anyone with comp XFI 230/236?
08-22-2009, 05:50 PM
#1
Staging Lane
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anyone with comp XFI 230/236? ive got an 96' LT4 Vette 6speed with limited mods:
- 5 angle valve job on otherwise bone stock LT4 heads
- GM LT4 hotcam (218/228, .525/.525 w 112lsa on 1.6 rockers)
- Comp 981 springs
- free mods
- tune
the car put down 344rwhp and trapped 116mph with the stock clutch. ive since upgraded the clutch and am now looking for a bit more power than the hotcam delivers
so ive thought about comps XFI series cams. recently i was pondering using the larger one (242/248, .584/.579 w 1.6 rockers), but was thinking that may be a bit too much for a street driven 350 car. so ive been leaning more towards the slightly smaller grind (230/236 .576/.570 w 1.6 rockers)
while obviously more powerful than the hotcam i currently have, any guesses exactly how much more usable power this cam would make?
- 5 angle valve job on otherwise bone stock LT4 heads
- GM LT4 hotcam (218/228, .525/.525 w 112lsa on 1.6 rockers)
- Comp 981 springs
- free mods
- tune
the car put down 344rwhp and trapped 116mph with the stock clutch. ive since upgraded the clutch and am now looking for a bit more power than the hotcam delivers
so ive thought about comps XFI series cams. recently i was pondering using the larger one (242/248, .584/.579 w 1.6 rockers), but was thinking that may be a bit too much for a street driven 350 car. so ive been leaning more towards the slightly smaller grind (230/236 .576/.570 w 1.6 rockers)
while obviously more powerful than the hotcam i currently have, any guesses exactly how much more usable power this cam would make?
08-22-2009, 06:13 PM
#2
The 242 duration one has been tested on a stock shortblock to not peak yet before the pcm runs out of capability at 7000rpms, lesson being Comp's rpm ranges are WAY off for a 350ci LT1. Most of us agree you want to stay under 230 degrees on a stock shortblock. A PROPERLY spec'd cam in the mid to upper 220s is going to give you all the rpm the stock shortblock can safely handle.
Those springs are unlikely to handle the XFI lobes which were designed specifically with the capability of beehive springs in mind. Beehives with their light retainers and other benefits manage to control a given cam with less overall pressure.
The XFI lobes are hard on parts so overbuild things a bit is going to be a good practice and the 113LSA they offer is based on the assumption people are going to aim too big as you are and for emissions reasons, the computer can handle a tighter LSA and it will make the car faster to a point.
The light LT4 valves will make these lobes a little easier to control, at least you have that going for you. IMO the LT4 valves are the only part of the engine worthwhile over LT1 parts.
http://advancedinduction.com/AiProductsCK.html
This is what I use for valvetrain, works pretty well last night was 12.2 at 111mph from 4250lbs and comfortable enough for the wife to nap in if we go on a 2 hour trip. Easy and reliable enough that the first pass she ever made down the dragstrip was in this car and was 12.4.
Those springs are unlikely to handle the XFI lobes which were designed specifically with the capability of beehive springs in mind. Beehives with their light retainers and other benefits manage to control a given cam with less overall pressure.
The XFI lobes are hard on parts so overbuild things a bit is going to be a good practice and the 113LSA they offer is based on the assumption people are going to aim too big as you are and for emissions reasons, the computer can handle a tighter LSA and it will make the car faster to a point.
The light LT4 valves will make these lobes a little easier to control, at least you have that going for you. IMO the LT4 valves are the only part of the engine worthwhile over LT1 parts.
http://advancedinduction.com/AiProductsCK.html
This is what I use for valvetrain, works pretty well last night was 12.2 at 111mph from 4250lbs and comfortable enough for the wife to nap in if we go on a 2 hour trip. Easy and reliable enough that the first pass she ever made down the dragstrip was in this car and was 12.4.
