BORE SHROUDING TEST: 4.03" vs 3.91" Edelbrock RPM Heads Really Fit a 318? Project Mission Impossible

[MOPAROFFICIAL]

Every build they do... someone should copy it and leave out the "tricks$"
Compare the power. ... then do something like add a cool can to the fuel line ice packs on the intake and see if you recreate that two horsepower you lost... if you even did lol
Remember they are talking flow bench horsepower and not dynoed horsepower. What you see is not always what you get

 

[Newbomb Turk]

What I find appealing is bore notching, offset dowels and **** like that are RACE modifications.

If you are doing this on something that isn’t max compression, race rpm (that means your standard 7k and below street **** isn’t race rpm), max effort induction and tuned headers you are pissing directly into the fan.

You can find way more power for far less effort than doing that.

I say this because the “street” guys constantly ***** that not everyone is building a race engine yet when Wood or Vizard drop a nonsensical modification video the street guys all think they can do a simple mod and rotate the earth.

I have little respect for Wood or Mr Vizard any more.

BTW and FWIW it’s worth, this all started with another internet/youtube god who isn’t a machinist or an engine builder or even a half assed competent tuner.

Just garbage all around.

 

[273]

Here's the 2.02 in the 318 bore, looks to me if you offset down the valve would be more towards the widest part of the bore, or maybe it's just the angle of the picture.

 

[318willrun]

For all the work and money spent, it's no longer "mission impossible". Should change the name. It should be called "it better or else".... It's a 318. You want 2.02's, bolt 'em on. You want to fuss about shrouding, get a 360 (dime a dozen) and bolt on the eddy's. Goodness, we had 2.02's on 318's in the '80s'. Cars ran great.

 

[Newbomb Turk]

Here's the 2.02 in the 318 bore, looks to me if you offset down the valve would be more towards the widest part of the bore, or maybe it's just the angle of the picture.

View attachment 1716489034

Here’s a small fact.

The junk 23 degree Chevy head has the valves open OFF the center of the bore.

The 18 degree Chrysler head has the valves open on the CENTER of the bore.

What dies that mean?

For the same size bore and valve, the Chevy shrouds the valve sooner and more than the SBM.

I’ve run 2.055, 2.080 and 2.100 valves on a 4.04 and made more power every single time.

And I never notched a bore, never used offset dowels. Ever.

And the 2.08 and 2.100 valve engine both made 2 hp/cid or better.

How many articles, videos and YouTube hacks have you seen where the SBC guys notch their bores? I’ve seen NONE.

The biggest valve I use on 23 degree Chevy junk is a 2.08. Never notched a bore or used offset dowels on those either.

Never lost power with the bigger valves on that junk either.

 

[273]

Here’s a small fact.

The junk 23 degree Chevy head has the valves open OFF the center of the bore.

The 18 degree Chrysler head has the valves open on the CENTER of the bore.

What dies that mean?

For the same size bore and valve, the Chevy shrouds the valve sooner and more than the SBM.

Yes, I know

I’ve run 2.055, 2.080 and 2.100 valves on a 4.04 and made more power every single time.

Never said you wouldn't

And I never notched a bore, never used offset dowels. Ever.

And the 2.08 and 2.100 valve engine both made 2 hp/cid or better.

How many articles, videos and YouTube hacks have you seen where the SBC guys notch their bores? I’ve seen NONE.

The biggest valve I use on 23 degree Chevy junk is a 2.08. Never notched a bore or used offset dowels on those either.

Never lost power with the bigger valves on that junk either.

Never said you wouldn't.

So do you think a stock 318 bore wouldn't lose 15-25 cfm from a 250 cfm head across the board compared to a stock 340 bore ? And if you do if notching/blending gave back 75%+ of that flow it might be worth doing it ? To me it's just info, hasn't been back up or verified or dyno'd but might be something to think about if doing a 2.02 318.

No one is thinking this is info handed from God, I never seen anyone test flow in a 318 bore so it's somewhat interesting, that's all, don't know what the big deal is other than who's doing the test, if it was someone on here bet there be lot less negativity.

 

[MOPAROFFICIAL]

They should do set with 1.94 intakes and call it a day.

 

[273]

They should do set with 1.94 intakes and call it a day.

Cause their using Edelbrock heads for the build and trying to get some/all the flow back by going with a 318 bore, just cause they want to, it is what it is, I don't see the big deal.

 

[Newbomb Turk]

Yes, I know

Never said you wouldn't

Never said you wouldn't.

So do you think a stock 318 bore wouldn't lose 15-25 cfm from a 250 cfm head across the board compared to a stock 340 bore ? And if you do if notching/blending gave back 75%+ of that flow it might be worth doing it ? To me it's just info, hasn't been back up or verified or dyno'd but might be something to think about if doing a 2.02 318.

No one is thinking this is info handed from God, I never seen anyone test flow in a 318 bore so it's somewhat interesting, that's all, don't know what the big deal is other than who's doing the test, if it was someone on here bet there be lot less negativity.

Lose 15-25 CFM over what? Not notching the bore?

