I'm sure you all get tired of these "help me with my engine build" type of posts, so I'll try to be respectful of your time. I've finally finished the suspension rebuild and disk brakes on my '66 Cortez Motorhome and I'm ready to rebuild the engine.

When I planned this build almost two years ago, I bought all the parts to do it this way:

- original 1966 225 to be bored .060 over and oiling improvements (have new old stock Clevite pistons, moly rings, and NOS 225 rods)
- 1972 Cyl head with oversized valves, 3 angle valve job, some unshrouding work and bowl blending; 340 Valve springs & retainers.
- MP244 Cam & NOS elgin lifters
- Weber 38DGES Carb on offy manifold
- Dutra Dual exhaust (modified rear manifold)
- New Rollmaster Double roller timing chain
- Teflon crank scraper
- Electric fan

Now, some new options are available:
Erson RDP Cam (Doc can you tell me which RDP grind?)
K1 rods with Wiseco pistons (I'm thinking the 3.504")

The Cortez has a 4 speed manual FWD transaxle with 4.71:1 gear ratio. it weighs 10-12k lbs fully loaded.

Considering all of this, and the fact that I already have the other build parts, would the horsepower and torque gains be worth the additional $1200 for the new options? (I can afford it, but don't want to throw money down the drain either). Or, Would you suggest something else?

Thank you for listening

-Moose

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1966 Clark Cortez, Industrial /6

i have no base to compare a long rod to a stock rod engine, but if i were as far into the build as you are the only change i would make is the cam and go with a reverse pattern, to give you some increase in the lower rpms, torque is what you need.

I'd use a very mild reverse dual pattern cam or the MP244 and use stock valve springs and retainers. 340 springs are completely unnecessary. I really don't think the K1 rods and Weisco pistons are worth the cost in such a low RPM application.

I would spend the money to have the combustion chamber volume and the piston deck height checked so you can calculate the compression ratio. I would also spend the money to check and likely change the cam's installed centerline.

Are you going to Y the two exhaust pipes together into a single? I would.

What do you have for an ignition system?

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Joshua

I agree. Don't bother with K1/Wiseco, and you really don't need the crank scraper either. 244 MP or similar cam is fine.

I wil repeat what Josh said in big letters - HEAD WORK IS KEY.

Lou

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Home of Slant6-powered fun machines since 1988

Thanks so much for the quick responses!

My plan for the exhaust is to have 2.25" pipes mandrel bent and brought to a 2.5" Y. Then gradual reductions down to a 2" exit. I will use a magnaflow straight thru exhaust and a resonator.

It currently has an MSD 6a and electronic ignition.

I will do basic porting per Doc's instructions, then have the shop do bowl blending after the hardened seats are installed.

Once the chamber volume and deck height is known, I will have the block decked and head shaved to achieve a target 9.5:1 compression ratio (I figure to take the amount to be cut and remove half from each.)

I am going to do the block and head oiling improvements myself, as well as weight match the pistons and rods. Then have the whole rotating assembly balanced.

A mechanic friend is going to help me do the engine assembly, and we will carefully degree in the cam. (if I remember correctly, installed retarded 3* for torque.)

Since I already have the crank scraper and 340 valve springs, can I presume there's no harm in installing them?

If I have anything wrong or am missing anything please correct me, I want this to be right from the git go. I also appreciate any suggestions on how to do it better.

Thanks again for your advice, I appreciate it.

-Moose

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1966 Clark Cortez, Industrial /6

Cam gets advanced for low-end torque, not retarded. But you'll want to spend the time and effort to degree-in the cam, not just line up the dots and then advance it.

Agree with the others: K1 setup and crank scraper aren't cost-effective in your application.

Think very carefully before you buy that Magnaflow "muffler"; unless you like boomy exhaust drones at cruising speed (resonator or no resonator) you might save yourself money and aggravation by using a Walker #50051 instead. I put one on my truck and Reed put one on his van (see here for movie w/sound and link to Walker rebate) and we were both really pleased with it. It's a giant muffler — an OE replacement for '04-'05 year range Dodge Ram pickups. There's room under your Cortez for a big muffler, and "big" is what you want for high flow with low noise.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

340 valve springs in this application are just extra load which will use power to create heat and wear out the valve train faster. I would use new stock springs.