08-22-2009, 11:05 PM
#3
Look at the the COMP XFI 466. 218/224 duration with .570/.565 lift w/1:6 RR
part # 07-466-8
Your LT4 valves will help but expect to swap in 26918 Bee Hive springs and associated locators and retainers if going with the XFI.
Dwayne and others have good results with the AI stuff. They could grind you something specific to your set up
Lingenfelter also makes a good cam for stock 350.
You may likely need better springs for whatever cam you select pending cam choice and specs of the 981's
....ymmv
part # 07-466-8
Your LT4 valves will help but expect to swap in 26918 Bee Hive springs and associated locators and retainers if going with the XFI.
Dwayne and others have good results with the AI stuff. They could grind you something specific to your set up
Lingenfelter also makes a good cam for stock 350.
You may likely need better springs for whatever cam you select pending cam choice and specs of the 981's
....ymmv
08-23-2009, 02:43 PM
#4
TECH Apprentice
You can also run the comp 941 valve springs which will work with the retainers you already have. They are a pacoloy spring which is a much better steel and can take alot more abuse than the 981s. They seem to be pretty underated by the given specs, because mine on stock heads wound up being 185 lbs on the seat and 470 over the nose with stock cam. So they should be plenty stiff for the XFI lobes. I think they are just shy of $200 for a set.
08-23-2009, 02:55 PM
#5
http://www.compcams.com/Technical/In.../Files/189.pdf
Meant for a 1.8 installed height, stock is more like 1.7 that is why they were so stiff.
Comp seems to not recommend them on the street either. Might do some digging and find out why. Some alloys do not like being used cold as happens a lot on a street car.
Meant for a 1.8 installed height, stock is more like 1.7 that is why they were so stiff.
Comp seems to not recommend them on the street either. Might do some digging and find out why. Some alloys do not like being used cold as happens a lot on a street car.
08-23-2009, 06:49 PM
#6
TECH Apprentice
[QUOTE=96capricemgr;12114641]http://www.compcams.com/Technical/In.../Files/189.pdf
Meant for a 1.8 installed height, stock is more like 1.7 that is why they were so stiff.
Comp seems to not recommend them on the street either. Might do some digging and find out why. Some alloys do not like being used cold as happens a lot on a street car.[/QUOTE
They prolly dont recommend them for street use, for flat tappet cams due to their stiffness and the fact that oil has had all the zinc and phosphorus taken out for emission purposes. As far as roller cams you can put about what you want to on them within a realistic range. Stock LT1 cams are billet so they can handle it, and you know the XFI cams need some good spring pressure or a light valvetrain. Its prolly not the alloy that dont like the cold starts, every engine has to start cold at some point. Its prolly due to the flat tappet cams not having sufficient oil supply for the first couple of secs of a cold start and the stiffer springs tend to be tough on the lobes. Thats why flat tappets need the zinc and phosperous to keep metal to metal contact from happening. But if the spring can survive in the roundy round engines it should hold up just fine on a street engine. Just my 2 cents.
Meant for a 1.8 installed height, stock is more like 1.7 that is why they were so stiff.
Comp seems to not recommend them on the street either. Might do some digging and find out why. Some alloys do not like being used cold as happens a lot on a street car.[/QUOTE
They prolly dont recommend them for street use, for flat tappet cams due to their stiffness and the fact that oil has had all the zinc and phosphorus taken out for emission purposes. As far as roller cams you can put about what you want to on them within a realistic range. Stock LT1 cams are billet so they can handle it, and you know the XFI cams need some good spring pressure or a light valvetrain. Its prolly not the alloy that dont like the cold starts, every engine has to start cold at some point. Its prolly due to the flat tappet cams not having sufficient oil supply for the first couple of secs of a cold start and the stiffer springs tend to be tough on the lobes. Thats why flat tappets need the zinc and phosperous to keep metal to metal contact from happening. But if the spring can survive in the roundy round engines it should hold up just fine on a street engine. Just my 2 cents.
