heads and intake for 427 sbc

[ptuomov]

I think it's fine to suggest a supercharger or ITBs, if they solve the stated problem and there's no constraint in the question saying no superchargers or ITBs. I suggested ITBs because they'd not only potentially solve the problem but would also be cool on a sports car, especially on a Corvette.

However, I think it's clear that once the original poster gives an "informed no" to supercharging, ITBs, or anything really, it's time to drop that topic.

Everyone should do what they want and what they can, and no more reason other than want+can is needed. It's a hobby.

[F-BIRD'88]

You could have and should have gotten the car and did some road testing while trying a few things out to solve the drivability problems at 2000 rpm in OD.
One being try loosening the valve lash to the max practical for that cams ramps. less effective valve duration and overlap.

Does that make it better?

I posted previously in your prior threads on this car on other
things yoy can try out. Did you try any of it?

To solve the drivability issues you have to try stuff.
Its not that hard.

[F-BIRD'88]

When the car owner gets a real all in cost estimate on a true 650 hp N /A
427 sbc he may revisit the practicality of supercharging
his car. Supercharging gets it ALL DONE at a affordable price and will last...

[F-BIRD'88]

If you want to try loosening the lash as much as it takes to
eliminate the drive surge at 2000 rpm just drive at low rpm
under 4000 rpm, and short term.
Do not rev the piss out if it with the lash opened up that much beyond the ramps... Then progressively close the lash up till the drive serge returns... You won't hurt it and will learn something usefull.
Again do not rev it way up. just test drive it.
Find the sweet spot.
Then yoy can measure the cam at that lash point and plan
you next cam... Cam king can help.
Its the true valve events timung that matters.

[RevTheory]

Something I'd personally be inclined to test, and I'll probably get strung up for this, is a 30* cut on the face (combustion chamber side) of the intake valve so the piston doesn't puke into the intake port as much as it approaches TDC.

That might be a decent approach if the customer is leary of more lift in his street car. If he's unwilling to up the lift to favor 50* seats, killing low-lift flow may solve the O/D cruise issue but fall short on his goal of increasing hp up top.

Just a thought...

[cpmotors]

im freshening a 427 cu sb i put together about 10 years ago for a street driven 69 vette. The engine was an 11 to 1 mechanical roller cam engine.250 260 on 106. dart 210 heads i ported that flowed 290 220 at 600 from memory and a super victor with a 750 hp holley. the engine made 565 hp at 6k and 550 ft lbs. I've talked about this thing on here before. It runs great but the problem is that with the manual 5 speed in overdrive its cammy and rough at about 2 k on the highway. Obviously the cam is the issue and i thought about trying a dual plane but the car is getting brand new aftermarket suspension and he wants more power in the 630 to 650 range.
in the interest of time constraints im going to replace the heads intake and cam. was thinking about dropping the compression a half point and going with around a 230 cc fully ported 23 degree head new taller super victor and a smaller cam around 8 degrees less on 110. looking for advice before i start oredering parts

fwiw- I used Chad's VFactor 2.5 Profiler heads on a 4.155" x 3.875" 420" combo, with a 2925 milled @ 2.75° to fit the 16" filter housing under the hood of a 1977 LeMans GT. 11.1:1 with a 237° @ .050" HR, .670"/.660" lift with 1.7 rocker, QFT 1050AN 4150 carb. It managed 604 observed @ 6400 and 560lb-ft observed @ 5000.

[turdwilly]

I think as this supercharger trend is evolving here on speedtalk.

The need for a forced induction category may be in order. Recommending superchargers in threads like this is absurd, and I'm not supercharger hater, I actually think their cool and own a supercharged car.

But the context of this thread(and many others) makes supercharger recommendations completely irrelevant and senseless.

Didn't help over on YB. They have a dedicated supercharged section yet it's the same there. Some people insist boost is the only logical direction, even when the OP has clearly stated that they want to stay normally aspirated, & will continue to try to convince them that they are just wrong for wanting to stay NA.

