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Well it's just about a year and a half ago since my last post. I just retired a few weeks ago and now am ready to work on the 74 and get it done. I have been doing a lot of thinking, talking to different people, rereading the thread here with opinions from members who have more knowledge than I do on engine building. At this point I am still undecided on which direction to take.
Case in point, one person suggested to change out the pistons if I use the "215" heads. His thoughts are that since the heads are worked and now have oversized valves, that they would "flood" the cylinders with more fuel than the stock LS4 pistons could handle causing the engine not to run correctly. He is suggesting to get higher compression pistons to prevent the "fuel flooding" from happening. Again, I do not have enough knowledge to know if this is correct or not. Also here again as a reminder are the specs of the cam that I am intending to use...... Retro-Fit Hydraulic Roller. Great mid range torque and power. Likes 2000 RPM stall converter and works great in towing applications with lower gearing. Largest for inboard/outboard performance marine use.
•Advertised Duration (Int/Exh): 272/280
•Duration @ .050 (Int/Exh): 221/229
•Gross Valve Lift (Int/Exh): .575/.575
•LSA/ICL: 112/106
•Valve Lash (Int/Exh): Hyd/Hyd
•RPM Range: 1800-5800
•Includes: Cam & Lifters (#72431-16)
Don't know if I want to take the bottom end totally apart, especially with the low mileage. I am also thinking of just selling the roller set-up that I have, maybe pick another cam, get my original "781's" done, sell the "215's" and call it a day......
Or get different pistons, (I think may have been mentioned in this thread) and continue on......
Although my first concern is getting the car back on the ground, and being that it will give me time to decide, I still need to make that decision regardless.
Again my original goal is to have a very good running 454 that won't run out of breath @ 4500rpm's. I don't need a rocket, I have the 94 ZR-1 that accomplishes that feeling.
I am probably limiting myself since I am staying with the TH400 and the 3.08 gears. Invested to many $$ in the rear to change gears.
Hope everyone is doing well, and thoughts, opinions, are always welcomed................................ ...thanks.....Tom
Last edited by 74 LS4-454; 06-06-2016 at 12:23 AM.
Close to almost 2 years since last posted in this thread....
the 74 is still not back together.....and I ended up tearing the engine completely down......more on that later......
we were having a discussion on the "215" heads going along with the Lunati Roller cam and the valve spring pressure from the Isky valve springs that were installed on the heads prior to me changing from flat tappet to roller cam.....so doing some research.....here are the specs for the valve springs of both cams.....
Isky......valve springs installed on the "215" heads
OD Inner.... 1.005
OD Outer... 1.530
ID Inner.... .730
ID Outer..... 1.110
Seat Pressure 135 lbs @1.875"
Open Pressure 395 lbs @1.225"
Rate Per Inch...... 400
Coil Bind...... 1.160"
Max Net Lift..... .650"
Lunati recommended valve springs for the Hyd Roller Cam
OD Inner....
OD Outer... 1.540
ID Inner.... .794
ID Outer..... 1.140
Seat Pressure 142 lbs @1.940"
Open Pressure 402 lbs @1.250"
Rate Per Inch..... 377
Coil Bind....... 1.089"
Max Net Lift
The questions are......
are the Isky valve springs sufficient enough to handle the Lunati Roller
Cam?
if not, can the machine shop make adjustments with shims to get the correct specs?
or do I need to have the Lunati valve springs installed?
Thanks for any info....Tom
Last edited by 74 LS4-454; 02-27-2018 at 01:53 AM.
From 8 to 9 compression is 4%. From 9 to 10 is 2-3% increase in power. I wouldn't replace pistons in a 10k original mile block for that little power increase. I would rather you went with a roller cam. Bit more money, but a LOT more than 3 or 4% power increase. 215 are pretty good heads. Not the restrictive bathtub chambers like the earlier closed chambers. More like a 100cc open chamber.
From 8 to 9 compression is 4%. From 9 to 10 is 2-3% increase in power. I wouldn't replace pistons in a 10k original mile block for that little power increase. I would rather you went with a roller cam. Bit more money, but a LOT more than 3 or 4% power increase. 215 are pretty good heads. Not the restrictive bathtub chambers like the earlier closed chambers. More like a 100cc open chamber.
I am not replacing the pistons......but will put new rings on them.....
I am using the Lunati roller cam....as the Isky flat tappet is long gone.....
I need to know if the difference between the 2 spring pressures I mentioned above is crucial enough that I need to change over to the Lunati springs.....is that pressure difference enough to damage the engine if not changed, or is it so minor as to not make a difference???
And the "215" heads I have are 100cc's.....
And I decided to go with a tri-power setup......so a lot of changes are in the works......
Just got off the phone with a Lunati tech.....who said I will be fine with the springs....as there is only a 7 lb difference on the seat and open pressure between the two valve springs.....no problem at all....
if you want HP, your gonna need to upgrade your pistons.
