Good evening, this is my first post as a new member on Moparts.

I am new to the Gen 3 Hemi platform and starting to gather parts for a new build. I am looking to build a 426 stroker based on a 6.1 block. I have a Molnar 4.080 crank, rods with .866 pins, Milodon pan, pickup, windage tray and oil pump. I have new apache heads as well. I am looking to build a carbureted engine in the 650hp plus range.


Can anyone tell me if the Edelbrock 7528 dual quad intake for early 5.7 heads can be adapted to apache heads? If so, would it be a serious bottleneck for the output I am looking for? I ask because I have a new one in the box. If it can't be made to work, is the Modman worth looking at for dual quads? I have seen mixed reviews on these, specifically being very poor on carb signal due to large plenum, as well as high rpm oriented due to short runners. If neither of these dual quads is actually a viable option with good results, I had looked at the Arrow/Prefix intake for a single carb.

What header size is recommended?

Camshaft?

I have many questions and know little of the Gen 3 Hemi at this point. I currently runa 408 W2 combo with a tunnel ram. Car is a mostly hot street machine that will also see strip action. Any input appreciated. The car is a 69 Swinger, 18 spline 4 speed, Gear Vendors, 4.10 geared Dana 60, and aluminum flywheel.

There is nothing wrong with my current combo, I'm just looking to kick it up a notch.

Holley Hi-RAM with dual quad top or Prefix Drag Pak copy.
1 7/8 headers
Others can recommend a cam, probably custom.
Sounds like a good combo and welcome to the board.

Thanks very much for the welcome message!

As for the HI-RAM or Drag Pak intake, I would be unable to use as they won't fit under my hood. I currently have my tunnel ram W2 engine hidden under a six pack scoop. I would consider a Hemi scoop for more clearance. I would take a slightly lesser manifold over bare carbs sticking out of the hood.

This is one of the issues with the G3 , Hood Clearance , HI- Ram and an EFI top will fit, The twin 4bbl top and a pair of Carbs ...it'll be siting in to the 6-pak scoop.
Edelbrock 2x4 Intake as a Carb intake , has some issues, cylinder's 1,4,6,7 run lean , the bend into the intake port is harsh. as for the intake conversion to square port , it can be done.
MOD man , as a carb intake, with 2x4 top it's ok doesn't have the lean issues like the Eddy , but it's down on potential, it's much better as an EFI intake,

A few years ack(2021-2022) we took a 417motorsports Hi ram/Modman adaptor (https://417motorsports.net/products/gen-3-hemi-mod-man-adapter-plate) used a blank Hi-ram top machined it for an old Kenn Bell Bigmouth 148mm TB to sit on top, it did what we wanted and fit under the hood in a 67 Cuda.......but For a Carb application , I think there might be TOO much plenum...Not suggesting it , just tossing it out there .

When it comes to the G3 , Intakes are limited, one of the reasons is the Intake port is horizontal , it's hard to make that turn and still have enough velocity to keep fuel in suspension.

OCPerformance (https://oc-performance.com/the_1st_single_4bbl_gen_3_hemi_dual_plane) has a dual plane intake that actually works well as a carb intake, power option wise it's better then Modman or Eddy's 2x4., it's 1,4,6,7 is just as sharp of an approach into the port but doesn't stall as much as the Eddy ( (EDIT , after re-reading your post, OCPerformance will not easily meet your 650HP goal)

I'm very pro Prefix Intake for any street carb application G3 ( https://store.prefix.com/products/arr-cas-1010-gen-3-hemi-non-efi-intake-manifold )
Holley's single plane (300-931) is on sale for under $500 at a lot of their approved outlets, it'll fit under the hood, it's not Ideal but it's a better power option than either the Eddy 4x2 or the Modman in Carb application. (EDIT , after re-reading your post, Holley 300-931 will not easily meet your 650HP goal)

Depend on the Power level you want, Prefix intake, holley 950 Howards SKU# 786965-13 (.626/.600lift 231/237 @.050 109 CL) and any of the OEM square intake heads , will get you 590-660hp depending on effort , same set up with the Eddy 2x4 your looking mid 500s (still nothing to sneeze at)



