I have a 548 BBC on methanol, 14.25:1, afr 335 heads, 700 lift and 280 dur @ .050 112 LSA cam, and an edelbrock 454r intake. It's always ran well but I feel like it's always been a little lazy up top and was wondering if an intake with a larger plenum volume would help wake it up a little. Was curious if anyone has a similar combo and has played with intakes at all.

How many RPMs is "up top"?

7000ish

I'm sure someone much smarter than me like Top38 will reply but I'd say the cam and head are the limiting factor on this combination but I could be totally wrong.

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Originally posted by SP 124X:
I'm sure someone much smarter than me like Top38 will reply but I'd say the cam and head are the limiting factor on this combination but I could be totally wrong.

This /\ .700 lift and those heads are probably not enough to feed those cubic inches. I have dyoed some motors and when they reach max flow of the heads powerband dies off quickly.

I think a cylinder head on the smaller side tends to ET well, but maybe not make the big peak dyno number or good mph for the ET.

If you’re looking for more, I’d add a good 0.100 to that cam lift.

quote:

I have a 548 BBC on methanol, 14.25:1, afr 335 heads, 700 lift and 280 dur @ .050 112 LSA cam, and an edelbrock 454r intake.

What's it run ?? Weight ??

quote:

Originally posted by Lenny5160:
I think a cylinder head on the smaller side tends to ET well, but maybe not make the big peak dyno number or good mph for the ET.

If you’re looking for more, I’d add a good 0.100 to that cam lift.

Agree on both.

Someone at our track has a 582 with patriot 320 heads. It goes 7.50 @ like 174 with a 1.05 60’, lightweight driver.

How much intake vacuum does it build in high gear?
Post some time slips..

This is what it typically runs in decent air. 60 ft 1.249 330 ft 3.608 660 ft 5.608 MPH 122.59. Car weighs 3050. Vacuum in high gear I'm not sure but I'd guess around 10 to 12 inches.

Vacuum generated by the engine not the vacuum pump

quote:

Originally posted by B.C.Malibu:
Vacuum generated by the engine not the vacuum pump

What are you getting at? Plenum vacuum? No idea. I'd assume close to if not 0

This message has been edited. Last edited by: Jimmy Francisco,

I have a 540 with similar compression on methanol. I ran a heavily ported pro1 325 cc head for years, although it now has a 355cc pro 1. The cam I use has 780/.745 lift. Can’t remember the duration but I think it’s in the 290s. Lobe separation is 112. When I switched to the 355cc head it also picked up significantly. I’ve also tried a dart intake, and edelbrock (which I think was a super Victor) and a profiler over the years. The profiler worked the best in my opinion and what I run now. Net is if you don’t want to spend thousands on heads I think a cam would go along ways. I don’t have experience with your intake so can’t say if it is better or worse than anything I tried.

Yes plenum vacuum

quote:

Originally posted by rtpaske:
I have a 540 with similar compression on methanol. I ran a heavily ported pro1 325 cc head for years, although it now has a 355cc pro 1. The cam I use has 780/.745 lift. Can’t remember the duration but I think it’s in the 290s. Lobe separation is 112. When I switched to the 355cc head it also picked up significantly. I’ve also tried a dart intake, and edelbrock (which I think was a super Victor) and a profiler over the years. The profiler worked the best in my opinion and what I run now. Net is if you don’t want to spend thousands on heads I think a cam would go along ways. I don’t have experience with your intake so can’t say if it is better or worse than anything I tried.

Thanks for the input. From what I've seen if you're gonna error in cylinder head size it seems like the penalty is worse to go too big than too small. Part of the reason why I went with that cylinder head initially. It's very consistent and runs good was just considering an intake change because of how easy it is to swap (and relatively cheap). Might try another just for the heck of it. Can always go back if it doesn't like it

quote:

Originally posted by Jimmy Francisco:

quote:

Originally posted by rtpaske:
I have a 540 with similar compression on methanol. I ran a heavily ported pro1 325 cc head for years, although it now has a 355cc pro 1. The cam I use has 780/.745 lift. Can’t remember the duration but I think it’s in the 290s. Lobe separation is 112. When I switched to the 355cc head it also picked up significantly. I’ve also tried a dart intake, and edelbrock (which I think was a super Victor) and a profiler over the years. The profiler worked the best in my opinion and what I run now. Net is if you don’t want to spend thousands on heads I think a cam would go along ways. I don’t have experience with your intake so can’t say if it is better or worse than anything I tried.

Thanks for the input. From what I've seen if you're gonna error in cylinder head size it seems like the penalty is worse to go too big than too small. Part of the reason why I went with that cylinder head initially. It's very consistent and runs good was just considering an intake change because of how easy it is to swap (and relatively cheap). Might try another just for the heck of it. Can always go back if it doesn't like it

And sell it to the next guy who has always wondered. LOL

Based on the weight of the car and its current performance all the numbers look OK. I don't really see to much ET vs MPH.

As stated above, low rpm motor, small cam duration and lift, it's not going to like rpm. Another factor regarding rpm is the fuel and size of the motor. Alky could use a bigger intake and add those cubes it is possible that's the cork. Has it been ported at all? If you come across a Super Victor, may be worth a try. But it's also possible the cam is the cork,,, or a combo of both... If the car feels like its laying over before the finish line, it could be out of breath. To test that, try shifting at different rpms and see what the sweet spot is, look for the best MPH vs shift rpm.

For sure a cam and intake should wake it up.

quote:

Originally posted by Jimmy Francisco:
This is what it typically runs in decent air. 60 ft 1.249 330 ft 3.608 660 ft 5.608 MPH 122.59. Car weighs 3050. Vacuum in high gear I'm not sure but I'd guess around 10 to 12 inches.

Don't see anything lazy about those numbers at that weight!!Looks hard to beat....Shouldn't need any more rpm's.....

I agree with the previous post, those are very decent numbers for a 3050 pound car. At some point the search for extra RPM doesn't translate into better ET's, just more stress and possible failure of engine components.

Spend your hard earned money elsewhere, possibly vehicle weight reduction. Less weight to pull = Better results.

Bob

quote:

Originally posted by Jimmy Francisco:


Thanks for the input. From what I've seen if you're gonna error in cylinder head size it seems like the penalty is worse to go too big than too small. Part of the reason why I went with that cylinder head initially. It's very consistent and runs good was just considering an intake change because of how easy it is to swap (and relatively cheap). Might try another just for the heck of it. Can always go back if it doesn't like it

As for error on small side I disagree. From my experience if you have enough rear gear and stall converter go big and it will be faster. Now if gear is to high or a stall too low it will pull it out of powerband and really hurt it.

Sounds to me like it needs more cam and better flowing heads. I do not think an intake would help much because it is probably not the big restriction here. Certainly would not hurt it to try but I doubt it will help.