lktna

Well the engine started out at a L98. Only thing left that is L98 is the block. It still needs tuned but I don't think it is to bad for a bunch of junk. LOL Here are the specs on the engine.

1989 L98 350 .030 over
Speed Pro .030 over pistons with .125 dome and 2 relief valves and floating pins 10.75 compression based on 64 cc head
Scat Pro Stock I-Beam Connecting Rods with 3/8 cap bolts
Comp Cams XR288 roller cam
Intake Duration at 050 inch Lift 236
Exhaust Duration at 050 inch Lift 242
Duration at 050 inch Lift 236 int./242 exh.
Advertised Intake Duration 288
Advertised Exhaust Duration 294
Advertised Duration 288 int./294 exh.
Intake Valve Lift with Factory Rocker Arm Ratio 0.520 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio 0.540 in.
Valve Lift with Factory Rocker Arm Ratio 0.520 int./0.540 exh. lift
Lobe Separation (degrees) 110
Dart Iron Eagle 64cc combution cambers, 2.05 intake and 1.60 exhaust stainless steel valves with 215 intake runners
Valve springs O.D.: 1.437 I.D.: .760
Description: Dual w/Damp
Seat Pressure: 135 @ 1.750 Open Pressure: 285 @ 1.250
Rate: 300 Coil Bind: 1.062 Max Lift: .625
Crane Gold full roller rockers 1.5 ratio
Pro Products Hurricane intake gasket matched to Felpro gasket 1206
750 Speed Demon carb with 76 jets in primary and 84 in secondary
Victor Reinz Head Gasket 4.100 bore .026 compressed
ARP head studs
HEI distibutor with all MSD componants

Orr89RocZ

iTrader: (20)

Big cam for a 355. Could use more spring pressure as that combo should go up near 6500 rpm no problem. Not bad numbers but i'd expect abit more, especially torque. should gain abit more with tuning, whats the air fuel ratio on the run?

lktna

I still have to put the bungs in my headers so I don't know the air fuel ratio. The cam is a little smaller than what will be in it next year. I was expecting more out of it myself but this is a good starting point and now I can make up my mind on weather I want to tear it back apart and stoker it or work with what I have.

Damon

For a DynoJet those numbers seem a little "soft" to me. You should have more upstairs than that. Things get a little raggedy above 5000. Maybe it's the tune, maybe who knows what.

I can't point to much that really stands out as a problem with that combo other than the valve springs. 986s are really for flat tappet cams. 987s would probably be a better choice for a roller, or even some appropriate beehives to get rid of a ton of retainer weight. Rollers like the XR have ramp rates that are really off the charts compared to any flat tappet cam. They appreciate higher spring rates and really appreciate taking weight out of the valvetrain to keep things under control as the RPMs rise (beehives with itsy-bitsy retainers on top).

For a cheap upgrade I suggest the Comp 987s- they are the same diameter as your 986s but have a higher 370 lbs/in spring rate (vs. 320 for the 986s), with everything else comparable. Drop-in replacements, basically.

With aggressive aftermarket roller cams beehives seem to be the ultimate solution these days, though. They remove a LOT of weight from the valvetrain and don't need absurd spring rates to keep the valvetrain under control that traditional (straight) valve springs require. Of course, this technology doesn't come cheap.

Orr89RocZ

iTrader: (20)

I wouldnt go too much bigger of a cam. Its not gonna help on that combo. You already have a pretty big cam for a 355 and its not putting out the numbers/rpms the combo should be. Once its tuned up properly, I think the numbers will go up abit but the heads i believe are limiting your numbers even tho they are a 215cc head. Valve springs should be changed to better match the cam as well. That may help the higher rpm power numbers, as I think you may be seeing some valve float on that setup. For rpm over 6200 rpm where that motor should be running, i'd go with 150lbs on the seat and mid high 300's open. I ran 165 lbs on the seat and 410 open on my setup that ran to 6800, never had a problem

lktna

From everything that I have read that cam falls off in power right at 6000 to 6200. I have been in contact with Lloyd Elliot and he is going to grind a cam for my engine. I am changing my springs out this winter to a 160 seat pressure and the cam he said he would grind for me would be a .612/.612 and 248 @ .050 duration.

Orr89RocZ

iTrader: (20)

What rpm are you trying to turn? I had a simple 230/245 cam on a 109 lsa and it turned peak hp at 6300 rpm and didnt fall off til 6600+ and this was on a 383

The 236/242 cam on other motors i've seen pulls all the way to near 6800 rpm on 355's.

Damon

Just to jump in again on this, I agree with the above posts. Lots of people think rollers fall off quickly over 6000 but that's often becuase they aren't adequately controlling the valves up that high. I.e. valvesprings/valvetrain issues. Happens with lots of roller cam setups, even some fairly modest ones like yours.

alltpi

iTrader: (1)

tyty

alltpi

iTrader: (1)

215 cylinder head is killing your low speed torque and it's not giving you any horsepower.... switch the cylinder heads 195 afr's or trickflow's will net you about 20-30 more pounds of torque and about 60-75 horsepower those iron dart's suck had them big waist of money not unless about 400-600 dollars in porting

lktna

I thought about the heads being to big, but didn't think would hurt it that much. Even when I had the engine at 6400 I didn't hear anything that sounded like the valves floating. The cam that is in the engine has a 110 lobe seperation.

Orr89RocZ

iTrader: (20)

Probly wont hear valve float, but will notice a flat lining of power. That cam is good to over 6500 rpm in a 355. Your not pulling that from your dyno graph. Your flatlining at 5500-6000 so it looks like float may be an issue. Granted its not tuned 100% but i would guess valve float is happening

Before a cam swap, maybe try much more aggressive springs? Patriot extreme gold or AFR 8019's are great little springs with alot of pressure and decent price. Good to 650 lift but i'd shim them .015 or so to get abit more seat pressure. That will be near 160lbs on the seat and 400 open which WILL control that cam. They did great for my high rpm 383.

IF you do the cam swap anyway before trying that current cam with fresh springs, you MUST get stiff springs. I'd go with the above mentioned springs shimmed .015 atleast for 165-170 lbs on seat. Will handle that .612 custom grind fine. I ran .603/.613 with plenty of clearance

Heads arent big for a 355 for that rpm range but will kill low end. Need gear and higher stall to get it moving but once it does it will move. THe only thing is iron eagles arent great flowing heads out the box. Any 195-220 cc aluminum head just about will destroy those iron eagles. I think that would be a better investment than new cam

lktna

There are shims on the valve springs now. I believe they are .015 or a .020. Yea trust me it is no where near tuned. I can build the engine, get it and get it running, half way adjust the carb to where it runs pretty decent and set the timing and that is about it. After that I become lost. As for the stall and gears I don't have to worry about a stall since I am a 4 speed car. Yes I said a 4 speed car! The engine is in a 1971 Nova SS and gears I have 4.10's.

Orr89RocZ

iTrader: (20)

oh my fault didnt read that. 4spd is nice!

Even with shims, the rates on those springs now arent enough to seriously increase pressure to acceptable levels

lktna

Thanks for the info. Well it is almost time for it to be put up for the year and get the body work and paint done. So I guess I will pull the engine and redo it as well.

D_Smith87

I just got a xr288, im running springs that came off a set of afr195s, worked well in my buddys last setup, very fast for a 3500 lb jeep.

Damon

Thread is 6 years old.