Technical Nick's 1950 331 Cadillac with 390 Heads Engine build

My 1950 Caddy Series 61 2dr Coupe, as wonderfully original as it is, has been reliable but lacking in oomph. So earlier this year on the way back from Pendine VHRA Hot Rod Races in Wales UK (not 'Wales England' as they're two separate Nations within the UK) i decided that i'd rebuild the engine this winter.

The car is a timewarp, purchased new in 1950, used until 1961 and then put in a Maryland barn under tarpaulins until it was recommissioned (fuel lines, brake lines bearing re packed etc) in 2007. I brought it to the UK in 2011 where it had done less than 500 miles since being dragged out of the barn. You couldn't wish to find a more original car.

So i wanted to rebuild the engine, warm it up but retain some of the patina of its age and externally fit parts that may have been fitted to a Rod in the fifties. I plan to pull a 1950 Silver Streak Alien eye Clipper Travel Trailer with it when done so i'll have to work on the drive train and rear suspension too no doubt.

I whipped the engine out approx 6 weeks ago. This is the first V8 I've built, my engine building experience limited to 4 cylinder UK Rally cars such as Ford Escorts, Vauxhall Nova's, Minis and Avengers etc. Hence I've done a lot of reading. HAMB has been invaluable and i openly admit that my build follows paths forged and freely communicated by HAMB members c322348, Roothawg, Dyce & Marcus to name just a few. Thank you so much for sharing. But also invaluable reading has been David Vizard's, my go-to engine building guru, 'How to Build HP' & 'Port & Flow Test Cylinder heads' plus A Graham Bell's 'Performance Tuning'.

After 6 wks or so of researching, designing, sourcing parts and scratching heads I've taken the plunge & yesterday bought the parts for my rebuild. Thanks to many of you on here for freely sharing your knowledge & hard won experience that has enabled me to press on confidently with my stab at this engine. It was a 160HP @ 3800rpm engine, but the exhaust flap was stuck partially closed on the left hand bank so i bet i'll only have been getting 120HP out of it. I'm targeting that it'll be a 370CuIn 350HP+ @ 5000rpm engine going back in. Here is the spec I've settled on- a few compromises but hey ho. I'm sure i'll break the down stream drive train so thinking about sourcing a 59-62 Scrap Caddy, importing it in a container & stripping the parts off it.

- 1959 Caddy 390Heads (had them magnflux & pressure checked)
- original 331 crank but re-balanced with new parts (i wanted a 390 crank but couldn't find on in the UK at the time so am sticking with the 331 stroke, it'll do and will lessen any clearance issues)
- SCAT 2-454-7100-2200 H Beam stainless rods 7.1" ctrs (up from 6 5/8") with a small end bush to reduce it from 0.990" (BBC) to 0.927" (SBC Wrist pins in the Ross Pistons)
- Ross 90455 forged aluminium pistons + block bored to 4.030" (up from 3 13/16")
- CR set at 10.5:1 up from 7.5:1
- Steve Long Cam Int 0.478" lift 214deg @ 050 Exh 0.486" 218deg @ 050 110 deg LCA (wanted 108deg LCA but we're regrinding old cams rather than starting with a blank)
- Manley custom stainless valves, 11217-8 blank 1.6" Exh (up from 1.5" in 390 or 1.44 in 331), 11216-8 blank 2.02" Int (up from 1.875" in 390 or 1.75" in 331). 30deg seat on Int with 20deg back cut + David Vizard 'conformation groove' on face. 45deg seat on Exh with 30 deg back cut and 0.025" rad on face. Bead type valve locks + wear caps.
- PAC 1220 Beehive, flat wire Valve springs & 10deg retainers. Having to cut wider spring seats on the heads to accommodate.
- Porting & head work by yours truly- port CSA sufficient as is for good gas flow speed, just cleaning & flaring into new hard valve seats with some port bias where i can to promote barrel swirl.
- Sanderson Headers CAD391 with black ceramic. Bit of a compromise as the primaries are shorter than ideal but key in twisted crank lower revving V8 is to have good long length secondaries, perhaps 48" or more (directly from Vizard).
- Weind WCFB Intake with 1957 reconditioned 2x4 Carter AFB's. A compromise again as i couldn't find the Weind AFB intake (flows lots better you lot advise). May move to Offy 3X2 intake & Stromberg 97's Carb set up if Offy ever do start selling that intake again, plenty of room under the hood.
- new Caddy 390 rockers & shafts (wanted Aluminium but none available so trying to work out if i can modify a FordFE 390 set which looks similar)
- Trend custom length hollow pushrods
- 390 Timing cover with rubber seal
- The Ford rear crank main seal posted in the Cadillac Technical thread.
- Chevy Hyd tappets

