LT4 HOT Cam swap questions?
10-13-2000, 05:46 PM
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LT4 HOT Cam swap questions?
I am going to get an LT4 "HOT" cam for my car here in a few weeks. What else will I need to buy to do the swap, what assemply lubes, new parts, gaskets, and such? What will all of this cost me?
------------------
1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission with 2.77:1 Rear End
Current Mods: Edelbrock TES 1 5/8" Headers, Hooker Aerochamber Cat-Back System, Performance Resource Chip with 160* Thermostat, Accel Ignition Components, K&N Filters, All Free Mods, Falken ZIEX Z-Rated Tires.
Best ET : 14.32 @ 97.7mph
(corrected for elevation)
------------------
1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission with 2.77:1 Rear End
Current Mods: Edelbrock TES 1 5/8" Headers, Hooker Aerochamber Cat-Back System, Performance Resource Chip with 160* Thermostat, Accel Ignition Components, K&N Filters, All Free Mods, Falken ZIEX Z-Rated Tires.
Best ET : 14.32 @ 97.7mph
(corrected for elevation)
10-13-2000, 08:50 PM
#2
Dan,
Much of the advertised lift/duration available with the LT4 "hot" cam is derived from the use of 1.6:1 rocker arms. In an apples-to-apples comparison, the LT4 "hot" cam has basic lift numbers of .492"/.492", 210°/221°, 112° LSA with "standard" 1.5:1 rockers.
By fair COMParison, Comp Cams has a similar grind, the 266HR-14, with .500"/.510", 210°/220°, 114° LSA. The longer lobe separation angle can make the engine a little more manageable at idle and low RPM, keeping the ECM happier than the LT4 "hot" grind. If you want to go a little deeper into the cylinders, the 276HR-14 goes at .510"/.510", 220°/230°, 114° LSA. The longer LSA still makes the grind able to coexist with an ECM, but the lift numbers with 1.5:1 rockers way outperform the LT4 "hot" grind. If you want to get vicious, you can go with 1.6:1 rockers on either of these grinds to completely munch the LT4 "hot" profile. Or really goofy would be the 290HR-12 with lumps of .510"/.540", 230°/244°, 112 LSA. This would almost definitely require a custom PROM, AFPR, probably larger injectors, and lots of new tires. I'll bet the price is a little better as well. These grinds are made for the LT1/LT4 engine family (just like the GM cams) but will work with the Gen I SBC with a shorter dowel pin (just like the GM cams).
As far as necessary items, you'll need the camshaft, a new timing set (don't even consider using the old chain and sprockets unless you just installed them yesterday), larger valve springs and the necessary head machining, spring retainers and locks, valve stem seals, a gasket set, fresh coolant mix, fresh oil and filter, and the better part of an otherwise boring weekend. If the lifters are worn at all, a new set would be in order. The same goes for the distributor gear and rocker arms.
As long as you're machining the heads for the necessarily larger valve springs, you should seriously consider pulling the pressed rocker studs and tapping for screwed studs. A set of studs is about $15.00 at the GM parts counter, and they are as good as anything with vowels in the name. The same goes for springs, retainers, and locks. The entire set of LT4 springs, which are more than adequate for the task, will set you back about $70.00 if you order the parts in kits instead of individually. That includes springs, lightweight retainers, and 10° locks. Teflon seals should be included with a good gasket set, which will be another $90.00 - $110.00. The roller chain timing set should be less than $ 70.00. If you can't resist the temptation once the heads are off for spring seat machining, the new larger valves you'll want to install should take another $150.00 out of your wallet, plus the $160.00 for machining with deep port pocketing. The few other items you'll want to have on hand are penetrating oil, a dial indicator, a caliper for checking spring height, a degree wheel, anti-seize compound, penetrating oil, RTV sealant, an engine hoist and/or floor jack with engine lifting fixture, and lots of patience.
