Hot Rod Forum banner
1 - 11 of 11 Posts

·
Registered
Joined
·
18 Posts
Discussion Starter · #1 ·
Hi.

I need a intake manifold that fits the ports on mu double hump 3782461 heads.

The intake ports are 50.30mm x 28.77mm something like 1.98" x 1.13".

Is there a intake manifold that match the ports?

If not I have read it’s important that the intake manifold has smaller ports then the heads, something about turbulence with sharp corners and edges.

The engine (327 with full roller) has dyno results 360hp @ 5700rpm with Edelbrock C3B intake with intake ports 49.45mm x 32.0mm (not a good match)

I have three intake manifolds on the shelf:

Edelbrock C3B intake with intake ports 49.45mm x 32.0mm (1.95" x 1.26")
Holley 300-38 Street Dominator with intake ports 43.2mm x 27.0mm (1.69" x 1.08")
Edelbrock performer 2101 47.75mm x 28.96mm (1.88" x 1.14")

I don’t have the time or tools to port the heads, but I can port a intake manifold.

Any suggestions on intake manifold, or a manifold that I can port to match the heads?

Or is it overrated to match the manifold to the heads with only 360hp?

Automotive tire Gas Automotive exterior Bumper Automotive lighting


Motor vehicle Hood Automotive lighting Vehicle Vehicle registration plate
 

·
Registered
Joined
·
424 Posts
You could simply gasket match the intake to the heads, odds are you will not find one already correct size for reason you stated. Small intake ports are better then port larger then the heads. For 360 horse probably not worth the effort, plus would not a big difference until you start getting to 5800 rpms and above and if you were looking to spin that high and higher you would be running a single plane intake.

I vote for run it as is
 

·
True Hotrodder
Joined
·
1,955 Posts
I have a Weiand intake for sale that is a great match for that set of heads - it was pretty much built for that engine combination.

 

·
Registered
Joined
·
15,301 Posts
The C3B is specifically made for the 461 head. It is essentially a copy of the GM, Corvette manifold that was used with those head’s.

You actually need to map the mate to see where there are misalignments, simply modifying the head ports or those of the intake without reliable and repeatable mating alignment may make matters worse than better. The physical dimensions themselves do not provide the needed information.

Bogie
 

·
True Hotrodder
Joined
·
1,955 Posts
The C3B is a good intake for a street car and if that's were the bulk of the vehicle's use is going to be then it's a good choice. One thing that works well is to take 4 bolts that fit the intake mounting holes. Drop the intake and gasket in place and screw the bolts in a few turns. Mark the bolts right where they come out of the intake. Remove them and cut them on those marks, then cut a slot across the top. Now you can use a screwdriver if you need too but it makes it real easy to keep the intake and gasket indexed to the heads while you work on it plus you can simply lift the intake on and off.
 

·
Registered
Joined
·
18 Posts
Discussion Starter · #6 ·
Thanks for all the answers.

Got some answers from Holley. The Weiand Street Warrior 8120WND, 8125 and 8126 have Port Size: 1.84” height 1.12" width. Good enough to port match.

Any toughs on those? My first reaction was the low RPM range, i have stall at 3000 so a higher RPM range should be better, maybe a carb spacer will do the trick?
 

·
Registered
Joined
·
18 Posts
Discussion Starter · #8 ·
You need to pick where you want that engine to live, you'll never have both ends of it.
The bottom and the heads will not be dissembled, new rebuild, i can change the intake and port it, some good torque att 3000 and rev to 6000-6500 would be nice.

Setup:


My experience with this motor is none, just bought it, build for a corvette, still not in the car. The engine has only done 3-4 hour in dyno since rebuild with intake C3B and Holley 650 DP before i bought it.

I have only removed the intake to take a look att the lifters and realized that the port on the intake was bigger then the port on the heads, so i thought i could fix this.


Block specs:
GM 3782870. Date May 27 1965 (E275).
Flint June 14 1965 (VIN F0614EA).
Line honed.
Crankshaft milled 10/20 and balanced.
New standard pistons and piston rings.
New main bearings, rod bearings and cam bearings.
New high-performance oil pump.
New timing set.
New thrust button & wear plate (retro-fit).
New solid roller lifters (retro-fit).
New push rods.
New hydraulic roller cam, Comp Cams Xtreme Energy 218/224 (XR270HR-10, 12-422-8).
New high performance oil pump.