After re-reading your post,

Here's what I'd build(and have built) Aim for 11.5-12.50 compression , these g3s will run on pump 93 at that level of compression, don't need much more then 20-22 degrees of total timing.
.866 pins will be fine we've gone 810hp with .708 pins and 1.88 rod journals, that engine has almost 20k street miles on it.
Apache /BGE heads , send them to Katech ( great CNC program) for $1200 you get a legit 375 CFM @.600 lift. with some work and 2.18 intake valve, 400 @.700 is not unheard of....but keep in mind .650lift + at the valve is Not CHEAP and for your 650hp goal not necessary.
Stock rockers will be fine.
Sell that Eddy intake, use the money for a Prefix cascar intake, but you'll still need that 6-pak scoop......Holley 300-931 will fit under the hood and give you roughly the clearance as a SBM Holley street dominator, but reaching 650hp will be a choir , 590hp doable
Headers, don't be afraid of 2in primary , 1 7/8 will get you there and be fine . , you'll most likly not spin this thing high enough to need 2 1/8 primary.
Cams ; Off the shelf
I'm partial to Howards cams for the NON-VVT stuff and high effort G3 builds, Both their .600/600 & .626/.600 lift cams will achieve your 650hp goal
Comp Part# 112-305-11 is .633/.619, 224/234 @ .050 115 LSA works well with Apache/BGE heads makes the same power with the Prefix as the Howards, but with a Hi-RAM and 2x4s it'll make more then the Howards.
Comp part# 112-337-11 is .635/.635 229/221 @ .050 117 LSA , this cam revs to the MOON and is better suited for well ported eagle heads with a smaller exhaust valve , 1.625/1.63.
Custom cams,
Cam motion is the best cost/value , every cam I've bought from them when I cam doctor it , it's spot on ,
Powell Machine INC out of SC is another custom cam guy to talk to, I have not used any of his stuff yet, but we had a 440G3 dart block , 4.185X4.00 out of the box AFR BlackHawk heads on the dyno last month (12/16/24) that made 1.84 hp/CI on 93OCT with one of his cams , idled like an old school BBM with a MP .509 (108 LSA version) cam....yes 810hp @ 7400 , now we all now Dyno is different than real world installed results. but even if it only 750real world HP it's still better then most people will ever see out of a 440 CI BBM.

Thank you TAY, for the very informative post! This is just the type of info that I need.

I believe the HI-RAM with carbs would be far too tall for my six pack scoop. My current Pro Dominator W2 has little room for air filters as it is, the Pro Dominator is a short tunnel ram.

I see many of the Gen 3 Hemi cams have much wider LSA than I am used to with LA architecture stroker. My current cam has an LSA of 106. What is the relationship between LSA and these high flowing heads?

Thanks for the input.

From my experience the wider LSA's is due more to 90% of the G3 builds being Computer EFI , Emissions being a factor, OEM engine management is not a big fan of the narrow LSA . keep in mind the bread and butter sales of G3HEMI is computer controlled.

When Hughes Engines was still selling G3 cams, a lot of their cams had narrow LSA's a few 106&108's they worked great in carb applications but the few I used were hard to get a good solid Idle in 04-08 OEM hemi cars/trucks. they had a .645/.630 , 244/240 106 LSA install it at 104 CL and it would scream to 8k , make power up to 7700 in 413-430 CI engines.

There are several reasons new hemis tend to be a bit wider LSA than a wedge.

1. The valves can physically interfere with each other with too big a lobe and too narrow LSA because they open towards each other. In a wedge they could never touch even if you open both of them an inch.

2. During overlap on a wedge a small amount of air and fuel will flow from the intake valve swirl thru the chamber and go out the exhaust valve... in a hemi that air and fuel makes a straight shot right thru the chamber and out the exhaust so more of it blows thru there... A wider LSA reduces this. This combined with exhaust blowing back up the intake is what causes idle instability with a bigger cam or tighter LSA.

3. (or maybe you could call it 2.1)The fuel in an EFI engine is squirted right on the back of the valve when the valve is closed so that when the valve opens the fuel is sucked in first and then the air mixed with it. Too much over lap means the initial air fuel charge going into the chamber is very rich and since some of the initial charge goes out the exhaust this initial charge of fuel goes straight out the exhaust before the valve closes so you are actually trapping lean mixture in the chamber but the average mix going out past your O2s will be OK. Even with a carb the fuel will separate and puddle on the back of the valve while the air bounces back up the port.

Very informative, thank you.

What would be a favorable LSA for the application like I've described?

My 2 cents on the intake. The Prefix looks to be a good piece. My lightly massaged BGE heads (359 @ .600”) had zero loss when the intake was bolted to the head.

