On a Buick 350 with TA performance Stage 1 Dual Plane, and a stock Qjet, would a 1 inch spacer hurt low end torque?
No, it increases it. Longer plenum runs build velocity. Velocity is key to lowend torque at lower engine RPMs. The 350 almost always gets a kick in the but on low end (and better HP at higher RPM) with the correct spacer. And the spacer will allow some cross flow (like a modified dual plane) between plenums. A "carb adapter", say square bore, or two bbl, to q-jet or versi visey, is not the same thing. (Sez Cap'n Oblivious)
I've got one under my Qjet ( '69 350 , stock intake ) . no road test time yet . but it sounds good as it sits . I believe the general opinion on the 1" spacer is that it helps a little low and midrange . I had one so I figured i'd give it a try . adds a little plenum volume . I use a 1" 4 hole on my 360 dodge truck ( spreadbore and square bore ) , seems to run fine . open spacer ( on a dual plane intake like yours ) bad , 4 hole spacer good . i'm sure someone on here has a better road/track comparison for ya . maybe even some dyno info ?
Curious about this myself. Right now I have the cast iron intake with a QJet built by Mark N. One of these days I'll swap for my TA stage1 intake and was wondering if it would benefit from a spacer and which kind. Never used one before. I'm .2 from 13s so I'm trying to squeeze out everything I can to beat my buddy and his chevy
I've found in actual testing opening the plenum on a 350 either stock intake or TA will hurt low RPM torque and add very little to the top. Unless you have a huge cam and already no power under 3000 RPM don't waste your time. If you insist on using a spacer make it a 4 hole, NOT open. Plenum volume is not an issue on the 350 Buick. Not something you want to add more of.
Hey Mark, I'm @ 35* All In by 2400, 13 initial. I have tweaked the timing many times and think I found the sweet spot. Not sure if headers will give me a better time but I've since installed some hookers so we'll see. And I still need tires can't launch Full Throttle
Steve pretty much hits it on the head. Jason, as in any question about performance you need information about your complete setup to give a real answer. In my experience even though some people claim the 350 is loaded with torque you have to figure against what? A SBC? If you have gears, a decent converter, a nice sized cam and you're shifting at 5500+ the 1" open may be the way to go. Anything less and the 1" 4-hole is probably going to net you some low and midrange torque. On my fairly heavy '76 with 455 with a B4B, good stall converter, and 3.42's the 4 hole worked down into the low 12's before the open 1" finally pulled even. I run a 1000 TQ so that provides plenty of air and that may be a reason the 4 hole ran so well at that ET. I would say if you are not able to run mid-low 13's with a 350 then the open spacer is probably worth nothing at best. I've never seen a 4-hole spacer hurt the performance of any mild setup and almost always feels better down low. Matt, what tires are you running? My '76 used 255 60 15 M/T Drag radials right into the 11's. At that point sometimes traction was a bit iffy but sometimes it hooked great. My suspension is also very tight but it still hooks (higher rate lowering springs, big front and rear sway bars, handling shocks). Down in the low 11's I'm now running 295 50 15 DR's and I removed the front swaybar for a bit more suspension action. Headers have to be a good addition to that setup. The only spacer to consider with a stock intake is the 4-hole because of the possibility of reversion with all that metal in there for the air coming out of the carb to slam into. Of course with your stall converter low rpm torque shouldn't be your problem. Just thought I'd mention that longer runners add torque(like the extra 1" runner in a 4 hole spacer, not much but something) while a larger plenum may add top end power IF you need the extra volume, like if you had an undersized carb, but even a 750 Q-Jet is plenty on most 350's. Of course spacers are cheap and if you hit the drags try both kinds. Get wood or phenolic spacers for the heat reduction in the carb. I've spent wayyyyyyy more on junk that picked up nothing. If you can't afford a spacer you're in the wrong hobby.
I have a 1/2" wooden spacer, mainly out of necessity. '78 Qjet on a '70 intake with carb mounted kickdown, linkage would touch. Carb is noticeably cooler (but still warm) than the engine.
On Dave Visner's engine dyno, I had a two inch open spacer on my Buick. Dave told us to try one of their 2", 4-hole "super-suckers" he had in the cell. It didn't raise the peak HP or Torque numbers, but it brought the torque curve up and made it more of a flatline. He gave it to me. Still on the engine.
Seems opinion is on both sides. I know on alot of engines longer runners do help bottom end (I.E. the TPI.) I have also read and heard what Underdog and Smokey have said about spacers, that it actually doesn't help low end. I actually have a 1 inch plastic 4 hole, the holes match the Qjet. I didn't notice an improvement but other things were changed at the same time so its hard to tell. Someday when I have time I may take it back off, try and find my old manual choke wire to put back on, and see if I notice a difference going back.
General rule, the more high RPM oriented the cam is the more the engine likes plenum volume. Longer runners produce more torque. Cases in point 1980's TPI Chevy small blocks and 1990's Dodge 360 Magnum both had excellent torque but would not run much over 5000 RPM if that. It you measure the runner length on a 350 or 455 the runners are longer than most other engines of the era. No surprise they also make more torque than most engines of the era. Same with Caddy engines I would suspect. 455's are much the same as for the volume requirements. On a dual plane intake you likely won't gain much. They really love single plane intakes and huge carbs. Then you have to consider the major difference between the 350 and 455. The 350 is a long stroke and the 455 is a short stroke. In fact they have virtually the same stroke. Relative to each s bore size. This "draws" air in differently. Think of it as a gasp verses a deep breath. This makes the intakes requirements totally different. However both intakes (350 and 455) are very similar. This might explain why the BBB likes the shorter runner, open plenum and it really has not proven to help a 350 much. At least we have not seen anyone really make a difference with it yet. Matt 35 total and only 13 initial? keep the 35 total, limit your mechanical advance to 15 or 17 and add initial timing. It will make a big difference in response. Spacers are cheap and it doesn't hurt to try but you have to adjust the carb and timing to match. Get data, either dyno or track time. Butt dynos lie. Standard disclaimer all combos are different, don't blow it up, your mileage may vary, ETC, blah blah blah. Wow that's a lot of words. Now I know how Gary feels. Kidding G.