Im saying it’s BULLSHIT. I can’t be more clear.

I’ve never installed a larger valve and lost power IF the port could at least half assed support the valve area. Ever.

Guys are getting all worked up over flow numbers. That’s the best way I know of to lose power.

 

[Newbomb Turk]

Cause their using Edelbrock heads for the build and trying to get some/all the flow back by going with a 318 bore, just cause they want to, it is what it is, I don't see the big deal.

I’ll tell you what the big deal is.

Too many guys will fuckup the notch and LOSE power.

The 3-4 CFM might, MIGHT gain you 8 hp. And that’s on a well sorted, well tuned engine.

Just ridiculous.

 

[273]

Lose 15-25 CFM over what? Not notching the bore?

3.91 VS 4.03 bore, there was 15-25 cfm loss

Im saying it’s BULLSHIT. I can’t be more clear.

I’ve never installed a larger valve and lost power IF the port could at least half assed support the valve area. Ever.

Again, No one is saying you would

Guys are getting all worked up over flow numbers. That’s the best way I know of to lose power.

Strawman, No one is

 

[Newbomb Turk]

3.91 VS 4.03 bore, there was 15-25 cfm loss

Again, No one is saying you would

Strawman, No one is

15-25 CFM loss with no notch to the notch? 100% horse ****.

I’ve spent more time than I care to remember at my flow bench and Im telling you my testing says Thats straight bullshit.

Buy a flow bench and test it for yourself. Or believe the garbage that Wood and Vizard are pumping out.

 

[273]

15-25 CFM loss with no notch to the notch? 100% horse ****.

I’ve spent more time than I care to remember at my flow bench and Im telling you my testing says Thats straight bullshit.

Buy a flow bench and test it for yourself. Or believe the garbage that Wood and Vizard are pumping out.

Whatever

 

[Newbomb Turk]

Whatever

Exactly. I’ve been proving that shot wrong for decades.

So whatever.

Better yet, buy a flow bench, test it out and build an engine with unshrouded bores and and shrouded bores and find out how much power you lose.

 

[fishmens67]

In the end Salter will show them how it's done. lol
I'm looking forward to his Mopar 383 600hp pump gas build.

 

[Newbomb Turk]

In the end Salter will show them how it's done. lol
I'm looking forward to his Mopar 383 600hp pump gas build.

It’s just like WTF? Bore notching isnt new. It’s not trick. It is what it is.

And BTW and FWIW you WILL lose CFM going from a 4.04 bore to a 3.91 bore and you can’t notch it enough to make it better. EVER. Especially if the rings are up on the piston where they should.

You can’t go deep enough before the top ring is running into the notch. And you can’t make it wide enough because you run into the fire ring.

Unless you use a gasket bore way too big which kills compression and makes the engine dirty.

 

[RAMM]

It’s just like WTF? Bore notching isnt new. It’s not trick. It is what it is.

And BTW and FWIW you WILL lose CFM going from a 4.04 bore to a 3.91 bore and you can’t notch it enough to make it better. EVER. Especially if the rings are up on the piston where they should.

You can’t go deep enough before the top ring is running into the notch. And you can’t make it wide enough because you run into the fire ring.

Unless you use a gasket bore way too big which kills compression and makes the engine dirty.

Back in the day Vizard was a huge proponent of addressing "crevice volume" , meaning he did NOT agree with things like bore notching so I find this strange. The last engine i did this bore notching to--was in 2009 and I've never done it since. It does lose power in the double digits and it does make it "dirty" as in poor VE/poor BSFC/poor BSAC. Bore notching is no bueno IME. J.Rob

 

[MOPAROFFICIAL]

Cause their using Edelbrock heads for the build and trying to get some/all the flow back by going with a 318 bore, just cause they want to, it is what it is, I don't see the big deal.

They could change the valve and a valve job..since they like to spend... remove all the seats for .010 oversized ones and start building around what works best for this bore size and less around those pos ootb edelcrocks...but had they just done some iron mag style heads, all this fruitless exploring wouldn't be necessary.
This isn't a well thought out build imo.
This is, to me, is just like the guy that has the "three-quarter Cam" and wants to build around it with a stock compression 318 engine.
Maybe Jizards last run with this 8 hole fleshlight they playing with

 

[Earlie A]

When I saw the results of the first 'masking tape' video I really had doubts about the validity of the testing, especially the 27 cfm difference that was claimed between the 3.91" bore and the 4.03" bore. This morning I finally got around to making a 3.91" bore adapter plate for the flowbench and flowing a stock Edelbrock head. I used an Edelbock 2.02 valve but with a back cut angle of 35 degrees. After flowing at 3.91" the bore adapter was recut to a 4.03" bore and flow tested again. The maximum difference was 6.1 cfm at 0.900" lift. The 27 cfm difference that Andy saw was because of the tape job, not the bore size.

Anyway, in my spreadsheet below pay attention to the handwritten numbers, not the typed numbers. In the column labeled 'Difference' the red numbers are where the 4.03 bore flowed lower than the 3.91. The green numbers are where the 4.03 flowed higher.