I'm just glad the LS crowd is finally beginning to realize that's a bad-ass platform that will run like a scalded monkey NA with the correct plan just like any other good platform. For years 90% said you have to boost an LS or they won't run...WTF

I will concede that the suggestion of supercharging may be more warranted in this thread, due to the original specific needs put forward by the OP. But again - they have stated that supercharging is not in the cards.

[gnicholson]

If you want to try loosening the lash as much as it takes to
eliminate the drive surge at 2000 rpm just drive at low rpm
under 4000 rpm, and short term.
Do not rev the piss out if it with the lash opened up that much beyond the ramps... Then progressively close the lash up till the drive serge returns... You won't hurt it and will learn something usefull.
Again do not rev it way up. just test drive it.
Find the sweet spot.
Then yoy can measure the cam at that lash point and plan
you next cam... Cam king can help.
Its the true valve events timung that matters.

yes i appreciated your thoughts and i was going to try more tuning changes but he decided he wanted the engine gone through at the same time hes getting the suspension updated. the stated hp goal is a little optimistic. job one here is to make sure this thing has no drivability issues .obviously the cam is going to have less duration and wider. if i can add more lift and intensity without hurting reliablity even better. ive talked to chad about the cyl heads and whatever i do im going with him. i was looking at the race prepped 215 afr .i would do alot more experimenting if this was mine but i have time constraints. i would love to add an eaton supercharger but thats not what he wants.looking to keep the cyl head and manifold on the small side

[kimosabi]

Have you considered a Quadrajet? I run a Qjet on a 10.7:1 500 hp 400 sbc, Performer RPM intake, AFR 210 heads and part throttle cruise is awesome. Runs mellow as a stocker on the primaries. Secondaries pop open it's like a damn Vtec engine and there's no so called "bog" what so ever. If anything they open too fast. Super response. A Qjet can support 650hp no problem.

[gnicholson]

i love q jets . i must have 50 stored here.

[F-BIRD'88]

The key to that was the Performer RPM dual plane intake with plenum divider.
A superstock Race prepped Qjet makes 650hp when on a 700HP superstock motor.
If you were to take the S/S Qjet off a S/S 350 SBC and replace it with say a 950 Holley
that motor would pick up a ton of top end power around 50hp.

On this motor I believe that he super vic intake is more than half the problem
at 2000 rpm part throttle. I believe a Plenum divider added to this intake will change its whole nature at
2000 rpm without giving up the farm at 6500rpm.
Going to a perf RPM intake would be a easy swap and also will be very different at 2000 rpm
and Not give up the farm at 6500 rpm either.
I bet this car has never been drag raced with this 427 motor.

You won't see the benefit gain in low low rpm torque (2000 ish rpm) , throttle response and drivability on a engine dyno test because the dyno can't load and pull the engine down that low in a stable loaded fashion,
but you will sure see the effect when you drive the car. The plenum divider's effect can be dramatic
on this single plane racing intake right at this low low rpm range.
It cuts the overlap reversion in half and doubles the signal to the carb at low rpm.

Q jets are great street/strip carbs. Thus my dual Qjet 6 venturi custom prototype set up.
GM/Rochester should have done this 6 venturi 2 center primaries/4 big secondaries in a single "Six-JET carb body in 1969 on the BBC 427-435HP engine. About 1300 cfm @1.5". Much cheaper production cost thus more profitable than 3 Holley 2bbls of a tri power induction. Minimal retooling of the existing 4 bbl manifolds plenum/carb pad for this Six-JET carb.
The resulting longer 6 BBL single carb body would allow more float bowl volume and room for a additional fuel inlet. 75 to 80% of the existing QJET carb parts would be used.

The Holley Barry Grant "Street Demon" carb is a good candidate for this Six venturi carb design too.
2 Google Valve secondaries with center primaries. Easily adaptable to existing 4 bbl intake with a bolt on carb adapter. Easy retooling of existing single 4bbl intake for dedicated "Six Shooter" intakes.

If you have 50 QJETS on hand, you can build and play with many dual Qjets prototype setups....
My Six Venturi setup (using 2 inline Qjets) is easy to do. The front primaries of the front Qjet carb are not used, not exposed to the intake plenum. It is strickly a secondary carb in this prototype.