If you can resist the new valves, you'll only need to match the gasket openings in the heads and intake/exhaust sets. I recently "worked" my heads and cam in a similar fashion for less than $1,000.00 total, including a cleaned/matched set of injectors, new freeze plugs, pushrods, and some assorted fasteners, hoses, and hardware. The bottom end was a few more bucks, but that is a pretty accurate number for the valve train and head work. If your rotating assembly and holes are still in good condition, you could likely not have to touch the bottom end.
------------------
Later,
Vader
------------------
"Make Me Bad"
Adobe Acrobat Reader 4.0
Much of the advertised lift/duration available with the LT4 "hot" cam is derived from the use of 1.6:1 rocker arms. In an apples-to-apples comparison, the LT4 "hot" cam has basic lift numbers of .492"/.492", 210°/221°, 112° LSA with "standard" 1.5:1 rockers.
By fair COMParison, Comp Cams has a similar grind, the 266HR-14, with .500"/.510", 210°/220°, 114° LSA. The longer lobe separation angle can make the engine a little more manageable at idle and low RPM, keeping the ECM happier than the LT4 "hot" grind. If you want to go a little deeper into the cylinders, the 276HR-14 goes at .510"/.510", 220°/230°, 114° LSA. The longer LSA still makes the grind able to coexist with an ECM, but the lift numbers with 1.5:1 rockers way outperform the LT4 "hot" grind. If you want to get vicious, you can go with 1.6:1 rockers on either of these grinds to completely munch the LT4 "hot" profile. Or really goofy would be the 290HR-12 with lumps of .510"/.540", 230°/244°, 112 LSA. This would almost definitely require a custom PROM, AFPR, probably larger injectors, and lots of new tires. I'll bet the price is a little better as well. These grinds are made for the LT1/LT4 engine family (just like the GM cams) but will work with the Gen I SBC with a shorter dowel pin (just like the GM cams).
As far as necessary items, you'll need the camshaft, a new timing set (don't even consider using the old chain and sprockets unless you just installed them yesterday), larger valve springs and the necessary head machining, spring retainers and locks, valve stem seals, a gasket set, fresh coolant mix, fresh oil and filter, and the better part of an otherwise boring weekend. If the lifters are worn at all, a new set would be in order. The same goes for the distributor gear and rocker arms.
As long as you're machining the heads for the necessarily larger valve springs, you should seriously consider pulling the pressed rocker studs and tapping for screwed studs. A set of studs is about $15.00 at the GM parts counter, and they are as good as anything with vowels in the name. The same goes for springs, retainers, and locks. The entire set of LT4 springs, which are more than adequate for the task, will set you back about $70.00 if you order the parts in kits instead of individually. That includes springs, lightweight retainers, and 10° locks. Teflon seals should be included with a good gasket set, which will be another $90.00 - $110.00. The roller chain timing set should be less than $ 70.00. If you can't resist the temptation once the heads are off for spring seat machining, the new larger valves you'll want to install should take another $150.00 out of your wallet, plus the $160.00 for machining with deep port pocketing. The few other items you'll want to have on hand are penetrating oil, a dial indicator, a caliper for checking spring height, a degree wheel, anti-seize compound, penetrating oil, RTV sealant, an engine hoist and/or floor jack with engine lifting fixture, and lots of patience.
If you can resist the new valves, you'll only need to match the gasket openings in the heads and intake/exhaust sets. I recently "worked" my heads and cam in a similar fashion for less than $1,000.00 total, including a cleaned/matched set of injectors, new freeze plugs, pushrods, and some assorted fasteners, hoses, and hardware. The bottom end was a few more bucks, but that is a pretty accurate number for the valve train and head work. If your rotating assembly and holes are still in good condition, you could likely not have to touch the bottom end.
------------------
Later,
Vader
------------------
"Make Me Bad"
Adobe Acrobat Reader 4.0
10-14-2000, 12:26 AM
#3
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Wow, thanks Vader. How much of all that stuff do I ABSOLUTLEY need, I am trying to do this on a budget.
