Thunderbolt iv timing

[MikDee]

Mik...:facepalm: Please READ THE BOOK, there is no, repeat NO, valve adjustment on the Gen V engines, just button them up, torque the rocker bolts to 45lb-ft and THAT IS IT!

Also, on firing order. The cam has quite an effect on firing order. Yes, the pistons will continue to go up and down in the same order, but remember there is always 2 pistons at TDC at a time. One will be firing (compression/power stroke) and the other will be 'on the rock'. It's the positions of the cams on the camshaft that will determine which stroke that cylinder is on, hence the firing order. A very good example is the Ford 302 engine. Standard factory firing order and the firing order of the Mercruiser '888' is different... Why? Because the 888 uses the Ford 351 cam, not the standard 302 cam....

K55, try this. It's a longshot, but I think you're there now. With the engine running as best you can get it, remove the spark plug leads one by one. You should be able to notice a drop in revs when each lead is lifted. Albeit a small drop with a big V8, but you should be able to hear it. If any cylinder doesn't drop, it's a problem. If you have 2 cylinders that don't drop, check their positions in the firing order. If they are opposite each other (opposites would be 1 & 6, 8 & 5, 4 & 7, 3 & 2)... Try swapping just those 2 cylinder spark plugs and see if that's any better.... I guess you see where I'm looking here....

Chris....

Chris, I got your private message, but can't reply since this new format is capturing all my posts, & messages, and filling up my mailbox without my knowledge? It won't let me send any messages.
The OP doesn't specify if it's a Gen V motor, apparently he doesn't know? he mentioned the heads might have been changed? So, how am I supposed to know? No, as I said, a camshaft is NOT gonna change the firing order! Basically, big block, or small block, a Chevy cam is always the same firing order, unless we're talkin a reverse rotation motor (which is another story). By the way, I'm well familiar with the Merc. 888 I had that in one of my boats yrs ago, and also knew it was based on the Ford 351. Trying to find a matching used 4bbl manifold for one, is like trying to find "hens teeth".

 

[achris]

Mik, read post #31, "The rockers had a bolt, no nut"... That alone makes it a Gen V.... And the cam can determine the firing order.. Read this article -> http://www.precisionenginetech.com/tech-explained/2009/06/03/special-firing-order-camshafts/ Particularly the 5th paragraph...

 

[MikDee]

Mik, read post #31, "The rockers had a bolt, no nut"... That alone makes it a Gen V.... And the cam can determine the firing order.. Read this article -> http://www.precisionenginetech.com/tech-explained/2009/06/03/special-firing-order-camshafts/ Particularly the 5th paragraph...

All good info Chris, but it doesn't pertain here. It's just the average guy putting in an average mild hi-performance cam. Technology changes often, sometimes daily I think, although I've heard of this firing order change on experimental engines, it is not a commonplace thing,,, Yet. It amazes me the power, economy, & durability combined, that GM has gotten out of these latest even smaller engines, like the LS series.

 

[achris]

klawton55, how did you go with the suggestion I made?

 

[klawton55]

So I got it figured out today, and am ashamed to say that I had two plug wires crossed. I checked them several times but where they were routed I guess i confused two. I took my dvom meter and ohm each wire and found no continuity on two, I switched them and sure enough started right up and I was able to time it. The saying goes keep it simple stupid, and I sure feel stupid. Well that and sunburnt since we got out on the lake today. But I will take it! Thanks achris and everyone for all the help. I even watched one of your YouTube videos achris and adjusted my shift cable. Man it feels good to be on the water again.

 

[Bt Doctur]

Glad to find out you found what was wrong ,now go enjoy it

 

[klawton55]

Thanks its great to be on the lake again!

 

[MikDee]

Good for you klawton! been there, Done that,,, Glad you got it all straightened out though, that's the main goal of ALL of us here!
I'd love to see, & hear that Big Block Scream! But, you gotta let it break in right. Good Luck, & Enjoy

 

[achris]

Great news... Good to hear it's sorted. Mik, please email me (as per my last PM).