304 Intake Manifold Swap - CommodoresPlus

This topic contains 160 replies, has 10 voices, and was last updated by Immortality 8 years, 1 month ago.

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August 22, 2016 at 6:20 pm #19214
exec24
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i still have some left, slowly getting rid of them via ebay

when i did count up the spare fittings i had left over they added up to a bit over $900 rrp

im finally down to the last 10 or so fittings
August 22, 2016 at 6:28 pm #19216
VRSenator065
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I am heading over the the Bendigo swap meet with the old man in November, thought I might take my box with me and see if I can flog some off there, along with the tons of other spare crap I have accumulated….
August 22, 2016 at 6:37 pm #19218
cava454
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Bring the car. U owe me a drive.
August 22, 2016 at 6:39 pm #19220
VRSenator065
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Don’t think that’s gonna happen (but the drive will one day)
September 6, 2016 at 5:42 pm #19466
Immortality
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So the last major piece of the puzzle has finally arrived

Now that I have that I can dummy fit it to the engine and start sorting out the wiring looms etc.
- This reply was modified 8 years, 2 months ago by Immortality.
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September 6, 2016 at 6:20 pm #19469
VRSenator065
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Looks great mate, gotta love that!
September 6, 2016 at 8:07 pm #19472
Immortality
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Yeah, I’m quiet happy I went with the billet alloy one instead of the cast alloy jobbie from Edelbrock.

This Aeroflow one is actually rated at 1375cfm even though it has the same venturi size as the Edelbrock @ 1.75″ but this one has much better tapered runners into the butterflies as well as the butterfly shafts have been machined down etc which may account for the extra rated flow? It really is a bit big for this engine but should be ideal for future plans.
September 7, 2016 at 4:23 am #19473
doz10
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looks the goods mate can’t wait to see it in the bay, not long now
September 7, 2016 at 9:54 am #19474
VRSenator065
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Just thinking out loud, is it possible to remove the linkage between the two shafts and just operate on one pair of butterflies in the current set up then go the full 1375cfm once you need it later on? Might be dumb ass, just thinking your would more or less double the air speed through the two throttles which might be happier at the lower power needs?
September 7, 2016 at 4:14 pm #19476
Immortality
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doz10 wrote:

looks the goods mate can’t wait to see it in the bay, not long now

Cheers, Some more braided lines and fitting to sort out for the booster vacuum and coolant bypass and it’ll be ready to bolt on.

VRSenator065 wrote:

Just thinking out loud, is it possible to remove the linkage between the two shafts and just operate on one pair of butterflies in the current set up then go the full 1375cfm once you need it later on? Might be dumb ass, just thinking your would more or less double the air speed through the two throttles which might be happier at the lower power needs?

That’s fairly much exactly what I’m going to do.

I can alter the secondary linkage to limit how far they open. I’ll use the MAP sensor to work out the optimum by how much of a vacuum it pulls at WOT through the rev range.
- This reply was modified 8 years, 2 months ago by Immortality.
September 7, 2016 at 4:44 pm #19478
VRSenator065
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Yep, so basically like a mechanical secondary 4 barrel carb. I was thinking it may have been easier tune wise if you totally disconnected them for now but sounds like you are onto it. Keep us posted, nice project!
September 7, 2016 at 5:06 pm #19479
cava454
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Will it effect air distribution?
September 7, 2016 at 5:10 pm #19480
Immortality
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Good question…. Don’t know but I’m sure the plugs will tell all.
September 7, 2016 at 7:11 pm #19482
VRSenator065
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Worked for vac seondary 4 barrels?
September 8, 2016 at 8:57 am #19495
Immortality
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Ordered more hose and fitting to do the coolant bypass and booster vacuum lines.

Never planned on any of this, things always get out of control when it comes to cars and modifying stuff…….

Going to hold off on coating the manifold as I’m contemplating getting another set of heads to give a quick port and mill the crap out of to get the CR up to make the cam viable that I’m intending to throw in at a later stage.

No rush at this stage as the job change has been put off (unfortunately).
September 8, 2016 at 8:58 am #19496
VRSenator065
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Lol, how quickly things escalate, you never end up doing less, just more and more and more…….
September 8, 2016 at 9:35 am #19499
Hoopstar
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VRSenator065 wrote:

Just thinking out loud, is it possible to remove the linkage between the two shafts and just operate on one pair of butterflies in the current set up then go the full 1375cfm once you need it later on? Might be dumb ass, just thinking your would more or less double the air speed through the two throttles which might be happier at the lower power needs?

Funny, I was speaking with Craig from Torque Power about this exact thing just the other day.

During some back to back track testing he did exactly what you’re suggesting and disconnected the secondaries in a 1000cfm TB and found the car ran no slower. His suggestion was to run one of CRD’s 750cfm throttle bodies.

Theoretically a 1375cfm throttle body will support enough air for a 304 turning at over 15,000rpm with 100% VE or a 355 at 13,000+ rpm.

Interestingly a 304 turning at 7,500 rpm and a 355 to 6500 rpm only require around 660cfm (at 100% VE) – around the same as just running the primaries only . If you do the calcs with a more realistic 85% VE of a nicely matched street engine, the 660cfm throttle body will support 8800 rpm (304) & 7500 rpm (355).

Just some food for thought and would certainly be worth some testing..
September 8, 2016 at 9:47 am #19500
VRSenator065
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^great info mate, I do think its easy to get caught up with “this is good, so more must be better.” Strett cars after all are a compromise.
September 8, 2016 at 10:24 am #19502
Immortality
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Good info indeed

Just doing some quick maths, the stock TB (65mm) has a surface area roughly 3318mm², a 70mm TB is approx 3848mm² (ignoring the butterfly shaft).

Each pair of the 1375cfm TB is 3103mm² so slightly less than the 65mm TB. So testing with the primary only is probably a good start. This TB has the butterflies opening inwards which is supposed to improve air distribution?

Interestingly, I’m planning on running the same cam as an associate but that engine is still running the banana’s manifold and 70mm TB and the intake is starting to pull a vacuum at high rpm WOT indicating the intake is restricting it.
- This reply was modified 8 years, 2 months ago by Immortality. Reason: add
September 8, 2016 at 1:46 pm #19507
Hoopstar
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Out of interest , what is the size of each bore on the 1375cfm throttle body?
- This reply was modified 8 years, 2 months ago by Hoopstar.
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