08-24-2009, 03:25 AM
#7
On The Tree
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this is the cam that i have in my firebird and its works great even with a stock stall and 2.73's. great power band and still plenty of low end tq. managed a best of 13.01 @ 109.5 at around 3800 lbs race weight (me 160lbs, full gas tank and a BIG *** stereo in the car) and i cut some crappy 60' times (2.3) got to love 2.73's lol
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08-24-2009, 09:44 AM
#8
I run the 230/236 cam in my 396LT1 Vette. Its a very streetable cam in a 396. If tuned right I am sure you can get a decent idle with a stick car and 350.
I would run a 220-225 intake and 225-230 ex, personnally. But thats me, if I had the LT4.
I use Pacs 981 spring as it was recommended by Comp Cams. They are installed at 1.8 on my Ported LT1 castings, old port job by CNCheads of FL.
425rwhp/418ft/lbs tq through 700R4 with 3.75 gears and Vigilante.
Also, 941 springs SUCK *****. I broke several of them with a Hot Cam , just idleing. They are single springs that are VERY stiff. WEAK. Not designed for a street vehicle at all IMHO>
I would run a 220-225 intake and 225-230 ex, personnally. But thats me, if I had the LT4.
I use Pacs 981 spring as it was recommended by Comp Cams. They are installed at 1.8 on my Ported LT1 castings, old port job by CNCheads of FL.
425rwhp/418ft/lbs tq through 700R4 with 3.75 gears and Vigilante.
Also, 941 springs SUCK *****. I broke several of them with a Hot Cam , just idleing. They are single springs that are VERY stiff. WEAK. Not designed for a street vehicle at all IMHO>
08-24-2009, 11:24 AM
#9
Staging Lane
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i thought i had the comp 981 springs... but after some digging found out i actually have a crane spring. not sure which one though. i think theyre the ones that come in a set with retainers. have to do some more research...
found some info:
Chevrolet V-8 92-99 350 cu. in. LT1 ------------------------------PN 10308-1
(w/Aluminum cylinder heads)
Valve Spring PN 99893-16 Steel Retainer PN 99951-16
Lock PN 99097-1 Shim PN 99050-1
The installed height using this kit on LT1 engines with factory aluminum heads should be
set between 1.875” and 1.850”. Make sure all valve springs are assembled at the same
height. The springs will provide sufficient pressure when installed within this range. The
hardened shims are used to replace the factory lower spring seats. Make sure there is
clearance between the rocker arm and the retainer throughout the rocker arm travel.
Clearance should be a minimum of .020”.
- Recom’d installed spring pressure and height (valve closed)-------------130 lbs.@ 1.850”
- Open checking pressure and height ---------------------------------------------402 lbs.@ 1.150”
- Maximum recommended valve lift and RPM ----------------------------------.600” - 7000 RPM
found some info:
Chevrolet V-8 92-99 350 cu. in. LT1 ------------------------------PN 10308-1
(w/Aluminum cylinder heads)
Valve Spring PN 99893-16 Steel Retainer PN 99951-16
Lock PN 99097-1 Shim PN 99050-1
The installed height using this kit on LT1 engines with factory aluminum heads should be
set between 1.875” and 1.850”. Make sure all valve springs are assembled at the same
height. The springs will provide sufficient pressure when installed within this range. The
hardened shims are used to replace the factory lower spring seats. Make sure there is
clearance between the rocker arm and the retainer throughout the rocker arm travel.
Clearance should be a minimum of .020”.
- Recom’d installed spring pressure and height (valve closed)-------------130 lbs.@ 1.850”
- Open checking pressure and height ---------------------------------------------402 lbs.@ 1.150”
- Maximum recommended valve lift and RPM ----------------------------------.600” - 7000 RPM
Last edited by tpivette; 08-24-2009 at 11:40 AM.
