Building a Stage 2 Crossflow

[musew]

Hi all,

I’m in the process of building a 1600 motor for use in my Morgan 4/4. The objective is to improve performance significantly over the “GT” spec, but no racing. Basically a Stage 2 build.

Here’s what I’ve got so far:
1. 711M block out of a 71 Pinto. This engine had been rebuilt to stock spec some years ago by an authorized Ford rebuilder. Bored .030” oversize. Crank and rod bearings turned down .010”.
2. 1300 Nural pistons.
3. Kent 224 cam kit with double valve springs.
4. Double timing chain with vernier sprocket.
5. Steel pulley.
6. ARP rod bolts.
7. Pistons, rods, and crankshaft balanced.
8. Oversized valves installed in head. Head bench-flowed
All the new parts were supplied by Burton Power. Balancing was done by local machine shop. Valve job was done by semi-local well known Formula Ford engine builder.
Concerns:
1. The head is not the “uprated” variety but the older style with a very small combustion chamber cast in. I have read where this is not preferred.
2. The FF builder put very large, race spec, valves in the head:
Inlet valve 1.625"(41.3mm)
Exhaust valve 1.360"(34.5mm)
Burton recommends 39.5 inlets and 34 exhausts. Is this a problem?
3. The FF builder did not install hardened valve seats, claiming “you don’t need them”.
4. Burton claims the 1300 pistons will produce something like a 10.5:1 compression ratio.

When I measure the actual volumes, I get something like 15.5:1 (!) without considering the combustion chamber volume in the head or the head gasket thickness. I think I’d like to be somewhere around 9.5 for a stage 2 build. I’ve been told that a thicker (Cometic) head gasket will produce a lower CR, but that I may have to shave the pistons.

I’m considering obtaining a new alloy head with hardened seats and appropriately sized valves. This would address concerns 1-3 but make concern 4 even worse.
Does anyone have any experience with using 1300 pistons in a 1600 engine with an uprated (no combustion chamber) head? If so, what CR did you achieve and how?

Thanks for any response to this admittedly long-winded appeal.

Warren

[L2Man]

Hi Warren,
Sounds like a collection of parts rather than a engine built to a spec?
I am not sure its a query for this forum.
I would use a contact us approach to a couple of builders with pretty good reputations;
Joe at throb nozzle racing or Harris Performance engines in Maidstone kent, both have web
Sites.
A bit of informed advice may save you a fortune.
Good luck
Brendan

[musew]

Thanks Brendan.
I've emailed both of the organizations you suggested.

Still hoping someone here can offer a bit of practical advice.

Thanks again,
Warren

[L2Man]

I will ask my brother when he returns from a Stag week in Ireland
as he builds my twin cams and some other classic ford engines too.

cheers


Brendan

[MLI]

Hello Warren

I understand the US version of the 711M crossflows were mostly LC (low comp ratio) 8:1 CR spec, i.e. 711M block fitted with the early 1600cc Cortina mk2 head (with a shallow chamber).

The 224 cam you've got has a high lift, but not that long duration, so I would guess a CR of somewhere around 9.0-10.0:1 would suffice, when using 98 octane fuel (or 95 octane fuel with an octane booster additive?).

Kent Cams says in their catalogue that you will need to pocket the pistons further when fitting the 224, you can check this by doing a dummy build, put some plasticine on top of each piston, rotate the engine by hand a few times, then strip the engine and measure the thickness (of the now compressed) plasticine.
If your new 1300 pistons is of the (european) 711M type, they've got valve cut outs/pockets, and your head is chambered as well, so you might be OK already, but still worth checking.

It's also worth measuring the CR in a cylinder + one of the chambers in the head, see
https://www.youtube.com/watch?v=V7V40ZWNgCo
You can then calculate the CR (you will need to know the chamber volume in the head, the volume above the piston when it is on top, and the thickness of the head gasket).
Yes, the 711M 1300 pistons with valve pockets would give a CR around 10.5-11:1 in a 1600cc crossflow with a flat head, slightly less with a chambered mk2 Cortina style head.

When fitting the double timing chain/vernier, the "nose" of the crankshaft needs to be relieved/machined a little for clearance (the wider double chain will run a bit closer to the crank).

The valve sizes you've got are roughly the same as a Vulcan Maxiflow 1 head, maybe a bit large for your application, but could end up working fine with your high lift cam, try it and see.
There are different opinions as to what size valves to go for in a crossflow head, see
http://oldschool.co.nz/2011/forum/index ... ing-guide/

With your current engine spec, I don't think there will be a lot of difference between a chambered head and a flat head, if the chambered head has been properly done/set up, and the CR is within reason.

Without hardened seats for the exhaust valves, you will need to use a "lead replacement" additive, like Castrol Valvemaster (or equivalent), to avoid any valve seat recession issues.

Ivey Engineering in the US has always replied to my crossflow questions, so might be worth sending them an email?

Good luck!

[musew]

MLI,

Thanks very much for your reply. Lots of good information here.

I'll check with Ivy. Might end up buying an alloy head from them.

Thanks again,
Warren