What would be the most lift that could be safely run on pressed in studs on sbc heads, 291s?
Max lift for pressed in studs
DV327
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The use of a stud girdle is required once you get into spring pressures used for solid rollers
Although lift matters its more spring rate that will pull them out. My 68 L79 pulled two studs on a 151 cam that 223/223 with .447 lift. Now did someone float it before I got the motor maybe. I will never know since the car was put away this way since 1983. When I did my engine I left the pressed in studs in but didn't realize two pulled out until after I got my heads back from the machinist and set the lash. I can tell you I wasn't happy about that either. He only replaced the two pulled with a sleeveless screw in stud to correct it since he wanted $450 to do them all and I have been running it like that for a year. I have almost always replaced pressed in the past but this time I wanted to keep it stock not to mention save a few. So if you are going flat cam I wouldn't go over .500 lift or much more then a stock Chevy solid cam spring which I believe have a seat around 110 pounds. You can not run a hot roller cam with pressed in studs IMO with the very fast ramps.
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PAC makes some really nice beehive springs that fit the SBC heads I have used them on LS heads also and used them on Roller hydraulic, flat tappet hydraulic and solid flat tappet.
The spring rate is 313.
If you set them up at 110 seat pressure they will rev a SBC to 7000+ rpm and with 313 rate your open pressure at .500" lift will be 266 psi open.
I run them with a 280h in 305 heads with stock studs. 7000 rpm easy and daily.
I hate the Z springs Even the 943X I have broke them with the little 268H in about a year of hammering on it.
Had some on a larger comp magnum and broke one in under a year of daily driving.
No bind issues.. It is just quality control is not what it used to be.. When GM was using old style springs like that they seemed better.
I have some and will never run them.
Nothing but PAC on my SBC engines now.
Hate breaking things and when you get a bunch of back to back with different manufactures names on the box but basically the same old spring with dampner.. you no longer have faith in them.
More than you wanted to know.
The spring rate is 313.
If you set them up at 110 seat pressure they will rev a SBC to 7000+ rpm and with 313 rate your open pressure at .500" lift will be 266 psi open.
I run them with a 280h in 305 heads with stock studs. 7000 rpm easy and daily.
I hate the Z springs Even the 943X I have broke them with the little 268H in about a year of hammering on it.
Had some on a larger comp magnum and broke one in under a year of daily driving.
No bind issues.. It is just quality control is not what it used to be.. When GM was using old style springs like that they seemed better.
I have some and will never run them.
Nothing but PAC on my SBC engines now.
Hate breaking things and when you get a bunch of back to back with different manufactures names on the box but basically the same old spring with dampner.. you no longer have faith in them.
More than you wanted to know.
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They figured something out with the L31 Vortec heads. I pulled studs out of one pair and I'm not going to do any more, they were tougher than any I ever tried.
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I didn't read close enough. Overlooked the pressed in stud part
Jeff I asked my machinist about using beehive springs and he basically said it takes some machining to get them to work on the older hump heads. Was he just feeding me bad info?
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When we rebuilt a SB400 (73 block and heads) for my son's 73 Vette, we went with a Comp Cams hyd rioller (sorry, I forget the specs, but it seems the lift was about .512) and beehive springs. The machinist recommended the beehive springs so that there would be enough spring pressure and NO NEED to modify the spring pockets. Engine is on its second year and ZERO issues so far.
The heads are bone stock GM 400 heads that were mildly massaged and had screw-in studs and guide plates added.
By the way, all first generation small block heads have a 1.25in spring pocket diameter.
The THEORY behind the beehive springs is that they will fit in the stock pocket, have stock height with more pressure, but don't get coil bind with hi-lift cams (higher than stock).
We Also went with 2 1/2in manifolds and a FULL 2 1/2in exhaust system with off road mufflers from Corvette Central. The car now has BB performance from a roller cammed SB400.
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My son's 73 Vette was an EXTREMELY nice factory air car with (tired) base 350 and Turbo 400 and he wanted to bump the power and also maintain (as close as possible) a factory appearance. I had a pair of finned valve covers and an early Z28-LT1 manifold in the attic and a nice 780 Holley. So we sorta kinda built it to resemble a 70-72 LT1 engine (no such thing in 73).
On Corvettes, the LAST year for 2 1/2in manifolds, was 1965. After that, ALL small blocks only had 2in manifolds.