------------------
1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission with 2.77:1 Rear End
Current Mods: Edelbrock TES 1 5/8" Headers, Hooker Aerochamber Cat-Back System, Performance Resource Chip with 160* Thermostat, Accel Ignition Components, K&N Filters, All Free Mods, Falken ZIEX Z-Rated Tires.
Best ET : 14.32 @ 97.7mph
(corrected for elevation)
------------------
1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission with 2.77:1 Rear End
Current Mods: Edelbrock TES 1 5/8" Headers, Hooker Aerochamber Cat-Back System, Performance Resource Chip with 160* Thermostat, Accel Ignition Components, K&N Filters, All Free Mods, Falken ZIEX Z-Rated Tires.
Best ET : 14.32 @ 97.7mph
(corrected for elevation)
10-15-2000, 11:21 AM
#5
Dan,
At the very minimum, you'll need the camshaft, gasket set, valve springs and retainers/keys.
It is possible to use the aftermarket tapered valve springs that don't require head machining, but I have no experience with these. The advertised cost of these springs is just about equal to the LT4 spring sets plus machining costs. The stock valve springs would be beyond their range of operation and into the binding range, which will start doing serious damage to the rest of your valve train. If you break a valve spring, you may trash your lower end as well.
You can save the old timing chain, but I wouldn't recommend it. If your chain fails with the additional load of a new, higher lift cam, you risk slamming a piston into a valve.
You can re-use the roller lifters if they are in good condition. That is a fairly low-risk option, since the failure of a lifter would most likely not cause any collateral damage.
You can use the stock pressed-in rocker studs, but they will tend to work loose over time with those lifts. As a temporary safety maesure, you can drill and pin the studs in the head, but the cost of the pin kits is almost as much as a set of screwed studs ($18.00 - Mr. Gasket). A good 7/16-14 tap to prep the holes is another $8.00, but you get to keep it when you're finished. Once the holes are tapped, changing to guide plates in the future is as easy as changing rocker cover gaskets.
You can use your original push rods and rockers if the rods are straight and the rockers have pivot slots long enough to prevent binding at the mounting studs. The push rods are easy to inspect for bending and clear oil holes. The rockers will have to be observed closely when checking the cam for spring clearance and correct pushrod length, so watch the slot/stud clearance at the same time. The stock rockers will be on the edge of their travel at higher lifts, so don't chance it if they don't offer a little extra space. As a side note, my stock LT1 rockers had enough slot length to operate with the Comp cam, so I did that for the first few hundred miles for easier break in at the 1.5:1 ratio. I suppose I could have kept running them and left the roller-tips in the package.
I'm guessing you could cut the cost in half by skipping the machining and head work, but you might end up doing it later to repair the problems that arise from the shortcuts taken now. If you can do any of the machining yourself, you can save a lot of cash and some time that you'd spend waiting for the machinist. I end up doing most of the spring seat, stud, and deep porting work myself for those and other reasons.
If/when you undertake the project, you might want to visit this page for idea on installation and setup of the camshaft: http://www.cranecams.com/instructions/instruct.htm
The rest of the parts and modifications are optional. I just always throw them out for consideration, since I can't resist doing more with the heads once they're off the case. Understanding that most of the power availaable in a SBC is through the valve train and heads, I have a tendency to want to maximize my time while in there.
Incidentally, I didn't mention it earlier, but that is a pretty impressive 1/4 time for a 2.77 Borg axle. A higher stall converter might drop you another few tenths if you're so inclined, but those are decent numbers from the stock package with only external mods.
------------------
Later,
Vader
------------------
"Make Me Bad"
Adobe Acrobat Reader 4.0
At the very minimum, you'll need the camshaft, gasket set, valve springs and retainers/keys.
It is possible to use the aftermarket tapered valve springs that don't require head machining, but I have no experience with these. The advertised cost of these springs is just about equal to the LT4 spring sets plus machining costs. The stock valve springs would be beyond their range of operation and into the binding range, which will start doing serious damage to the rest of your valve train. If you break a valve spring, you may trash your lower end as well.
