Another hood clearance issue 3947801 or 3963569 intakes?
09-30-2014, 07:37 PM
#1
Drifting
Thread Starter
Another hood clearance issue 3947801 or 3963569 intakes?
Here's my deal. I'm building a 454 to put in my 70 'vette with an M-20 and 3.36 rear. I located a good rebuildable core with a set of 781 heads for a great price. Intent is to run Probe 18cc dome forged pistons to get me around 9.4 CR. I'm still toying with cams but leaning towards the Lunati Voodoo:
•Advertised Duration (Int/Exh): 262/268
•Duration @ .050 (Int/Exh): 219/227
•Gross Valve Lift (Int/Exh): .530/.542
A quick run thru camquest says I should see 450HP+ and 500 lb-ft with headers.
I don't have an intake and the options are very limited with the stock BB hood (no I don't want an L-88). From all I've read only the old Street Dominator and Torker II fit. Not sure either one of those fit the bill for a fun street car. Obviously I can try and locate a factory 390HP Q-jet pancake intake (3947801). They pop up on ebay for $300-$350 now and then. The last option is the LS6 intake (3963569). It fits and they now make a repro for $299.
Seems to me the factory 801's small plenum volume and boundary layer drag in the ports would limit flow and the engine would run out of steam pretty quick. The port mismatch between the 569 intake and the 781 is well known, but between the two, it seems to me the increased plenum volume and larger flow area - accelerating into the smaller port - might a) give better flow and b) give more velocity to fill the cylinder.
Any engine gurus wanna chime in on an opinion between the two, or offer up some previously unknown short BBC intakes? No, Performers, Stealths, and Action Plus's don't fit (dammit).
Looking forward to your thoughts.
•Advertised Duration (Int/Exh): 262/268
•Duration @ .050 (Int/Exh): 219/227
•Gross Valve Lift (Int/Exh): .530/.542
A quick run thru camquest says I should see 450HP+ and 500 lb-ft with headers.
I don't have an intake and the options are very limited with the stock BB hood (no I don't want an L-88). From all I've read only the old Street Dominator and Torker II fit. Not sure either one of those fit the bill for a fun street car. Obviously I can try and locate a factory 390HP Q-jet pancake intake (3947801). They pop up on ebay for $300-$350 now and then. The last option is the LS6 intake (3963569). It fits and they now make a repro for $299.
Seems to me the factory 801's small plenum volume and boundary layer drag in the ports would limit flow and the engine would run out of steam pretty quick. The port mismatch between the 569 intake and the 781 is well known, but between the two, it seems to me the increased plenum volume and larger flow area - accelerating into the smaller port - might a) give better flow and b) give more velocity to fill the cylinder.
Any engine gurus wanna chime in on an opinion between the two, or offer up some previously unknown short BBC intakes? No, Performers, Stealths, and Action Plus's don't fit (dammit).
Looking forward to your thoughts.
09-30-2014, 07:50 PM
#2
Le Mans Master
Farrrrrrrr from an engine guru, but have you considered a chokeless Holley carb? Not sure the difference in clearance between your hood and my 77, but my 454 with Performer rpm intake, 750 carb, and a drop base air cleaner with a flat top offers plenty of room and then some. Car starts right up all the time. Just a thought, good luck.
05-27-2016, 09:31 AM
#3
There are guys over at the Team Chevelle forum running the cast iron version of that Q jet intake on LS5 Chevelle builds into the 11s...Also, that cam is too small IMO. You should be able to make 1.1 HP per CID, so a 460 (.030 over 454) should make 506 HP and a 468 (.060 over) should do 514.8 HP.
Last edited by c6silver; 05-27-2016 at 09:36 AM.
05-27-2016, 12:06 PM
#4
Safety Car
[QUOTE=69L71;1587944143]Here's my deal. I'm building a 454 to put in my 70 'vette with an M-20 and 3.36 rear. I located a good rebuildable core with a set of 781 heads for a great price. Intent is to run Probe 18cc dome forged pistons to get me around 9.4 CR. I'm still toying with cams but leaning towards the Lunati Voodoo:
•Advertised Duration (Int/Exh): 262/268
•Duration @ .050 (Int/Exh): 219/227
•Gross Valve Lift (Int/Exh): .530/.542
A quick run thru camquest says I should see 450HP+ and 500 lb-ft with headers.
I don't have an intake and the options are very limited with the stock BB hood (no I don't want an L-88). From all I've read only the old Street Dominator and Torker II fit. Not sure either one of those fit the bill for a fun street car. Obviously I can try and locate a factory 390HP Q-jet pancake intake (3947801). They pop up on ebay for $300-$350 now and then. The last option is the LS6 intake (3963569). It fits and they now make a repro for $299.
Seems to me the factory 801's small plenum volume and boundary layer drag in the ports would limit flow and the engine would run out of steam pretty quick. The port mismatch between the 569 intake and the 781 is well known, but between the two, it seems to me the increased plenum volume and larger flow area - accelerating into the smaller port - might a) give better flow and b) give more velocity to fill the cylinder.
Any engine gurus wanna chime in on an opinion between the two, or offer up some previously unknown short BBC intakes? No, Performers, Stealths, and Action Plus's don't fit (dammit).
Looking forward to your thoughts.[/QUclearence.
You Dont want a performer or it won't fit? We fit a performer 2.0 under a stock chevelle hood which don't have a hole lot clearness.
•Advertised Duration (Int/Exh): 262/268
•Duration @ .050 (Int/Exh): 219/227
•Gross Valve Lift (Int/Exh): .530/.542
A quick run thru camquest says I should see 450HP+ and 500 lb-ft with headers.
I don't have an intake and the options are very limited with the stock BB hood (no I don't want an L-88). From all I've read only the old Street Dominator and Torker II fit. Not sure either one of those fit the bill for a fun street car. Obviously I can try and locate a factory 390HP Q-jet pancake intake (3947801). They pop up on ebay for $300-$350 now and then. The last option is the LS6 intake (3963569). It fits and they now make a repro for $299.
Seems to me the factory 801's small plenum volume and boundary layer drag in the ports would limit flow and the engine would run out of steam pretty quick. The port mismatch between the 569 intake and the 781 is well known, but between the two, it seems to me the increased plenum volume and larger flow area - accelerating into the smaller port - might a) give better flow and b) give more velocity to fill the cylinder.
Any engine gurus wanna chime in on an opinion between the two, or offer up some previously unknown short BBC intakes? No, Performers, Stealths, and Action Plus's don't fit (dammit).
Looking forward to your thoughts.[/QUclearence.
You Dont want a performer or it won't fit? We fit a performer 2.0 under a stock chevelle hood which don't have a hole lot clearness.
Last edited by bluedawg; 05-27-2016 at 12:32 PM.
05-27-2016, 01:34 PM
#5
The Performer and it's similar cousins from other manufacturers aren't as good as a lot of people make them out to be (this is NOT about the RPM or Air Gap intakes). A BBC with a stock Q jet intake will make more low end torque than almost any other setup (up to around 3000 rpm anyway). A simple move like removing the front to back dividers and cutting a slot .500" wide x .500" deep between the secondaries of the carb will allow the engine to breathe much better, helping to equalize the stock intake to a Performer above 3000 rpm...it's a workable option for Vette owners unwilling to change hoods, and works with cast iron LS5 or LS4 intakes too...