The manifolds we used are the Chinese replacements (distributed by Dorman for about $50). There was no such thing as 2 1/2in front pipes for his car with a T400, so we ordered a system from Corvette Central with full 2 1/2in pipe, EXCEPT, for the very first few inches, which is reduced down to 2in. I had my favorite muffler guy cut off the 2in section, expand the pipe and make 2 1/2in ends to fit the manifolds (below).
What effect or improvement is provided by the 2 1/2in manifolds and pipes is unknown. But for sure, the new system with freer flowing manifolds, pipes and off road mufflers, compared to the previous 2in manifolds, stock pipes and stock mufflers is a considerable improvement. For an equivalent car/system with headers, on the street, I seriously doubt that there would be a noticeable (if any) difference between headers and 2 1/2in manifolds.
BUUUUUUUUUUUUUUUUT, this ONLY pertains to a Corvette, because none of the above is pertinent to a Chevelle since there is not, and never has been, a 2 1/2in small block manifold for a Chevelle. Which I hate! We have a strong SB400 in our 70 conv and I really wish Chevy had made small block 2 1/2in manifolds for a Chevelle.
Anyway, bottom line, my son's 73 Vette with the roller cammed SB400 runs very strong like a scalded dog! I guarantee that against a 73-74 Vette with a stock 454, it would be in trouble.
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I did have a slight issue with the last TPI heads and PAC beehive springs.
This was yesterday..The spring would not sit flat in the exhaust spring pocket.
Some springs would andd others were just barely up off the bottom.
Seems the set of heads I got had the deepened hole had a small taper on the Exhaust side.
I needed to shim the springs anyway and the shims were 1.250 and .060" thick and that let the PAC 1218 spring sit perfectly.
Some of the springs measured 1.3" at the base.
Stick them in a tight hole and they probably will have a hard time rotating and when they do it will relieve the pocket on the head and result in cast iron sparklies.
I have ran log exhaust manifolds on a 350" that ran very strong 245 PSI 7000 rpm shifts ported double humps.
Headers gave me more low end power Top end was the same.
I did port the exhaust manifolds and raist the runner height on them and open the exit quite a bit and ported way up into the runners and the exit.
I ran the same manifolds on a 388" with ported iron heads and it ran out of steam at 5800 rpm. Past that and it just nosed over.
Seemed a little low to me.
Stuck full length headers on it to see if it would gain power anywhere.
OH MAN! It revved to 6700 rpm and slowly flattened out after that.
Lesson learned.. Cubes need to breathe.
This was yesterday..The spring would not sit flat in the exhaust spring pocket.
Some springs would andd others were just barely up off the bottom.
Seems the set of heads I got had the deepened hole had a small taper on the Exhaust side.
I needed to shim the springs anyway and the shims were 1.250 and .060" thick and that let the PAC 1218 spring sit perfectly.
Some of the springs measured 1.3" at the base.
Stick them in a tight hole and they probably will have a hard time rotating and when they do it will relieve the pocket on the head and result in cast iron sparklies.
I have ran log exhaust manifolds on a 350" that ran very strong 245 PSI 7000 rpm shifts ported double humps.
Headers gave me more low end power Top end was the same.
I did port the exhaust manifolds and raist the runner height on them and open the exit quite a bit and ported way up into the runners and the exit.
I ran the same manifolds on a 388" with ported iron heads and it ran out of steam at 5800 rpm. Past that and it just nosed over.
Seemed a little low to me.
Stuck full length headers on it to see if it would gain power anywhere.
OH MAN! It revved to 6700 rpm and slowly flattened out after that.
Lesson learned.. Cubes need to breathe.
u was fed bad info on the springs , i had a set of 461 fuelie heads i didnt have to cut the pockets , they set up nice and i ran a 488 lift never pulled a stud :thumbsup:
Why are people getting on here busting chops saying it has nothing to do with lift…? It has just as much to do with lift as it does spring psi. You’re not running a heavier spring without a higher lift. You know what the guy meant, just answer is question. If you don’t know the answer, just move on.
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Cool story, bro.
I thought the Batman picture was less brutal than a moderator would be. I believe a lot of thread resurections happen because of the RELATED THREADS section listed at the bottom of each page.
Besides, who didn't get a laugh at The Caped Crusader when they were younger?
Besides, who didn't get a laugh at The Caped Crusader when they were younger?
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