350 build timing issues any suggestions on current build
 

Hello, new member looking for a little advice on currently built engine, I think have an 89 sea ray 190 bow rider originally powered by 260 mercruiser , bought boat with crack block and missing most necessary engine parts like heads intake carb, I reworked another block, stock bore, flat top speed pro pistons ,scat stock cast steel crank and full floating rods, aluminum heads, 190cfm in.72 cfm ex. 2.02/1.60 valves 64cc heart shaped chambers , stainless 1.6 ratio full roller rockers hardened 1 piece push rods,(.465/.488) .496/.520 lift/w rockers 225/235 @050 278/289 dur 112 lobe sep. 1800-6000 rpm range, edelbrock performer with a holley 9015 (4160) 750cfm, roughly 9.5:1 compression I'm thinking a little over carbed, I did have to rejet and take the 76 it came with out and drop to a 68 jet, had way too much fuel would flood itself out on full throttle, now it runs pretty good but not like I thought it might, to me feels like stock 260 been having issues with timing, I've been through and double checked all my work(20yr master tech) and I'm baffled on the fact that my balancer mark when running is at roughly 11 o'clock and the pointer is at 2. And cant get it where it needs to be wont run, I've taken the boat out a few times timed by ear and really no big issues just a little doggy on take off and slight stumble from cruising to wide open if hammered. I'm thinking over carbed and timing, just never ran into the timing mark issue , and I have checked the balancer against a known good, I have a buddy with a 23'baja stock bottom end ,stock cast vortec heads and a slightly smaller comp cam and blows me away does 60 mph, anyone have any ideas on this timing issue and maybe my carb size, any help would be greatly appreciated,

What timing set do you have in it? I have done it, and seen others do it with the 3 timing key sets, get them off and not setup correctly. Bring #1 up on TDC on compression stroke and check your pointer, both valves should be closed. Timing by ear, aint gonna do it. Put a timing light on it.

Thank for the reply, I used a standard double roller timing set, single key way setup, and when I originally set up the chain I had everything top dead and the timing Mark's are right on, that's why I am so confused, I even had another mechanic buddy scratching his head, he started over tore it down and re timed the whole motor ,same issue I figured timing had alot to do with it just been unable to time it correctly because of the Mark's not lining up

Something is way off. What type of distributor?

Pertronix flame thrower II , the ignition module on the mercruiser setup crapped out and was cheaper to replace it with more options for adjustments due to the mods already made, I've moved #1 around and reset distributor, called pertronix to make sure there was not a #1 position on distibutor, they say to make #1 wherever and run firing order, I've been wrenching a long time and never seen this other than balancer spun or wrong balancer, I'm using same balancer that boat came with

Pertronix flame thrower II , the ignition module on the mercruiser setup crapped out and was cheaper to replace it with more options for adjustments due to the mods already made, I've moved #1 around and reset distributor, called pertronix to make sure there was not a #1 position on distibutor, they say to make #1 wherever and run firing order, I've been wrenching a long time and never seen this other than balancer spun or wrong balancer, I'm using same balancer that boat came with

You can't tune an engine wihout getting the timing fixed first.

When you have that squared away,
For now, i'd set total for 32*Degrees. Initial should be somewhere between 10-16*degrees. 14-16* should idle better. Don't change totalfrom 32*F though.

Thank you for the timing specs, I've Been trying to figure out my timing issue, balancer and mark dont line up,

Once i can figure this timing issue out, so I can time it I'm gonna see how it runs off those specs

Are you a ford guy and mixing up the cyl#'s for the chevy :)

what timing cover and indicator are you using? there are three different locations for tdc on balancers and three different locations for the tdc indicator. you need to find tdc for #1 based on the piston and see where the balancer and indicator are.

To confirm the timing mark you have to bring the #1 piston to TDC and verify the mark on the balancer is lined up with the mark on the timing pointer. If your harmonic balancer was for a different engine design the mark could be in one of 3 places. The good news is you can just paint a mark on there.
If you think the crank is not spec, look up the part information by it's part number in Scat's info, or call their tech line. You never know.