The second picture shows that the chamber of the Edelbrock head is only slightly larger than the 318 bore size of 3.910". The third picture shows the head properly located on the 3.91" bore adapter. The chamber does overhang the bore, but only slightly. Any amount of cylinder overbore will fix this mismatch. There is no need for any notching.

Last two pictures are the before and after shots of the bore adapter. It is made from Baltic Birch plywood which is a high quality pattern maker's plywood often used for jigs and fixtures. It has many more plys than a typical plywood (for additional stability) and is manufactured with waterproof adhesives.

 

[rumblefish360]

I meant with dowels...
Knowing someone would nit pick it, i edited to include offset boring.
I recommend for fun.. that you go to your local machine shop and ask them to offset your bores x amount each and pay attention to the look on their face as you say ask.
Next.. move guides .. and don't forget to reverse the pistons ;)

LMAO! That was freakin funny.

 

[Newbomb Turk]

When I saw the results of the first 'masking tape' video I really had doubts about the validity of the testing, especially the 27 cfm difference that was claimed between the 3.91" bore and the 4.03" bore. This morning I finally got around to making a 3.91" bore adapter plate for the flowbench and flowing a stock Edelbrock head. I used an Edelbock 2.02 valve but with a back cut angle of 35 degrees. After flowing at 3.91" the bore adapter was recut to a 4.03" bore and flow tested again. The maximum difference was 6.1 cfm at 0.900" lift. The 27 cfm difference that Andy saw was because of the tape job, not the bore size.

Anyway, in my spreadsheet below pay attention to the handwritten numbers, not the typed numbers. In the column labeled 'Difference' the red numbers are where the 4.03 bore flowed lower than the 3.91. The green numbers are where the 4.03 flowed higher.

The second picture shows that the chamber of the Edelbrock head is only slightly larger than the 318 bore size of 3.910". The third picture shows the head properly located on the 3.91" bore adapter. The chamber does overhang the bore, but only slightly. Any amount of cylinder overbore will fix this mismatch. There is no need for any notching.

Last two pictures are the before and after shots of the bore adapter. It is made from Baltic Birch plywood which is a high quality pattern maker's plywood often used for jigs and fixtures. It has many more plys than a typical plywood (for additional stability) and is manufactured with waterproof adhesives.

View attachment 1716490072

View attachment 1716490075

View attachment 1716490076

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View attachment 1716490081

Thank you for that. That’s exactly what my testing showed years ago.

 

[mygasser]

and that 6.1 cfm would be slightly less once the 318 block is bored 30 over like the 360 bore you tested.
neil.

 

[273]

When I saw the results of the first 'masking tape' video I really had doubts about the validity of the testing, especially the 27 cfm difference that was claimed between the 3.91" bore and the 4.03" bore. This morning I finally got around to making a 3.91" bore adapter plate for the flowbench and flowing a stock Edelbrock head. I used an Edelbock 2.02 valve but with a back cut angle of 35 degrees. After flowing at 3.91" the bore adapter was recut to a 4.03" bore and flow tested again. The maximum difference was 6.1 cfm at 0.900" lift. The 27 cfm difference that Andy saw was because of the tape job, not the bore size.

Anyway, in my spreadsheet below pay attention to the handwritten numbers, not the typed numbers. In the column labeled 'Difference' the red numbers are where the 4.03 bore flowed lower than the 3.91. The green numbers are where the 4.03 flowed higher.

The second picture shows that the chamber of the Edelbrock head is only slightly larger than the 318 bore size of 3.910". The third picture shows the head properly located on the 3.91" bore adapter. The chamber does overhang the bore, but only slightly. Any amount of cylinder overbore will fix this mismatch. There is no need for any notching.

Last two pictures are the before and after shots of the bore adapter. It is made from Baltic Birch plywood which is a high quality pattern maker's plywood often used for jigs and fixtures. It has many more plys than a typical plywood (for additional stability) and is manufactured with waterproof adhesives.

View attachment 1716490072

View attachment 1716490075

View attachment 1716490076

View attachment 1716490080

View attachment 1716490081

Thanks for the testing, that's what I figured before was around 6 cfm, seen a 305 VS 350 bore and they got similar.

Wonder why their 3-D printed bore inserts didn't show any difference, maybe the don't have the head in the correct location like they think they do, since he don't have the dodge plate.

 

[mygasser]

Thanks for the testing, that's what I figured before was around 6 cfm, seen a 305 VS 350 bore and they got similar.

Wonder why their 3-D printed bore inserts didn't show any difference, maybe the don't have the head in the correct location like they think they do, since he don't have the dodge plate.

and the 305 is less than 3 3/4" so much smaller than a 318.
neil.

 

[Earlie A]

Thanks for the testing, that's what I figured before was around 6 cfm, seen a 305 VS 350 bore and they got similar.

Wonder why their 3-D printed bore inserts didn't show any difference, maybe the don't have the head in the correct location like they think they do, since he don't have the dodge plate.

That would be my guess. I use pins to locate the head to the fixture, just like the pins used in the block.