It should go back in looking like an engine that was rodded in the 50's, with some patina to it (i'm purposefully not painting the rusty Caddy rocker covers). And, with that cam & exhaust, it should sound burbly & cool. Can't wait to get the machining done and on with the building.

 

Wow, you really have been doing your homework. Sounds like it’s coming together nicely. No offense but umm, do you have any pictures?


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Wow! That was fast! Thanks for posting this up!

 

A very exciting day for an Engine build, received most of the new parts. When the block & heads come back from the caustic bath, I’ll paint them Cadillac Dark Blue & then it’s off to the machine shops. A little worried about my block though. The water jackets were solid with rusty debris & even after a thorough jet wash after welch plugs removed, were still oily inside. Either there is a crack somewhere or the head gasket has leaked oil into the water somewhere. I’ll have it crack tested before machining.

 

Ray gun, a bunch of your pics are red X’s


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""When the block & heads come back from the caustic bath, I’ll paint them Cadillac Dark Blue & then it’s off to the machine shops''.
Ray, you might want to paint after the machine shop is finished. Do you have a shop in your area capable of baking your castings ? That method cleans best of any ...

 

RaygunUK

It is post #3 and #4 from 10/13


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Need more pics RaygunUK


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That old Caddy looks to be in great shape. I like what you are doing here, look forward to seeing the progress.

 

Hi All,

Current status is that the Con Rods are having the little end bushes made and big ends narrowed to suit the journal width of the crank, one of the '59 Cadillac 390 heads is being airflowed as stock so i have some baseline flow figures and the block is being pressure checked for cracks before scanning the cylinder walls to check thickness before boring. Also, my exciting new valves have arrived form Manley, details above in this thread. Unfortunately no David Vizard 'Conformation groove' groove has been cut into the face of the intake valves though. I'll chase Manley in case they have a reason why other than just an error.
The original 331 valves are the dirtier ones on the left (or top), the new ones in the middle & the 390 valves on the right.

 

Hi, could you check if the pics show up when you log in from a PC. from what i'm reading, the HAMB Mobile App sometimes shows pictures as RedX's whereas they're fine from a PC.

 

Yup, it was the way that i'd uploaded the images (by using the Add Media option) in post #3 and #4 that does not allow them to be shown on the HAMB App. see below for the missing images in #3.

 

And the images in post #4.

 

I'll be following this. I have a 331 out of a 54 Caddy, that I'm installing in my 34 Chevy coupe.

 

Progress, good & bad, very bad. Two cylinders of one of the Caddy 390 heads has been air flow tested in its standard form. We’ve done this at 10” of Water pressure drop & I’m trying to make sense of my results compared to another std 390 head that has flow figures published on this forum. When I’ve worked that out I’ll publish the results.
The block has been crack tested by pressurising water in the jackets and has proven to be good & crack free. BUT, the wall thicknesses in the standard 331CuIn, 3 13/16” Bore range from 0.250” down to 0.157”. I’ve planned to re bore this out to 4.030”, so that is a 0.205” larger bore or 0.103” off the wall thickness. I understand that minimum wall thickness to run with should be about 0.200”, hence there is no way that my original matching numbers block will take this re-bore, dammit.
My options are to either to re think the plan entirely to stick with my original block, or find another 331 block with thicker cylinder walls.
Does anyone have access to 2 or 3 331 engines or blocks so that I can try to find a thicker wall version?