[user-9274568]

im freshening a 427 cu sb i put together about 10 years ago for a street driven 69 vette. The engine was an 11 to 1 mechanical roller cam engine.250 260 on 106. dart 210 heads i ported that flowed 290 220 at 600 from memory and a super victor with a 750 hp holley. the engine made 565 hp at 6k and 550 ft lbs. I've talked about this thing on here before. It runs great but the problem is that with the manual 5 speed in overdrive its cammy and rough at about 2 k on the highway. Obviously the cam is the issue and i thought about trying a dual plane but the car is getting brand new aftermarket suspension and he wants more power in the 630 to 650 range.
in the interest of time constraints im going to replace the heads intake and cam. was thinking about dropping the compression a half point and going with around a 230 cc fully ported 23 degree head new taller super victor and a smaller cam around 8 degrees less on 110. looking for advice before i start oredering parts

fwiw- I used Chad's VFactor 2.5 Profiler heads on a 4.155" x 3.875" 420" combo, with a 2925 milled @ 2.75° to fit the 16" filter housing under the hood of a 1977 LeMans GT. 11.1:1 with a 237° @ .050" HR, .670"/.660" lift with 1.7 rocker, QFT 1050AN 4150 carb. It managed 604 observed @ 6400 and 560lb-ft observed @ 5000.

What did it make corrected?

[gnicholson]

The key to that was the Performer RPM dual plane intake with plenum divider.
A superstock Race prepped Qjet makes 650hp when on a 700HP superstock motor.
If you were to take the S/S Qjet off a S/S 350 SBC and replace it with say a 950 Holley
that motor would pick up a ton of top end power around 50hp.

On this motor I believe that he super vic intake is more than half the problem
at 2000 rpm part throttle. I believe a Plenum divider added to this intake will change its whole nature at
2000 rpm without giving up the farm at 6500rpm.
Going to a perf RPM intake would be a easy swap and also will be very different at 2000 rpm
and Not give up the farm at 6500 rpm either.
I bet this car has never been drag raced with this 427 motor.

You won't see the benefit gain in low low rpm torque (2000 ish rpm) , throttle response and drivability on a engine dyno test because the dyno can't load and pull the engine down that low in a stable loaded fashion,
but you will sure see the effect when you drive the car. The plenum divider's effect can be dramatic
on this single plane racing intake right at this low low rpm range.
It cuts the overlap reversion in half and doubles the signal to the carb at low rpm.

Q jets are great street/strip carbs. Thus my dual Qjet 6 venturi custom prototype set up.
GM/Rochester should have done this 6 venturi 2 center primaries/4 big secondaries in a single "Six-JET carb body in 1969 on the BBC 427-435HP engine. About 1300 cfm @1.5". Much cheaper production cost thus more profitable than 3 Holley 2bbls of a tri power induction. Minimal retooling of the existing 4 bbl manifolds plenum/carb pad for this Six-JET carb.

are you suggesting fabricating a complete sheet metal divider for the super victor?

[F-BIRD'88]

Yes make a plenum divider out of thick strong plate aluminum that fits in the Supervic plenum
so it is fully divided. Could be a (split or 4 hole) carb spacer with the plenum divider attached to it.
Best if it seals tight in the manifold plenum. The carb spacer supports the divider.
Make the plenum divider out of plenty thick material so its strong. There is a storm going on in that plenum
at WOT. This splits the carb volume of any one cylinder (and splits the reversion in 1/2) but that opens the door to a MUCH BIGGER carb, (or 2 4bbl carbs)
Thus the BIG 6 venturi setup.

Do not use thin sheet metal for the divider. The engine will eat it.
Use plate steel if making the plenum divider of steel. Again integrate the plenum divider into a carb spacer
so it is well supported in the plenum.

[F-BIRD'88]

Further: I believe a total solution will include a new roller cam with a bit less duration and overlap.

I believe CamKing would be a great source for this. He has a lot of powerful roller cam lobes to work with
to dial in your new cam to suit this car and how it is used.
Send him a email or a private message with all the info on this car-- engine so he can come up with a great new custom roller cam
that better suits this car. The car may well end up a quicker/faster car, all said and done.
It will have a much stronger and BROADER torque curve and operating RANGE.