Head specs:
Double hump 3782461, date I184 September 18 1964 or 1974.
Milled valve seats.
Cut spring pocket to fit COMP Cams 986 springs.
New full roller rocker arms.
Valves 2.02” and 1.60”.
New retainers and locks.
New COMP Cams 986 springs .540 lift.
Valve lash clearance 0.008”. (I think i will make this 0.004")


Other specs:
Intake Edelbrock C3B. (On dyno)
Mallory breakerless ignition distributor.
Accel Ignition Coil – SuperCoil – Street – Strip – 140001.
Accel Super stock 8mm spark plug wire.
New Holley 650 dp street hp.
Rear tires 255/60 R15.
Car weight 1790kg = 3946lb.
Exhaust: long tube Flowtech headers, 1-5/8" tubes , 3.0" collector, a 3” reducer to 2.5” X-pipe, two small simons sport mufflers.
3000 stall converter.
Rebuild and prepped TH350.
8.2" BOP rear with 3.73 with a limited slip unit. (Not build yet)
Will run on 93 octane (US) / 98 octane (EU).

Engine only ran in dyno 3-4 hours. [email protected] outside car before i bought it.

I am trying to get it to run a little better with port matching, that's all and a fun street car with Corvette engine. I know the 327 like to rev, but i don't know the limits with the heads and i still want to have som torque at 3000rpm.


617009
Font Parallel Handwriting Rectangle Number
 

·
Registered
Joined
·
15,301 Posts
You’re making excellent power for a 327.

The 461 head would more likely to be from 1964 rather than 1974. By 74 the 327 was out of production by several years and even though the fueling head were also used on early 350’s by 74 GM was focused on lowering emissions with larger volume, open chamber head’s, though fueling head’s were offered over-the-counter at the parts desk by Chevrolet.

In the U.S. these head’s have become rare, enough so there are some manufacturers making copies as they are a requirement in some racing classes so the supply of originals has been used up in the nearly 50 years since they were last used on a production engine.

Port matching is not as effective as thought of, certainly gone on maximum effort engines where rules or lack thereof permit it. That said the lesser disruption to flow is where the manifold edges are inside those of the intake. But this is a generality, the manufacturer may identify the need to present the opposite situation especially along the floor of the runner to either stall the lower flow to improve its ability to make the sharp turn into the valve pocket and or this may be done to reintroduce an identified flow of liquid fuel traveling the bottom of the manifold back into the air stream. So it is possible that “correcting” the manufacturer’s design will make performance worse rather than better. It is important not to get caught up in hot rodder theory as much of it is not correct and old ideas and habits unfortunately carry forward for decades long after being disproven to be effective.

In your case, well all such cases, it is necessary to know where the intake manifold actually aligns with the head. Simply having the passage dimensions is not telling you this. Thes things exist in XYZ, Euclidean space where face dimensions alone of the head and intake port s do not necessarily indicate their alignment. To figure this out you need to know what that alignment is which means you need a reliable and reportable means of getting these parts assembled and to mark where they align. Gasket matching is simply not going to get you there. This is hard to do with any accuracy.

zbogie
 

·
Registered
Joined
·
18 Posts
Discussion Starter · #10 ·
You’re making excellent power for a 327.

The 461 head would more likely to be from 1964 rather than 1974. By 74 the 327 was out of production by several years and even though the fueling head were also used on early 350’s by 74 GM was focused on lowering emissions with larger volume, open chamber head’s, though fueling head’s were offered over-the-counter at the parts desk by Chevrolet.

In the U.S. these head’s have become rare, enough so there are some manufacturers making copies as they are a requirement in some racing classes so the supply of originals has been used up in the nearly 50 years since they were last used on a production engine.

Port matching is not as effective as thought of, certainly gone on maximum effort engines where rules or lack thereof permit it. That said the lesser disruption to flow is where the manifold edges are inside those of the intake. But this is a generality, the manufacturer may identify the need to present the opposite situation especially along the floor of the runner to either stall the lower flow to improve its ability to make the sharp turn into the valve pocket and or this may be done to reintroduce an identified flow of liquid fuel traveling the bottom of the manifold back into the air stream. So it is possible that “correcting” the manufacturer’s design will make performance worse rather than better. It is important not to get caught up in hot rodder theory as much of it is not correct and old ideas and habits unfortunately carry forward for decades long after being disproven to be effective.

In your case, well all such cases, it is necessary to know where the intake manifold actually aligns with the head. Simply having the passage dimensions is not telling you this. Thes things exist in XYZ, Euclidean space where face dimensions alone of the head and intake port s do not necessarily indicate their alignment. To figure this out you need to know what that alignment is which means you need a reliable and reportable means of getting these parts assembled and to mark where they align. Gasket matching is simply not going to get you there. This is hard to do with any accuracy.

zbogie
Thank you for all the info.

I have looked up some dyno test with and without portmatching the intake manifold, its not mush to gain in those cases 1-3% hp.
The dyno test seems to gain more with a good intake like Edelbrock Air Gap 7501 or Edelbrock 2701.
 
1 - 11 of 11 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top