1995 4.3 valve springs n lifters?

philbullet

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Iam still having some trouble with this rebuild back fireing at higher rpm's,My mechanic brother wants to change lifters now, after we changed to valve springs to a stiffer high proformance type for the 262 cam we lost some oil preasure and now have a tapping noise(probably valves)He now want to change the lifters to match the valve springs.May be why oil prasure dropped now.
He seem to think because we put the cam from origanal block into the truck eng. block and with the stock valve spings and lifters it may be way it's back firing out of carb.. If that make sence in my typing.LOL
This heads and valve where also stock auto that he reworkd.He has a valve griding mechine setup.
 

Tail_Gunner

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Iam still having some trouble with this rebuild back fireing at higher rpm's,My mechanic brother wants to change lifters now, after we changed to valve springs to a stiffer high proformance type for the 262 cam we lost some oil preasure and now have a tapping noise(probably valves)He now want to change the lifters to match the valve springs.May be why oil prasure dropped now.
He seem to think because we put the cam from origanal block into the truck eng. block and with the stock valve spings and lifters it may be way it's back firing out of carb.. If that make sence in my typing.LOL
This heads and valve where also stock auto that he reworkd.He has a valve griding mechine setup.

You need to post a bit more detailed info..... Engine type tbi mpi or carbed..roller cam counter balanced...it may sound like brain damage but that is what is and needed
Could you post a link to the exact cam you installed along with you head casting's and engine casting's...Is this engine a balanced shaft hydraulic roller or flat tappet non balanced..
 
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NHGuy

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So if you put in a cam without lifters it should be a roller. Cams and flat tappet lifters are sets. You can't reuse existing flat lifters on a different cam. If you did get a cam and lifter set, and you find a flat lobe, rinse out the shrapnel in your motor and pray it didn't get in any bearings.

When you get new lifters you should soak the lifters overnight in motor oil, coat the cam lobes and lifter faces in assembly lube before putting them in the motor, and use break in oil (Joe Gibbs Driven is best).
You break in a new cam with weak valve springs, do the math for lift and if the new springs are more than 300 lbs at full open you will need to use the old weaker springs just for the break in.
On first start up the engine should IMMEDIATELY be run to 1800 to 2500 rpm and varied back and forth between those engine speeds for half an hour.
Then put the good springs back in, and change to a high zinc oil like Quaker State Defy or get some zinc additive. You need zinc for old school cams and lifters, it's not in modern motor oils because it hurts catalytic converters.
 
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pureinsanity

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If I understand right you took the cam out of your original boat engine and put it in the used truck engine. Correct? If so, did you replace the cam bearings in the truck engine? If not you put a used cam on used bearings and their wear is not matched. This is where you would be loosing your oil pressure. As for the back firing it could be the cam, springs or timing (ign or cam to crank). The noise is probably due to the oil pressure being low and not keeping the lifters pumped up good enough which also could be causing the back fire.
 

Bondo

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If I understand right you took the cam out of your original boat engine and put it in the used truck engine. Correct? If so, did you replace the cam bearings in the truck engine? If not you put a used cam on used bearings and their wear is not matched. This is where you would be loosing your oil pressure. As for the back firing it could be the cam, springs or timing (ign or cam to crank). The noise is probably due to the oil pressure being low and not keeping the lifters pumped up good enough which also could be causing the back fire.

Ayuh,..... Or a Lean condition,....
 

philbullet

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Sorry for the delay, had Internet trouble while offshore.
motor is a 4.3 Lx carb., balancer, everything rebuilt.
same cam 262, and lifters where used in this block they where also checked for flat spots.
originally motor was worked on before,not sure what was done, found heat temp. Button thing on freeze plus , so may have been rebuilt before, matter of fact it was .30 bored over that why he didn't want to use it.
Only cam ,lifters, and wire harness was used in new block.
cam was a 262 original but not sure on lifters but they where roller type.
I have ordered new marine roller lifters and will change them and try again.
As previously posted we change the springs with his tool while heads where still on motor and after that is when oil presume dropped and tapping noise started.
So he thinks the lifters or 1 or 2 etc. May be weak and may have been a problem in the old block.
hope that all make sence.
LoL.
 
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Tail_Gunner

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http://forums.iboats.com/forum/engin...95-4-3-lx-coil

Can someone combine threads

So you have a roller cam with a balanced shaft engine thunderbolt 4 igntion and the new vortec heads...Vortec heads and a t-bolt 4 how did you set your base timing???/ i noticed in the old thread she pops at 2500 rpm and that's where your at full advance Vortec heads run at about 32/34 total timing does anyone have a graph of the t4 timing curves

MCM V-6 262 CID (4.3L) with Thunderbolt IV Module Part Number: 805361T-1 Identification Mark: V6-14 Module Advance: 14? Initial Timing: 8? BTDC Total Advance: 22? 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5? 10? 15? 20? 25? 30? 35
 
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philbullet

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Correct, timing set at 8? rpm 650-700 .
timing is advancing, he has checked that.
 

gm280

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Any time you upgrade one thing I a used engine, you force new forces on the other old used parts. I better plan of attack is to change everything as a new set and then it all works together properly. You may be FIXING things for a while going at it as new here and there issues. JMHO! There are reasons cam companies sell their cams with cam, lifters, springs, keepers and so on...
 