You are right that the carburetor is too big for the 350, Unless it has vacuum secondaries. If it has them then the carb will self adjust to the intake air volume.
Go back and reset the idle jets to 1.25 turns from the seats. Time it to eight degrees BTDC at 750 rpm and then adjust your idle jets (probably down) for best running at 750 rpm with proper mix.
Now bring the RPMs up til the advance maxes out. Don't let it pass 32 degrees. I think that distributor gets it's all in advance at 2800 or 3200 rpm. If you do this on the trailer don't keep it revved too long, Just be up there long enough to get a number. If the distributor doesn't get 32 degrees you can adjust it for all-in timing.
Then, set idle to 750. Final adjust the mixture by turning in one idle screw til you get a stumble then back out a bit til it's smooth. Adjust the idle back to 750 or 725,Now set the other idle mix screw. Reset the idle rpm as needed.


I bet you have so much fuel running through there that it takes more timing to stay running. I've done it to myself, so I thought I'd throw this idea out there.

what did the harmonic balancer on the engine come from?some of the trucks used different timing chain covers and balancers due to placement of accessories.my guess is you have mismatched cover and balancer.

you said the balancer and cover are factory correct?? I think that's what you said...the only variable has to be the crank then...my guess is its keyed slightly different than the factory crank...that said..just get the motor to TDC and paint mark the balancer to the pointer showing true 0...doesn't really matter that the marks don't line up..just make a new one...that's my suggestion for what its worth lol

The outside of the harmonic balancer possibly slipped around the inside. Not sure I'd use a 29 year old harmonic balancer

A Holley 4160 is a vacuum secondary carb. Same as 4150 except use the secondary plate controlled by vacuum.
The spring for the vacuum control can be changed to adjust the secondaries.

I did not read any of the this -- just the headline, sorry if it has been discussed. just adding maybe some helpful info. Make sure cam timing is correct / TDC and you have the correct sized balancer. Make sure it did not slip either. ( the outer vs inner of the balancer ) If you are using timing TAPE make sure the tape is for the correct sized balancer. Man do i see that one alot being wrong. ie: . The timing tape is sizes specific per balancer. If you are using a pointer make sure it is correct for the correct balancer,

Sorry I've been away, been working alot, gonna work on it tomorrow roll it around to top dead and recheck the marks, if it's a crank key way issue ,I'll just remark it and go from there, if the balancer itself did spin ,I'll replace it..it still looks fairly new, but ya never know, I did have a couple good back fires with the old merc distributor, maybe it slipped, and if every thing lines up...then ..... idk.. I'd really like to get it timed right. i know this motor could run way better and push my boat faster than 50 mph and get it out of the water alot quicker , it does run way better after down jetting the cab ,just this timing issue, thank you for all the great info, I wil lk definitely try out the tuning timing processes mentioned and get back with everyone with what I find

I did have a sbc balancer spin on me. Rubber got old and it moved. Maybe compare key way to another balancer in the shop to see if it is close?

Off the subject and not anything to do with your timing marks, but what are you running for exhaust? stock manifolds and risers? That cam is really pushing the limits on duration for reversion and then you added a few more degrees effective duration with the 1.6 rockers. Your hesitation and stumble may very well be some reversion. Just trying to save you more headaches.

Fixed. Figure led it out
 

Been a while since I’ve been back, new job has me working a lot and took most of the summer to gut my boat and replace transom, stringers , foam and floor, after I put the motor back in and started to tinker with the timing to figure out my issue. I took valve covers off , pulled timing cover and distributor... started over verified cam and crank timing, spot on , reset to top dead reinstalled distributor. Still ran off spun around to tdc again and retarded to distributor 1 tooth and when I fired it up I started easier was idling high so I tweeted it down 650 rpm. Still running and camming really nice. Pulled out timing light and I had visible marks again set my base the reset idle , made couple slight advance spring adjustments, jetted carb down from a 74 to a 68 primary 74 secondary and she runs like a scalded dog. Up prop to 21 cleaver from an 18 4 blade ( the 18 was interesting and some fun) and can still twist 6500 rpm and launches pretty hard , I spun the drive coupler the last time out and couldn’t run over 3800 without free revving , coupler this year and a 23 cleaver to see what she does.