You can save the old timing chain, but I wouldn't recommend it. If your chain fails with the additional load of a new, higher lift cam, you risk slamming a piston into a valve.
You can re-use the roller lifters if they are in good condition. That is a fairly low-risk option, since the failure of a lifter would most likely not cause any collateral damage.
You can use the stock pressed-in rocker studs, but they will tend to work loose over time with those lifts. As a temporary safety maesure, you can drill and pin the studs in the head, but the cost of the pin kits is almost as much as a set of screwed studs ($18.00 - Mr. Gasket). A good 7/16-14 tap to prep the holes is another $8.00, but you get to keep it when you're finished. Once the holes are tapped, changing to guide plates in the future is as easy as changing rocker cover gaskets.
You can use your original push rods and rockers if the rods are straight and the rockers have pivot slots long enough to prevent binding at the mounting studs. The push rods are easy to inspect for bending and clear oil holes. The rockers will have to be observed closely when checking the cam for spring clearance and correct pushrod length, so watch the slot/stud clearance at the same time. The stock rockers will be on the edge of their travel at higher lifts, so don't chance it if they don't offer a little extra space. As a side note, my stock LT1 rockers had enough slot length to operate with the Comp cam, so I did that for the first few hundred miles for easier break in at the 1.5:1 ratio. I suppose I could have kept running them and left the roller-tips in the package.
I'm guessing you could cut the cost in half by skipping the machining and head work, but you might end up doing it later to repair the problems that arise from the shortcuts taken now. If you can do any of the machining yourself, you can save a lot of cash and some time that you'd spend waiting for the machinist. I end up doing most of the spring seat, stud, and deep porting work myself for those and other reasons.
If/when you undertake the project, you might want to visit this page for idea on installation and setup of the camshaft: http://www.cranecams.com/instructions/instruct.htm
The rest of the parts and modifications are optional. I just always throw them out for consideration, since I can't resist doing more with the heads once they're off the case. Understanding that most of the power availaable in a SBC is through the valve train and heads, I have a tendency to want to maximize my time while in there.
Incidentally, I didn't mention it earlier, but that is a pretty impressive 1/4 time for a 2.77 Borg axle. A higher stall converter might drop you another few tenths if you're so inclined, but those are decent numbers from the stock package with only external mods.
------------------
Later,
Vader
------------------
"Make Me Bad"
Adobe Acrobat Reader 4.0
10-15-2000, 06:11 PM
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Vader,
I just recently stabbed a Comp 269 HR into a buddies' L-98. We used the 1.5 rockers for fear of introducing a valve to a piston.
This stick is 218/224 @ .050 with lift in the low 500's on a 112* LSA. He already had new springs, etc.
Seems pretty strong (better than the LT-4 production cam he had in there), but here's my question:
He has a custom chip by Ed Wright that was burned for his stock injectors with LT-4 combo. He still has the stock injectors, 52MM TPI unit, Ed chip, and ported stock base, but now has a much taller/fatter cam.
I'm thinking his next improvements should be another chip, bigger injectors, and better base. He has 9.5 to 1 compression, TES system, and good ignition.
Whatcha think darkman?
BOR
The pooterball thrill seeker.
I just recently stabbed a Comp 269 HR into a buddies' L-98. We used the 1.5 rockers for fear of introducing a valve to a piston.
This stick is 218/224 @ .050 with lift in the low 500's on a 112* LSA. He already had new springs, etc.
Seems pretty strong (better than the LT-4 production cam he had in there), but here's my question:
He has a custom chip by Ed Wright that was burned for his stock injectors with LT-4 combo. He still has the stock injectors, 52MM TPI unit, Ed chip, and ported stock base, but now has a much taller/fatter cam.
I'm thinking his next improvements should be another chip, bigger injectors, and better base. He has 9.5 to 1 compression, TES system, and good ignition.
Whatcha think darkman?
BOR
The pooterball thrill seeker.
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