Need new motor for my Scarab, please help me do it right!

Gentlemen,

Thanks for all of your input in the thread I've linked above from last year. I've finally pulled the trigger on the Vortec 350 new from GM as @TomZ mentioned in the post. I'm now trying to decide on what cam to order for the new build. I'm looking at the comp cam XM270hr or the LT4 hotcam that TomZ suggested in the post.

What to do!?

Also, I'm assuming these springs will support both cams with their advertised lift? https://www.alexsparts.com/valve-spr...ssure-vsk4h50/

Please let me know what cam I should purchase, or if there are other cams more suitable for this build.

Finally, I have a rebuilt Quadrajet to pair with this combo, will that be OK or do I need to look at a smaller CFM Carb?

Just want to make sure I'm doing it right this time as to not have any issues this summer!!

Thanks in advance!!

i have a xm270hr in my vortec 350 i have Alex's parts valve springs rpm intake stainless marine exhaust 3 seasons on it with no issues makes good power runs mid 60 in a 20 baja

I did a vortec head upgrade to a 350 2 years ago, also upgraded to a roller cam, I had comp do a special grind(no extra charge) to work with the vortec heads(has to stay under a certain lift) and target max RPM of 5500-5700. boat has run great for last 2 seasons, now had to change distributor to get rid of factory rev limiter. Used a 600 edelbrock carb, which I would like to change to a holley after seeing power gains switching to them.

Those cams are pretty damn close. Durations at .050 is exactly the same, LSA is the same and lift is very damn close. For some reason the hotcam says its best suited for 1800-5800 RPM and the XM270HR I think was 1200-5200.

I am in the process of building the same motor you are and opted for the comp cams XM270HR. I also went with edelbrock aluminum etec 170 heads, a DUI ignition, EMI exhaust and a Canton 7 qt oil pan.

Based on what I have read, you cannot go wrong either way for the cam.

You might want to research more on the springs. The springs in your link look a little light on the seat pressure for a roller cam and in the ad they say they are for a hydraulic flat tappet cam. If you get the XM270HR, just ask the folks at comp cams what they recommend for a spring. I know they have a beehive spring that is supposed to get you the clearance in order to run more lift on those stock vortec heads. Not sure if it requires machining or not.

alex's parts valve springs allow you to use a cam greater than .450 lift without machining the heads behive springs will work also

What is "Alex's Parts"? That spring kit states it is for flat tappets.

they would have to do a longer valve to get the clearance if not machining the guides ?

https://www.alexsparts.com/valve-spr...ssure-vsk4h53/

Thanks for all of the insight, Gentlemen. Much appreciated!

I will call on the springs and see if they're suitable for my setup or if I need to switch to the beehive springs instead. I rant these on a previous, flat tappet cam on my old merc 260 sbc with vortec heads and they worked well until I detonated and blew the engine up.

The beehives aren't too expensive so I'm not opposed to making the switch..

Another question..

I'm a bit unclear on what all I need to swap in order to put this Vortec engine into my boat which had an 86 model Merc 260 in it?

I've read different things on the flywheel, coupler, starter, manifolds, water pump, etc. needing to be changed over to a different style to fit. I've also read that in 1986 Merc switched to the 1 piece rear seal and the flywheel and coupler is the same as on the Vortec's and will bolt right on.

Can anyone shed light or a link on what I need to do to make this engine fit? Would like to go ahead and have all parts on hand to make the swap.

Thanks!