100hp in pieces

[Schurkey]

Fel Pro top end gasket set
#hs7733pt16

How thick are those head gaskets?

Wild Guess: Given that the pistons are ~.025--.027 in the hole, those gaskets are too thick for proper quench/squish.

When it was me, I had the block zero-decked--cut .025. Looking back, I should have had the block cut .015 and used a thinner head gasket.

 

[JeremyNH]

Full roller rockers or you are wasting your money. Friction reduction is at the roller fulcrum, not the tip.

We're probably not arguing but just to be clear I'm not using roller tips. Just made in the USA stamped steel 1.6 rockers for late model SBC. I wanted the ratio and given that the motor is low revving I didn't think rollers would add that much benefit. The ramjet uses the same cam and when it had full roller 1.6s it was rated slightly above the current model which uses standard stamped 1.5s. Both HP and torque fell with the switch (my understanding is that Crane simply stopped making them so GM dropped the part) but in the single digits so the difference was marginal, not the 12-20HP roller manufacturers claim and that's with the higher ratio. The question on the ramjet is: was the gain due to ratio, rollers, or both? Given that the ramjet uses the 395 cam and looking at where it makes power it's not a high revving engine either. So my thoughts are that it's mostly if not entirely the ratio. The Elgin 1.6s are also only $93 for 16 including the nuts and bails.

 

[L31MaxExpress]

We're probably not arguing but just to be clear I'm not using roller tips. Just made in the USA stamped steel 1.6 rockers for late model SBC. I wanted the ratio and given that the motor is low revving I didn't think rollers would add that much benefit. The ramjet uses the same cam and when it had full roller 1.6s it was rated slightly above the current model which uses standard stamped 1.5s. Both HP and torque fell with the switch (my understanding is that Crane simply stopped making them so GM dropped the part) but in the single digits so the difference was marginal, not the 12-20HP roller manufacturers claim and that's with the higher ratio. The question on the ramjet is: was the gain due to ratio, rollers, or both? Given that the ramjet uses the 395 cam and looking at where it makes power it's not a high revving engine either. So my thoughts are that it's mostly if not entirely the ratio. The Elgin 1.6s are also only $93 for 16 including the nuts and bails.

Except the new Ramjet has 1.5 full rollers

I can tell you the difference between stock rockers and 1.6 full rollers was 12 hp at peak at the wheels on my TBI 350. It reved more smoothly across the whole power band. Up near 5,000 rpm where it shifted at WOT it was up nearly 18 hp at the wheels. I later bored the Edelbrock 3704 TBI manifold to 2", added a 1" open center TBI spacer and a 454 TBI unit. Went from 178 hp to 204 hp at peak and held close to 200 rwhp to 5,000 rpm. Torque jumped up from 278 to 304.

 

[L31MaxExpress]

19210724 is the part number for the 1.5 full roller rocker on the current version of the Ramjet 350. The lift and the roller fulcrum are worth roughly equal power gains. The 1.6 to 1.5 ratio change dropped it about 6 hp and matching torque. The roller fulcrum portion is worth the same or more. On a HT383 going from a stock stamped steel rocker arm to a 1.6 full roller added 20 hp and nearly 20 ft/lbs of torque when tested. With a factory LT4 cam in it for 20K, shifting at 5,500 rpm my L31 had almost completely worn the pivot balls through the GM rocker arms. I swapped Crane 1.6s on it and the valvetrain was much quieter.

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[Super_chevy]

Those LS6 springs will coil bind at 1.200". If you install at the Vortec 1.700 or 1.720, I forget, that .525" of lift will not fly. With .050" offset locks you may only have .025" to coil bind. Unless those retainers gain you coil bind clearance too? Also, those rockers have been known to suck. Don't get the wrong idea, I didn't come in here to **** on your mods, but I don't want to see you find this out the hard way either. Have you done headers and junked the 1 7/8" headphones yet? That's the other part of the 350ish hp equation with the LT4 cam.

The heads are being machines to .600 to allow .550 max lift so it would be an issue

 

[L31MaxExpress]

L31 crate engine went in the Express van at 57k. This was at 77K shortly after the 1.6s went on it. Stock S10 4.3 converter, stock 96 LT4 cam, 1.6s and shorty headers into the factory 3" dual to the muffler exhaust. Smoothly pulled to 5,500 rpm. Tuned 97 black box PCM. Had the crappy flowing hecho en mexico 062s on it even.

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[Supercharged111]

The heads are being machines to .600 to allow .550 max lift so it would be an issue

This is worded strangely. How exactly are the heads being machined? I imagine they'll punch the spring seat down some, but what you said doesn't convey that.

 

[L31MaxExpress]

How thick are those head gaskets?

Wild Guess: Given that the pistons are ~.025--.027 in the hole, those gaskets are too thick for proper quench/squish.

When it was me, I had the block zero-decked--cut .025. Looking back, I should have had the block cut .015 and used a thinner head gasket.

Have one on the stand next to me at the shop with the heads off. Circa 2006 1-ton GM Goodwrench L31, the one with 4 bolt mains and the single roller timing chain. Checked 1 and 6 at TDC. Pistons are exactly 0.023" down the bore on both sides. With the stock 0.028" compressed head gasket that is already 0.051" quench. Not that the terrible GM open dish piston offers much quench to start with. On this engine I ran 0.016" steel shims. Better than the factory and way better than those thick rebuilder gaskets.

 

[L31MaxExpress]

I believe the actual head gaskets in those sets are 7733PT-2 which are 0.39 compressed. 0.039 and 0.023 open the quench to a wide 0.062". Will cost power and knock resistance.

 

[Super_chevy]

This is worded strangely. How exactly are the heads being machined? I imagine they'll punch the spring seat down some, but what you said doesn't convey that.

The spring and retainer combination will allow for great maximum lift combined with machining down the valve guides and if they need to possibly longer valves. However the combination can be found countless times across the internet where no machining was needed at all to fit the Lt4 cam as long as it was combined the the ls6 springs and comp cams retainers.