For this heavy a vehicle and that short a duration cam I think 9.5:1 is pretty aggressive. I would target 8.5:1. Most 225s as delivered are 8:1 or less.

Having used both Magnaflow and Walker Dynomax mufflers I have found I prefer the Dynomax. I think it's because the Dynomax doesn't rely solely on the fiber material for sound attenuation. So this Dynomax muffler would be my choice for an RV.

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Joshua

Thanks again, guys! I originally thought of the Walker Quietflow mufflers but gave up on it since they don't publish the size chart online. The 50051 sounds like just the ticket.

Josh, I'll take your advice about the valve springs and compression ratio.

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1966 Clark Cortez, Industrial /6

Definately on that... the funny part about that though, is the Erson cam I got that was ground 4 degrees advanced, I used my last MP roller timing set, and when I lined the dots up...it was 'spot on' for the .050 degree check numbers for the intake side...so either the timing set was good or the cam grinder didn't fall asleep...
Head work, RDP cam, work towards moderate compression for the heavy vehicle, distributor timing needs to shift toward the 40 degree range as 50 degrees vacc+mech+initial will be a bit heavy...I'd love to see a vacc. gauge map vs. rpm and road/load conditions for a Cortez...I think a bit less initial, heavy advance springing on the mech side, and a lighter vacc pod (6.5R at best) might be the key...

-D.Idiot

In my experience, I like the 244 MP cam degreed at 101 or so. I had it at 99 and it was soft up top. 103 is where I have it now, which is great all around but you may want a big more low end. It is really almost a stock cam. Degreeing is definitely worth the time.

Personally, I'd run a bit bigger cam and a little more comp on your vehicle, but there are many opinions here as you can see.

Lou

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Home of Slant6-powered fun machines since 1988

lou i second that ,a mid range cam 460/470lift and 9.5/1 compression that works with supreme gas will make a better hauler.

Lou, Just to be sure I understand the disty curve you are recommending: I would want a total of about 40*, maybe 10 initial with a heavy spring for slow mechanical advance. I'll have to look at what governor I have.

I think one of the new RDP cams might be worth my while. Maybe I'll shoot for compression of about 9:1?

I appreciate the discussion, you guys are great!

-Moose

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1966 Clark Cortez, Industrial /6

If you get the dynamic compression ratio too high you'll end up having to use less than optimum spark timing to keep it from pinging. If the cooling system won't keep the engine cool the pinging and spark advance problems will only get worse. Using a later intake valve closing lowers the dynamic compression ratio, but it also moves the torque curve to a higher engine speed. Long valve durations are not for heavy vehicles as you need all the off-idle and low speed torque you can make just to get moving and you have one of the heaviest slant vehicles built.

You might find it educational to look at the cam and compression specifications for a couple different 440s or 413s. Look at the specs for the passenger car version and the medium duty truck version. You will find much lower compression ratios and shorter valve open periods in the truck versions.

Having done a fair amount of towing with a 318 van and having used a couple different cams in the van I know that heavy vehicles are very sensitive to a loss of torque at low speed. Even very small losses in torque. 10ft/lbs in high gear is 47 ft/lbs at the wheels. Multiply that by your 1st gear ratio and see what a seemingly small difference will make.

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Joshua

i have towed with v8 and six`s, more lift with moderate duration increases hp and torque which is what you need in a heavy truck,yes the cooling system will be pushed but with a /6 you can get a large enough rad to compensate. if the reverse pattern cam does it job it will increase torque in the lower rpm`s even with more duration on the intake. putting more timing on a high compression engine at part to half throttle will not produce preignition as if it was at full throttle and when towing if you have to floor it to keep moving then the truck or load is way to much for the engine.

27-30 deg full mechanical advance, all in around 3000 RPM with a reasonably heavy spring. 10 deg initial advance. Add 14-19 deg vac advance w/adjustable pod. I would not go over 9:1, and probably use Doug's (Erson) RDP grind (270 int/254 exh?). Everyone will have their own opinions here, so you will have to choose.

If I were going all the way here, I'd stroke the crank to 4.4" and bore 0.060". Again, the best money and time you can spend is on headwork. You want a mild motor, but that makes about 200 HP and 250+ ft-lbs.

Lou

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Home of Slant6-powered fun machines since 1988