, so that is a bit of a restriction. However, we did do all the other stuff. The engine has pistons with good valve relief, and 10:1 compression ratio, etc. The experiment did work, and the car put 302hp to the wheels. It makes really good low end torque, good power across the band, peak around 5300rpms, so perfect shift points, etc. We saved a few thousand over going to a stroker rotating assembly, and I don't think we lost anything by sticking with a 306.

Kurt

Did y'all port the Cobra intake? I thought about doing that as well with set up for the 94 Cobra but for right now I'm going to put the setup in my cig in that car and see how I like it. If I were to rebuild the later I might just do it 306 and port the Cobra intake and because I'm pulling the stock motor out of the car. If I were to keep the car and want to do a rebuild or later I'll definitely consider a lot of options here last to rebuild maybe use the Cobra intake and the trick flow heads long tube headers x pipe 75 mass air 70 throttle body 24lb injectors with a chip programmable tune.

And on a side note speech-to-text is super stupid

 

[General karthief]

Now here is something to consider, if you have the original engine in the 94 cobra I would keep the block and install it back into the cobra when you get your engine stuff sorted. That model was only for 2 years and they are/will be getting good money if the parts/pieces match.

 

[a91what]

I am going to politely disagree once again, lots of dyno sheets out there showing that a 347 with 170cc heads making over 400HP. A fellow over at the corral ran the 170 heads and tfs1 cam on a 363 with a bit of boost. made well over 700 HP to the tire.

I would like to read one of these tests you claim show a 0 power gain.

 

[from6to8]

Now here is something to consider, if you have the original engine in the 94 cobra I would keep the block and install it back into the cobra when you get your engine stuff sorted. That model was only for 2 years and they are/will be getting good money if the parts/pieces match.

is that block different than the GT's? I actually thought about selling the entire engine. Has 270 k. One older guy wants to go efi 302 in his 60' something car that has a v6. I thought about selling everything out of it to him. But also thought about keeping it in case i get rid of the car and someone wants the stock setup with the car.

 

[revhead347]

I am going to politely disagree once again, lots of dyno sheets out there showing that a 347 with 170cc heads making over 400HP. A fellow over at the corral ran the 170 heads and tfs1 cam on a 363 with a bit of boost. made well over 700 HP to the tire.

I would like to read one of these tests you claim show a 0 power gain.

Understood. I don't think those results are typical though. I'm going to dig and see if I can find one of those tests.

Kurt

 

[revhead347]

Now here is something to consider, if you have the original engine in the 94 cobra I would keep the block and install it back into the cobra when you get your engine stuff sorted. That model was only for 2 years and they are/will be getting good money if the parts/pieces match.

We actually did use the original block, but I don't think it matters much. There is some misconception about the concept of numbers matching cars. I am by no means an expert, but I have had to look into it before. There is no master list of part numbers that identify what part actually went in which car. The experts who evaluate cars for originality have general ideas of what parts could have gone into which cars, and by that logic make a reasaonble guess on whether an engine is original or not. Being that the shortblock from a GT was unchanged from 93'-95' and the same on the Cobra, I doubt anyone could tell.

The idea was to keep the Cobra as original looking as possible. The intake was ported by TMoss, GT40x heads that look real close to stock, etc. We also did some nice touches. We put an original distributor condom on it, it has an OEM battery, We milled the logo off a BBK throttle body, black ignition coil, and I even managed to stuff a 75mm PMAS air meter into the factory filter box.

Kurt

 

[revhead347]

I'm working on it. So far I have determined that this discussion has been taking place on Stangnet for almost a decade, as I ran across another thread where I mentioned the old MM&FF test back in 2010.

Will a 347 work with stock H/C/I?

So, another chapter in my little on-going saga to get my car reliable again, I believe I may have bad rings in the #1 cylinder on my stock/junkyard motor. I really don't want to spend a bunch of time/money rebuilding the short block, oy vey! Now, before go crazy with how stupid of an idea...

www.stangnet.com

Kurt

 

[revhead347]

This is the Cobra engine for anyone interested. I think we did go back and put an original appearance black ignition coil on eventually.

