LH / RH Rotation Dizzy Replacement

Hi all

Been reading a few post on this topic but thought I'd ask again to get a clear picture before I replace my older dizzy's. I'm looking to see if my Crusader 270's, circa 1987, will take a "standard LH rotation" distributor. My configuration setup is below and I will be headed over to the boat soon to check the dizzy rotation.

• Crusader 270's SBC
• Existing Mallory points dizzy (YL670AV)
• Straight shafts, borg and warner tranny (not v-drives)

In reading some of the posts up here its clear that rotation differs depending upon your set up. What I'm trying to find out is is will my crusaders accept the "standard LH rotation" distributors. I am thinking yes even though my configuration consist of LH and RH rotation engines (obviously). The dizzy will still rotate the same way, right? Is there anything specific I should look for before I pull the trigger and purchase 2 LH rotation dizzy's?

And does anyone have an opinion of EST vs. mechanical advance? Which is "better"?

Thanks!

I can say with 99.5% confidence that all right-hand rotation Crusader spin the distributor the same direction as the left-hand Crusader. You can prove your set up to yourself by removing your engines' distributor caps, engaging the starter and watching the direction of the rotors. Instead of using a chain to connect the crankshaft and camshaft (which drives the distributor), on right-hand Crusaders the camshaft is driven by gears meaning only the crankshaft rotates right-handed.

I have ESTs on my 1977 Crusader 270s. They work OK if you replace the module inside with the genuine GM version (Delco part number D1965A). It's been pointed out on here that the advance curve as RPM increases is different than the mechanical OEM curve.

I am not saying EST is the best. There are very few choices out there for marine engines. I would look closely at the Davis Unified offerings.

Thanks DJR, and I agree as I'm also 99.9% sure of the standard rotation and having the dizzy's rotate the same way on both engines. I'll pop the cap to verify as that is the easiest way.

As far as what type of distributor - I've seen the Delco EST ones, i know about the MSD's as well but they are costly with the additional module. They also have a "ready to run" version that I looked at but i have subsequently found a pair of Mallory YLM 624AV LH rotation that I could use. They are mechanical advance if I'm not mistaken. I have no idea which is best - the Mallory's or the Delco EST or the MSD "ready to run". Any opinion?? I did see the DUI's and hear great things about them but the only hang-up is they are not SAE J1171 certified. Many have said that is hog wash but I got a young family and wouldn't want to put them at risk, even slightly, and I think the insurance companies would have issue IF they ever caught them as an issue. I don't know because they would be the easiest option as they are reliable, reasonable and have available parts.

Uncertain which way to go, should just flip a coin!

Sorry, but I don't really have an opinion between the choices. I'm just a boat owner, not a mechanic.

I will say though that the "Delco EST" distributors many sell online for the SBC marine engines are just aftermarket auto distributors. The ones I purchased are marked "GM04". I Googled and found that these are manufactured by Spectra Premium. They don't have any J1171 certification shown on them; however, the vent holes are covered by fine-mesh screens so ...who knows?

Good luck

If they are 1987 vintage (+/-) & nobody has had them apart, then yes, they both take the 'standard (LH)' distributors...some of what you may have read likely comes from those not familiar with the GM product line from that era...

On the choices, in no particular order, here's my 2₵:
the DUI's are tested to the SAE standard and are 'approved' for marine use. their only real drawback is the costs...some have had clearance issues as their 'normal' caps are taller.

If you found a pair of 'old' Mallory YLM624AVs, I'd be inclined to grab them...you can dial in the timing curve if you need to. The 'newer' versions are typically Sierra 'clones' and I haven't found anybody that's been happy with their quality...things may have changed but I wouldn't bet on it.

On the EST's...they work but have fixed ignition timing curves (unadjustable; in the module) when used in stand alone (not ECU) mode. I personally do not like the curve as it is rather steep and goes to full advance very quickly...that said, many have been used on both the SBCs and the BBCs as standard equipment for years. Also, beware of any clones due to quality concerns...If you do go this route, my suggestion is to set the timing at full advance and live with what you get at idle as long as the engine restarts once at operating temp...in other words, don't go thru the 'timing plug' exercise...

Mark - thank you for your point of view as it was exactly what I was looking for! I'm going to pull the trigger on the older Mallory's as I know you can still get replacement modules and parts so seems like a good choice. You mention the ability to adjust the timing curve. Do you happen to know how or maybe there is a manual on the adjustment process? I only as because since they are used I have no idea if they have been adjusted and they aren't coming with a manual so I'd have to take a guess at how to confirm and or make changes.

As usual - thanks!

Oh, they are used....given that nugget, I'd say the best thing would be take them to your local 'distributor shop' and have them checked (mechanically) and then get them to measure the curve in each right now. if it matches your needs, you are done. I'd say the only 'weak' point is that the springs and weights will rust over time and I haven't seen an owners manual that tells one to give them some attention every winterization (at a minimum).

adjustments the the timing curve is usually done with the springs...if you need something different, there are a few non-traditional tweaks that can be done but I've never seen a standard production engine that required them. If you can't find the mallory kit, the aforementioned distributor shops usually have alternatives.

If you don't have a shop you can visit (preferred alternative) there are several shops on the www. Best bet is to check with the local car club - they should be to tell you where to get your distributor work done.