I would have your heads, gone thru also, minimum checked out.
valve springs must match cam, especially with additional lift.
these are the SRP pistons I used for my 454 build.
Ok......just got off the phone with a reputable machine shop in my area.. I decided that I will let them check out the heads to make sure the spring pressure is correct.....as it seems from my previous posts that the open pressure may have been installed lower than what I mentioned above.....
I also got prices on other machine work on the block and they seem very reasonable.....and even on assembling the short block......this way I will feel better knowing the bottom end is assembled correctly....
Right now thinking about using the stock flat top pistons with the closed chamber heads...we shall see.....
I always wanted tri-power....I already have a set-up....I like to try it.....if it doesn't work out.....I still have my 427/390 factory aluminum intake with my Q-Jet to install....
Just looking for a nice cruiser with power that won't run out of breath @4500 rpm's....like the stock LS4 did in 74.....
Tri Power will work. I run it on my 454. Total carb cfm is 916.
Hello Tom....I think that some people are leary with the 3x2's.....
I am more than confident with all of the info I have from you that it will perform just fine......getting everything into place for the system now....have ordered some items already and need to get a few more... I will begin disassembling the carbs in the next few days.....
Things are starting to come together......hopefully the engine will be ready to fire up before summer....at least that is my goal.....I still need to get the 74 put back together and back on the ground......
Tom
Last edited by 74 LS4-454; 02-27-2018 at 03:29 PM.
If it's going to be a daily driver and get 10,000 miles a year, you need to redo the seats. For a drive around town go to the car show Tuesday night at the drive-in, the original seats are going to be fine.
[QUOTE=69Vett;1596687382]I would suggest do the heads properly. by a machinist.
hardened seats, new valves, guides,seals, alot more than just spring pressure.
Originally Posted by derekderek
If it's going to be a daily driver and get 10,000 miles a year, you need to redo the seats. For a drive around town go to the car show Tuesday night at the drive-in, the original seats are going to be fine.
Thanks for the suggestions......appreciated......but everything that you mentioned and more has been done to these heads.....and bigger valves too.....
Will have limited mileage as I have other vehicles to drive.....
so here are today's events with some pics......
Went out to the 74 today.....to pick up the "215" heads to drop off at the machine shop......although I spoke to the owner who seemed to be very knowledgeable......there was a bad review from last year....so I am a little hesitant to drop them off to get the spring pressure checked.....further investigation needed!!!
Unwrapped these for the first time since 2009 when I purchased them.....they do look good....here are some pics.....
Also if anyone has a good recommendation for a machine shop in the Metro Philly area....let me know.......thanks...
Last edited by 74 LS4-454; 02-28-2018 at 04:29 PM.
Heads are done and you're just replacing Rings. What do you need in machine shop for? Just a couple guys used to run a speed shop up in Bristol that are playing around in the garage still these days they bought a short block off me last year. They seem to know what they're about.
I guess you know of Fonse performance in Sicklerville is New Jersey.
I do need to get the spring pressure checked to make sure they are within specs for the roller cam.......did not know of Fonse performance.....but will check them out......thanks for the info.....
If I had the equipment or access to it.....I would attempt to do it myself....but having a good machine shop is a better alternative.....
This and a 60 buck harbor freight 1 ton arbor press. https://m.ebay.com/itm/JEGS-Performa...MAAOSwDkVaV3o7 then I cut wooden dowel to 1.88 or 1.9 and 1.2-whatever for installed height and compressed pressure. You can also up installed pressure with a set of shims. I checked the springs that came with my 215 heads sitting 20 or more years. They were still fine.
I have a very simple question to ask.......and that is if the valve spring is installed at the correct height and it yields the desired seat pressure......would that mean that the open pressure is automatically determined at the correct collapsed height??? so if my Isky springs were set @135 lbs at IH.......then is it safe to believe that the open pressure would be the stated 395 lbs as per the spec??? Reason I ask this is......I have seen videos that show how to obtain the correct seat pressure from various methods......but it seems the only way to determine open pressure is by measurement only......another words....there is no adjustment made to get the correct open pressure......only an adjustment made to get the correct seat pressure....which yields the "correct" open pressure as per specs..... If this is the case....then there is no reason for me to get the valve springs checked......because they were installed @135 lbs seat pressure which would give 395 lbs open pressure as per specs by the installed height and collapsed height readings??? I hope this makes sense.... thanks for any info.......
How long have the springs been sitting mounted on the valves? Mine sat for 20 or more years and we're good. I think the potential problem can arise when an engine sits assembled for a long time and 3 or 4 valves are sitting open for years. I think you will be ok. There is also this type. I doubt super accurate, but will tell you if some are weaker than others., and you use it on an assembled engine. https://www.summitracing.com/parts/mor-62390
Last edited by derekderek; 03-02-2018 at 03:18 AM.
06-06-2016, 12:20 AM