I agree that the Prefix CASCAR intake is the best choice for performance and hood clearance.
I've used both the OCP and CASCAR. The OCP worked great on a stock engine but my combo really liked the CASCAR.I would love to try the Hi Ram , dual carbs sticking out through the hood looks cool.

Thanks to all who have responded! Very good information being shared here.

It seems like the Gen 3 Hemi platform can tolerate more compression, and need less camshaft and timing than wedge LA engines to power.

Although I'd love a dual quad, I'm not willing to just for appearances if the performance isn't there. I'm leaning toward the Cascar manifold.from prefix. For exhaust I will look into 1 7/8 or 2". I have a Thumper 950 CFM 4150 carb I believe will be perfect for this.

Ive contacted Hughes about cams, waiting on a response. I was curious to see if any of their old grinds are available but perhaps no longer listed due to poor sales. I'm kind of wondering if a 110-112 might be a good range for LSA? As I did with my last build, I will contact a few grinders for their opinion.

My W2 setup is running great, I will continue collecting parts for the new build as the wallet allows.

Thanks again!

Used to run a 340 W2 combo in a dragrace car. Ran low 10's. Recently switched to Gen 3 Hemi, 426 cube, 6.1 block, Manley crank, Oliver & Diamond 12.5 pistons. Small custom hyd roller cam, only .618 lift, Apache heads -stock out of the box, no porting, stock valves, Pac springs, stock rockers and shafts, but with dragpak intake and 950 carb (did fit under my cowl hood) 2" TTIs. Made 780hp on a reputable 902 dyno. Dart weighs 2850, went low 9.40's and over 140mph 2nd time out. Still have some tuning and chassis work yet, but very impressed with G3 stuff so far. Shorter intake on this probably wouldn't hurt it to bad and still fit under your hood.

Are you willing to share cam specs? Thanks for your reply, sounds like a wicked combo!

It'll be interesting if Hughes gets back to you about a cam, they pulled all of the G3 items from their website 2 years ago.

They did respond. They have 2 Gen 3 Hemi cams left to sell, $200 each. A little smaller than I had figured I need unfortunately.

Something to chew on,

This Dyno sheet is of the 380CI 2005 5.7Block build (3.937X3.90), that’s in my 04 fat a$$ SLT ram , this past summer truck ran a best of 10.59 ,128MPH with pass at Island in Nj and Maple grove in Pa it ran a best of 10.65 @ 128mph , all on 93oct , truck is 4400lbs race weight , 1st pass is normally 10.70s @ 120s ,

Engine management system is the OEM 04 NGC3 ,Trans is a 727 all the normal 727 upgrades, 4500 stall, 4.88’s in a 9.25 rear with ford 9in ends(to eliminate the c-clips) Calvert GM1500 split leaf springs, Caltrac bars.

Engine , all parts were left over from different projects ,

Winberg crank , Honda 1.88dia rod journal , Pankl 6.24 C to C rods, J&E pistons with 12.5cc dome,.787 Pin DIA Pin height is 1.05, .009 deck clearance with .028 thick head gasket. 12.9 to 1 compression.

Eagle heads, 2.125X6mm Titanium intake valve, 1.60X8mm stainless exhaust valve. Chambers were enlarged to 74CC by “soften” the flat , basically a 5 degree pitch from the chamber to the head gasket DIA(3.95). upper part of the exhaust port was matched to a 1 ¾ round header tube, while the flat of the “D” shape was left alone. On the Intake side, floor was lowered by roughly 1/8th inch to the short side, sides were welded up to match pushrod pinch and the roof was filled in to remove the Spring pocket from the path of air flow. Intake port opening is 1.64X2.05 matched to a welded up Drag pak 4500, Fuel Injectors moved up about an inch higher on the runner, when I made the port opening in the head smaller , the OEM Injector path was blocked. that's how far the roof is lowered compared to stock. .....All said and done Flow is 340/240 at .650 lift.

Cam is custom grind, .635/.620 240/240 @ .050 112 LSA installed at 108. IN opens 4 BDTC, IN Closes 40 ABDC, EX opens 53 BBDC, EX closes 1 ATDC.

. this pile of used dyno mule's parts is 1.86HP/CI on pump 93.

Now that is impressive!

What were you going for with the port modifications?

To make the intake port constant, remove min cross section.

RIchard Holdener did a terrific video you may want to look at.

The Edelbrock actually looks like a good option: