Greetings. I would like to ask for some opinions regarding cylinder head selection. I am a fairly experienced engine builder / tuner in the Ford FE and MOPAR arena. Some SBC. This is for my 69 L-71 427. I bought this car as a near perfect, highly detailed restoration. The builder did incredible work, betond my abilities or patience in the complete restoration realm. The engine was done by a reputable builder. From what I have seen, things like over the nose geometry for the rockers, Guide plate clearance, , general build detail, show me that the engine was built by someone that gave a **** and had the correct skills. Here is where it gets off the rails a bit.

The engine codes as a 427 only block. It is set up correctly to the part numbers with the 2300 series Holley's and correct factory snowflake intake manifold. Digging deeper, the engine was built with an Eagle, forged rotating assembly. Flat tops, 030 over and stroked to 461 CI. Runs well. Reminds me of a just broke in, burly tugboat with a roller cam. Big torque, slow revving. Like a burly tow truck. Here are the build parameters.

- 461 CI (030 over 427 @ 4.155' stroke (net 461 ci) Block code 3955270
Edlebrock Performer RPM heads (PN 60555)
Howards Roller Cam (HRC CL120255-12) .578 /.618 (231-235 on a 108 C/L ) Installed as-ground
Comp Cams rockers (#1620) ultrapro 1.7 ratio
Ignition- MSD 6AL with MSD Pro-Billet (Curves are worked on distributor machine and on the numbers suggested by ()Tuned by Lars)
TKX 5 speed- 3:90 gears
Carbs-enrichment 10.0-13.5 AFR (Runs like a swiss watch, plugs perfect, all good. Stock vacuum pot springs on outboards. Comes in a lot late for my liking, but I have left it alone for now to lessen variabilities durning tuning
Exhaust- Ram manifolds through mandrel bent 2.5" tube to Borla 2.5" see through the middle muffs (Non-chambered)

My issue: Car runs flawlessly, but is missing what I am certain is about a 100 HP. Torque is excellent and will pull from idle smoothly. The rev limiter is set at 5800 RPM. Honestly, it feels like that is about where it wants to get pissed and start making serious steam. It is what I call a slow reving engine. Generally, I try to build a high lift, short duration valve event in the cam timing and that generally produces a very eager rev cycle into the engine. This engine while definitly not like steeping in poop, is just not where it sould be. Why they wanted to stroke a near perfect geometry engine makes no sense to me. But I don't know a lot about the BBC particulars. I fell that the issue lies in these cylinder heads. It starts getting excited right around the rev limiter. I have coaxed what I can from the timing figures. These heads spec as a 315CC intake runner with a 2.19 intake valve. Rectangular intake [ports.

I am looking at the Brodix Race Rite 26 degree head 119 CC chamber / 270CC runner-OVAL intake port. I am hoping to utilize the Howards cam that is in-place now. May I please ask the 427 guys tthat have some experience to weigh in on this? A big question mark for me is in swapping from the rectangular port that I now have to the oval port Brodix. Will the factory tri-power manifod and ram exhaust manifolds be ok?

 

I Have 427 with 115cc oval port 270 RaceRites under an oval port tripower with a CompCams LS6 flat tappet solid lifter cam with 1.8 rockers and all forged bottom end with about 11 to 1 compression. Mine will rev past my 6300 rpm rev limiter. If I get it on a chassis dyno I may pull the rev limiter off to see where it peaks, I figure its around 6800 to 7000rpm is where it will start to drop off. Mine loves to rev and pulls great. Some of those bigger heads are too big and will run out of signal and leave the top end soft. Do you know what your motor wants for flow and what its expected to do for HP. I built mine to be around 525hp-550hp and I think its there. The old rule of thumb was double the port volume was what you could expect to get for max HP. If your motor is expected to be in the 600-650 hp plus range then those old heads might have held. I know for my build the 270s are perfect. From what I have read you will be fine with the oval port head on the rectangle port intake with the proper gaskets.

 

These are what my numbers look like with a similar cam profile to yours with my 1.8 rockers.
What is your compression ratio and what are the specs on those Edelbrock heads? I know my 396 with the same cam on stock heads was a complete dog, but just swapping on my Brodix 270s, that motor would rev like a 327 on steroids...these heads are magnificient. I just dont know what they will flow for engine displacement requirements

 

I have heard bad reviews on Edelbrock flow numbers, have you searched other forums on those heads?

 

I found this Richard Holdner test I had bookmarked. He runs the 270s on big motor with prettty good results...6:30 time mark
towards the end he runs some Edelbrock RPM heads but they are CNC ported which isnt close to the same as a regular as cast head. It pretty much supports what I said earlier that those heads you have are probably too big

 

heres a good comparison

 

This is great data Mr Rogers (I live in a town called Rescue-kinda funny). Who did the FEA on this? Pretty compelling correlation to port velocity and power development. We (my somewhat educated and decently practiced tribe) all kind of anectdotally understand that suspended fuel particualte, remains that way as a function of velocity, but its just super bad *** to see it this clearly illustrated. I really appreciate you posting this up. If you do not object, I am going to use this as a teaching tool. I just did a long sit down with my son, explaining valve event timing. I was not getting through super well. The 1/2 speed relationships etc. Then it dawned on me. First, that I am actually a dumb, horny animal (proves my mother-in law is indeed correct-that bitch) and that an engine does not recognize anything but time. At least in relationship to events. Whatever needs to happen has to happen within a limited amount of time. So I took a clock and marked it in degrees, just above the numbers. Bingo. Lift and duration now make sense. To wit he says, "Is that why we have roller cams and followers, because with really high lift and duration, the angles are really steep and the other kinds wont follow as good without impossible spring pressures?" I wept openly...My son ladies and gentlemen.......My son.

 

feel free.... You should get yourself a Dyno Sim. I think mine is DynoSim 6. YOu can learn alot just from changing flow datat or cam data to see where things fluctuate from small changes. The second video I posted from Richard he exp0lains alot about mid range flow numbers where we live most of the time so you see why the numbers and HP goes up. I spend a lot of time studying and learning about this stuff and came up with my build by myself....I would have gone with AFR full CNC if I had that kind of cash, It took me a while to save up for those Race Rites..I also have a highly modified tripower setup. Its still the same cfm and oval port intake but I have mechanical linkage and accelerator pumps on all 3 carbs

 

Whoa. Did you mod out the 2300 series Holley from a center carb or hang pump bowls on the outboards? Im assuming you put metering blocks in as well? I have some serious hours with Holley metering blocks and a Bridgeport. Idle well bleeds, main well boosters, etc.. Sounds like a rightous project. I will def check out the digital dyno program. Car is proper. Sounds like a ripper.

 

The Edlebrock RPM series, from several sources, seem to be the lowest CFM numbers. They for sure seem to enlist a fair amount of bad press and cranky reviews. I had a long conversation with Kirk at Howard's Cams today. This was very enlightening and helpful. He is a wealth of historic data and know how. I can't recommend Howard's highly enough. Great quality valve gear, straight talk and in my opinion, probably the best total value in high quality top end components today. If one takes advantage of the technical support they offer, it is a no brainer. They are a big fan of the Brodix due to the quality of the castings / forgings. I have been at this awhile and remember when things like seat recession or rocker studs not staying put were a real problem. They still see this with several brands of aluminum heads. Almost never do they see it in a brodix head. That works for me. It looks like we are going to put in some really expensive solid rollers and go with a low-lash, solid set-up on my now hydraulic cam. I want really crisp response and this will help. They claim that a set up like mine will go 10-15K miles between adjustments with no issue. I dont plan to buzz it 6500 every day and a 3x per year lash adjustment is accpetable to get what Im looking for.

 

Ford bases on the outboards, had to drill the passages for the accelerator pump circuit, side hung float bowls, theres no idle circuit but i do use stock metering blocks. Cant use center carbs as they are onlyb325 cfm versus 350cfm on the stock outboards.
I do use a proform center fuel block that i modded to move the idle restrictors down to the mixture screw. Its supposed to up the circuit pressure. I also installed adjustable air bleeds so i can fine tune my AFR. As well as a light weight flywheel and a smaller fluid damper so it revs really fast.....

I also planed all the mating surfaces to eliminate any leaks due to warping. I did find that i had to use a sealant on the intake gaskets to keep oil from seeping into the intakes....big difference...

 

I dig it. Been drilling 10/32 brass screws with jet reamers eh? Lol. Super nice mod you did. Is the gang fully progressive, or does it open the outboards together at some center carb opening point? I got my hands on the diaphragm spring kits to tune these stock outboards. They seem way late opening to me. Reading the development papers for the Chevrolet L71 Tri-Power, it seems like it was a near pure marketing move. To be fair, the fuel/air distribution track is pretty good, the carbs are ok as well. Its the damned vac operated dead heads that leave a lot to be desired. You did an amazing job in working that out. Nicely done.

If this car was not so well and faithfully restored, The 4 48 IDA WEBERS I have in the shop would be getting the work up.

 

You would be better off with 50s. Im looking at 4 50 dco s. Mike Pierce used to own Pierce Manifolds. I ve had a few conversations with him and found a jetting calculator the goes by engine cid that corroborates what he told me. He said 48s are on the hairy edge for adjustments for a 427 like ours. I bought those springs and was adjusting usuing that route but it wasnt fast enough. I have adjustable progressive linkage that start around 5/8 to 3/4 pedal and are all fully open at wot.

 

When i had my 327 i had a hydraulic roller with solid roller lifters. Loved that motor to 7200 rpm....up until the rollers exploded...needle bearings....when i go back im using bushed bearings. Been looking at Isky lifters. They are about $1200 last i checked...but Im more isterested in the 8 stack and A/C before i pull the motor apart....but i would be pulling the intake........

 

I was just thinking of when i had the vacuum outboards and i could get them to open faster but without squirters they would bog then light off. If i got them tuned correctly then it was a smooth push and i wanted that instant kick in the head

 

well since you are already in there…. Take a good look at the Jones lifters. The best quality around IMHO. Roller followers, given pin lube capabilities, are all about machining and assembly tolerance. Slack be the enemy, especially for stuff that has a load and acceleration and change of direction. Aint it always the recip stuff? Jones builds a first class roller in either iteration. Risky Isky. I know his grandson. He ground cams and made billet rods for our IKF race karts. Good kid. Check out Jones. We used the Webers on 427 windsor Fords. The 48’s with the right chokes (venturi) were a monster mid range carb. Not at all happy with much cam overlap or dilution -reversion. But given a clean intake signal, I don't think a better carb exists for metering between 1500-5500 RPM. We didn't twist these into the soprano section. Generally, a 6k redline that lived a long time.

 

You got picks of your 8 stack setup?

 

Double

 

i do. I will snag some pics when back at the shop on Monday. Photobucket has a bunch of stuff I need to get. Thats how long ago we were doing Cobra’s. Pretty much everything comes out of Pierce Manifolds in Hollister California. These guys forgot more about Webers and custom intakes than the rest of us will likely ever know. And ridiculously helpful. If you want to hang a side draft on a Russian Rototiller, Pierce is where to find the stuff to make it happen. There was also a guy that took the Weber bodies and tucked a pencil injector into them. I think it was an Accel DFI. They looked really good and he did pretty much all the work on a Bridgeport manual mill. Unless you knew what you were looking for, they looked legit.