Kurt

 

[from6to8]

This is the Cobra engine for anyone interested. I think we did go back and put an original appearance black ignition coil on eventually.

Kurt

I can dig it

 

[96pushrod]

Understood. I don't think those results are typical though. I'm going to dig and see if I can find one of those tests.

Kurt

An engine with more displacement will always bring in more air and fuel for any given engine speed, that’s what the bigger cylinder is designed to do.

Possibly with a much bigger flow restriction than some 170cc heads could you see similar peak numbers with 302 vs 347 hp/tq numbers, just at different engine speeds, but that doesn’t happen often.

The bigger head will tend to make more power everywhere though when done correctly, but the 170cc will still get the job done.

 

[90sickfox]

I thought there is a partial vin on the block and a date stamp in the coding of the factory heads. Numbers matching means those numbers match the car....correct ? Even the hoses and belts have dates of manufacture printed on them. Every part ( just about ) has an incrypted date code. These codes are used to track defects for recall and tsb purposes. These are the things people look for in concourse and numbers matching cars.

@redhead347

 

[revhead347]

An engine with more displacement will always bring in more air and fuel for any given engine speed, that’s what the bigger cylinder is designed to do.

Possibly with a much bigger flow restriction than some 170cc heads could you see similar peak numbers with 302 vs 347 hp/tq numbers, just at different engine speeds, but that doesn’t happen often.

The bigger head will tend to make more power everywhere though when done correctly, but the 170cc will still get the job done.

In theory, it will bring in marginally more air from the pressure gradient difference. I doubt the pressure gradient difference would translate much into the real world. I'd rather spend that $1500 on dyno time, and suspension tuning at the track.

Kurt

 

[Noobz347]

date stamp in the coding of the factory heads

There are but they are the ones you are familiar with E5 blah blah blah, E6, E7... That portion is what dates them from what I recall.

 

[revhead347]

I thought there is a partial vin on the block and a date stamp in the coding of the factory heads. Numbers matching means those numbers match the car....correct ? Even the hoses and belts have dates of manufacture printed on them. Every part ( just about ) has an incrypted date code. These codes are used to track defects for recall and tsb purposes. These are the things people look for in concourse and numbers matching cars.

@redhead347

Like I said, I am not an expert. It's a range of parts though. Cobras and GTs were manufactured concurrently. The date range on the block could match a GT, or a Cobra. A good appraiser, looks at a car, acknoledges that the block was cast in April of 1994', and the body rolled off the line in June of 1994, and speculates that the block was most likely the one that came with the car.

Kurt

 

[General karthief]

is that block different than the GT's? I actually thought about selling the entire engine. Has 270 k. One older guy wants to go efi 302 in his 60' something car that has a v6. I thought about selling everything out of it to him. But also thought about keeping it in case i get rid of the car and someone wants the stock setup with the car.

the block has the the last numbers matching the vin on the car, a numbers matching car is worth more. They are stamped on a machined flat spot next to the gasket rail by the back of the manifold on the right side.

 

[revhead347]

the block has the the last numbers matching the vin on the car, a numbers matching car is worth more. They are stamped on a machined flat spot next to the gasket rail by the back of the manifold on the right side.

I'll have to check that out. Get my borescope out and look up there in the Cobra. Unfortunately, the block I used for my first 347 in my 95' came out of my 93' GT. The second block was a Motorcraft piece. Good things to know. I am definitely not the most knowledgeable person on how to match numbers on a car. Even though we did use the original block in the Cobra, I don't think it will matter much. There are still too many aftermarket parts in it. That is to assume that a numbers matching 94' Cobra will ever mean anything. We always assume that having an original car will have a good investment on return. There are so many cars that I thought would hold value. I told one of my friends never to change anything on his 03' Z06. That thing is a pumpkin now; just about couldn't give one away. I thought my Focus would hold value, and it's not doing well. I thought my MR2 would hold value, and lost it at the bottom of the market. You could wait 10 years to score a solid OEM MR2 now, and not find one, and if you did, you'd pay through the nose. Bottom line is that there is never a secured investment in a car. We simply aren't doing this for the money, and that's a good thing.

Kurt