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Discussion Starter #21
I have a 3000 stall speed and 3.73 rear gear. I was suggested a bullet racing cam
250/256 629 in 638ex 112 lsa solid roller camshaft and told running single plane and Holley xp 950 with my head should get to me close to the 700 mark. That's the only reason I was truly considering using the heads in stock form. I keep getting mixed reviews on them some say they are good others say they are Chinese junk
 

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Ok I have not PERSONALLY dealt with these heads myself, sorry. I know of a few guys that have and have good success. ARE they a GREAT head, no and YES there are better heads.

YOU HAVE THEM SO GET THEM CHECKED! If they can be used confidently by you people USE THEM.

That's the problem with the internet, ask 10 guys the same question, you'll get 10 different answers usually. And sometimes it's just people either not knowing how to do something, or not making $$$ or enough $$$ compared to another product or line THEY represent.

From what I recall, there cast in China and machined and assembled in the USA, I think in Alabama. Some people just really DO NOT like China anything. Now I'm NOT saying Scott is wrong, or biased or anything like that. We do disagree from time to time. He said my Flotek 290's went TURBULENT after .800 lift??? We my heads do NOT. And Chad Speier who set up my bare casting plus valves said the same thing.

I would get them checked and follow their head guys recommendation. Best bang for the buck there. Then go with a single plane intake, but most likely a bit bigger cam. Should be able to get real close to your goals....

Good Luck, John
 

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Discussion Starter #23
Ok with slight head work and single plane intake which would make the power range I'm looking for [675-725hp n/a) hydraulic roller or solid roller?
 

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I would run a solid. I have never used hyd roller with BBc. No SEARCH on this site sucks since the change and also going by my log-in, I couldn't find the thread. BUT I did a thread about low-lash solid roller that was quite informative.

You have a big heavy car. You need to run some RPM's out of that. As well as some gear to get it moving. 4.10's are MIN with that weight. AND they work well with nitrous.

So do a custom solid roller, low or tight lash, see about peak power about 6800-7000 BUT can carry the power well to 7200 to 7400 RPMs. Get a single plane with the puck so your not as bad on hood clearance, or a fogger. Might also want to look at the Sniper EFI for 800Hp. Call Bob at Madcap for 1 and get his advice on them too. The 950 is a small for a 540.

FYI the shop did a SBC 406 pump gas, street roller 20 yrs ago. It made over 680Hp BUT needed a 1150 Dominator. You goals can be done. Might need to be a bit creative, but can get there.
 

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Your goal is easily accomplished with the heads you have. Switch to a 454r and solid roller. As far as dont worry about flow above .800 comment that’s bs. No good head porter says that. It’s important. Not the most important thing but it is important because it tells the story of what’s happening in the port.
 

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Eric, you are correct that over .800 lift tells you something. But will will not effect and engine or cause problems when your running 640 lift cams? I simplified it more for here, but it's not a major concern on these milder BUDGET motors.

I have a pump gas motor posted here. GM 074 head GM 198 intake that we did the porting on. Has a .715 [email protected] .050 cam. So we should have kept working the head to .950 lift to worry about what's happening?? I'm not the head porter, my boss is. We DO look .050 past for obvious reason.

Please explain why one would look for what the flow is doing .200" PAST where max lift will be for these mild street car builds? INFO is always good. Thanks
 

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Eric, you are correct that over .800 lift tells you something. But will will not effect and engine or cause problems when your running 640 lift cams? I simplified it more for here, but it's not a major concern on these milder BUDGET motors.

I have a pump gas motor posted here. GM 074 head GM 198 intake that we did the porting on. Has a .715 [email protected] .050 cam. So we should have kept working the head to .950 lift to worry about what's happening?? I'm not the head porter, my boss is. We DO look .050 past for obvious reason.

Please explain why one would look for what the flow is doing .200" PAST where max lift will be for these mild street car builds? INFO is always good. Thanks
It has to with air speed. The typical reason a port backs up say at .800 is because the local air speed has now reached the point where the port can no longer sustain that speed. It doesn’t do at .600 because the port isn’t moving enough air to create the critical velocity in the troubled area. Now flowbenches only pull 28inches of vacuum. A live engine pulls much much more vacuum. So on a live engine you will reach the critical speed of the troubled part of the port at lower lifts because it achieves the dangerous air speed sooner. So on a bench it backs up at .800 but a live engine it might happen at .500.
 

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Ok that's understandable, thanks Eric. I see where your coming from and get the idea. Little different or maybe simplified more from what I was told by a few heads guys.

But like you said, MIGHT happen at .500! Then again might not till after .700 as well. differentiating design and combos will respond different. Foxwell keeps coming with the saying "it's the math." And that to is true to an extent. It's how one manipulates that math in a given application and gets rewarded with a better end result, correct.

It's like when a guy asks me "what's the peak tq and at what RPM on a drag race motor"? So peak RPM 10200(shift point) Peak Hp is 1432 @9700 and peak tq is 8400 @ 8100. So going down the track, the convert stall about 900RPM past peak tq. Launches about 9300, shifts at 10,200 and falls back about 7/800. This is fast NA stuff. And yes we still deal with some tq, the lower peak tq RPM is never seen though a run, therefore isn't much of a concern on if were killing off some tq for quicker ETs.
 
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