Another 4200 RPM stumbling/cutting out question...

[mustangfrank]

Messed around with the dizzy trying to see if there was a sweet spot, retarded it until I got an error and advanced it until it started spark knocking (on pure 93 octane). Dead horse...she likes to be right at the factory mark.

Pulled both #1 valve springs to get them checked...to be continued.

[mustangfrank]

Turns out it was valve float. The head was shipped later than the rest of my parts in the kit and I think thats when an error occured. They were supposed to have installed "Z28" springs but since they shipped the cam a month earlier someone goofed.

They did install SBC springs but they measured 105 seated and 210 open, which is actually less open pressure than stock. Good news is my machinist had a new set that measured 110 seated and 285 @1.21". Other than driving me nuts for a week trying to figure it out I guess it was a good thing to break the cam in with lower tension springs.

My machinist recommended doing another full 30 minute cam/engine break-in so I dropped the oil/filter and did another bottle of ZDDP.

Runs right up to the redline/shift point now, pulls harder throughout the entire range. I'm getting a tiny bit of spark knock during WOT and it seems a little lean on top but I should be able to tune those issues out. Also the valvetrain was dead quiet for a Jeep and after springs installed it is audible, not bad just like a stock Jeep. I'll double check the preload or just get an aluminum valve cover.

Thanks to all who helped, this forum has been my go to source before during and after my stroker build. I'm headed outside to clean and detail the Jeep so my 24 year old son can take "delivery".

[Cheromaniac]

I thought the stock valve springs were only good up to .430 lift?

That's correct. However it's probably better to use the stock valve springs for the cam break-in and then upgrade them to Mopar P5249464 (rated to 0.525" lift).

[F1boats]

Having the same problem who did your head ? I have change every part you can name expect crank sensor. Titan did my 4.9. Thanks for any and all info. Peace <><

[mustangfrank]

Having the same problem who did your head ? I have change every part you can name expect crank sensor. Titan did my 4.9. Thanks for any and all info. Peace <><

Titan...

[F1boats]

Thank you very much

[F1boats]

Can you send me your name or call Chuck at Titan he recalls nothing of your problem bumming me out !
F1boats@comcast or Chuck at 888-477-8066 Please help ! Thank you very much

[Cheromaniac]

Well, my friend Majid e-mailed CompCams to get their opinion on this issue and this is what they said. The CompCams cams have fast valve opening/closing ramp rates so if you use stock valve springs, the valves will float at ~4200rpm and this seems to be a common issue. CompCams said that the cure is stiffer valve springs.
Majid's ordered a set of Mopar 5249464 springs with matching retainers/locks and after he's installed them, he'll let me know if that cured the problem.

Majid's now a very happy camper. After following my advice to upgrade the valve springs, his engine pulls hard all the way to 5200rpm so the original problem was indeed valve float.

[F1boats]

Did Titan do your engine ? Thanks for any info

[Cheromaniac]

No. I built my own stroker and Majid's engine is a modified 4.0 with a CompCams 68-232-4. He reused the stock valve springs after the cam swap and his engine ran into a "wall" at 4200rpm due to valve float.
My stroker has the stock cam and pulls to 5200rpm with the stock valve springs.

[Freakin A Scrib]

I thought that the stock springs would bind when using the -232- cam because of the amount of cam lift..... ?????

[mustangfrank]

Well, my friend Majid e-mailed CompCams to get their opinion on this issue and this is what they said. The CompCams cams have fast valve opening/closing ramp rates so if you use stock valve springs, the valves will float at ~4200rpm and this seems to be a common issue. CompCams said that the cure is stiffer valve springs.
Majid's ordered a set of Mopar 5249464 springs with matching retainers/locks and after he's installed them, he'll let me know if that cured the problem.

Majid's now a very happy camper. After following my advice to upgrade the valve springs, his engine pulls hard all the way to 5200rpm so the original problem was indeed valve float.

Glad to hear that.

[Brian E]

Having the same problem who did your head ? I have change every part you can name expect crank sensor. Titan did my 4.9. Thanks for any and all info. Peace <><

Titan in Ocala did mine a few years back and I fought with the engine falling on its face every time I hit over 4000rpms.
I also had them replace the cam three times due too lobe failure, and one cracked head. I finally took it to my friend in Gainesville who is an extreme race engine builder with so much knowledge it mind boggling. I got him the specs from Comp and we checked the cam "which turned out to not be what I ordered from Titan" so he figured out what the cam was then calculated it and found they set it up at full coil bind and not enough seat pressure. He set me up with custom retainers he cut and made for me from big block Chevy ones, ordered the right springs then bam red line constantly. Titan should stick to Briggs and Straton rebuilds, even then I would not buy one from them. WARNING THEY OPENED ANOTHER SHOP IN ORLANDO FL! Cant be any better.
PS I removed the cam they installed
"a Seal Pro 4.2L stock replacement bulk rebuild cam with a 430 lift" and installed a Comp 69-235-4, this cam is a little rough on idle and freaks the ECM out once in a while on hot start but its a rocket on the highway after 2500 rpm. I do not recommend it for daily driving, fuel mileage, or offroad slow going, and I am about to change down to the 68-232-4, fingers crossed.

PS to all, if you live in Florida Dave Rumping in Gainesville is the most detail oriented machinist you will ever find.
Check out his 5.0 Mustang cover car on July 17 2001 and there write ups on his other car in the same mag. He also won Orlando Fl fastest street machine and the Gator Speedway HP shoot out in his class small block, 903 HP rear wheel!

He recently built a 2.5 Jeep motor that really kicks A S S. Porting, flow work, you name it.

My original stroker with the crap cam got 17 miles to the gallon in my TJ 4.56 gears and 33" tires NV3550 HWY.
The Comp 69-232-4 everything else the same I am getting 11-12.5:(

[F1boats]

Motor going back to Titan now 4200 rpm problem and possible rod knock, low oil pressure ect. Chuck say's he will make it right. I do like Chuck hope he comes thru.

[dwg86]

Good luck. Titan doesn't have a good reputation with the Jeep stroker engine.