Silvertip

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I really doubt the cam, lifters, and spring swap has caused a drop in oil pressure. Mixing used & new valve train parts is not a good idea and your mechanic brother should know that.. Were push rods checked for excess wear and straightness. A bent push rod can cause issues - especially if one is bound up during theassembly process. How does that happen? Simple -- the push rod may not have been seated in the lifter when the rocker arm nut was tightened. Through all of this we have no idea what the oil pressure was on the donor engine before and after the change. If you are comparing the oil pressure between the original and donor engine than a few psi difference is not an issue as no two engines will every read exactly the same. You say the noise you hear is "probably" valve noise. That's easy enough to determine and again, your brother should know how to isolate that noise. Nobody has mentioned firing order so make sure plug wires are on the correct plugs. Incorrect firing order can sometimes sound ok at idle but quickly goes bad with a little throttle. Carburetion is certainly a possibility as mentioned.
 

Boat Doctor1

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Ill agree with most! esp. the one above here!! Id look into the valves needing a valve job or even a valve that was cut badly if rebuilt!! Springs can be weak too- ill bet no one checked any springs pressures before assembly on the heads -if even heads were done (rebuilt??)
 

flipbro

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I agree valves liffters cam wont cause low oil preasure.. But the fin steal from things wearing will cause bearing damage at these high rpms
 

philbullet

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I really doubt the cam, lifters, and spring swap has caused a drop in oil pressure. Mixing used & new valve train parts is not a good idea and your mechanic brother should know that.. Were push rods checked for excess wear and straightness. A bent push rod can cause issues - especially if one is bound up during theassembly process. How does that happen? Simple -- the push rod may not have been seated in the lifter when the rocker arm nut was tightened. Through all of this we have no idea what the oil pressure was on the donor engine before and after the change. If you are comparing the oil pressure between the original and donor engine than a few psi difference is not an issue as no two engines will every read exactly the same. You say the noise you hear is "probably" valve noise. That's easy enough to determine and again, your brother should know how to isolate that noise. Nobody has mentioned firing order so make sure plug wires are on the correct plugs. Incorrect firing order can sometimes sound ok at idle but quickly goes bad with a little throttle. Carburetion is certainly a possibility as mentioned.

I think some are misunderstanding previous post.
motor has been completely rebuilt, new oil pump, pistons, bearings, etc.
oil motor is still needing more run time for breakin.
oil presume dropped after we changed valve springs (NEW)and push rods are st right and in lifter seats.
will try the new lifters when they come in
 

Tail_Gunner

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Your 262 roller cam what is the lift?? Many have .500 which is to much for stock vortec heads and would bind the springs.
 

philbullet

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Not sure on that,id have to ask brother.Ill check before cranking up,but cam was out of original motor.
Update, got the new lifters in and after removing intake notice 1 push rod bend bad (exhaust valve) and 2 other where a lil warped.
Could have been some of the trouble with backfiring before but after changing the springs it did a job on that one for sure.
I cleaned up some spare's and checked all others,replaced the 3 bent one's.
I preprimed the new lifters and replaced,hoping this does the job with these this new springs and lifters.
Gone crank it up in morning letting silicone dry over night.
 

philbullet

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Are stock vortex heads (truck) different from mercruiser 4.3 vortex head?
 

NHGuy

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Vortec heads can only tolerate a certain amount of valve lift. Look up clearance before you put the valve covers on. Turning over the engine by hand (without the lifters pumped up) won't necessarily show you bind. You might need to machine the valve guides to accomodate your high lift cam. Also you need to be sure your springs won't bind on their coils. You can look up their available travel.
You already probably figured out that you need to make sure the pushrods are properly seated in the lifters and the rockers. You also need to check your rocker geometry. The rockers have to center on the valve stems and the pushrods. And find out whether you are using self guided rockers. If they are not self guided you will need to change to a self guided style or install guide plates for the pushrods. Guideplates have their own requirements.
On a roller cam you have to use a cam button, if you don't the cam will get out of place and the lifters will slide off the edges of the lobes. Could ruin the distributor gear too.
It's all a package, has to all be considered. I'd say get all your spec's together and go join the hotrodder.com forum. Those guys know all this stuff.
 
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philbullet

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Vortec heads can only tolerate a certain amount of valve lift. Look up clearance before you put the valve covers on. Turning over the engine by hand (without the lifters pumped up) won't necessarily show you bind. You might need to machine the valve guides to accomodate your high lift cam. Also you need to be sure your springs won't bind on their coils. You can look up their available travel.
You already probably figured out that you need to make sure the pushrods are properly seated in the lifters and the rockers. You also need to check your rocker geometry. The rockers have to center on the valve stems and the pushrods. And find out whether you are using self guided rockers. If they are not self guided you will need to change to a self guided style or install guide plates for the pushrods. Guideplates have their own requirements.
On a roller cam you have to use a cam button, if you don't the cam will get out of place and the lifters will slide off the edges of the lobes. Could ruin the distributor gear too.
It's all a package, has to all be considered. I'd say get all your spec's together and go join the hotrodder.com forum. Those guys know all this stuff.

UPDATE.
We checked valve clearance we his tool and mic and they are .435 so he put a spacer and other keepers to make up differences. BAD thing is he only had enough to do 2 valves.Got to order more keeper.
hoping this will solve backfiring and other isue.
I'll keep up to date.
Thanks guys.
 
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