 

RaygunUk, I believe the caddy heads that were flowed in earlier thread were done at 28” of water, which is the standard figure most flow work is done to. Is it possible to rerun yours at 28”?


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Hi, Is1jy, yes ive taken the head back to the bench for another run at 28". will have results shortly.

 

Here are the results from my 1950 331 block wall thickness ultrasonic measurement. Clive Bond of Ultimate Race Cars in the UK tested it and he pointed out that the thinnest parts tended to be at the bottom of the cylinders. Perhaps the years of sitting stationery with water in the jackets has just eaten the walls away? There may be just enough thickness for a very light 30thou skim in the bores to use this block as a basis for a rebuilt stockish 331 engine.

 

Here are the flow results from the two runs that I've had done, at 102 Water & 28" water pressure drop, on the stock Cadillac 390 heads. this is my baseline before installing the larger valves and any de-shrouding and porting that I do. I notice that the 28 inch numbers compare well to the Heads that HAMB Member C322348 had done and do not show that dip in flow that he saw at 0.300". Mind you, every flow bench is different and each test is set up differently, done in different ambient conditions etc. so it is perhaps misleading to directly compare.

 

Just found a rough / rusty 331 in the UK and am about to knock the pistons out of that block to see if the wall thicknesses are any good for my use.

 

Ray gun,
For a 331 block to be a candidate for the larger bore of 390, it has to be a 1955 block, I believe. It shared same platform as 365, and later for 390


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Hi, I’m not convinced that can be the whole picture, didn’t the 55 lose the bellhousing cast on the back of the block but C322348’s is bored to 4” & still has the bellhousing. I’ve just seen that he mentioned that Chris at CAD500 has some knowledge on this, I’ll mail him too. Have you seen that written anywhere re the 55 blocks?

 

I just found this data from "The Ultimate American V8 Engine Data Book" which should help a little.

 

RaygunUk
I think it is possible to punch out the earlier block to 4”, if your sonic Check shows good material thickness on all sides...hope your other block checks good


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Hi, that is what I heard too so I was confident with my Series 61 1950 9Mxxxx block. But it has the thin patches on the cylinder walls. I’ll keep digging to see if anyone has any defining knowledge on this.


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Well my Engine build, original 331 matching numbers block with later 390 heads, has taken a wrong turn. The original block is good, but has thinner patches on the cylinder wall thicknesses so I cannot use it to bore out to 4.030” to suit the 390 heads. Hence my next step was to find an alternative 49-54 block, the one with the bellhousing part cast in.
I found a seized half engine plus block in Essex, I’m in the UK, & proceeded to take it apart. It is a 4Rxxxxx block, so I think it is from a ‘52 with power steering. Obviously, with the pistons seized solid I couldn’t turn it over, so unbolting 15 of the 30 bolts around the Torus was impossible as they were inaccessible inside the half bellhousing.
After a cup of Tea & a bit of a think I decided to turn the whole thing upside down, remove the oil pan, pump, mains & big ends, then lift the whole crank & gearbox assembly out of the bottom as one piece. It was messy & fiddly but it did eventually come out as the photos show. The trouble is though, this engine has broken a rod which punched pieces of the cam shaft up through the block into the valley!
So with this new block being little more than scrap, I’m back to first base.

My new plan, rebuild the original matching numbers 331 block with a 0.030” overbore using the original 331 heads cleaned up a little, Isky 270H cam, Offenhauser Intake, 9.5:1 compression & twin Stromberg 97’s. That will get an engine back in my car and get me going for the summer.

PLUS, decide on which block to hunt for to build a fast street Caddy engine using the 390 heads & all the parts listed earlier in this thread. Do I hunt for a 49-54 block to keep with the early Hydramatic & fit it back into my ‘50 Caddy, or do I go for a later 56-62 block to fit into a later car?


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